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Meca, Juan Balderas. "Rate effects of rapid loading in clay soils." Thesis, University of Sheffield, 2005. http://etheses.whiterose.ac.uk/15053/.
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The study of the relationship between the shear strength of the clay and the rate at which it is loaded is relevant to the application of a new rapid load pile testing technique called Statnamic. There are problems associated with interpreting the test results in clay soils due to the non linear variation in shear resistance with rate of shearing. An investigation has been conducted for two clay soils which were used in an associated research project. These were a reconstituted kaolin clay (KSS) used for model pile tests and undisturbed glacial clay taken from a full scale prototype pile testing site near Grimsby. Monotonic and multistage strain controlled triaxial tests were carried out on both clays using a, pneumatic computer, controlled rapid load triaxial system at rates from 0.001 mm/s to 200 mm/s. The shear strength increased and the excess pore pressure decreased as the rate of shearing increased. A power law was proposed relating dynamic and static shear strength. The damping coefficients and hence the rate effects, defined as a function of strain, were similar for both clays Based on the triaxial test results and a back analysis of Statnamic and "static" constant rate of penetration data from the associated model and full scale pile tests in both clays, a non-linear model has been proposed relating the static resistance of a pile to the measured Statnamic load taking into account the rate effects and the inertia of the pile. The non-linear model was used to develop a new multistage interpretation method for the analysis of Statnamic tests in clays.
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Garner, Michael Paul. "Loading Rate Effects on Axial Pile Capacity in Clays." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2016.pdf.
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Aguilar-Espinosa, Aaron Alejandro. "Effect of variable amplitude loading on fatigue crack growth rate." Thesis, Oxford Brookes University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496022.
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Fatigue crack growth (FCG) is a major cause of failure in many engineering components and structures that are subjected to dynamic loading conditions. Several models have been proposed for estimating crack growth rate da/dN under various conditions. The majority of work reported has focused on constant amplitude (CA) loading and some for variable amplitude (VA) loading. The estimation of da/dN under VA loading is complex due to effects of several factors such as plasticity, crack tip blunting, residual stresses, crack tip closure and crack tip branching which are associated with different levels of loading. These factors which cause acceleration or deceleration of the crack growth are known as interaction effects. Crack closure has been identified to be one of the main interaction factors, and finite element (FE) models have been developed to quantify it in terms of crack opening stresses. There are however still a number of issues regarding the modelling parameters such as mesh size, element type, number of loading increments and material hardening models that should be used and on whether crack closure represents the interaction effects sufficiently. Also modelling long crack lengths has been perceived to be too computationally intensive and therefore studies focus on short crack lengths only.
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Unosson, Mattias. "Constitutive equations for concrete materials subjected to high rate of loading." Licentiate thesis, Linköping University, Linköping University, Solid Mechanics, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5721.
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Continuum mechanics is used to model the mechanical behaviour of concrete structures subjected to high rates of loading in defence applications. Large deformation theory is used and an isotropic elastic-plastic constitutive equation with isotropic hardening, damage and strain rate dependent loading surface. The hydrostatic pressure is governed by an equation of state. Numerical analysis is performed using the finite element method and the central difference method for the time integration.
Projectile penetration is studied and it is concluded that it is not suitable to use material description of the motion of both the target and the projectile together with an erosion criterion. Instead, the material description should be used only for the projectile and the spatial description for the target. In this way the need for an erosion criterion is eliminated. Also, in the constitutive model used it is necessary to introduce a scaling of the softening phase in relation to the finite element size, in order to avoid strain localization.
Drop weight testing of reinforced concrete beams are analysed, where a regularisation is introduced that renders mesh objectivity regarding fracture energy release. The resulting model can accurately reproduce results from material testing but the regularisation is not sufficient to avoid strain localization when applied to an impact loaded structure. It is finally proposed that a non-local measure of deformation could be a solution to attain convergence.
The third study presents the behaviour of a concrete constitutive model in a splitting test and a simplified non-local theory applied in a tensile test. The splitting test model exhibits mesh dependency due to a singularity. In the tensile test the non-local theory is shown to give a convergent solution. The report https://www.diva-portal.org/liu/webform/form.jsp#paper0is concluded with a discussion on how to better model concrete materials.
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Song, Zhenhuan. "Computational mesoscale modelling of concrete material under high strain rate loading." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7637.
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Cement-based composite materials are widely used in engineering applications. The strength and damage patterns of such materials depend upon the properties of the constituent components as well as the microstructure. Three scale levels are generally recognized in the analysis of the mechanical behaviour of composites, namely, macro-scale, meso-scale, and nano- or atomistic scale. Modelling of the mechanical properties at the meso-level provides a powerful means for the understanding of the physical processes underlying the macroscopic strength and failure behaviour of the composite materials under various loading conditions. This thesis endeavours to develop effective and efficient mesoscale models for cement-based composites, especially concrete, with a focus on dynamic analysis applications and in a three-dimensional stress-strain environment. These models are subsequently applied to investigate the intrinsic microscopic mechanisms governing the behaviour of such material under complex and high rate loadings, such as those due to shock, impact and blast. To cater to the needs of dynamic analysis under complex stress conditions, a general 2-dimensinal (2D) mesoscale modelling framework is further developed with the incorporation of the 3-D effect. This framework integrates the capabilities of MATLAB programming for the generation of the mesoscale geometric structure, ANSYS-CAE for finite element mesh generation, and the hydrocode LS-DYNA for solving the dynamic response of the model. The 3D effect is incorporated via a novel pseudo-3D modelling scheme such that the crucial lateral confinement effect during the transient dynamic response can be realistically represented. With the above mesoscale model a comprehensive investigation is conducted on the dynamic increase factor (DIF) in the concrete strength under compression, with particular focus on the variation trend at different strain rate regimes, and the key influencing factors. The wave propagation effect under high strain rate is scrutinised from a strip-by-strip perspective, and the correlation between the externally measured stress-strain quantities and the actual processes within the specimen is examined. The contribution of the material heterogeneity, as well as the structural effect (inertia), in the dynamic strength enhancement is evaluated. The classical Brazilian (splitting) test for the dynamic tensile behaviour of concrete is also investigated with the aid of the mesoscale model. Of particular interest here is the validity of such an indirect setup in reproducing the tensile behaviour of the specimen under high strain rates, as well as the effect of the heterogeneity in the dynamic tensile strength. Complications are found to arise as the loading rate increases. The change of the damage patterns with increase of the loading rate and the implications on the interpretation of the results are discussed. As an ideal solution to modelling of the 3-D effects, a methodology for the creation of a complex real 3-dimensional mesoscale model is put forward in the last part of the thesis. A geometric concept, called convex hull, is adopted for the representation of aggregates, and this makes it possible to utilize the relevant algorithms in computational geometry for the present purpose of generation of random 3-D aggregates. A take-and-place procedure is employed to facilitate the generation of the complete 3-D meso-structure. Associated techniques are developed for fast detection of particle inclusion-intersection. An example 3D mesoscale model is presented and representative numerical simulations are carried out to demonstrate the performance of the 3-D mesoscale modelling scheme.
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Ceritano, Davide Walter. "Sex-Based Differences in Calcaneal Injury Tolerances Under High-Rate Loading." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99103.
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In this experiment, average calcaneal fracture force is measured across male and female groups. The purpose of this experiment is an analysis of alternatives exploring the importance of sex-based criteria in models representing injuries typical in underbody blast environments. Seventeen (17) right legs were harvested at the knee from cadavers representing three anthropometries: 50th percentile male (6), 75th percentile female (6), and 5th percentile female (5). Care was taken to preserve anatomically correct geometry as the legs were cut to equal lengths, the tibia and fibula were potted in Dyna-Cast®, flesh and ligaments were excised from the inferior surface of the calcaneus, and a small Dyna-Cast® pad was poured and sanded flat – interfacing with the exposed calcaneal surface. Each test specimen was mounted in a custom fixture and exposed once to high-rate axial loading characterized by a constant acceleration and 25.4mm intrusion, achieving an average speed of 4.7m/s (σ = 0.3m/s) in 10ms. Input acceleration was measured by an Endevco 7264c accelerometer and a Denton 2513 six-axis load cell measured reaction force proximal to the specimen. A VR Phantom v9.1 camera recorded x-ray imagery at 2k frames per second. Data were collected by a TDAS Pro data acquisition system at 20k samples per second and filtered in accordance with SAE J211. Time of fracture, established through x-ray imagery, was used to determined fracture force from the electronically synchronized load-cell data. 100% injury was recorded.
Average calcaneus fracture forces were reported as follows: 5406N (σ = 780N) for 50th percentile males, 4130N (σ = 1061N) for 75th percentile females, and 2873N (σ = 1293N) for 5th percentile females. Statistical significance was established between the reported averages according to three ANOVA tests: One-way (p = 0.0054), Brown-Forsythe (p = 0.0091), and Welch's (p = 0.0156). Unpaired Student's t-test confirmed significant differences between 50th percentile male vs 75th percentile female (p = 0.0469) and 50th percentile male vs 5th percentile female (p = 0.0030); the t-test did not show significance between the two female groups (p = 0.1315). Average impulse-to-fracture was calculated for each group and found to be not statistically significant.Master of Science
A marked shift can be found in combat wound epidemiology towards a predominance of extremity injuries sustained from explosives. The Warrior Injury Assessment Mannequin (WIAMan) Project sought to develop a baseline dataset of post-mortem human surrogate responses to realistic explosive loading and correlate it to a highly instrumented mannequin for the further development of combat vehicles and personal protective gear. The following experiment exists within the WIAMan paradigm as an analysis of alternatives exploring the adequacy of the above mentioned baseline dataset in directly representing both male and female injuries. More specifically, this experiment interrogates the differences in average fracture forces between male and female calcanei across three anthropometries: 50th percentile male, 75th percentile female, and 5th percentile female. Testing was carried out on 17 right cadaver legs cut to equal lengths, potted proximally in Dyna-Cast®, with the inferior surface of their calcanei exposed; a small Dyna-Cast® pad was poured for each calcaneus and sanded flat. Each test specimen was fixed to a Denton 2513 six-axis load cell proximally and exposed to a high-rate, constant acceleration, 25.4mm displacement aligned with the calcaneus along the long axis of the leg bones. Fracture time, established through x-ray images recorded at 2k frames per second with a VR Phantom V9.1 camera, was used to determine load cell force measurement at fracture. Average calcaneus fracture forces were reported as follows: 5406N (σ = 780N) for 50th percentile males, 4130N (σ = 1061N) for 75th percentile females, and 2873N (σ = 1293N) for 5th percentile females. Statistical significance was established between the reported averages according to three ANOVA tests: One-way (p = 0.0054), Brown-Forsythe (p = 0.0091), and Welch's (p = 0.0156). Unpaired Student's t-test confirmed significant differences between 50th percentile male vs 75th percentile female (p = 0.0469) and 50th percentile male vs 5th percentile female (p = 0.0030); the t-test did not show significance between the two female groups (p = 0.1315). Average impulse-to-fracture was calculated for each group and found to be not statistically significant.
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Schultz, Rickey Lynn Jr. "Influence of pollutant loading rate on seasonal performance of model constructed wetlands." Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/schultz/SchultzR1207.pdf.
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Constructed wetlands (CW) are a viable alternative wastewater treatment technology for many wastewater types. However, recommended loading rates vary widely between regulatory agencies. A greenhouse experiment was carried out for approximately 19 months to study the effect of loading rate, plant species selection, temperature and season on pollutant removal in bench-scale constructed wetlands. The wetlands were operated in batch mode at batch lengths of 3, 6, and 9 days, corresponding to loading rates of 210, 105, and 70 kg COD/ha·d, respectively. Greenhouse temperature cycled from 4°C to 24°C. Treatments included plant species Carex utriculata, Schoenoplectus acutus and Typha latifolia and unplanted controls. Water and air temperature, redox potential, COD, SO ₄ ²-, NH ₄+, PO ₄ ³- and pore volume were monitored throughout the study. Data from the current research is compared with a previous study performed under similar conditions, but with a 20 day batch length resulting in a loading rate of 32 kg COD/ha·d. Performance of all treatments and loading rates was compared on the basis of percent COD and SO ₄ ²- removal, redox potential, and remaining NH ₄+ and PO ₄ ³- concentration. There were strong interactions between loading rate, plant species and temperature. Within species, pollutant removal typically decreased with an increase in loading rate at all temperatures. Planted treatments generally improved pollutant removal at all loading rates and typically removed more NH ₄+ and PO ₄ ³- at 24°C than at 4°C. However at lighter loading rates Carex and Schoenoplectus showed little temperature effect for COD removal, and had more SO ₄ ²- remaining and increased redox levels at 4°C. However, as loading rate increased these species tended to have poorer COD removal at colder than warm temperatures. These results indicate that the ability of some plant species to increase aerobic respiration due to increased oxygenation in winter, and thus mitigate typical temperature effects on COD removal, is limited by higher organic load rates. Although not the focus of this study it was observed that wetland column porosity varied with season and with wetland age. Column porosity was lower for older columns and during winter.
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Cherrill, Hugh Edward. "The influence of loading rate on excess pore pressures in triaxial tests." Thesis, City University London, 1990. http://openaccess.city.ac.uk/7674/.
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The research described in this dissertation is concerned with coupled loading and consolidation in triaxial tests and with selection of rates of loading in routine tests to avoid errors due to incomplete drainage or non-uniform pore pressures in fine grained soils. The work consisted of a combination of laboratory tests in which pore pressures were measured within triaxial samples, numerical analysis using the CRISP geotechnical finite element program and theoretical analysis. Both constant strain rate and constant stress rate loading were considered. The work demonstrates the applicability of CRISP to coupled loading and consolidation analyses and its limitations are discussed. The influence of loading rates on pore pressures in triaxial tests and upon the soil parameters obtained from them is investigated and deficiencies in the current procedure for choosing rates of loading are revealed. A new method is proposed which permits a rational choice of loading rate based on the drainage characteristics of the sample and on the magnitude of the errors which can be accepted. Non-uniformities of stress, strain and specific volume in triaxial samples and the influence of loading rate on these non-uniformities is also investigated.
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Fernie, R. "Loading rate effects on the energy absorption of lightweight tubular crash structures." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272800.
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RODRIGUES, SUELEN. "INFLUENCE OF LOADING RATE ON THE BOND STRENGTH BETWEEN CFC AND CONCRETE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=15133@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Neste trabalho é realizada uma investigação experimental sobre os efeitos de cargas de impacto sobre a resistência de aderência entre o compósito de fibras de carbono e o concreto. O objetivo foi verificar a influência da taxa de carregamento sobre a resistência de aderência. O programa experimental consistiu em ensaios de quarenta e cinco corpos-de-prova, constituídos de blocos de concreto e tiras de fibras de carbono coladas nas laterais opostas dos blocos. As variáveis de estudo foram a resistência à compressão do concreto (25 MPa, 45 MPa e 65 MPa) e a taxa de carregamento que variou de um mínimo de 1,92 MPa/s (estático) para um máximo de 438685 MPa/s (dinâmico). Os resultados dos ensaios mostraram que a resistência de aderência foi afetada pela taxa de carregamento.
An experimental investigation on the effects of impact loading on the bond strength between carbon fiber composite and concrete is described in this work. The objective was to verify the influence of loading rate on the bond strength. The experimental program consisted on testing of forty five specimens made of concrete blocks and carbon fiber strips glued on opposite sides of the block. The variables studied were the concrete compressive strength (25 MPa, 45 MPa and 65 MPa) and loading rate which varied from a minimum of 1,92 MPa/s (static) to a maximum of 438685 MPa/s (dynamic). Test results showed that the bond strength was affected by loading rate.
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Said, Mohd Noor Bin Mohd. "Effect of loading rate on the fracture toughness of structural steel weld metal." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 1989. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=59650.
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Ahmad, Sahrim Haji. "High strain-rate behaviour of polymers using blast-wave and impact loading methods." Thesis, Loughborough University, 1988. https://dspace.lboro.ac.uk/2134/7496.
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Daily, Jeremy S. "Dissipated Energy at a Bimaterial Crack Tip Under Cyclic Loading." Wright State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=wright1150865012.
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Gunasilan, Manar. "Crack arrest capability of aluminium alloys under dynamic loading." Thesis, Toulouse, ISAE, 2018. http://www.theses.fr/2018ESAE0027/document.
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Les structures aéronautiques peuvent être soumises à des sollicitations sévères telles que les collisions, les impacts de volatiles, etc … Sous l’effet de ces sollicitations rapides, qui du fait de leurs temps caractéristiques très courts limitent les transferts thermiques, le matériau peut dissiper l’énergie dans des zones de déformation localisée qui peuvent conduire à une ruine prématurée de la structure. Le travail de la thèse porte sur la définition d’une méthodologie expérimentale destinée à étudier les conditions de rupture de matériaux à haute résistance à vocation aéronautique consécutives à un endommagement dynamique. Ce travail comprend : •la mise au point d’essais rapides de cisaillement ; •des observations microstructurales des matériaux avant et après sollicitation ; •la simulation numérique des essaisAeronautical structures may be submitted to severe loading such as collisions, bird strike, etc. Under dynamic loading, involving quasi adiabatic conditions, the material may dissipate energy within zones of localised deformation wich may lead to the premature failure of the structure. The PhD work aims at defining an experimental methodology devoted to study the conditions of fracture of aeronautical, high strength materials intervening after dynamic damage. Tasks include notably: * definition of dynamic shear tests * microstructural observation of the material before and after loading * numerical simulation * Development of fracture criterion
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Rypl, Rostislav, Miroslav Vořechovský, Britta Sköck-Hartmann, Rostislav Chudoba, and Thomas Gries. "Effect of twist, fineness, loading rate and length on tensile behavior of multifilament yarn." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244041881719-95100.
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The idea underlying the present study was to apply twisting in order to introduce different levels of transverse pressure. The modified structure affected both the bonding level and the evolution of the damage in the yarn. In order to isolate this effect in a broader context, additional parameters were included in the experiment design, namely effects of loading rate, specimen length and filament diameter (directly linked to the fineness of the yarn). These factors have been studied in various contexts by several authors. Some related studies on involved factors will be briefly reviewed.
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Teo, Wern Sze. "The performance of carbon-fibre composite joints : pre-bond moisture and loading rate effects." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501293.
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Bergschneider, Cara Renee. "Determining an Appropriate Organic Matter Loading Rate for a Created Coastal Plain Forested Wetland." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/34698.
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Past research indicates that created non-tidal wetlands in the mid-Atlantic region are considerably lower in soil organic matter than native forested hydric soils. However, optimal loading rates for created wetland soil reconstruction have not been rigorously established. Our objective was to determine appropriate organic amendment loading rates for a Coastal Plain mitigation wetland based on 1) soil properties reflective of hydric soil development, 2) the formation of redoximorphic features, and 3) the growth and vigor of hydrophytic vegetation. The study contained wet (CCW-Wet) and dry (CCW-Dry) experiments, each receiving 6 compost treatments (0 Mg/ha untilled and 0, 56, 112, 224, and 336 Mg/ha tilled). Over the 1.5-year monitoring period, redox potential decreased and redoximorphic feature formation increased with compost loadings up to 112 Mg/ha. Surface bulk density decreased with loadings up to 224 Mg/ha, while no treatment differences were noted in sub-surface bulk density. In the CCW-Dry experiment, soil moisture peaked in the 224 Mg/ha treatment, while soil moisture in CCW-Wet increased consistently across all loadings. Total biomass in CCW-Wet and Betula nigra L. growth in both experiments increased with loading rate. Total biomass in CCW-Dry and Quercus palustris Muench. growth in both experiments peaked at 112 Mg/ha, although differences were not significant. Collectively, these findings indicate that 112 Mg/ha of high quality organic amendment was optimal for inducing hydric soil conditions and positive hydrophytic vegetation response. Incorporating compost at rates exceeding 112 Mg/ha is challenging and leads to higher surface elevations and redox levels in the initial growing season.Master of Science
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Lloyd, Jeffrey T. "Microstructure-sensitive simulation of shock loading in metals." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51853.
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A constitutive model has been developed to model the shock response of single crystal aluminum from peak pressures ranging from 2-110 GPa. This model couples a description of higher-order thermoelasticity with a dislocation-based viscoplastic formulation, both of which are formulated for single crystals. The constitutive model has been implemented using two numerical methods: a plane wave method that tracks the propagating wave front; and an extended one-dimensional, finite-difference method that can be used to model spatio-temporal evolution of wave propagation in anisotropic materials. The constitutive model, as well as these numerical methods, are used to simulate shock wave propagation in single crystals, polycrystals, and pre-textured polycrystals. Model predictions are compared with extensive existing experimental data and are then used to quantify the influence of the initial material state on the subsequent shock response. A coarse-grained model is then proposed to capture orientation-dependent deformation heterogeneity, and is shown to replicate salient features predicted by direct finite-difference simulation of polycrystals in the weak shock regime. The work in this thesis establishes a general framework that can be used to quantify the influence of initial material state on subsequent shock behavior not only for aluminum single crystals, but for other face-centered cubic and lower symmetry crystalline metals as well.
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Wong, Sik Lun. "Fatigue crack growth rate under sequential non-proportional mixed mode I and II loading cycles." Thesis, University of Sheffield, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339906.
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Brown, Gilbert Mark. "Optimal steering of a second stage boost vehicle subject to loading and roll rate constraints." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14739.
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Gonzales, Manny. "The mechanochemistry in heterogeneous reactive powder mixtures under high-strain-rate loading and shock compression." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54393.
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This work presents a systematic study of the mechanochemical processes leading to chemical reactions occurring due to effects of high-strain-rate deformation associated with uniaxial strain and uniaxial stress impact loading in highly heterogeneous metal powder-based reactive materials, specifically compacted mixtures of Ti/Al/B powders. This system was selected because of the large exothermic heat of reaction in the Ti+2B reaction, which can support the subsequent Al-combustion reaction. The unique deformation state achievable by such high-pressure loading methods can drive chemical reactions, mediated by microstructure-dependent meso-scale phenomena. Design of the next generation of multifunctional energetic structural materials (MESMs) consisting of metal-metal mixtures requires an understanding of the mechanochemical processes leading to chemical reactions under dynamic loading to properly engineer the materials. The highly heterogeneous and hierarchical microstructures inherent in compacted powder mixtures further complicate understanding of the mechanochemical origins of shock-induced reaction events due to the disparate length and time scales involved.
A two-pronged approach is taken where impact experiments in both the uniaxial stress (rod-on-anvil Taylor impact experiments) and uniaxial strain (instrumented parallel-plate gas-gun experiments) load configurations are performed in conjunction with highly-resolved microstructure-based simulations replicating the experimental setup. The simulations capture the bulk response of the powder to the loading, and provide a look at the meso-scale deformation features observed under conditions of uniaxial stress or strain. Experiments under uniaxial stress loading reveal an optimal stoichiometry for Ti+2B mixtures containing up to 50% Al by volume, based on a reduced impact velocity threshold required for impact-induced reaction initiation as evidenced by observation of light emission. Uniaxial strain experiments on the Ti+2B binary mixture show possible expanded states in the powder at pressures greater than 6 GPa, consistent with the Ballotechnic hypothesis for shock-induced chemical reactions. Rise-time dispersive signatures are consistently observed under uniaxial strain loading, indicating complex compaction phenomena, which are reproducible by the meso-scale simulations. The simulations show the prevalence of shear banding and particle agglomeration in the uniaxial stress case, providing a possible rationale for the lower observed reaction threshold. Bulk shock response is captured by the uniaxial strain meso-scale simulations and is compared with PVDF stress gauge and VISAR traces to validate the simulation scheme. The simulations also reveal the meso-mechanical origins of the wave dispersion experimentally recorded by PVDF stress gauges.
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Kuhn, Peter [Verfasser]. "Characterization of the Intralaminar Fracture Toughness of Polymer Composites under High Rate Loading / Peter Kuhn." München : Verlag Dr. Hut, 2021. http://nbn-resolving.de/urn:nbn:de:101:1-2021100123350329094730.
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Simha, Chityalla Harimanoj. "High rate loading of a high purity ceramic : one dimensional stress experiments and constitutive modeling /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Wagle, John. "Kinetic and Kinematic Characteristics of Accentuated Eccentric Loading." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etd/3484.
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The current investigation was an examination of the kinetic and kinematic characteristics of the back squat using accentuated eccentric loading (AEL) and cluster set programming strategies. Trained male subjects (age = 26.1 ± 4.1 years, height = 183.5 ± 4.3 cm, body mass = 92.5 ± 10.5 kg, back squat to body mass ratio = 1.8 ± 0.3) volunteered to complete four different load condition sessions involving traditionally loaded straight sets (TL), traditionally loaded cluster sets (TLC), AEL cluster sets (AEC), and AEL straight sets where only the first repetition of each set used eccentric overload (AEL1). The use of AEL increased eccentric work (WECC) and eccentric rate of force development (RFDECC) but did not result in the expected potentiation of subsequent concentric output. Interrepetition rest, however, appears to have the largest influence on concentric peak power (PP), rate of force development (RFDCON), and average velocity (MV). Additionally, the current study was an investigation of the efficacy of novel methods of ultrasonography technique that can be applied to monitoring training response. Compared to lying measures of the vastus lateralis (VL), standing ultrasonography measures of muscle thickness (MT), pennation angle (PA), and cross-sectional area (CSA) were more strongly and abundantly correlated with dynamic and isometric strength performance. Finally, the present study was an exploration of the genetic underpinnings of performance outcomes and muscle phenotypic characteristics. The polymorphisms of two candidate genes (ACTN3, ACE) typical of strength-power athletes were used. ACTN3 RR tended to result in greater type II fiber CSA and alter maximal strength, while ACE DD tended to influence RFD through the presence of more favorable type II-to-type I CSA ratios. Overall, the current investigation provided valuable insight into the characteristics of advanced programming tactics. Furthermore, the ultrasonography measurement and genetic aspects of the current investigation may serve as a framework to inform monitoring practice and generate hypotheses related to the training process.
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Loh, Beng Heng. "Behaviour of railway track subgrade under cyclic loading." Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/2100.
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The railway track foundation of fine-grained soil subgrade, under repeated loading of cyclic nature, can gradually build up excess pore pressure and result in progressive shear failure at a stress level much lower than the monotonic loading strength of the soil. It is widely accepted that a threshold stress exists, above which, the induced stress generates large shear deformation and; below which, the soil deformation become stabilized irrespective of the number of loading applications. Previous studies into the behaviour of fine-grained subgrade under cyclic loading had mainly involved slow loading rate. The advance in transportation technology and the required efficiency of transporting goods and commuting passengers demands higher train speed and heavier loads. Consequently, better understanding on the behaviour of fine-grained subgrade under higher rate of loading (i.e. cyclic frequency) will be necessary as it influences the build-up of excess pore water pressure and strain accumulation of subgrade soil, hence the stability of the railway track. In addition, current design approaches to the railway tracks foundation of fine-grained subgrade have largely been empirical or semi-empirical unique to a range of geological characteristic, operating and traffic condition. The rationalization and reformulation of design approach may be required if general design means will to be devised.In this research, an in-depth study of undrained triaxial testing on the behaviour of a typical fine-grained reconstituted kaolinite clay soil, simulating the characteristic subgrade responses exhibit under the passing axles / wheel load of the contemporary train speed was performed and discussed. Four series of both static and cyclic undrained triaxial test were conducted. The static undrained triaxial test provides the behavioural benchmark and a prior indication on the maximum stress level from which the cyclic stress level can be apportioned. The cyclic undrained triaxial test simulates the behaviour of clay subgrade under a large number of passing axles/wheel load. The results of the testing described and characterized the stress / strain behaviour for saturated kaolinite clay of various consolidated state and stress history. In particular, it described the general concept of cyclic stress equilibrium state and resilient state, and detailed the characteristic pattern of the line of cyclic stress equilibrium state which dictates the way in identifying the threshold stress (or critical level of cyclic stress). The study demonstrated that, using effective stress analysis, the threshold stress can be obtained for clay under high cyclic loading rate. In conjunction with the stress response, the deformation and resilient characteristics of various series of cyclic undrained triaxial tests carried out on the saturated clay was described. Apart from highlighting and confirming the influence of consolidated state and stress history on the threshold stress and deformation characteristics, influence of the cyclic loading frequency simulating higher train travelling speed was also investigated and examined.Using the framework of critical state soil mechanics, the study described the existence of cyclic stress equilibrium state surface CSESS within the stress state boundary surface SSBS for saturated clay under cyclic undrained compression. A form of analytical / theoretical model was established which enables threshold stress to be ascertained without resort to lengthy laboratory testing at the preliminary design stage of railway track foundation design. Developed from the “original Cam-clay” model and validated by the cyclic triaxial test data on reconstituted kaolin clay, the theoretical model which described the CSESS enables the prediction of threshold stress (or critical level of cyclic stress) of general saturated clay soil under undrained cyclic compression to be made from the fundamental properties of the soil, based on the designed consolidated state and the stress history of subgrade soil.In addition, this study proposed a new approach which rationalized and reformulated the current state of design and management process of railway track substructure involved clay subgrade. The rational approach was developed based on the comprehension of “lower-bound threshold stress” and potential strengthening and densification of fine-grained subgrade soil through progressive and deliberate incremental loading of the track foundation. Concept of “Managing current lower-bound threshold stress” for clay subgrade was elaborated. The readily use of the developed theoretical model and design charts for predicting the threshold stress could offer a key advantage for the new approach over current practices.
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Wytrykush, Laura G. "Effect of soil loading rate on microbial activity during co-composting of diesel-contaminated clay soil." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ57596.pdf.
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Vankov, Dmitri Andreevich. "Influence of Loading Rate and Shear-Displacement Magnitude on the Pore Pressure Generation at Sliding Surface." 京都大学 (Kyoto University), 2000. http://hdl.handle.net/2433/157199.
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要旨pdfファイル:タイトル「すべり面での過剰間隙水圧に及ぼす載荷速度及びせん断変位振幅の影響に関する研究」本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである
Kyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第8170号
理博第2192号
新制||理||1159(附属図書館)
UT51-2000-F74
京都大学大学院理学研究科地球惑星科学専攻
(主査)教授 佐々 恭二, 教授 奥西 一夫, 教授 竹本 修三
学位規則第4条第1項該当
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Carroll, Kevin M., Jake R. Bernard, and Michael H. Stone. "Skeletal Muscle Hypertrophy, Maximal Strength, and Rate of Force Development: Effects of Resistance Training Loading Strategy." Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etsu-works/4574.
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Husovitz, Kari J. "The Influence of Hydraulic Loading Rate on Nitrification Performance in a Two-Stage Biological Aerated Filter Pilot Plant." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/40626.
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A two-stage (carbon oxidation stage one, ammonia oxidation stage two) biological aerated filter was operated for 10 months on-site at a domestic wastewater treatment plant. Over the study, the system was operated at different hydraulic loading rates that resulted in a range of applied organic and ammonia mass loadings. Performance was monitored regularly for water quality parameters in the effluent and along the length of the reactors. It was found that nitrification performance was significantly influenced by organic loading rates greater than 1.2 kg cBOD5/m3-d. Additional experiments were conducted in which a constant mass of ammonia was applied (Phase 1: 1.40 ± 0.08 kg NH3-N/m3-d; Phase 2: 1.31 ± 0.02 kg NH3-N/m3-d) to the N column, the second stage of the system, over a range of hydraulic loading rates (5.1 -15.8 m/h). Phases of testing were defined by the background hydraulic loading rate applied to the system (Phase 1: 8.3 m/h; Phase 2: 7.1 m/h) at which the reactors were allowed to reach a steady effluent quality for at least one week prior to testing. Organic loading was minimized and kept relatively constant throughout the hydraulic loading rate experiments (0.65 ± 0.2 kg cBOD5/m3-d) in order to obtain an evaluation of nitrification capacity with minimal competition from heterotrophic bacteria. Results indicated that nitrification performance improved by 17% as the applied velocity increased over the indicated range. A steady-state biofilm model capable of predicting substrate flux was applied to the data in an attempt to explain the improvement in performance with hydraulic loading rate from a fundamental standpoint. Mass transfer coefficients, KL, were derived from the model for conditions in which the experimentally observed flux correlated with the model predictions. Derived KL values were lower than estimations offered by correlation equations but increased with velocity at a similar rate. The model failed to account for changes that may have occurred in biofilm kinetics and structure throughout the length of the reactor.Master of Science
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Ziv, Michael. "A study of the behavior of the GRP hat-stiffened panel bondline under high strain rate loading." Thesis, Monterey, California. Naval Postgraduate School, 1995. http://hdl.handle.net/10945/26270.
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Higgins, Daniel Louis. "The response of metals with different crystal structures to high strain rate loading and other mechanical tests." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7724/.
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The effect of cold-rolling prior to shock loading was investigated in copper and tantalum. Annealed copper was shocked at a peak pressure of 5.08GPa; cold-rolled copper was shocked at peak pressures of 5.87GPa, 5.96GPa and 9.60GPa; as-received tantalum was shock loaded at a peak pressure of 7.20GPa, and cold-rolled tantalum was shocked at a peak pressure of 7.20GPa. The microstructures of the materials were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the mechanical responses were investigated using compression and hardness testing. The effect of varying temperature and strain rate on tantalum during compression was investigated. Tantalum was compressed at 20°C at 10⁻³s⁻¹, 10⁻¹s⁻¹ and 2x10³s⁻¹, and at 10⁻¹s⁻¹ at -40°C and 170°C. Quasi-static compression tests applied 70% strain to the samples and the higher strain rate sample, compressed by Split Hopkinson Pressure Bar (SHPB), was compressed to 19% strain. The microstructures of the materials were investigated using (SEM) and (TEM), and the mechanical responses were investigated using hardness and compression testing. The microstructures of adiabatic shear bands (ASBs) produced by firing a shaped projectile from a single stage gas gun to cause the collapse of a thick-walled cylinder (TWC). The propagation of the ASBs along the cylindrical axis of the TWC was Also investigated. The microstructure was investigated using (SEM), (TEM) and scanning transmission electron microscopy (STEM).
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Ko, Tae Young. "SUBCRITICAL CRACK GROWTH UNDER MODE I, II, AND III LOADING FOR COCONINO SANDSTONE." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/193702.
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In systems subjected to long-term loading, subcritical crack growth is the principal mechanism causing the time-dependent deformation and failure of rocks. Subcritical crack growth is environmentally-assisted crack growth, which can allow cracks to grow over a long period of time at stresses far smaller than their failure strength and at tectonic strain rates. The characteristics of subcritical crack growth can be described by a relationship between the stress intensity factor and the crack velocity. This study presents the results of studies conducted to validate the constant stress-rate test for determining subcritical crack growth parameters in Coconino sandstone, compared with the conventional testing method, the double torsion test. The results of the constant stress-rate test are in good agreement with the results of double torsion test. More importantly, the stress-rate tests can determine the parameter A with a much smaller standard deviation than the double torsion test. Thus the constant stress-rate test seems to be both a valid and preferred test method for determining the subcritical crack growth parameters in rocks. We investigated statistical aspects of the constant stress-rate test. The effects of the number of tests conducted on the subcritical crack growth parameters were examined and minimum specimen numbers were determined. The mean and standard deviation of the subcritical crack growth parameters were obtained by randomly selecting subsets from the original strength data. In addition, the distribution form of the subcritical crack growth parameters and the relation between the parameter n and A were determined. We extended the constant stress-rate test technique to modes II and III subcritical crack growth in rocks. The experimental results of the modes I, II and III tests show that the values of the subcritical crack growth parameters are similar to each other. The subcritical crack growth parameter n value for Coconino sandstone has the range of 34 to 38 and the parameter A has the range of 1.02x10⁻² to 6.52x10⁻² m/s. The effect of confining stress, specimen size, and water saturation on subcritical crack growth under mode II loading has also been investigated. Finally strength parameters for Coconino sandstone were determined experimentally, including tensile strength, uniaxial compressive strength, cohesion, internal friction angle, in-plane / our-of-plane shear strength and the fracture toughness under mode I, II, and III loading.
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Salih, Sarmed. "Rate-dependent cohesive-zone models for fracture and fatigue." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/ratedependent-cohesivezone-models-for-fracture-and-fatigue(d8bfee97-1a75-4418-8916-b5a7cf8cdfd9).html.
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Despite the phenomena of fracture and fatigue having been the focus of academic research for more than 150 years, it remains in effect an empirical science lacking a complete and comprehensive set of predictive solutions. In this regard, the focus of the research in this thesis is on the development of new cohesive-zone models for fracture and fatigue that are afforded an ability to capture strain-rate effects. For the case of monotonic fracture in ductile material, different combinations of material response are examined with rate effects appearing either in the bulk material or localised to the cohesive-zone or in both. The development of a new rate-dependent CZM required first an analysis of two existing methods for incorporating rate dependency, i.e.either via a temporal critical stress or a temporal critical separation. The analysis revealed unrealistic crack behaviour at high loading rates. The new rate-dependent cohesive model introduced in the thesis couples the temporal responses of critical stress and critical separation and is shown to provide a stable and realistic solution to dynamic fracture. For the case of fatigue, a new frequency-dependent cohesive-zone model (FDCZM) has been developed for the simulation of both high and low-cycle fatigue-crack growth in elasto-plastic material. The developed model provides an alternative approach that delivers the accuracy of the loading-unloading hysteresis damage model along with the computational efficiency of the equally well-established envelope load-damage model by incorporating a fast-track feature. With the fast-track procedure, a particular damage state for one loading cycle is 'frozen in' over a predefined number of cycles. Stress and strain states are subsequently updated followed by an update on the damage state in the representative loading cycle which again is 'frozen in' and applied over the same number of cycles. The process is repeated up to failure. The technique is shown to be highly efficient in terms of time and cost and is particularly effective when a large number of frozen cycles can be applied without significant loss of accuracy. To demonstrate the practical worth of the approach, the effect that the frequency has on fatigue crack growth in austenitic stainless-steel 304 is analysed. It is found that the crack growth rate (da/dN) decreases with increasing frequency up to a frequency of 5 Hz after which it levels off. The behaviour, which can be linked to martensitic phase transformation, is shown to be accurately captured by the new FDCZM.
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Gomez, Eddie F. "Effects of Organic Loading Rate on Reactor Performance and Archaeal Community Structure in Mesophilic Anaerobic Digesters Treating Municipal Sewage Sludge." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268065746.
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Kraska, Jenna Marie. "The Relationship between Isometric Force Characteristics and Vertical Jump Height under Various Loading Conditions." Digital Commons @ East Tennessee State University, 2008. https://dc.etsu.edu/etd/1965.
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Purpose: to examine the relationship between isometric force characteristics (IF) and vertical jump height under various loading conditions. Sixty-three collegiate athletes participated in this investigation. Athletes performed static jump (SJ) and countermovement jumps (CMJ) with 0 and 20kg, and isometric mid-thigh pulls on a force plate. Force-time curve analysis was conducted for each isometric pull and jump to determine force related characteristics. Jump height (JH) was derived from flight time. Isometric forces were normalized using allometric scaling: absolute force/ (body mass(kg)0.67)= IPFa. Results: There was a strong positive correlation between isometric peak force and isometric rate of force development (IRFD). Stronger athletes had smaller decrements in jump height with additional loading. Conclusion: The ability to produce higher peak and instantaneous forces and IRFD is related to JH and smaller differences between weighted and unweighted jumps. A weighted jump may be a practical method of assessing relative strength levels.
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Bose, Rana. "Unloading using auger tool and foam and experimental identification of liquid loading of low rate natural gas wells." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5890.
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Low-pressure, low-producing natural gas wells commonly encounter liquid loading
during production. Because of the decline in the reservoir pressure and the flow
capacity, wells can fall below terminal velocity. Identifying and predicting the onset
of liquid loading allows the operators to plan and prepare for combating the liquid
loading hence saving valuable reserves and downtime. The present industrial
applications of artificial lift, wellhead pressure reduction by compressor installation
at the wellheads and reduction in tubing size are costly and often intermittent. The
thesis examines the above aspects to generate a workflow for identifying and
predicting the liquid loading conclusively and also assessing the application of
Auger Tool and foam combination towards achieving a cost effective and more
efficient solution for liquid unloading.
In chapters I-IV, I describe the process of using production surveillance software of
Halliburton Digital Consulting Services, named DSS (Dynamic Surveillance
Software), to create a workflow of identifying the liquid loaded wells based on well
data on daily basis for field personnel and engineers. This workflow also decides the most cost effective solution to handle it. Moreover, it can perform decline
analysis to predict the conditions of liquid loading.
In chapters V-VIII of the thesis, I describe the effort of handling the problem of
liquid loading in a cost effective manner by introduction of an inexpensive Auger
Tool in the bottomhole assembly and using WhiteMax surfactant soapstick from
J&J Solutions. Four different combinations of well completion and fluid were tested
for performance in respect to liquid hold up, pressure loss in the tubing, unloading
efficiency and critical flow requirement. The test facilities and instruments, along
with the operational methods, are discussed in chapter VI.
Except for the reduction of the operational envelope with the inclusion of Auger
Tool, the performance improved with the insertion of Auger Tool. The best
combination of Auger and foam system could be a result of flow modification by the
Auger Tool caused by reduced pressure loss and increase in drag coefficient and
also by reduced density and surface tension of foam.
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Barre, Vincent Henri. "Determination of a local damage threshold criterion for a laminate glass/epoxy under an intermediate rate of loading." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/18216.
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Wang, Qiang. "FILTER PERFORMANCE UNDER SIMULATED REAL-WORLD CONDITIONS." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4464.
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Evaluating the performance of filter media for filtration applications is essential to assure design engineers and users that filter device will deliver promised performance for specific applications under the environmental stress. The study of particle loading characteristics of filter media in the laboratory setting is typically performed under the steady flow conditions, i.e., at the constant particle concentration and flow rate. In reality, filtration products are operated under the situations that the flow rate and mass concentration of particles are varied in time. The success of translating the laboratory data to estimate the performance of filter media in the fields is thus limited. It is necessary to investigate the performance of filter media under the real-world conditions, i.e., unsteady flow rate and mass concentration to bridge the gap.
The overall goals of this research are (1) to study the performance of filter medium under unsteady conditions (i.e., the performance of respirator filter media under simulated breathing conditions); and (2) to investigate the issue of non-uniform particle deposition on HVAC filter panels. A new experimental setup was developed to accomplish the former goal. Numerical modeling tool, Computational fluid dynamics (CFD), was applied to achieve the latter objective……
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Mellott, Stephen Richard. "Tensile, Creep, and Fatigue Behaviors of Thermoplastics Including Thickness, Mold Flow Direction, Mean Stress, Temperature, and Loading Rate Effects." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1344541288.
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Pashak, Riley. "Susceptibility to Ankle Sprain Injury between Dominant and Non-Dominant Leg During Jump Landings." UKnowledge, 2019. https://uknowledge.uky.edu/khp_etds/66.
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Ankle sprains are one of the most common injuries within athletics in the United States with approximately one-million student athletes experiencing ankle sprains each year. Studies argue excessive or rapid ankle inversion occurring from jump landings may cause ankle sprains. Also, the effect of limb dominance on risk of ankle sprain is not well documented.
The aim of this study was to determine if there is an affect of leg dominance on landing mechanism of the ankle joint that predisposes either ankle joint to greater risk of ankle sprain.
Twelve recreationally active subjects were recruited and completed four maximal vertical jumps. Ground reaction force, marker position data and maximal vertical jump height were collected using two Bertec Force plates, a 10-camera motion capture system, and a Vertec Vertical Jump Trainer, respectively. Cortex and Visual3D software programs were used to process the motion capture data and to calculate peak vertical ground reaction forces(vGRF), loading rate, and ankle joint moments. There were no statistically significant differences in ankle joint moment or loading rate between limbs, but peak vGRF were significantly higher (p < 0.05) in the non-dominant ankle. The results suggest the non-dominant ankle displays higher injury potential, as the non-dominant leg accumulates a larger peak landing force.
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Seidt, Jeremy Daniel. "Plastic Deformation and Ductile Fracture of 2024-T351 Aluminum under Various Loading Conditions." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268148067.
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Wagle, John P., Christopher B. Taber, Kevin M. Carroll, Aaron J. Cunanan, Matt L. Sams, Alexander Wetmore, Garett E. Bingham, et al. "Repetition-to-Repetition Differences Using Cluster and Accentuated Eccentric Loading in the Back Squat." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/4665.
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The current investigation was an examination of the repetition-to-repetition magnitudes and changes in kinetic and kinematic characteristics of the back squat using accentuated eccentric loading (AEL) and cluster sets. Trained male subjects (age = 26.1 ± 4.1 years, height = 183.5 ± 4.3 cm, body mass = 92.5 ± 10.5 kg, back squat to body mass ratio = 1.8 ± 0.3) completed four load condition sessions, each consisting of three sets of five repetitions of either traditionally loaded straight sets (TL), traditionally loaded cluster sets (TLC), AEL cluster sets (AEC), and AEL straight sets where only the initial repetition had eccentric overload (AEL1). Eccentric overload was applied using weight releasers, creating a total eccentric load equivalent to 105% of concentric one repetition maximum (1RM). Concentric load was 80% 1RM for all load conditions. Using straight sets (TL and AEL1) tended to decrease peak power (PP) (d = −1.90 to −0.76), concentric rate of force development (RFDCON) (d = −1.59 to −0.27), and average velocity (MV) (d = −3.91 to −1.29), with moderate decreases in MV using cluster sets (d= −0.81 to −0.62). Greater magnitude eccentric rate of force development (RFDECC) was observed using AEC at repetition three (R3) and five (R5) compared to all load conditions (d = 0.21–0.65). Large within-condition changes in RFDECC from repetition one to repetition three (∆REP1–3) were present using AEL1 (d = 1.51), demonstrating that RFDECC remained elevated for at least three repetitions despite overload only present on the initial repetition. Overall, cluster sets appear to permit higher magnitude and improved maintenance of concentric outputs throughout a set. Eccentric overload with the loading protocol used in the current study does not appear to potentiate concentric output regardless of set configuration but may cause greater RFDECCcompared to traditional loading
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Amar, Kshitij. "AN ANALYSIS OF RGD CELL ADHESION MOTIF USING QUARTZ CRYSTAL MICROBALANCE TO UNDERSTAND THE LOADING RATE OF CELL LIGAND INTERACTION." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2202.
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It is now well accepted that mechanical environment partly defines the cellular behavior. The understanding of cell interactions with mechanical microenvironment is the most crucial step to control cell functions in disease and development. Living cells utilize cell surface receptors to interact with the ligands present in mechanical environments. Over the last few decades, several dominant techniques such as AFM, optical tweezers, magnetic tweezers, biomembranes force probes etc. have been extensively used to characterize the ligand-receptor interactions at the molecular level. These studies provided a plethora of information regarding molecular force loading and unloading features. However, these rupture forces have been shown to be strongly dependent on the rate of force application. Yet, it remains poorly understood what is the rate at which cells apply forces via ligand-receptor interactions that consequently defines rupture force relevant to living cells. Our goal is to create a bulk sensor that can detect the rate of cellular force application during early stages of cell adhesion and spreading. We hypothesize that using a quartz crystal microbalance (QCM), an ultra-sensitive piezoelectric device, can provide us with changes to the resonant frequency of the device due to the cellular probing (force application) of the QCM surface, and from the frequency shift we can isolate a mass change on the surface, calculate the coupling coefficient of the cells with their interaction with the substrate. A self-assembled monolayer (SAM) will be functionalized on top of the quartz crystal bonded with gold, the top component of which is the cyclo-RGD that interacts with the αv β3 integrins on cell membrane, henceforth we’ll study the ligand-receptor interaction. The loading rate was quantified through the experiment for variable cell numbers and loading rate and peak force generated on the surface due to ligand-receptor interaction was calculated. The loading rate found was the mean of all cells applying force cumulatively on the surface.
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Ribeiro, Fernando Salimon [UNESP]. "Índice de sucessos de implantes osseointegráveis que receberam carga imediata unitária: avaliação clínica de curto período em humanos." Universidade Estadual Paulista (UNESP), 2004. http://hdl.handle.net/11449/96201.
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O objetivo deste estudo foi comparar, em curto período de tempo, o índice de sucesso de implantes osseointegráveis unitários submetidos à carga imediata, colocados imediatamente após a exodontia, com implantes colocados em rebordos cicatrizados. Foram examinados 71 pacientes consecutivos totalizando 91 implantes, sendo 48 realizados em clínica privada e 43 em cursos de especialização em implantodontia, entre dezembro de 2001 a dezembro de 2003. Sessenta e três implantes foram instalados em alvéolos e 28 em rebordos. Os critérios utilizados para avaliar o índice de sucesso foram os descritos por Albrektsson e Zarb (1993). Após o período de avaliação, 87 implantes examinados enquadravam-se dentro dos critérios de sucesso (95,6%). Dos quatro implantes perdidos, três haviam sido colocados em alvéolos (índice de sucesso de 95,2%) e um, em rebordo (96,4%). A diferença entre os índices de sucesso dos dois grupos não foi estatisticamente significante (p=0,76, teste Qui-quadrado). Podemos concluir, dentro das limitações deste estudo, que o carregamento imediato de implantes unitários, seja colocado em alvéolo ou rebordo, representa uma alternativa terapêutica com alta previsibilidade, comparado aos resultados encontrados na literatura para implantes seguindo o protocolo convencional de dois estágios cirúrgicos.
The aim of this study was to evaluate, in a short period of time, the success rate of immediate loading of single-tooth implants: immediate versus non-immediate implantation. Seventy-one patients were examined, totalizing 91 implants, which 48 implants were placed in private practice office and 43 were placed in dental school, between December 2001 and December 2003. Sixty-one implants were placed in fresh extraction sites, and 28 were placed in healed sites. Criteria to evaluate success rate were previously described by Albrektsson and Zarb (1993). After follow-up evaluation, 87 implants fulfilled the success rate criteria (95,6%). Four implants were lost, and among these, three were placed in fresh extraction sites (success rate 95,2%), and one placed in healed sites (success rate 96,4%). Rates of success between both groups was not statistically significant (p=0,76, Qui-square test). Within the limitation of the present study, it could be concluded that single-tooth osteointegrated implants submitted to immediate loading, in immediate and non-immediate implantation, represent a therapeutic alternative with high predictability, compared to the conventional protocol.
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Lacroix, Daniel. "Behaviour of Light-frame Wood Stud Walls Subjected to Blast Loading." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24339.
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Deliberate and accidental explosions along with the heightened risk of loss of life and property damage during such events have highlighted the need for research in the behaviour of materials under high strain rates. Where an extensive body of research is available on steel and concrete structures, little to no details on how to address the design or retrofitting of wood structures subjected to a blast threat are available. Studies reported in the literature that focused on full scale light-frame wood structures did not quantify the increase in capacity due to the dynamic loading while the studies that did quantify the increase mostly stems from small clear specimens that are not representative of the behaviour of structural size members with defects. Tests on larger-scale specimens have mostly focused on the material properties and not the structural behaviour of subsystems. Advancements in design and construction techniques have greatly contributed to the emergence of taller and safer wood structures which increase potential for blast threat. This thesis presents results on the flexural behaviour of light-frame wood stud walls subjected to shock wave loading using the University of Ottawa shock tube. The emphasis is on the overall behaviour of the wall subsystem, especially the interaction between the sheathing and the studs through the nailed connection.
The approach employed in this experimental program was holistic, where the specimens were investigated at the component and the subsystem levels. Twenty walls consisting of 38 mm x 140 mm machine stress-rated (MSR) studs spaced 406 mm on center and sheathed with two different types and sheathing thicknesses were tested to failure under static and dynamic loads. The experimental results were used to determine dynamic increase factors (DIFs) and a material predictive model was validated using experimental data. The implications of the code are also discussed and compared to the experimental data.
Once validated, an equivalent single-degree-of-freedom (SDOF) model incorporating partial composite action was used to evaluate current analysis and design assumptions. The results showed that a shock tube can effectively be used to generate high strain-rate flexural response in wood members and that the material predictive model was found suitable to effectively predict the displacement resulting from shock wave loading. Furthermore, it was found that current analysis and design approaches overestimated the wall displacements.
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Awang, Draup Awang Jefri. "Numerical simulation of the structural response of friction stir welded aluminium 2139-T8 alloy subjected to complex loading configurations." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/numerical-simulation-of-the-structural-response-of-friction-stir-welded-aluminium-2139t8-alloy-subjected-to-complex-loading-configurations(a840bd28-102d-4c15-be6c-b4e72631e875).html.
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Friction stir welding (FSW) and aluminium alloy 2139-T8 are currently being considered for use in future military vehicles. However, stringent regulations on weld integrity under extreme loading conditions limit the adoption of new technologies. Moreover, current finite element (FE) based methods do not give reliable predictions of strain distribution in welds, which makes it difficult to assess the performance of structures. Therefore, an extensive research program was carried out to develop a generalised finite element (FE) based methodology to predict the response of welded structures under complex loading configurations. The methodology enables the complex distribution of mechanical properties arising from welding, which is linked to microstructural variation, to be incorporated into a macro scale structural model. The method is general, and is applicable for any heat treatable aluminium alloy under a range of joining processes. To achieve this, the microstructure of 2139-T8 alloy was characterised at a range of length scales, with particular emphasis on the size and distribution of strengthening Omega precipitates. 2139-T8 was subjected to bead on plate FSW to enable characterisation of the effects of processing on the local microstructure. In addition, kinetic data for 2139-T8 was generated, allowing a simple softening model to be developed; this allowed the post-weld strength distribution to be predicted. The model was also used to recreate bulk specimens of 2139-T8 with equivalent local weld microstructure, which was verified by transmission electron microscopy. Material with equivalent microstructure was used to estimate the local mechanical property distributions across the weld, including the initial yield stress and plastic response; the mechanical properties of 2139-T8 are known to be representative of 2139-T84. From observations of this combined data, a methodology was developed to enable the estimation of the complex mechanical property distributions arising during welding. Furthermore, an automated computer program was written to implement the property distributions into FE based models. The methodology was verified using data generated for 2139-T8 and was used to simulate the response of FSW 2139-T8 loaded in uniaxial tension. The simulations were verified experimentally using digital image correlation (DIC) and the methodology was shown to demonstrate increased accuracy and reliability over existing FE methods, with respect to strain predictions. In addition, the method eliminates the need to calibrate the structural model to a particular loading configuration. Theoretically, the models are insensitive to loading and this property was tested by extending the model to simulate the strain distribution of large scale welded panels subject to explosive blast loading. The simulations were verified against blast tests where FSW 2139-T84 panels were subjected to blast loading from the detonation of plastic explosive. The results indicate that the modelling methodology developed is capable of producing accurate and reliable predictions of strain distribution in welded structures under complex loading configurations.
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Yurtoglu, Mine Ender. "Mode Ii Fatigue Crack Growth Behavior And Mode Ii Fracture Toughness Of 7050 Aluminum Alloy In Two Orientations." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615581/index.pdf.
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Fatigue crack growth behavior of AA7050 T7451 aluminum alloy under mode II loading condition in two orientations was investigated. Compact shear specimens were prepared in TL and LT directions. A loading frame for mode II type of loading was manufactured. Using the loading frame and the specimen, KIIC values and mode II fatigue crack growth rates were calculated.
Fractographic analysis of the fracture surfaces of both mode II fracture toughness test specimens and mode II fatigue crack growth test specimens were done to examine the effects of mode II load.
KIIC values were measured between 1.3 and 1.5 times the KIC values for this alloy. As for mode II fatigue crack growth rates, TL orientation shows the highest mode II fatigue crack growth resistance.
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Briani, Ronaldo Valdir [UNESP]. "Relação da loading rate da força vertical de reação do solo e do momento abdutor do joelho com a dor femoropatelar." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/150802.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O estudo da loading rate de alterações biomecânicas em indivíduos com dor femoropatelar (DFP) tem crescido recentemente. Justifica-se o estudo dessa variável pela sua relação com lesões degenerativas articulares de diversas articulações, principalmente do joelho. No entanto, poucos estudos foram realizados para entender a relação da loading rate de parâmetros globais, como a força vertical de reação do solo (FVRS), com a DFP. Além disso, não foram encontrados estudos que tenham investigado a loading rate de parâmetros específicos da articulação do joelho que estão relacionados com a DFP, como o momento abdutor do joelho (MAJ). Portanto, os objetivos gerais dessa dissertação foram investigar a relação da loading rate de parâmetros globais e locais com a DFP. A coleta dos dados biomecânicos foi feita durante os gestos de subida e descida escada, antes e após a aplicação de um protocolo de sobrecarga. Esse protocolo consistiu de 15 subidas e descidas de escada com 35% do peso corporal alocado em uma mochila e com ritmo demarcado por um metrônomo (96 degraus/min). A dor auto-reportada das participantes também foi obtida tanto antes quanto após o protocolo de sobrecarga. Também foi solicitado que as participantes reportassem a dor referente ao mês anterior. No geral, nossos resultados mostraram relação entre a loading rate da FVRS e do MAJ com a DFP. Portanto, intervenções específicas devem ser aplicadas nessa população com o intuito de corrigir essas alterações e, consequentemente, diminuir a dor.
The study of the loading rate of biomechanical alterations in individuals with patellofemoral pain (PFP) has increased recently. One justify the study of this variable because of its relation with articular degenerative injuries, mainly at the knee. However, few studies have been done to understand the relation between the loading rate of the vertical ground reaction force (VGRF) and PFP. In addition, no studies were found in order to investigate the loading rate of specific parameters at the knee joint that are related to the PFP, such as the knee abductor moment (KAM). Therefore, the aims of this dissertation were to investigate the relation between the loading rate of local and global parameters with PFP. Data collection was performed during stair ascent and descent , before and after a loading protocol. The protocol consisted of 15 stair ascent and descent trials with 35% of the body weight allocated in a backpack. The rhythm was controlled by a metronome at 96 steps/min. Self-reported pain was obtained before and after the loading protocol. The average pain level at the last month was also obtained before data collection. In general, our results showed a relation between the loading rate of the VGRF and KAM with PFP. Therefore, interventions should be applied in order to correct these alterations and, consequently, decrease pain.
FAPESP: 2015/00406-2
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Tawadrous, Ayman. "HARD ROCKS UNDER HIGH STRAIN-RATE LOADING." Thesis, 2010. http://hdl.handle.net/1974/8474.
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Understanding the behavior of geomaterials under explosive loading is essential for several applications in the mining and oil industry. To date, the design of these applications is based almost solely on empirical equations and tabulated data. Optimal designs require accurate and complete knowledge of rock behavior under various loading conditions.
The vast majority of the properties available in the literature have been gathered by deforming the specimen slowly. These properties have been used to establish constitutive models which describe the behavior of rocks under static and quasi-static loading conditions. However, the dynamic properties and material constitutive models describing the behavior of geomaterials under high strain-rate loading conditions are essential for a better understanding and enhanced designs of dynamic applications.
Some attempts have been made to measure dynamic properties of rocks. Also, some trials have been made to devise material models which describe the behavior of rocks and the evolution of damage in the rock under dynamic loading. Published models were successful in predicting tensile damage and spalling in rocks. However, there are no established models capable of predicting compressional damage in rocks due to dynamic loading.
A recently-developed model, the RHT model, was formulated to describe the behavior of concrete over the static and dynamic ranges. The model was also formulated to predict compressional damage based on the strain rate at which the material is subjected to. The RHT model has been used successfully in several applications.
The purpose of this research was to characterize one rock type as an example of a hard brittle rock. The physical properties of the rock as well as the static and dynamic mechanical properties were investigated. These properties were used to calibrate the RHT model and investigate its potentials to predict compressional damage in brittle materials.
The calibrated model showed good precision reproducing the amplitude of the strain signals generated by explosive loading. It was also capable of predicting compressional damage with acceptable accuracy. Unfortunately, due to implementation restrictions, tensile and spall damage could not be captured by the model. The duration and shape of the strain pulse were also poorly modeled.Thesis (Ph.D, Mining Engineering) -- Queen's University, 2010-12-22 17:54:05.887
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Ma, Shang-Chih, and 馬上智. "One-Dimensional Consolidation under Different Rate of Loading." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/10420773198945084759.
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