Dissertations / Theses on the topic 'Shear Modulus'
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1
Harrison, S. Kate. "Comparison of Shear Modulus Test Methods." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/31772.
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This research compared the results of three tests: ASTM D 198 torsion, ASTM D 198 three-point bending and the five-point bending test (FPBT) using machine-stress-rated (MSR) lumber and laminated veneer lumber (LVL) to determine if the shear properties evaluated by the different test methods were equivalent. Measured E:G ratios were also compared to the E:G ratio of 16:1 commonly assumed for structural wooden members.
The average shear moduli results showed significant differences between the three test methods. For both material types, the shear moduli results determined from the two standard test methods (ASTM D 198 three-point bending and torsion), both of which are presently assumed to be equivalent, were significantly different.
Most average E:G ratios from the two material types and three test methods showed differences from the E:G ratio of 16:1 commonly assumed for structural wooden members. The average moduli of elasticity results for both material types were not significantly different. Therefore, the lack of significant difference between moduli of elasticity terms indicates that differences between E:G ratios are due to the shear modulus terms.
This research has shown differences in shear moduli results of the three test types (ASTM D 198 torsion, ASTM D 198 three-point bending, and the FPBT). Differences in the average E:G ratios per material and test type were also observed.
Master of Science
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Yung, See Yuen. "Determination of shear wave velocity and anisotropic shear modulus of an unsaturated soil /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20YUNG.
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Проценко, Олена Борисівна, Елена Борисовна Проценко, Olena Borysivna Protsenko, Вікторія Володимирівна Ємельяненко, Виктория Владимировна Емельяненко, and Viktoriia Volodymyrivna Yemelianenko. "The analysis of the elastic properties of armchair and zigzag single-walled carbon nanotubes." Thesis, Sumy State University, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20630.
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Computation simulation is a powerful tool for predictiong the mechanics models of elastic properties of armchair and zigzag single-walled nanotubes. The aim of this work is investigation and comparison of Young’s modulus, shear modulus and Poisson’s
ratio variations of armchair and zigzag tubes as functions of diameter. We obtained a set of concise, closed form expressions for the size-dependent elastic modulus, shear modulus and Poisson’s ratio of armchair (n, n) and zigzag (n, 0) nanotubes, which are basic for constructing mathematical models of elastic properties of SWNTs. We investigated armchair nanotubes with chirality (3, 3)–(40, 40) and zigzag (3, 0)–(40, 0) with diameters 4,2–54,2 Å and 2,4–31,3 Å respectively. We calculated Young’s modulus to be 0,26–2,95 TPa for armchair and 0,5–3,7 TPa for zigzag nanotubes. The shear modulus calculated for armchair nanotube appeared to be in the range of 0,2–2,0 TPa and for
zigzag one in the range of 0,2–2,7 TPa. Specifically, it was inverse dependences of Young’s modulus and shear modulus on diameter. The Poisson’s ratio was in range from 0,28 to 0,42 and from 0,27 to 0,39, respectively. Results of this research can be
used for design, analysis and evaluating of nanotubes unctioning and creating new materials based on CNTs.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20630
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Olsen, Peter A. "Shear modulus degradation of liquefying sand : quantification and modeling /." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2132.pdf.
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Olsen, Peter A. "Shear Modulus Degradation of Liquefying Sand: Quantification and Modeling." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1214.
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A major concern for geotechnical engineers is the ability to predict how a soil will react to large ground motions produced by earthquakes. Of all the different types of soil, liquefiable soils present some of the greatest challenges. The ability to quantify the degradation of a soil's shear modulus as it undergoes liquefaction would help engineers design more reliably and economically. This thesis uses ground motions recorded by an array of downhole accelerometers on Port Island, Japan, during the 1995 Kobe Earthquake, to quantify the shear modulus of sand as it liquefies. It has been shown that the shear modulus of sand decreases significantly as it liquefies, apparently decreasing in proportion to the increasing excess pore water pressure ratio (Ru). When completely liquefied, the shear modulus of sand (Ru = 1.0) for a relative density of 40 to 50% is approximately 15% of the high-strain modulus of the sand in its non-liquefied state, or 1% of its initial low-strain value. Presented in this thesis is an approach to modeling the shear modulus degradation of sand as it liquefies. This approach, called the "degrading shear modulus backbone curve method" reasonably predicts the hysteretic shear stress behavior of the liquefied sand. The shear stresses and ground accelerations computed using this method reasonably matches those recorded at the Port Island Downhole Array (PIDA) site. The degrading shear modulus backbone method is recommended as a possible method for conducting ground response analyses at sites with potentially liquefiable soils.
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Kinney, Landon Scott. "Pore Pressure Generation and Shear Modulus Degradation during Laminar Shear Box Testing with Prefabricated Vertical Drains." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7709.
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Liquefaction is a costly phenomenon where soil shear modulus degrades as the generation of excess pore pressures begins. One of the methods to mitigate liquefaction, is the use of prefabricated vertical drains. Prefabricated vertical drains provide a drainage path to effectively mitigate the generation of pore pressures and aid in shear modulus recovery. The aims of this study were to define shear modulus degradation vs. shear strain as a function of excess pore pressure ratio; define the effects of prefabricated vertical drains on the behavior of pore pressure generation vs. shear strain; and to define volumetric strain as a function of shear strain and excess pore pressure ratios. A large-scale laminar shear box test was conducted and measured on clean sands with prefabricated vertical drains spaced at 3-feet and 4-feet. The resulting test data was analyzed and compared to data without vertical drains. The results show the effect of increasing excess pore pressure ratios on shear modulus and curves where developed to encompass these effects in design with computer programing like SHAKE or DEEPSOIL. The data also suggests that prefabricated vertical drains effectively mitigate excess pore pressure build-up, thus increased the shear strain resistance before pore pressures were generated. Regarding volumetric strain, the results suggests that the primary factor governing the measured settlement is the excess pore pressure ratio. This indicates that if the drains can reduce the excess pore pressure ratio, then the resulting settlement can successfully be reduced during a shaking event. The curves for shear modulus vs. cyclic shear strain as function of pore pressure ratio were developed using data with high strain and small strain which leaves a gap of data in the cyclic shear strain range of 0.0001 to 0.01. Further large-scale testing with appropriate sensitivity is needed to observe the effect excess pore pressure generation on intermediate levels of cyclic shear strain.
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Akhi, Taohida Parvin. "Experimental investigation of effective modulus of elasticity and shear modulus of brick masonry wall under lateral load." ISIS Canada Research Network, 2011. http://hdl.handle.net/1993/5304.
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The primary objective of this research program was to investigate the effective modulus of elasticity and shear modulus of brick masonry walls under lateral load, and to to justify using the Jaeger and Mufti method to calculate the effective modulus of elasticity and shear modulus of brick masonry walls. The experimental program involved the testing of three unreinforced brick masonry walls under in-plane and vertical loads. Linear Variable Differential Transducers were used to record the horizontal and vertical displacements of the walls. The experimental results were used to evaluate the modulus of elasticity and the shear modulus of walls under flexure. The experimental results were compared to the finite element analysis results. It was found that the finite element analysis yields similar results to the experimental results. It was also found that the Jaeger and Mufti method to calculate effective modulus of elasticity and shear modulus of brick masonry walls is effective for design purposes.
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Lo, Kai Fung. "Small-strain shear modulus and damping ratio determination by bender element /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202005%20LOK.
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Rara, Angela Dominique Sarmiento. "Rolling Shear Strength and Modulus for Various Southeastern US Wood Species using the Two-Plate Shear Test." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104017.
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Cross-Laminated Timber (CLT) is an engineered wood product made by laminating dimensional or structural composite lumber in alternating orthogonal layers. Compared to Canada and Europe, CLT is a novel product to the US. With the additions included in the 2021 International Building Code (IBC), CLT material properties, especially rolling shear, would need to be explored. The increasing demand for softwood lumber, along with the increase of demand of CLT panel production, could place a burden and surpass the domestic softwood supply. Rolling shear is a phenomenon that occurs when the wood fibers in the cross-layers roll over each other because of the shearing forces acting upon a CLT panel when it is loaded out-of-plane. This study used the two-plate shear test from ASTM D2718 to measure the rolling shear properties of various southeastern US wood species: southern pine, yellow-poplar, and soft maple. A secondary study was conducted, using the same two-plate shear test, to measure the rolling shear properties of re-manufactured southern pine for CLT cross-layer application. The soft maple had the greatest average rolling shear strength at 5.93 N/mm2 and southern pine had the lowest average rolling shear strength at 2.51 N/mm2. Using a single factor analysis of variance (ANOVA), the rolling shear strength values from soft maple were significantly greater than yellow-poplar, which was significantly greater than the southern pine. For the rolling shear modulus, the southern pine and soft maple were of equal statistically significant difference, and both were greater statistically significant different compared to the yellow-poplar. The most common failure found from testing was rolling shear.Master of Science
Cross-Laminated Timber (CLT) is an engineered wood panel product, similar to plywood, constructed with solid-sawn or structural composite lumber in alternating perpendicular layers. The additions included in the incoming 2021 International Building Code (IBC) has placed an importance in expanding the research related to the mechanical and material properties of CLT. Also, with the increasing demand for softwood lumber and CLT panel production, the demand for the domestic softwood lumber could place a burden and surpass the domestic softwood supply. Rolling shear is a failure type that occurs when the wood fibers in the cross-layers roll over each other because of the shearing forces acting upon a CLT panel. This study used the two-plate shear test to measure the rolling shear properties of various southeastern US wood species: southern pine, yellow-poplar, and soft maple. A secondary study was conducted, using the same two-plate shear test, to measure the rolling shear properties of re-manufactured southern pine for CLT cross-layer application. The soft maple had the greatest average rolling shear strength at 5.93 N/mm2 and southern pine had the lowest average rolling shear strength at 2.51 N/mm2. Using a single factor analysis of variance (ANOVA), the rolling shear strength values from soft maple were significantly greater than yellow-poplar, which was significantly greater than the southern pine. For the rolling shear modulus, the southern pine and soft maple were of equal statistically significant difference, and both were greater statistically significant different compared to the yellow-poplar. The most common failure found from testing was rolling shear.
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Tai, Jui-He. "Effect of Void Fraction on Transverse Shear Modulus of Advanced Unidirectional Composites." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6591.
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In composite materials, transverse shear modulus is a critical moduli parameter for designing complex composite structures. For dependable mathematical modeling of mechanical behavior of composite materials, an accurate estimate of the moduli parameters is critically important as opposed to estimates of strength parameters where underestimation may lead to a non-optimal design but still would give one a safe one.
Although there are mechanical and empirical models available to find transverse shear modulus, they are based on many assumptions. In this work, the model is based on a three-dimensional elastic finite element analysis with multiple cells. To find the shear modulus, appropriate boundary conditions are applied to a three-dimensional representative volume element (RVE). To improve the accuracy of the model, multiple cells of the RVE are used and the value of the transverse shear modulus is calculated by an extrapolation technique that represents a large number of cells.
Comparing the available analytical and empirical models to the finite element model from this work shows that for polymeric matrix composites, the estimate of the transverse shear modulus by Halpin-Tsai model had high credibility for lower fiber volume fractions; the Mori-Tanaka model was most accurate for the mid-range fiber volume fractions; and the Elasticity Approach model was most accurate for high fiber volume fractions.
Since real-life composites have voids, this study investigated the effect of void fraction on the transverse shear modulus through design of experiment (DOE) statistical analysis. Fiber volume fraction and fiber-to-matrix Young’s moduli ratio were the other influencing parameters used. The results indicate that the fiber volume fraction is the most dominating of the three variables, making up to 96% contribution to the transverse shear modulus. The void content and fiber-to-matrix Young’s moduli ratio have negligible effects.
To find how voids themselves influence the shear modulus, the transverse shear modulus was normalized with the corresponding shear modulus with a perfect composite with no voids. As expected, the void content has the largest contribution to the normalized shear modulus of 80%. The fiber volume fraction contributed 12%, and the fiber-to-matrix Young’s moduli ratio contribution was again low.
Based on the results of this work, the influences and sensitivities of void content have helped in the development of accurate models for transverse shear modulus, and let us confidently study the influence of fiber-to-matrix Young’s moduli ratio, fiber volume fraction and void content on its value.
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Bryant, James William Jr. "Prediction of Linear Viscoelastic Response of the Loss Shear Modulus of Polymer-Modified Binders." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/31719.
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Current mathematical models, developed on straight asphalt binders, are inadequate to characterize the frequency dependence of response of polymer-modified asphalt binders. In an earlier study at Virginia Tech, mathematical models were developed to predict the storage and loss shear moduli of polymer-modified binders. However the model developed for the loss shear moduli is limited at high frequency (G" less than or equal to 10^7.5 Pa). This thesis presents a statistical modeling of loss shear modulus of polymer (random copolymers and thermoplastic block copolymers) modified binder. Data from dynamic mechanical analysis on modified binders, at temperatures between 5 and 75°C and frequencies ranging from 0.06 to 0188.5 rad/s, were reduced to dynamic master curves of moduli, and used to develop the model. Twenty-one polymer-binder blends prepared and tested earlier at Virginia Tech where included in the study. Realistic characterization of loss shear moduli values was obtained using the Gompertz statistical model. The model was validated by using mean square error of prediction (MSEP) in which a second set of frequency data was input in the model to obtain the moduli values, which were compared to the measured data of the second set. Although this model was successfully tested for shear loss modulus prediction of polymer-modified binders, caution should be exercised when it is applied, as such a model should be able to predict the storage modulus for a known phase angle.Master of Science
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Han, Zhong. "Modelling Stiffness and Shear Strength of Compacted Subgrade Soils." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35059.
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Compacted soils are frequently used as subgrade for pavements as well as commercial and residential buildings. The stiffness and shear strength properties of compacted soils, which are collectively denoted as Ω in this thesis, fluctuate with moisture content changes that result from the influence of environmental factors such as the evaporation and infiltration. For example, mechanistic pavement design methods require the information of resilient modulus (MR), which is the soil stiffness behavior under cyclic traffic loading, and its variation with respect to the soil moisture content determined from laboratory tests or estimation methods. Significant advances have been made during the last five decades to understand and model the variation of the Ω with respect to soil moisture content and soil suction (s) based on the principles of mechanics of unsaturated soils. There are a variety of models presently available in the literature relating the Ω to the s using different approaches. There are however uncertainties extending these models for predicting Ω - s relationships when they are used for a larger soil suction range. In addition, the good performance of these models are only valid for certain soil types for which they were developed and calibrated.
Studies presented in this thesis are directed towards developing a unified methodology for modelling the relationship between the Ω and the s using limited while easy-to-obtain information. However, more emphasis has been focused on the MR - s relationships of pavement subgrade soils considering the need for the application of the mechanistic pavement design methods in Canada. The following studies have been conducted:
(i) State-of-the-art review on existing equations in the literature for the MR - s relationships is summarized. A comparison study is followed to discuss the strengths and limitations of these equations;
(ii) A unified methodology for modelling the Ω - s relationships is proposed. Experimental data on 25 different soils are used to verify the proposed unified methodology. The investigations are applied on small strain shear modulus, elastic modulus, and peak and critical shear strength. Good predictions are achieved for all of the investigated soils;
(iii) Performance of the proposed methodology is examined for the MR - s relationships using experimental data of 11 subgrade soils. Reasonably good predictions are achieved for all of the subgrade soils;
(iv) Extensive experimental investigations are conducted on the MR - s relationships for several subgrade soils collected from various regions in Canada. Experimental results suggest non-linear variation in the MR with respect to s, moisture content and the external stress. The measured results are modelled using the proposed methodology with adequate success;
(v) Additional experimental investigations are performed to determine the variation of the elastic modulus (E) and unconfined compression strength (qu) with the s and the gravimetric moisture content (w) for several Canadian subgrade soils. An approach, which is developed extending the proposed unified methodology, is used to normalize the measured MR - w, E - w and qu - w relationships. It is shown that the normalized MR - w, E - w and qu - w relationships exhibit remarkable similarity and can be well described using the proposed approach. Such similarity in the normalized Ω - moisture content relationships are also corroborated using the experimental data on several other soils reported in the literature.
The proposed unified methodology alleviates the need for the determination of the Ω - s relationships which requires elaborate testing equipment that needs the supervision of trained personnel and is also time-consuming and expensive. In addition, experimental programs in this thesis provide detailed experimental data on the MR, E, qu, and soil-water characteristic curves of Canadian subgrade soils. These data will be helpful for the better understanding of the hydro-mechanical behavior of the Canadian subgrade soils and for the implementation of the mechanistic pavement design method in Canada. The simple tools presented in this thesis are promising and encouraging for implementing the mechanics of unsaturated soils into conventional geotechnical engineering practice.
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Copeland, David B. "Measurement of the complex shear modulus and its frequency dependence for viscoelastic materials." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17517.
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O'Connor, Bernard. "High strain deformation and ultimate failure of HIPS and ABS polymers." Thesis, Cranfield University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245417.
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He, Yi. "Effect of Additives on Crystallization of a Mixture of Fully Hydrogenated Canola Oil and Canola Oil." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503180621875492.
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Saeki, Junya. "Muscle stiffness of posterior lower leg in runners with a history of medial tibial stress syndrome." Kyoto University, 2018. http://hdl.handle.net/2433/232319.
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Rouholamin, Milad. "Shear Behaviour and Design of Roll-Formed Aluminium Lipped Channel Sections With and Without Web Openings." Thesis, Griffith University, 2020. http://hdl.handle.net/10072/398413.
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Recently, the use of aluminium sections as primary load bearing members has increased significantly in the building industry. Aluminium as a new constructional material has several advantages in building structures including corrosion resistance, durability, high strength-to-weight ratio, reduced cost of transportation and ease of erection and fabrication. The popularity of aluminium structures has attracted the attention regarding the efficiency and design of many sections, and roll-formed aluminium lipped channel beam (LCB) is one of these commonly used sections. However, aluminium LCBs are inclined to shear buckling failure due to its increased web slenderness and low elastic modulus compared to steel which has raised the issue about the failure of these sections.
Hence detailed experimental and numerical studies were conducted to investigate the shear behaviour of roll-formed aluminium LCBs, and to verify the current design rules to accurately predict the shear capacities. A total of 28 shear tests has been carried out using commonly available ten different aluminium lipped channel beams with varying heights and thicknesses to investigate the shear behaviour of roll-formed aluminium LCBs. The test specimens were loaded at mid-span at the shear centre until failure. Comparative study was also required between the obtained results from this investigation in order to propose improved design rules.
Finite element models of aluminium LCBs were then developed and validated with test results. A detailed parametric study including 120 models was also undertaken with different sections, web slenderness, aluminium grades and aspect ratios to obtain the shear strengths and shear buckling characteristics of aluminium LCBs. The ultimate shear capacities of aluminium LCBs obtained from the tests and finite element analyses (FEA) were compared with the current shear design rules of Australian/New Zealand Standard and Eurocode for both aluminium structures and cold-formed structures as well as direct strength method (DSM). The comparison showed that these current shear design rules are not suitable to predict the shear strengths of roll-formed aluminium LCBs. Hence new design rules were proposed in this study to accurately predict the shear capacities of roll-formed aluminium LCBs.
Web openings are incorporated in these sections to accommodate building services when they are used as beams. Hence, experimental and numerical studies were also conducted in this research to investigate the shear behaviour of these roll-formed aluminium LCBs with web openings. An aspect ratio of one was considered in this study. A total of 17 tests were conducted to investigate the shear behaviour of aluminium LCBs with circular web openings using three-point loading arrangement. Finite element models were also developed with appropriate loading and boundary conditions and validated using the experimental results. A detailed parametric study including 204 models was then undertaken using the currently available roll-formed aluminium LCBs with different thicknesses, grades and web opening sizes. The ultimate shear capacities and the shear capacity reduction factors obtained from the tests and finite element analyses were compared with the currently available design rules.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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Dunlap, Myles Derrick. "Experimental Measurement of the Utricle's Dynamic Response and the Mechanoelectrical Characterization of a Micron-Sized DIB." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/52862.
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Within the vestibular system are otolith organs, both the utricle and saccule. The primary function of these organs is to transduce linear head accelerations and static head tilts into afferent signals that are sent to the central nervous system for the utilization of image fixation, muscle posture control, and the coordination of musculoskeletal movement in dynamic body motion. The utricle of the red ear slider turtle was studied in this dissertation. The turtle's utricle is composed of several layers. The base layer contains a set of neural receptor cells, called hair cells, and supporting cells. The three layers above the base layer compose the utricle's otoconial membrane (OM) and are: 1.) a saccharide gelatinous layer, 2.) a column filament layer, and 3.) a calcite and aragonite otoconial crystal layer.
The primary goal of this research was to study the dynamic response of the turtle's OM to a variety of natural inertial stimuli in order to characterize its inherent mechanical properties of natural frequency ("n), damping ("), and shear modulus (G). The medial-lateral (ML) and anterior-posterior (AP) anatomical axes parameters were measured for the utricle. The ML axis median with 95% confidence intervals was found to be "n = 374 (353, 396) Hz, " = 0.50 (0.47, 0.53), and G = 9.42 (8.36, 10.49) Pa. The AP axis median with 95% confidence intervals was found to be "n = 409 (390, 430) Hz, " = 0.53 (0.48, 0.57), and G = 11.31 (10.21, 12.41). Nonlinearites were not found to occur in the OM for the tested inertial stimuli and no significant difference was found between the mechanical properties for the ML and AP axes.
Additionally, this research presents the initial steps to form a novel bio-inspired accelerometer based on the morphology of the utricle. The primary transducer element for this possible otolith organ inspired accelerometer design is a droplet interface bilayer (DIB). A DIB is a lipid bilayer that is formed when the interface of two aqueous droplets, that contain free-floating lipids, are joined. The aqueous droplets are suspended in a nonpolar environment (oil) and the oil/water interface forms a lipid monolayer. This research developed and used an experimental test setup to characterize the mechanoelectrical characteristics of a micron-sized DIB. This information, along with examples in the text, could be used to further design the aforementioned accelerometer.Ph. D.
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Larsson, David. "Accuracy Assessment of Shear Wave Elastography for Arterial Applications by Mechanical Testing." Thesis, KTH, Hållfasthetslära (Avd.), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160091.
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Arterial stiffness is an important biometric in predicting cardiovascular diseases, since mechanical properties serve as indicators of several pathologies such as e.g. atherosclerosis. Shear Wave Elastography (SWE) could serve as a valuable non-invasive diagnostic tool for assessing arterial stiffness, with the technique proven efficient in large homogeneous tissue. However the accuracy within arterial applications is still uncertain, following the lack of proper validation. Therefore, the aim of this study was to assess the accuracy of SWE in arterial phantoms of poly(vinyl alcohol) cryogel by developing an experimental setup with an additional mechanical testing setup as a reference method. The two setups were developed to generate identical stress states on the mounted phantoms, with a combination of axial loads and static intraluminal pressures. The acquired radiofrequency-data was analysed in the frequency domain with retrieved dispersion curves fitted to a Lamb-wave based wave propagation model. The results indicated a significant correlation between SWE and mechanical measurements for the arterial phantoms, with an average relative error of 10 % for elastic shear moduli in the range of 23 to 108 kPa. The performed accuracy quantification implies a satisfactory performance level and as well as a general feasibility of SWE in arterial vessels, indicating the potential of SWE as a future cardiovascular diagnostic tool.
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Selk, Rawley Jack. "Quick Shear Testing of Aggregate Base Materials Stabilized with Geogrid." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6571.
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The objective of this research was to apply a previously recommended laboratory testing protocol to specific aggregate base materials that are also the subject of ongoing full-scale field testing. The scope of this research involved three aggregate base materials selected from three sites where full-scale field testing programs have been established. The first and second field sites included five different geogrid types, categorized as either biaxial or triaxial, in a singlelayer configuration, while the third site included only the triaxial geogrid type in either a singleor double-layer configuration. Geogrid-stabilized and unstabilized control specimens were evaluated using the American Association of State Highway and Transportation Officials T 307 quick shear testing protocol. Measurements of load and axial displacement were recorded and used to develop a stress-strain plot for each specimen tested. The peak axial stress, the modulus to the peak axial stress, the modulus of the elastic portion of the curve, and the modulus at 2 percent strain were then calculated. Statistical analyses were performed to investigate differences between geogridstabilized specimens and unstabilized control specimens and to investigate differences between individual geogrid products or geogrid configurations. Depending on the method of data analysis, the quick shear test results indicate that geogrid stabilization, with the effect of geogrid stabilization averaged across all of the geogrid products evaluated in this study, may or may not improve the structural quality of the aggregate base materials evaluated in this study. The results also indicate that, regardless of the method of analysis, one geogrid product or configuration may be more effective than another at improving the structural quality of a given aggregate base material as measured using the quick shear test. All results from this research are limited in their application to the aggregate base material types, geogrid products, and geogrid configurations associated with this study. Additional research is needed to compare the results of the laboratory quick shear testing obtained for this study with the structural capacity of the geogrid-stabilized and unstabilized control sections that have been constructed at corresponding full-scale field testing sites. Specifically, further research is needed to determine which method of laboratory data analysis yields the best comparisons with field test results. Finally, correlations between the results of quick shear testing and resilient modulus need to be investigated in order to incorporate the findings of the quick shear test on geogrid-stabilized base materials into mechanistic-empirical pavement design.
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Curd, Jason M. "Unsaturated Soil Parameters From Field Stiffness Measurements." UKnowledge, 2013. http://uknowledge.uky.edu/ce_etds/11.
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The behavior of unsaturated soils depends heavily on material properties and soil conditions. In Geotechnical Engineering, compacted soils are frequently used as fill material, and quality control is vital to the construction process. There are few methods available to estimate the parameters associated with unsaturated soils based on field measurements, and a relationship between these factors could reduce testing time and lower construction costs. Undrained triaxial tests were performed on four clays representing a range of material properties in an effort to reach the maximum dry density, which provides the highest bearing capacity. Each clay was compacted at optimum moisture content, as well as wet and dry of optimum. Measurements were taken using the GeoGauge and shear wave velocities. An empirical approach was used to estimate the effect of a density gradient on soil suction. A relationship between the normal stress and matric suction produced a strong trend when plotted against a function of stiffness and the void ratio, which represents a density gradient. Another relationship between the GeoGauge and shear wave stiffness measurements was found, but no relationship with the material properties of the samples was observed, indicating that more in-depth research is needed to find a stronger relationship.
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Apaza, Marco Aurelio Flores. "Determinação do Gmáx através do método de análise espectral de ondas superficiais." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3145/tde-21082009-165223/.
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Esta dissertação apresenta o método de análise espectral de ondas superficiais (SASW) para a obtenção das variações do módulo cisalhante (Gmáx) com a profundidade, no domínio das deformações muito pequenas (abaixo de 0,001%). O SASW é um método sísmico in situ, não destrutivo, baseado na geração e detecção de ondas Rayleigh e na natureza dispersiva desta onda. Pela aplicação de um impacto na superfície do solo e detecção da onda em vários pontos, através de dois receptores, é construída uma curva de dispersão (velocidade de fase versus comprimento de onda). Esta curva de dispersão é, então, invertida. A inversão é um processo analítico para a reconstrução do perfil de velocidade de onda de cisalhamento (VS), partindo-se da curva de dispersão experimental de campo. O módulo de cisalhamento máximo de cada camada é facilmente obtido a partir do perfil de VS. No conteúdo teórico da dissertação discutem-se propriedades dinâmicas dos solos e descrevem-se as equações que dominam a propagação das ondas elásticas, tanto em meios homogêneos como em meios estratificados. A metodologia desenvolvida para a obtenção das curvas de dispersão, através da realização de ensaios SASW, apresenta os resultados obtidos em ensaios realizados na Cidade Universitária em São Paulo, sendo esses resultados comparados com estimativas feitas a partir de correlações baseadas em ensaios SPT existentes. Essas comparações permitem concluir que a metodologia SASW é uma boa alternativa para a determinação do perfil de rigidez (Gmáx) do solo, concordando com o nível de deformação envolvido nos ensaios. São desenvolvidos estudos de sensibilidade do método para verificar a influência na mudança dos parâmetros assumidos (peso específico, coeficiente de Poisson e espessuras das camadas) no processo de redução de dados (inversão) sobre o perfil final de VS, concluindo-se que o parâmetro que apresenta maior influência é o coeficiente de Poisson.This dissertation presents the spectral-analysis-of-surface-waves (SASW) method as a tool for obtaining the variations in the modulus shear (Gmax) with depth in the field of very small strains (below 0,001%). The SASW method is a nondestructive in situ seismic method, based on the generation and measurement of Rayleigh wave and on its dispersive characteristic nature. Throughout the implementation of an impact on the soil surface and the detection of the wave at various points by two receptors a dispersion curve is constructed (phase velocity versus wave-length). This dispersion curve is then inverted. Inversion is an analytical process for reconstructing the shear wave velocity profile from the experimental field. The shear modulus of each layer is readily obtained from the shear wave velocity profile. The theoretical content of the dissertation presents dynamic properties of the soils and is described in the equations that dominate the propagation of elastic waves, both in homogeneous media and in stratified media. The methodology developed to obtain the dispersion curves through the implementation of SASW test is defined, and results from tests carried out at the University Campus in São Paulo are presented and compared with values obtained from correlations based on SPT tests. These comparisons indicate that the SASW method is a good alternative to determine the profile of stiffness (Gmax) of the soil, agreeing with the level of deformation involved in the tests. Studies on the methods sensitivity are developed to verify the influence on the changing of the parameters given (natural unit weight, Poisson coefficient and thickness of layers) in reduction of data (inversion) on the final profile of VS. The conclusion is that the Poisson coefficient is the parameter with greater influence.
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Lombardo, Nick, and e56481@ems rmit edu au. "Properties of Composites Containing Spherical Inclusions Surrounded by an Inhomogeneous Interphase Region." RMIT University. Mathematical and Geospatial Sciences, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080408.143315.
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The properties of composite materials in which spherical inclusions are embedded in a matrix of some kind, have been studied for many decades and many analytical models have been developed which measure these properties. There has been a steady progression in the complexity of models over the years, providing greater insight into the nature of these materials and improving the accuracy in the measurement of their properties. Some of the properties with which this thesis is concerned are, the elastic, thermal and electrical properties of such composites. The size of the spherical inclusion which acts as the reinforcing phase, has a major effect on the overall properties of composite materials. Once an inclusion is embedded into a matrix, a third region of different properties between the inclusion and matrix is known to develop which is called the interphase. It is well known in the composite community that the smaller the inclusion is, the larger the interphase region which develops around it. Therefore, with the introduction of nanoparticles as the preferred reinforcing phase for some composites, the interphase has a major effect on its properties. It is the aim of this thesis to consider the role of the interphase on the properties of composites by modeling it as an inhomogeneous region. There is much scientific evidence to support the fact that the interphase has an inhomogeneous nature and many papers throughout the thesis are cited which highlight this. By modeling the inhomogeneous properties by arbitrary mathematical functions, results are obtained for the various properties in terms of these general functions. Some specific profiles for the inhomogeneous region are considered for each property in order to demonstrate and test the models against some established results.
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Al-Darwash, Mustafa, and Emanuel Nuss. "Mechanical characterization of DuraPulp by means of micromechanical modelling." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-43732.
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Södra DuraPulp is a relatively new eco-composite, made from natural wood fibers and polylactic acid (PLA), which comes from corn starch. Until now, there are only few applications for DuraPulp, mainly in the area of design. To find new fields of application, more knowledge about its mechanical material properties are of great interest.This study deals with characterizing the mechanical properties of DuraPulp in an analytical way by means of micromechanical modelling and evaluation with help of Matlab. The mechanical properties for PLA were taken from scientific literature. Not all properties of the wood fibers could be found in literature (particularly Poisson’s ratios were unavailable). Therefore, they partly had to be assumed within reasonable boundaries. These assumptions are later validated regarding their influence on the final product.Figures and tables were used to present and compare the in- and out-of-plane E-Moduli, shear moduli and Poisson’s ratios of DuraPulp. The calculated in-plane E-Moduli were then compared to those obtained from an earlier study, where DuraPulp was tested in tension. The results showed that experimental and analytical values are very similar to each other.Södra DuraPulp är en relativt ny eco-komposit, tillverkat av naturliga trä fibrer och polylactic syra som kommer från majsstärkelser. I dagsläget finns det få användningsområden för DuraPulp, huvudsakligen används det inom design. För att expandera användningsområdet behövs det mer kunskaper angående de mekaniska egenskaperna för materialet. Studien handlar om att karakterisera de mekaniska egenskaperna för DuraPulp på ett analytiskt sätt i form av mikro-mekanisk modellering och evaluering med hjälp av Matlab. De huvudsakliga mekaniska egenskaperna för PLA kunde hämtas från flera vetenskapliga källor, men de motsvarande mekaniska egenskaperna för fibrer kunde inte alla valideras. Delvis antogs dem i rimliga gränser och deras inverkan validerades med hjälp av en parameter studie.Figurer och tabeller användes för att presentera och jämföra in- och ut-plan E-Moduler, skjuvmoduler och tvärkontraktionstalen av DuraPulp. De beräknade in-plan E-modulerna för DuraPulp jämfördes med motsvarande E-moduler från en tidigare studie där DuraPulp genomgick dragtest. Resultatet visade att analytiska och experimentella värden överensstämmer bra med varandra.
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Hao, Gang. "Laboratory study of shear wave velocity and very small stain modulus of Macao marine clay under anisotropic stress condition." Thesis, University of Macau, 2008. http://umaclib3.umac.mo/record=b1783644.
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Assaf, Ihab Adeeb. "Shear strengthening of reinforced concrete beams using an external carbon fibre reinforced polymer (CFRP) composite of low elastic modulus." Thesis, University of Salford, 2007. http://usir.salford.ac.uk/26555/.
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Beam-column joints designed seismically are considered impractical due to the congestion of steel stirrups. Currently, CFRP is used for strengthening reinforced concrete structures that have reduced integrity due to corrosion of steel reinforcement or unintentional overloading. The aim of this thesis is to mitigate the congestion of steel stirrups in the beam-column joint regions using an externally bonded CFRP composite and to possibly propose initial 'new build' design rules. Experimental work was conducted on 24 reinforced concrete beams with different percentages of steel shear reinforcement and varying amounts of CFRP. Six of these were tested under cyclic load. Significant reduction was observed as the RC beams were subjected to load reversal significantly higher than their service load. 18 beams were tested under static load in order to find the contribution of the CFRP to the shear capacity with varying percentages of steel stirrups. The results show that the CFRP contribution to the shear capacity is significant at zero and low ratios and decreases with an increase in the percentage of steel stirrups. The CFRP contribution is reduced significantly at high percentages of steel stirrup as the mode of failure becomes flexural. For strengthened beams having no steel shear reinforcement, the CFRP contribution is evaluated using current design rules. Load sharing between the CFRP and steel stirrups was observed and this relationship is very important for development of the current design rules. An alteration in the mode failure for the strengthened beam having a moderate percentage of steel stirrups was observed and similar behaviour was noticed with the beam conventionally reinforced with high ratio of steel stirrups. This is very beneficial in practice where the congested steel causes problems. Finite element analyses were carried out using ANSYS to attempt to predict the behaviour of further beams, caveats for which are highlighted within the thesis. The results for load sharing between the CFRP and steel stirrups shows that the relationship between the CFRP contribution to the shear capacity and the percentage of steel stirrups is not proportional as observed experimentally. Future work recommends a repeat of the experimental test with more instrumentation. Experimental tests on more complex structures (i.e. beam-column joints) are recommended where the shear reinforcement and confinement could be provided through the CFRP and hence reduce the congestion of steel stirrups. Using other FE codes is also recommended with an increased budget.
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Zitko, Jarrett. "Effects of Random Cross-Sectioned Distributions, Fiber Misalignment and Interphases in Three-Dimensional Composite Models on Transverse Shear Modulus." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4268.
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Finite element analysis was implemented to evaluate the transverse shear modulus of a unidirectional glass/epoxy fiber-matrix composite based on pure shear displacement boundary conditions. Unit cells consisting of three-dimensional glass cylinders surrounded in square-cuboid epoxy matrices were modeled to represent "Representative Volume Element" (RVE) configurations in periodic and random-periodic square cell arrangements of variable size. Three RVEs were constructed and analyzed: A single unit cell, a 9-cell (3 x 3) array, and a 25-cell (5 x 5) array. Additionally, the unit cell was modeled to include an interphase. Three sets of cell arrangements were constructed and evaluated: a periodic square array, a transversely distributed random-periodic array, and a variable angularly aligned random-periodic array. Furthermore, scale and free-edge effects of the composites were studied by evaluating the shear modulus in incrementally increasing domains, as well as by isolating finite-sized domains called windows within the multiple-cell model, whereby the window is smaller than the array. Finite element software was subsequently utilized to create a three-dimensional mesh of the composite models studied. Each simulation consisted of exposing the respective domain to pure shear boundary conditions, whereby the model was subject to uniform transverse displacement along its boundary. Subsequent volumetric averaging resulted in computation of the apparent transverse shear modulus. The resulting numerically attained elastic shear modulus was then evaluated and compared to known predictive models in literature. It was shown that that the transverse random arrangement as well the random angular alignment of fibers within the composite structure had a marginal influence on the shear modulus. For random transverse distributions, a deviation in modulus of +1.5% was observed for the 25-cell array as compared to a periodic array of equal size. Similarly, a deviation of +0.3% was predicted for 25-cell arrays subject to random angular fiber misalignments up to ±0.143°, as compared 25-cell periodic arrays. Furthermore, increasing the composite medium by systematic, incremental augmentation model domains was shown to significantly lower the shear modulus in a convergent manner as G23 values dropped 33.5% from the nonhomogeneous single cell to the 9-cell model, and 2.6% from the same 9-cell to the 25-cell model, while observing the effects of a mesoscale window displayed little variance in modulus value as compared to the larger RVE from which the window was isolated from. Lastly, the predictive potential of the model developed by Sutcu for composites with interphases, and other commonly employed models for predicting the transverse shear modulus of unidirectional composites was also evaluated. Numerical results of nonhomogeneous interphase models for both periodic and random-periodic 25-cell arrays were found to be in excellent agreement with Sutcu's approximation. The shear modulus of the 25-cell, nonhomogeneous interphase model was found to lie within 3.5% of Sutcu's prediction. Volume averages for periodic arrays with no interphase were observed to lie in close proximity to Halpin-Tsai's model, displaying a variation of 7% for a 25-cell, single fiber model.
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Reubush, Stacey Diane. "Effects of Storage on the Linear Viscoelastic Response of Polymer-Modified Asphalt at Intermediate to High Temperatures." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/30838.
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The design and construction of roads with longer service lives is a priority of civil engineers. The selection of appropriate highway materials with respect to climatic and loading conditions may significantly increase the lifespan of pavements. One material receiving interest in the area of improved roadway performance is polymer-modified binder. The complex behavior of polymer-modified binders, particularly over time, is not yet well-understood by engineers. Therefore, an experimental study was performed to determine the effects of four years of storage at room temperatures (23°C) on the dynamic mechanical properties of polymer-modified binders at intermediate and high temperatures. A typical paving grade (AC-20) and three elastomeric modifiers, each at three concentrations were used. Initial tests were performed in 1995 to evaluate the effects of short-term aging as simulated by the Rolling Thin Film Oven Test (RTFOT) procedure. This study encompasses a second phase of testing occurring after the modified binders were stored at ambient room temperature (23°C) for four years. The study found that significant changes affecting the dynamic response of binders occur during long term storage at a temperature of 23°C. These changes are dependent on the type and concentration of modifier and may be beneficial. Additionally, four mathematical models describing the dynamic response of binders were evaluated and found to be variable in their ability to accurately predict response of modified binders. Most of these models are not well suited for prediction of the response of stored binders.Master of Science
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Duraisamy, Youventharan. "Strength And Stiffness Improvement Of Bio-Cemented Sydney Sand." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15533.
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This thesis explores the performance of small scale cemented soil columns produced using soil mixing with cement resulting from bacterially mediated reactions that precipitate calcium carbonate, a process often referred to as bio-cementation. Bio-cementation has received considerable research attention over the last decade as it has the potential to complement existing ground improvement techniques and mitigate environmental concerns with currently used materials. Previous research has concentrated on pumping and injection techniques because of concerns that bacteria will be unable to survive the stresses associated with industrial mixing processes, however it has been difficult to create uniform bio-cemented soil masses. In this thesis the ureolytic bacterium, Bacillus Megaterium, not previously reported in bio-cementation studies, has been investigated to determine its viability and efficiency as a microbe for mediating the calcite precipitation. It has been found that the highest hydrolysis rate is recorded when calcium concentrations are double the urea concentrations, and that significant amounts of calcite can be precipitated in a single mixing process. Unconfined compressive strength (UCS) tests and a series of triaxial tests have been conducted to quantify the effects of the bio-cementation on the mechanical response. Bender elements mounted in the triaxial cell have also been used to monitor the shear wave velocity during curing and shearing. The results of mechanical tests on the bio-cemented sand have been compared with tests on gypsum cemented and uncemented specimens. It has been found that bio-cementation by mixing produces homogeneous specimens with similar strengths and stiffnesses to the commonly used flushing or injection technique. To assess the performance of in-situ mixed, 38 mm diameter, bio-cemented sand columns a small scale in-situ mixing technique was used to create the model columns. Foundation tests have been performed at 1-g in a cylindrical tank with diameter of 600 mm. A significant improvement was observed in the response of foundations when placed on bio-cemented columns, and this was similar to the improvement from more conventional gypsum cements. These tests confirmed the feasibility of using an in-situ mixing technique with bio-cementation and provided valuable insight into the factors that must be considered in developing field applications. This thesis also has demonstrated repair strategies and techniques to encourage healing and self-healing should damage occur in foundations. Results from tests performed to investigate the ability of biocement to repair cemented soil columns are reported.
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Oh, Won Taek. "Simple Techniques for the Implementation of the Mechanics of Unsaturated Soils into Engineering Practice." Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23533.
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Over the past 50 years, several advancements have been made in the research area of the mechanics of unsaturated soils. These advancements can be categorized into two groups; (i) development (or improvement) of testing techniques (or apparatus) to determine the mechanical properties of unsaturated soils and (ii) development of (numerical, empirical or semi-empirical) models to estimate the variation of mechanical properties of unsaturated soils with respect to suction based on the experimental results. Implementation of the mechanics of unsaturated soils in conventional geotechnical engineering practice, however, has been rather limited. The key reasons for the limited practical applications may be attributed to the lack of simple and reliable methods for (i) measuring soil suction in the field quickly and reliably and (ii) estimating the variation of mechanical properties of unsaturated soils with respect to suction.
The main objective of this thesis research is to develop simple and reliable techniques, models or approaches that can be used in geotechnical engineering practice to estimate sol suction and the mechanical properties of unsaturated soils. This research can be categorized into three parts.
In the First Part, simple techniques are proposed to estimate the suction values of as-compacted unsaturated fine-grained soils using a pocket penetrometer and a conventional tensiometer. The suction values less than 300 kPa can be estimated using a strong relationship between the compressive strength measured using a pocket penetrometer and matric suction value. The high suction values in the range of 1,200 kPa to 60,000 kPa can be estimated using the unique relationship between the initial tangent of conventional tensiometer response versus time behavior and suction value.
In the Second Part, approaches or semi-empirical models are proposed to estimate the variation of mechanical properties of unsaturated soils with respect to suction, which include:
- Bearing capacity of unsaturated fine-grained soils
- Variation of bearing capacity of unsaturated fine-grained soils with respect to matric suction
- Variation of initial tangent elastic modulus of unsaturated soils below shallow foundations with respect to matric suction
- Variation of maximum shear modulus with respect to matric suction for unsaturated non-plastic sandy soils (i.e. plasticity index, Ip = 0 %)
In the Third Part, approaches (or methodologies) are suggested to simulate the vertically applied stress versus surface settlement behavior of shallow foundations in unsaturated coarse-grained soils assuming elastic-perfectly plastic behavior. These methodologies are extended to simulate the stress versus settlement behavior of both model footings and in-situ plates in unsaturated coarse-grained soils.
The results show that there is a reasonably good comparison between the measured values (i.e. soil suction, bearing capacity, elastic and shear modulus) and those estimated using the techniques or models proposed in this thesis research.
The models (or methodologies) proposed in this thesis research are promising and encouraging for modeling studies and practicing engineers to estimate the variation of mechanical behavior of unsaturated soils with respect to matric suction.
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Richardson, Anthony James. "Determination of nanogram mass and measurement of polymer solution free volume using thickness-shear mode (tsm) quartz resonators." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003282.
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Ku, Taeseo. "Geostatic stress state evaluation by directional shear wave velocities, with application towards geocharacterization at Aiken, SC." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45905.
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Evaluations of stress history and the geostatic state of stress of soils are ascertained on the basis of field geophysical measurements that provide paired complementary types of shear waves. It is well-established that multiple types of shear waves occur in the ground due to their directional and polarization properties. The shear wave velocity (Vs) provides the magnitude of small strain stiffness (G0) which depends on effective stress, void ratio, stress history, and other factors (cementation, age, saturation). Herein, this study examines a hierarchy of shear wave modes with different directions of propagation and particle motion from in-situ geophysical tests (HH, VH, and HV) and laboratory bender element data. A special compiled database from well-documented worldwide sites is assembled where full profiles of stress state, stress history, and several paired modes of Vs profiles have been obtained from crosshole tests (CHT), downhole tests (DHT), and rotary crosshole (RCHT). Reference profiles of the lateral stress coefficient (K0) are available from direct in-situ measurements (self-boring pressuremeter, hydrofracture, and push-in spade cells). Stress history is documented in terms of yield stress ratio (YSR) from consolidation testing and careful engineering geology studies. A methodology is developed that relates both the YSR and K0 to stiffness ratios obtained from directional shear wave velocities. In further efforts, means to extract reliable shear wave profiles from continuous downhole testing via a new GT autosource and seismic piezocone testing are outlined and applied to results from three test sites in Windsor/VA, Norfolk/VA, and Richmond/BC.
A driving impetus to this research involves the geologic conditions at the US Dept. of Energy's Savannah River Site (SRS) in South Carolina. Here, the overburden soils in the upper 60 m depths consist of very old Miocene and Eocene sediments, primarily layered deposits of sands, clayey sands, silty sands, and interbedded clays which exhibit an apparent and unusual stress history profile. Special geologic conditions include the dissolutioning of old calcareous sediments (Santee Formation) at depths of 40 to 50 m below grade, similar to karstic limestone deposits. As a consequence, caves, voids, and infilled soft soil zones occur within the soil matrix at these elevations, probably resulting in localized collapse of the overlying soil column. Based on conventional laboratory and in-situ test data conducted during geotechnical investigations at SRS, available interpretative relationships for assessing the soil stress history and geostatic stress states show scattered and inconsistent results. Complications abound in the systematic assessments of these geomaterials due to effects of very old ageing, cementation, desiccation, and diagenesis, as evidenced by unusual in-situ shear wave velocity profiles that decrease in magnitude with depth, as measured by CHT and DHT. Based on the findings of this study, it is recommended that a new set of shear wave velocity measurements be made at SRS to obtain HH waves (and complementary VH waves) needed for an independent assessment of YSR in the upper soil column.
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Štěpanovský, Vlastimil. "Problematika stárnutí asfaltových pojiv a směsí." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227164.
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Diploma thesis is particularly focused on ageing of asphalt mixtures and asphalt binders. In the theoretical part an array of methods simulating short term and long term ageing consequently is introduced. The main objective of the practical part was to carry out the long-term ageing test method BSA (Braunschweiger Alterung). Thereafter, specimens testing for stiffness properties according to CSN EN 12697-26 were made. After conducting the measurement on those, asphalt binder was extracted and processed to follow-up testing. The testing consisted of a range of methods – Penetration CSN EN 1426, Ring and Ball test CSN EN 1427, Determination of the Frass breaking point CSN EN 12593, Determination of complex shear modulus CSN EN 14770 and Dynamic viscosity using a dynamic shear rheometer (DSR). The given results were assessed in the last part in order to evaluate the rate of the binder degradation caused by the method BSA.
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Böhmer, Anna Elisabeth [Verfasser], and H. von [Akademischer Betreuer] Löhneysen. "Competing Phases in Iron-Based Superconductors Studied by High-Resolution Thermal-Expansion and Shear-Modulus Measurements / Anna Elisabeth Böhmer. Betreuer: H. v. Löhneysen." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1056955880/34.
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Malysz, Rodrigo. "Desenvolvimento de um equipamento triaxial de grande porte para avaliação de agregados utilizados como camada de pavimentos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/19046.
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Camadas granulares desempenham um importante papel no comportamento global de pavimentos, especialmente daqueles com revestimentos delgados ou sem revestimento. Para conhecer as características de resistência e deformabilidade de materiais componentes dessas camadas são realizados ensaios triaxiais. No caso de ensaios em materiais granulares, o corpo de prova deve ter diâmetro de pelo menos cinco vezes o tamanho máximo de partícula e altura igual a duas vezes o seu diâmetro. Como as especificações do DNIT permitem o emprego de agregados de até 5 cm em camadas de brita graduada ou solo-agregado, os corpos-de-prova devem ter diâmetro de 25 cm e altura de 50 cm. Equipamentos capazes de ensaiar corpos-deprova com estas dimensões são raros no mundo e inexistiam no Brasil até 2008. Com o intuito de superar esta carência e avançar no conhecimento do comportamento mecânico de agregados graúdos, a pesquisa relatada nesta tese teve como objetivos desenvolver um equipamento triaxial de grande porte capaz de aplicar carregamentos estáticos, monotônicos e cíclicos em corpos-de-prova de grandes dimensões (25 cm x 50 cm); bem como realizar e interpretar os primeiros ensaios. A concepção e a montagem do equipamento são descritas considerando as partes principais. Também é detalhada a instrumentação utilizada composta por: duas células de carga, três transdutores de deslocamento e dois transmissores de pressão. Para os primeiros ensaios foi escolhida uma brita graduada de basalto, anteriormente utilizada em pistas experimentais solicitadas por simulador de tráfego. Ensaios em corpos-de-prova de 10 cm de diâmetro e 20 cm de altura foram realizados para comparação com resultados de ensaios em corpos-de-prova maiores, realizados no novo equipamento. Os ensaios de módulo de resiliência foram conduzidos segundo o método de ensaio do DNIT, com algumas modificações para adequá-lo ao padrão internacional. Os ensaios triaxiais monotônicos e os cíclicos de deformações permanentes foram conduzidos tanto em multiestágios, quanto em estágio único de tensões. Os resultados obtidos foram interpretados segundo diversas teorias e modelos, obtendo-se parâmetros de resistência e de deformabilidade. Uma análise mecanística utilizando os parâmetros obtidos nos ensaios permitiu analisar o comportamento do material estudado como camada de pavimento. Conclui-se que o equipamento triaxial de grande porte atende as necessidades para as quais foi projetado, permitindo obter parâmetros para caracterização do comportamento de agregados graúdos e prever desempenho de pavimentos, quanto a deformações permanentes e ruptura por cisalhamento de camadas granulares.Unbound aggregates layers play an important role in the performance of thinly surfaced or unsurfaced pavements. In order to assess the strength-strain characteristics of soils and aggregates used in those layers, triaxial tests must be carried out on cylindrical specimens with diameter not smaller than 5 times the particle maximum size and height twice the diameter. Since Brazil National Roads Department allows using 2” aggregates in granular bases, specimens for triaxial tests should be at least 25 cm in diameter and 50 cm in height. All over the world there are only a few equipments for testing such specimens; and up to 2008 none of them in Brazil. Aiming at overcoming this deficiency and enhance the knowledge on the mechanical behavior of coarse aggregates, the objectives of research reported in this thesis were to develop a triaxial equipment capable of applying static, monotonic and repeated loadings on large specimens (25 cm x 50 cm) and perform and analyze the first tests. The design and assemblage of the equipment are describe, detailing its main components and the instrumentation, that included two load cells, three displacement transducers and two pressure transmitters. The first tests were carried out on specimens made of dense crushed aggregates, formerly used in APT test sections. Tests were also carried out on specimens with 10.0 cm diameter and 20.0 cm height, in order to compare their results to those of tests carried out in larger specimens tested in the new triaxial equipment. Resilient modulus tests were carried out according to the Brazilian standard, but some modifications were introduced to follow international patterns. Triaxial monotonic and repeated loading permanent deformation tests were carried out both in multiple stages and unique stage of stresses. The results were interpreted were calculated taking into account several theories and models, strength and strain parameters being obtained. A mechanistic analysis using parameters obtained in tests allowed analyzing the behavior of the studied aggregates making part of pavement layers. It is concluded the new triaxial equipment for large specimens fulfills the requirements that motivated its design and construction, making possible to obtain parameters for characterizing the behavior of coarse aggregates and estimating pavements performance regarding permanent deformation and shear failure of granular layers.
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Su, Yuhan. "Does Larinoides cornutus major ampullate silk have shape memory property?" University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1619530976411585.
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FOTI, Sebastiano. "Multistation Methods for Geotechnical Characterization using Surface Waves." Doctoral thesis, Politecnico di Torino, 2000. http://hdl.handle.net/11583/2497212.
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This dissertation deals with soil characterization methods based on surface wave propagation applied to geotechnical engineering purposes. This topic has gained much interest in the last decade because of the appealing possibilities given by non-invasive methods, which are at once very flexible and cost effective.
An overview of the properties of Rayleigh waves in layered linear elastic and linear viscoelastic media is presented, together with their applications for site characterization, of whose the SASW (Spectral Analysis of Surface Waves) method is by far the most well-known in geotechnical engineering.
The research has been mainly focused on the application of multistation methods, compared with the classical two-station approach typical of the SASW method.
Results from both numerical simulations and experimental testing are reported to compare two-station and multistation methods and to clarify the advantages that can be obtained using the latter ones.
In particular the research has been developed following two different directions: on the one hand the application of classical geophysical analysis tools (such as domain analysis and slant stack transform) to tests performed with impulsive sources. On the other one the possibility of obtaining from surface wave testing not only a stiffness profile, but also a damping ratio profile for the site. In this respect a new method for simultaneous measurements of Rayleigh dispersion and attenuation curves is proposed.
Regarding the first topic, the necessity of a multistation approach to determine the experimental dispersion test is essentially related to the spatial variation of phase velocity. Analyses in the frequency-wavenumber domain and in the frequency-slowness domain are very powerful approaches, still there was a need of studying the effects of the change of scale from geophysical applications to geotechnical ones. Indeed because of the peculiar properties of Rayleigh waves, surface testing is strongly affected by the distance travelled by the analysed wave. The numerical simulations performed in the research show that the phase velocity obtained using multistation methods with a limited number of receivers close to the source is not a modal value as it is for geophysical applications, but an apparent phase velocity arising from modal superposition.
The experimental tests showed the good performances of multistation methods when compared to the SASW method. In particular some drawbacks of the latter method, due essentially to its two-station nature, are avoided and the field-testing appears to be very promising for future applications. In particular the application of the frequency-wavenumber domain analysis can lead to much faster and more stable estimates of the experimental dispersion curve and the process is easily automated, with a great saving of time and less requirement for subjective decisions. Another important advantage is given by the stability with respect to a near field effects that lead to a better reconstruction of the dispersion curve for the low frequencies and hence to a deeper characterization.
The necessity of a new method for the simultaneous determination of surface wave dispersion and attenuation curves is linked to the strong coupling existing between the two. Such coupling is extremely important for the subsequent inversion process, in a consistent method leading from the field measurements to the stiffness and damping profiles.
The proposed method uses a new testing configuration, designed to measure the experimental transfer function. Successively a regression process of the complex quantity with the corresponding expression obtained modelling soil as a linear viscoelastic layered system leads to the experimental dispersion and attenuation curves.
Some preliminary results are reported showing very encouraging results, also if a more extensively testing programme is required for the complete validation of the method.
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Abdul-Salam, Bahira. "Behaviour of shear critical frp reinforced concrete one-way slabs." Thèse, Université de Sherbrooke, 2014. http://savoirs.usherbrooke.ca/handle/11143/5352.
Full textAbstract:
Résumé : Les dalles de tabliers de ponts et des stationnements sont exposées à des environnements agressifs en particulier au Québec et en Amérique du Nord en raison de l'utilisation de sels de déglaçage et des cycles de gel-dégel. La substitution des armatures d’acier par des armatures en matériaux composites de polymères renforcés de fibres (PRF) constitue une alternative intéressante qui connait beaucoup de succès ces dernières années. Le béton armé de PRF est durable, car l’armature n’est pas sujette à la corrosion électrochimique. Aussi l’armature de PRF possède une résistance en traction élevée et est légère.
En Amérique du Nord, l’utilisation des composites de PRF a suscité une attention toute particulière de la part des ingénieurs et des gestionnaires d’ouvrages. Plusieurs organismes dont des ministères de transport spécifient l’armature de PRF comme matériau structural dans leurs devis techniques pour lutter contre la corrosion et allonger la durée de service de leurs infrastructures.
Les dalles en béton armé sont souvent soumises à des efforts de cisaillement critiques. Actuellement les méthodes de calcul au cisaillement (à l’effort tranchant) de dalles unidirectionnelles en béton armé de PRF différèrent d’une norme à une autre. En effet, la majorité des équations proposées dans les normes et guides de conception ont dérivées à partir de relations empiriques.
Bien que des efforts de recherche considérables aient été consacrés dans ce domaine au cours de la dernière décennie, une meilleure compréhension du comportement au cisaillement et des mécanismes de rupture de dalles unidirectionnelles en béton armé de PRF est encore nécessaire. Dans cette recherche, un programme expérimental visant à étudier le comportement de dalles renforcées avec différents types de barres en PRF a été mis en place.
Vingt-deux dalles unidirectionnelles en béton renforcées avec des barres de PRF ont été construites et testées en flexion a quatre points jusqu’à la rupture. Les paramètres d’étude comprennent : le type et le taux d’armature, le diamètre de la barre, l’espacement et la configuration de l’armature ainsi que la résistance en compression du béton afin d’examiner leur effet sur la résistance au cisaillement des dalles.
Le comportement des dalles testées a été examiné en considérant le réseau de fissures, la charge ultime ainsi que les modes de rupture. Aussi, une base de données comprenant 203 poutres et dalles unidirectionnelles en béton armé de PRF rompues en cisaillement a été répertoriée et introduite dans les analyses.
Les charges de rupture en cisaillement des dalles testées dans le cadre de cette thèse ainsi que celles de la base de données ont été comparées à celles prédites par les équations de calcul proposées par la normes canadiennes CSA S6-06/S1 et CSA S806-12, ainsi que celles des deux guides de calcul ACI 440.1R-06 et JSCE-97. Les analyses effectuées ont montré que les valeurs prédites par les équations de calcul proposées par l’ACI 440.1R-06 sont très conservatrices, alors que celles prédites par celles de JSCE-97 sont en meilleur accord avec les valeurs expérimentales. Aussi, les résultats obtenus ont montré que les équations de la nouvelle norme CSA S806-12 prédisent bien la résistance au cisaillement expérimentale. Toutefois, une amélioration de l'équation de la norme CSAS806-12, conduisant à de meilleurs résultats, est proposée.
Par ailleurs, les résultats obtenus dans le cadre de cette thèse ont mené à une meilleure compréhension des mécanismes de rupture et des facteurs principaux qui contribuent à la résistance au cisaillement de dalles unidirectionnelles en béton armée de PRF. Enfin, des recommandations pour des travaux futurs y sont également formulées. // Abstract : Bridge deck and parking garage slabs are exposed to aggressive environments
particularly in the North American regions resulting from the excessive use of de-icing
salts. Fiber-reinforced-polymer (FRP) reinforcements have emerged as a practical and
sustainable anti-corrosive reinforcing material with superior tensile strength to overcome
the corrosion problem. High comfort level and increase use of the material is currently
seen. Protection and regulations policies of some Public North American agencies
currently include GFRP reinforcing bars as premium reinforcement. Shear behaviour in
RC slabs is examined since most of the bridge deck and parking garage slabs are shear critical.
However, there is still no agreement in FRP design codes and guidelines for
shear strength equations. Several design code equations are still based on empirical
relationships while recent developments are based on shear theories. The complex nature of shear phenomena which is influenced by many parameters, in addition to the existence of various schools of thoughts in shear, makes it difficult to find a general agreement on a unified equation. Huge research efforts are being established, however better understanding for the shear behaviour and failure mechanisms for unidirectional FRP RC slabs is still needed. In this research study, an experimental program was designed to investigate the shear behaviour of one-way concrete slabs reinforced with different types of FRP bars. A total of twenty one concrete slabs reinforced with FRP bars in addition to a steel reinforced slab were constructed and tested to failure under two-point loading. The variation in the concrete contribution to the shear strength V[subscript c] is investigated with respect to FRP reinforcement properties. Newly developed GFRP bars with high modulus, which were not previously investigated in the literature, are used. Different FRP reinforcement properties were included in the study such as reinforcement ratio, modulus of elasticity and axial stiffness, type of bars, and reinforcement configuration. Also, normal concrete and high strength concrete were considered in the research program. Analysis of the experimental results included the general behavior of the tested slabs, crack patterns, ultimate capacities, and modes of failure, load deflection relationships as well as the concrete and reinforcement strains.
Test results of the present investigation indicate an influence of the reinforcement type,
bar diameter, and the shear stiffness of the bars on the mode of failure and the shear
strength. The experimental investigation and analysis of test results provided better understanding of concerning mechanisms of failure and factors contributing to the shear capacity of FRP RC slabs. A refined shear model to the CSA S806-12 is introduced and found to provide better results compared to the existing design codes and guidelines. The model is based on regression analysis of an experimental database. The database is assembled from twenty five different studies in addition to the present investigation. The used database includes 203 unidirectional members reinforced with FRP bars (without shear reinforcement) failing in shear.
The model was evaluated through the experimental concrete shear capacities (V[subscript c exp]) of the database and found to provide good predictions. The experimental shear capacities of the database ( V[subscript c exp]) was compared to their corresponding predicted shear capacities (Vcpred ) using CSA S806-12, CAN/CSA-S6.1S1, ACI 440.1R-06, and JSCE-97. It was found that the ACI guide is very conservative. It can be noted that using this guide in its present form may reduce the economic competitiveness of fibre-reinforced polymers. JSCE recommendations are in better agreement with the test results. The Canadian CSA S806-12 equation was found to be in good fit with the experimental shear capacities.
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Smallwood, Cameron David. "Frequency Response and Recovery of Muscles and Effects of Wrapping the Lower Leg on Surface Velocity Measurements." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7503.
Full textAbstract:
This thesis is comprised of two studies. The objective of the first study was to find the frequency response and stiffness of the biceps brachii muscle group during recovery from exercise induced damage and to determine whether these data could be used to track muscle recovery by correlating changes in the frequency response with changes in muscle stiffness. Stiffness moduli were collected using Shear Wave Elastography (SWE) which were then applied to a proportional first mode frequency analysis. Data were collected for the muscle stiffness and frequency response for fifteen subjects (25.6 +- 4.5). By comparing the proportion of the square root of the SWE results, the variation in stiffness showed a less than 2 Hz change in first mode resonance for the control group. Frequency response results for the control group agreed with the modified SWE results and the proportion analysis. SWE results for the damage protocol group showed an average increase of 4 Hz. Frequency response results for the damage protocol group were sorted into three categories: three subjects had a change in frequency of peaks of at least 4 Hz in the positive direction; four subjects had an increase in amplitude, but no change in frequency of peaks; three subjects showed mixed responses like fewer resonance peaks, variable amplitudes, changes in peak bandwidth. This research allowed for the documentation of the in-vivo frequency response of the biceps brachii muscle. We believe that the frequency response of a muscle group may be used in the future to evaluate recovery from exercise induced damage. Lessons learned were also recorded for helping future studies in their efforts using an SLDV with human body testing.The second study focused on finding the effects on the surface velocity of tissue above and below a region of the lower leg wrapped in an elastic band when excited by an external source. Ten male subjects between the ages of 18-25 were seated in a chair with one foot placed on a vibrating platform. Two excitation frequencies were separately applied while three points along the leg were measured. A repeatability analysis, using results without the leg wrap, showed a 6.5%, 2.5%, and 10.5% variance in the x-, y-, and z-directions respectively, applying a 20 Hz frequency. With a 40 Hz frequency, the variations were 24%, 23.8%, and 28.4% respectively. A change in displacement of +38% and +10% occurred above the knee in the x-direction with 40 Hz and in the y-direction with 20 Hz, respectively. A change in displacement of -20% occurred below the knee in the x-direction with 20 Hz. A change in displacement of -24% occurred below the wrap location in the y-direction with 40Hz. With a confidence interval of 93%, surface velocity of the tissue located above the wrap increased, while the surface velocity of the tissue below the wrap decreased.
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Simanavičiūtė, Daiva. "Polistireninio putplasčio deformacijų ir šliejamojo stiprio tyrimai." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2008. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2008~D_20080930_090345-50422.
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Šiame baigiamajame magistro darbe nagrinėjama polistireninio putplasčio stiprumo savybės. Teorinėje dalyje pateikta literatūros analizė, bendros žinios apie polistireninį putplastį, gamybos būdai, panaudojimo galimybės. Išnagrinėta trijų didžiausių gamintojų Lietuvoje siūloma produkcija. Apžvelgti reikalavimai pastatų atitvarų šiluminei varžai, išnagrinėta termoizoliacinio sluoksnio storio pokytis nuo TSRS laikų iki dabar. Eksperimentinėje dalyje aprašomos naudotos medžiagos; jų charakteristikos; gniuždomasis stipris; šliejamasis stipris; išnagrinėta skirtingo tankio bandinių mikrostruktūra ir makrostruktūra. Aprašomi rezultatai, naudojant statistinės analizės programą atliekama jų analizė, suformuluojamos išvados.The present work of Master degree studies analyzes the properties of expanded polystyrene.Theoretical par of this work introduces analysis of references, general information on expanded polystyrene, manner of production and fields of application. The work analyzes production offered by three biggest manufacturers in Lithuania, reviews the requirements applicable to thermal resistance of enclosures of the building, analyses alteration of thickness of a heat insulation layer comparing the situation in Soviet Union time and nowadays. Experimental part describes the used material, their properties, compressive strength, shear strength; analyses microstructure and macrostructure of samples of different density. The work presents the results and analysis of the results by applying software of statistical analysis; formulation of conclusions.
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You, Therese. "Negative energy elasticity and a model for the behavior of the residual strain in doubly cross-linked gels fabricated by shear strain." Thesis, Uppsala universitet, Polymerkemi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-420125.
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Doubly cross-linked gels were fabricated based on tetra-poly(ethylene glycol) (Tetra-PEG) by shear strain. These are gels with two network structures present in the same polymeric network. The second network structure is introduced by applying a mechanical field to the first natural network structure. These doubly cross-linked gels indicated a negative energy elasticity supporting earlier findings where the energy elasticity was found significantly negative for Tetra-PEG gel. Acquired results indicate implications for past research on the elasticity of polymer gels where the energy contribution was approximated to zero. Obtained results also indicated that the modulus of rigidity for the doubly cross-linked gels is constant regardless of applied shear strain during fabrication. This would indicate that the same second network structure is formed for the interval of 25-800% applied shear strain. The residual strain for the fabricated gels can be well-described using an exponential fitting of the apparent shear modulus of the first network structure and an expression derived from the two-network theory and classic rubber theory. These theories also seem to predict the experimental residual strains for lower strain regions (<100%) quite well. However for larger strain regions (>100%) non-linear effects seem to affect the results causing a deviation. A slight increased modulus of rigidity was noted for the doubly cross-linked gels compared to the regular Tetra-PEG gel. However as the reproducibility of the concluded measurements could not be confirmed during this thesis the results are not conclusive and only indicate the conclusions mentioned above.
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Dostál, Filip. "Vliv druhu a dávky polymeru na vlastnosti modifikovaných pojiv." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409806.
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The diploma thesis is focused on polymer modified binders with different polymer doses. The theoretical part describes the history of the use of bitumen, the extraction of bitumen from oil and behavious of the polymer type SBS/SB, which is used in the diploma thesis on modified binders. Further, the theoretical part describes the empirical and functional tests of bitumen binders. In the practical part the results of indidual tests are presented and compared with the standard ČSN 65 7222-1. At the end of the diploma thesis are summarized results of work and evaluation of binders with the best achieved properties.
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Naji, Behnam. "Flexural Analysis and Composite Behavior of Precast Concrete Sandwich Panel." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1355331734.
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Papazoglou, Sebastian. "Elucidation of isotropic and anisotropic shear elasticity of in vivo soft tissue using planar magnetic resonance elastography." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16136.
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Die Magnetresonanzelastographie (MRE) stellt ein nichtinvasives Verfahren dar, welches die Bestimmung der in vivo Scherelastizität weicher Gewebe ermöglicht. Im Rahmen diese Arbeit wurden Methoden zur Bestimmung isotroper und anisotroper Scherelastizitäten anhand von MRE Wellenbildern entwickelt und evaluiert. Alle in dieser Arbeit vorgestellten Methoden basieren auf planarer MRE, d.h. auf der Aufnahme einer einzelnen Auslenkungskomponente innerhalb der Bildschicht. Dadurch wird die MRE erheblich beschleunigt. Allerdings stellen sich dadurch auch besondere Anforderungen an die Datenauswertung zur Bestimmung aussagekräftiger elastischer Kenngrößen. Anhand von planaren MRE-Experimenten an Gewebephantomen und menschlicher Skelettmuskulatur sowie mittels numerischer Simulation wird gezeigt, dass bei Beachtung weniger experimenteller Randbedingungen und einer darauf abgestimmten Datenauswertung, korrekte Elastizitäten ermittelt werden können. Ein besonderer Schwerpunkt der Arbeit liegt in der Analyse experimenteller Einflüsse wie Bildrauschen und -auflösung auf die ermittelten elastischen Kenngrößen. Des Weiteren werden Methoden zur Bestimmung anisotroper Elastizitäten sowie zur Analyse von Streueffekten im MRE-Wellenbild vorgestellt. Die behandelten Einflüsse auf die Amplituden und Wellenlängen im MRE-Bild, werden vergleichend diskutiert und zusammengefasst, um ein einfaches Verfahrensprotokoll zur Analyse experimenteller in vivo MRE-Daten zu entwickeln. Alle in dieser Arbeit verwendeten Methoden und Programme sind im Anhang zusammengefasst und auf Anforderung erhältlich.Magnetic resonance elastography (MRE) is a noninvasive method that allows the determination of in vivo shear elasticity of soft tissues. In this thesis methods for the determination of isotropic and anisotropic shear elasticities from MRE wave data were developed and evaluated. All methods presented in this work are based on planar MRE, i.e. they are based on the measurement of a single displacement component in the image plane. This way measurement time in MRE is greatly reduced. However, this imposes specific requirements on data evaluation in order to determine significant elastic constants. On the basis of planar MRE experiments on tissue mimicking gels, human skeletal muscle and numerical simulations it is demonstrated that correct shear elasticities can be determined, taking into account a small set of experimental boundary conditions as well as the employment of complementary data evaluation strategies. This thesis is particularly focussed on the analysis of noise and image resolution on the determined elastic constants. Moreover, methods for determining anisotropic elasticity and analyzing shear wave scattering effects on MRE wave data are introduced. The investigated influences on wave amplitudes and wave lengths are compared and discussed to develop a simple measurement protocol for the evaluation of in vivo MRE data. All methods employed in this work are summarized in the appendix along with the corresponding computer code, which is available on demand.
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Knighton, Jaren Tolman. "Investigation of Laboratory Test Procedures for Assessing the Structural Capacity of Geogrid-Reinforced Aggregate Base Materials." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/4443.
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The modulus of aggregate base layers in pavement structures can potentially be increased through the use of geogrid. However, methods for determining how much structural benefit can be expected from a given geogrid product have not been standardized. A laboratory testing protocol is therefore needed to enable evaluation, in terms of modulus or California bearing ratio (CBR), for example, of the degree of improvement that may be achieved by a given geogrid. Consequently, the objective of this research was to identify a laboratory test method that can be used to quantify improvements in structural capacity of aggregate base materials reinforced with geogrid. For this research, National Cooperative Highway Research Program Report 598 repeated load triaxial, American Association of State Highway and Transportation Officials (AASHTO) T 307 quick shear, and CBR testing protocols were used to test unreinforced and geogrid-reinforced aggregate base materials from northern Utah. Biaxial and triaxial geogrid were investigated in multiple reinforcement configurations. Several statistical analyses were performed on the results of each test method to identify the test that is most likely to consistently show an improvement in the structural capacity of aggregate base materials reinforced with geogrid. The results of this research indicate that, for the methods and materials evaluated in this study, calculation of the modulus at 2 percent strain from the AASHTO T 307 quick shear data is the test method most likely to consistently show an improvement in structural capacity associated with geogrid reinforcement. Of the three configurations investigated as part of this research, placing the geogrid at an upper position within a specimen is preferred. Given that the end goal of the use of geogrid reinforcement is to improve pavement performance, additional research is needed to compare the results of the AASHTO T 307 quick shear test obtained in the laboratory with the structural capacity of geogrid-reinforced aggregate base materials measured in the field. In addition, correlations between the results of the AASHTO T 307 quick shear test and resilient modulus need to be investigated in order to incorporate the findings of the AASHTO T 307 quick shear test on reinforced base materials into mechanistic-empirical pavement design.
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Chamming's, Foucauld. "Elastographie quantitative des tumeurs du sein et de la réponse au traitement." Thesis, Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCB152/document.
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Introduction : L’élastographie shear wave (ESW) est une technique récente d’échographie qui évalue quantitativement la dureté des tissus et permet d’améliorer la caractérisation des lésions mammaires. Comme toute nouvelle technique d’imagerie, l’ESW nécessite une validation préclinique pour définir les conditions d’utilisations et établir les limites des champs d’applications dans lesquelles la technique pourra être considérée comme valide. Matériels et méthodes : Dans une première partie effectuée au laboratoire de recherche en Imagerie nous avons étudié les éléments histologiques sous tendant l’image d’ESW sur un modèle de cancer du sein implanté chez la souris, au cours de sa croissance puis sous traitement. Dans une deuxième partie, nous avons étudié chez des patientes le rôle de la compression manuelle en ESW pour la caractérisation des lésions mammaires. Dans une dernière partie, effectuée en collaboration avec une équipe de l’Institut Langevin Ondes et Images, nous avons étudié la faisabilité d’un nouveau paramètre, le module de cisaillement non linéaire pour l’analyse des lésions mammaires. Résultats : Au laboratoire, nous avons établi des corrélations entre la dureté mesurée en élastographie et les caractéristiques histologiques des tumeurs, y compris sous traitement. Nous avons montré que la fibrose était associée à une dureté élevée et la nécrose à une dureté moindre. Notre étude clinique a montré qu’une compression manuelle minimale était nécessaire pour obtenir de bonnes performances de l’ESW et qu’une pression trop élevée devait être évitée. Enfin nous avons montré la faisabilité en imagerie mammaire d’un nouveau paramètre quantitatif obtenu en élastographie shear wave : le module de cisaillement non linéaire. Conclusion : A partir de travail de thèse, une meilleure compréhension de la part des éléments biologiques et techniques en ESW du sein est possible et des recommandations pour l’utilisation clinique peuvent être formulées. Nos observations cliniques ont entrainé la mise au point d’un nouveau paramètre diagnostique quantitatif : le module de cisaillement non linéaireIntroduction: Shear Wave Elastography (SWE) is a recent ultrasound technique assessing quantitatively tissue stiffness and improving breast lesions characterization. As every new imaging technique, SWE requires a pre clinical validation in order to define in which conditions it should be used and precise the applications for which the technique is validated. Materials and methods: First, in a research lab we have investigated the pathological features underlying SWE image in a breast cancer model implanted in mice, during tumor growth and under therapy. Secondly, we have studied in patients the role of manual compression in SWE for the characterization of breast lesions. Finally, in collaboration with on team from Institut Langevin Ondes et Images, we have studied the feasibility of a new parameter, the non-linear modulus, for breast lesion assessment. Results: in the research lab, we have shown correlations between stiffness as measured with SWE and pathological features of tumors, even on treatment. We have shown that fibrosis was associated with high stiffness values and necrosis with lowers. Our clinical study, showed that a minimal manual compression was required for optimal performance of SWE and that strong compression should be avoided. Finally, we demonstrated feasibility of a new parameter, derived from SWE, the non-linear modulus. Conclusion: Our work provides a better understanding of biological and technical elements of SWE. On the basis of our results, new recommendations may be made for the use of SWE in clinical practice. From our clinical findings, we developed a new quantitative parameter, which may be useful for the diagnosis of breast lesions, the non-linear modulus
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Svída, David. "Snižování vibrací a akustických emisí pohonných jednotek aplikací virtuálního motoru." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-233980.
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Doctoral thesis deals with combustion engine cranktrain vibrations and vibration analysis methods. The work applies new computational models aimed at powertrain vibration decrease. The computational models can be used in the first stages of powertrain development. Temperature dependences of the rubber shear modulus and loss factor characteristic are found by response analysis of the free damped vibrations in the first part of the thesis. Viscoelastic model parameters of two dampers with different rubber hardness are calculated using optimization methods. Temperature distribution inside the rubber part during the harmonic oscillation is calculated with the knowledge of previous values. Computational models together with a user interface are assembled in Matlab/Simulink software tool. Computational model results of the viscoelastic rubber damper are verified by measurements on a prototype diesel engine in the whole operating engine speed range. Torsional vibrations of the crankshaft with torsional damper are measured by POLYTEC laser rotational tools. The temperature distribution on the damper surface is obtained by Infratec VarioCAM thermographic system. Combustion pressures in the cylinder are measured by SMETEC Combi indication tools. Both the temperature distributions and combustion pressures are used for computational purposes. All the measurement procedures are described also in the thesis.
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Kaya, Mustafa. "A Study On The Stress-strain Behavior Of Railroad Ballast Materials By Use Of Parallel Gradation Technique." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12605026/index.pdf.
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The shear strength, elastic moduli and plastic strain characteristics of scaled-down ballast materials are investigated by use of the parallel gradation technique. Uniformly graded ballast materials chosen for the investigation are limestone, basalt and steel-slag. Steel-slag is a byproduct material of Eregli Iron and Steel Works, which is suitable to meet the durability test requirements as well as the electrical resistivity and the waste contaminants regulatory level. Conventional triaxial testing at a strain rate of 0.4 mm/min is used to obtain these characteristics for the scaled-down materials with a diameter of 100 mm specimen under a confining stress of 35 kPa, 70 kPa and 105 kPawhereas that of only 35 kPa is used to characterize the accumulated plastic strain. The angle of internal friction, f, and the apparent cohesion, c, may be conservatively taken to be 42o and 35 kPa for all materials. The elastic moduli values for all materials may be predicted within an adequate estimate for the engineering purposes by using the power law parameters, K and n, determined for L-9.5 (D50 = 12.7 mm), the coarsest gradation tested for limestone. K with a reference pressure, pr = 1 kPa and n values for L-9.5, respectively, are 4365 and 0.636 for initial
8511 and 0.419 for secant
25704 and 0.430 for unloading-reloading elastic moduli. The unloading-reloading moduli increased, as the number of cycles increased. An increase in unloading-reloading modulus at N = 20 obtained was roughly 15% for scaled-down limestone
10% for the basalt
and 5% for the steel-slag. The plastic strain after first cycle, &
#949
1, and the plastic strain coefficient, C can be represented as a function of mean particle size for each material type. For the limestone, basalt and steel-slag prototype size, D50 = 45 mm, &
#949
1 values of 0.59, 0.43 and 0.75 and C values of 0.54, 1.42 and 0.74 are predicted, respectively.
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Muhmood, Luckman. "Investigations of thermophysical properties of slags with focus on slag-metal interface." Doctoral thesis, KTH, Materialens processvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-26611.
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The objective of this research work was to develop a methodology for experimentally estimating the interfacial properties at slag-metal interfaces. From previous experiments carried out in the division, it was decided to use surface active elements like sulfur or oxygen to trace any motion at the interface. For this purpose the following experimental investigations were carried out. Firstly the density of slag was estimated using the Archimedes Principle and the Sessile Drop technique. The density of the slag would give the molten slag height required for the surface active element to travel before reaching the slag-metal interface. Diffusivity measurements were uniquely designed in order to estimate the sulfur diffusion through slag media. It was for the first time that the chemical diffusivity was estimated from the concentration in the metal phase. Experiments carried out validated the models developed earlier. The density and diffusivity value of sulfur in the slag was used to accurately capture the time for sulfur to reach the slag-metal interface. The oscillations were identified by calculating the contact angle variations and the interfacial velocity was estimated from the change in the surface area of the liquid iron drop. The interfacial tension was estimated from the contact angles and the interfacial dilatational modulus was calculated. Based on cold model experiments using water as well as mercury, an equation of the dependence of the interfacial shear viscosity on the interfacial velocity and interfacial tension was established. This paved way for the estimation of the interfacial shear viscosity at the slag-metal interface. The present study is expected to have a strong impact on refining reactions in pyometallurgical industries where slag/metal interfaces play an important role. From a fundamental view point, this provides a deeper insight into interfacial phenomena and presents an experimental technique to quantify the same.QC 20101130
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Anderson, Fredrik. "Rheological changes at the air-liquid interface and examining different kind of magnetic needles." Thesis, Karlstads universitet, Avdelningen för kemiteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-36540.
Full textAbstract:
The main objective in this work was to learn how the instrument, the Interfacial Shear Rheometer (ISR400), worked and to investigate how the rheological properties, storage modulus (elasticity), G' and loss modulus (viscous), G'', changes when the surface pressure at the air-liquid interphase changes. The second objective were to examine the different kind of magnetic needles used in the experiments and to conclude which type of needle is best for its specific field of analysis. It was concluded that the relative heavy needle with mass 70.6 mg and length 50 mm was best for systems where the viscous and elastic components are significantly large, where the inertia of the needle is not dominant. It also worked of using the heavier needle for a system of phospholipids. For the hydroxystearic acid (HSA) experiment that were tested on NaCl sub-phase there was a clear improvement after switching from the heavy needle (mass 41.5 mg; length 51 mm) to the relative lighter needle (mass 6.94 mg; length 34.7 mm). The values for the dynamic modulus therefore had a better agreement with reference literature. A spread layer of class II hydrophobins (HFBII) could be compressed to a surface pressure of 46 mNm-1. The G' and G'' values from the frequency sweep were discarded because the monolayer turned into a very viscous-like liquid, and the oscillating needle, after compression, was kind of stuck in the sub-phase and moved very staggering during a frequency sweep. The needle comparison experiment with silica particles 10 wt% Bindzil CC30 (BCC30), at pH 3.5 was done to see if there was any difference in the sensitivity for the needles at the interface which consisted of a pure 10 mM NaCl solution or a 10 mM NaCl solution with BCC30 added to it. The differences were negligible in terms of surface tension but there was a clear difference between the heavy needle and the light needle, when oscillating at higher frequencies (>≈6 rad/s). With this study, the understanding of ISR400 has increased largely. Several issues have been addressed and the results provide a good basis for further studies within the many areas the instrument can be used for. Despite the project's time limit, and the fact that the instrument was new and untested where the project was carried out, focus areas were prioritized so good results could be achieved within reasonable goals.Huvudmålet med detta arbete var att lära sig hur instrumentet ytskiktsreometern (ISR400) fungerade och undersöka hur de reologiska egenskaperna, elasticitetsmodulen G' och viskositetsmodulen G'', kommer att förändras när det sker en förändring för yttrycket vid gränsskiktet mellan luft och vätska. Det sekundära målet var att undersöka vilken typ av magnetiska nålar som är bäst att använda för respektive gränsskiktssystem. Av att använda den tyngre nålen med massan 70.6 mg och längden 50 mm kunde man dra slutsatsen att den är bäst att använda för system där de viskösa och elastiska komponenterna är signifikant stora, där nålens tröghet inte är dominant. Den fungerade även att mäta med i ett fosfolipidsystem. I experimentet med 12-hydroxy-stearinsyra (HSA) som utfördes på en subfas av NaCl, syntes en klar förbättring efter att byta från en tyngre nål (massa 41.5 mg; längd 51 mm) till en lättare (massa 6.94 mg; längd 34.7 mm). Värdena för dynamiska modulen stämde därför bättre överens med referenslitteraturen. Det utspridda lagret av klass II hydrophobins (HFBII) kunde komprimeras upp till yttrycket 46 mNm-1. Värdena för G' och G'' förkastades därför att monolagret förvandlades till en väldigt viskösliknande vätska, och den oscillerande nålen, efter kompressionen, satt fast i denna tröga vätska och rörde sig väldigt hackigt och oregelbundet under tiden ett frekvenssvep utfördes. Då en jämförelse av olika typer av nålar genomfördes med kiseldioxidpartiklar (10 % (viktsprocent) Bindzil CC30 med pH 3.5), för att se om det är någon skillnad i känslighet för nålarna vid gränssnittet, som bestod av en ren 10 mM NaCl-lösning eller en 10 mM NaCl-lösning med tillsatt BCC30. Skillnaderna var försumbara gällande ytspänningen, men det var en klar skillnad mellan den tunga nålen och den lätta nålen vid oscillering vid höga frekvenser (>≈6 rad/s). I och med detta arbete så har förståelsen för hur ISR400 fungerar förbättrats mycket sedan starten. Flera frågeställningar har behandlats och resultaten ger en bra grund för fortsatta studier inom de många områden som utrustningen kan användas till. Trots projektets tidsbegränsning, och det faktum att instrumentet var nytt och oprövat på platsen där detta arbete utfördes, så prioriterades fokusområden så att goda resultat kunde uppnås inom rimliga mål.