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1
Totty, Jennifer L. „Linear cellular copper in bending, compression and shear“. Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/16913.
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2
Shelton, Christopher Francis. „The mechano-sorptive creep of wood in bending“. Thesis, London South Bank University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329808.
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3
Heatwole, Edwin L. „Allowable bending strength enhancement of 2 by 4 lumber by tension and compression proofloading“. Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/53718.
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Research has established that correlations exist between bending and tension, and bending and compression strength of lumber. Because of this correlation, improvement in bending strength may be realized from proofloading in tension or compression.
The data utilized in a reliability analysis was from Galligan et al. (1986) that characterized the properties of 2-inch softwood dimension lumber with regressions and probability distributions. Randomly selected groups of 2 by 4 1650f-1.5E Hem-fir and No.2 KD Southern Pine were evaluated for bending strength. One group from each species was selected as a control and tested in bending. The other groups were proofloaded in tension and compression at two stress levels and the survivors were tested in bending to failure.
Based on the concept of equal reliability and utilizing the load distributions from Thurmond (1986), the tensile and compressive proofloaded strength distributions were compared to the control. The probability of failure for the control group is found, then with an iterative approach, the bending strength values of the proofloaded sample distribution are artificially altered by a factor K until the probabilities of failure for the proofloaded and control groups are similar. The K is a shift factor relating the amount the proofloaded strength distribution must be shifted on the x-axis to give the same reliability as the control.
Simple 5th percentile comparisons, the advanced first order second moment (AFOSM) and numerical integration analysis methods were used to evaluate increases in allowable bending strength from proofloading in tension and compression. Proofloading in tension or in compression both produced significant increases in allowable bending strength for the Hem-fir grade. Proofloading in tension to a target 15 percent breakage level, or 2,838. psi, yielded for the survivors an increase of 72 percent in allowable bending strength. The allowable bending strength increased 60 percent due to a compressive proofloading to a target 15 percent breakage level.
The allowable bending strength increased as the proofloading level increased for both tension and compression proofloading with the Hem-fir grade. The southern pine visual stress grade did not show a consistent trend between proofloading level and improvement in allowable bending strength. The lack of a trend between proofloading level and allowable bending strength was attributed to possible sampling error.
The fifth percentile analysis method, the AFOSM method and numerical integration method were compared. For lumber strength comparisons, a simple fifth percentile analysis was not the preferred method. The AFOSM method and the numerical integration method provided identical results in terms of their application in adjusting allowable bending stresses. It was not possible to show that the approximate AFOSM method can be used exclusively in lieu of the numerical integration method for reliability calculations.Master of Science
4
Svensson, Meulmann Sebastian, und Egzon Latifi. „Modelling and testing of CLT panels for evaluation of stiffness“. Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-104766.
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The use of timber in building structures is steadily increasing. cross laminated timber (CLT) is an engineered wood product made of an uneven number of layers of lamellas glued at an angle of 90 degrees to each other. This gives CLT high stiffness and strength to bending in all directions, and capability of taking load both in-plane and out-of-plane. Due to the large size of CLT elements, they allow for quick assembly of strong structures. Due to both economic and environmental reasons it is important for producers of CLT to optimize the use of the wood material by using the timber with higher stiffness and strength where it is most needed. This thesis is about evaluating the bending and shear stiffness of CLT elements, when used as plates, depending on the quality of wood used in the different layers. Four-point bending tests are carried out on elements of different compositions and a parametrized finite element model is created. Thus, the model is validated on the basis of experimental tests to evaluate the influence of different quality of different layers. The measured dynamic MoE proved to have good potential to be used as the longitudinal bending stiffness in an FE-model, with a deviation from the experimental tests of less than 1%. There is a strong correlation between the bending stiffness and bending strength of the plates. The effective rolling shear modulus in pine was calculated to be around 170 MPa for pine of dimension 40 x 195 mm2 . Grading the boards into two different classes used for different layers proved to increase the MoE of the plates by 11-17% for 3- and 5-layer CLT.
5
Olofsson, Kenneth. „Non destructive testing of paper products and tubes using transient bending waves“. Licentiate thesis, Luleå tekniska universitet, 1992. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17165.
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Fagergren, Fred Stile. „Using Non-Destructive Testing to Predict Bending Modulus of Carbon Infiltrated-Carbon Nanotubes“. BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/8817.
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Fabrication of carbon infiltrated carbon nanotubes (CI-CNT) can result in large mechanical property variation, and methods to characterize properties usually involve destructive testing. Finding a non-destructive way to test for stiffness of this material reduces the number of parts that have to be made. It also simplifies testing of complex parts. The stiffness of CI-CNT beams is related to the type of carbon material infiltrated between the carbon nanotubes (CNTs), how it interacts with the CNTs, and how much of it there is. The amount of material can be estimated using the density of the beam, and both the type of material and its interaction with the carbon nanotubes can be approximated through analysis of the Raman spectra taken at the surface. A combination of these two observations can be related to the effective material stiffness. The relationship can be fitted with a power function, with a variance of 1.41 GPa, which is about 11% of the maximum stiffness of the samples tested. This variance is similar to the larger variations in CI-CNT beam stiffnesses found in a single batch of beams.
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Maguire, Marcus J. „Transverse and Longitudinal Bending of Segmental Concrete Box Girder Bridges“. Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23670.
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Post-tensioned segmental concrete box girders have been in use in the United States since the early 1970s. This unique bridge system uses post-tensioning to connect many smaller concrete bridge segments into very efficient long span bridges. However, because of the slender components, localized transverse bending becomes more critical when compared to more conventional bridge types. Bridge owners are finding that ratings for standard loads and permit trucks are often controlled by the transverse behavior of the girders near concentrated wheel loads. The popular analysis methods used today range from two dimensional frame models to three dimensional finite element models of the entire bridge. Currently, engineers must make sound engineering judgments on limited available information, while balancing safety and economy. To quantify and understand longitudinal and transverse behavior, the results from three live load tests of single cell segmental concrete box girder bridges are presented. Each bridge was instrumented with longitudinal and transverse strain sensors on at least two cross sections as well as rotation and deflection sensors, when possible. Two dimensional transverse frame models and three dimensional shell models were compared to the test results for each subject bridge. The two dimensional frame analyses using the common bottom web pin and roller boundary conditions provide mean absolute percent error in excess of 250%. Conversely, the newly introduced boundary conditions using pin supports at the top and bottom of each web was shown to reduce mean absolute percent error to 82%, which is on the same order of magnitude as longitudinal beamline analysis.
The three dimensional shell models were insensitive to several changes including mesh fineness, number of spans modeled, and support conditions. Using uniform surface loading, the transverse modeling procedure was shown to provide significantly more accurate results than the common two dimensional frame models. A faster and more convenient analysis method using a program generated, structure specific, influence surface was also outlined. This method produced similar results when compared to the uniform surface loading method, while allowing additional automation for easier load application.
Ph. D.
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Cornwell, Matthew Allen. „Determination of the bending stiffness of copy paper and its dependence on temperature and moisture using laser ultrasonic lamb waves“. Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/19636.
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Bing, Julie Ann. „Pediatric Lower Extremities: Potential Risks and Testing Concepts“. The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313515676.
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Gex, Dominique. „Ultrasonic NDE testing of a gradient enhanced piezoelectric actuator (GEPAC) undergoing low frequency bending excitation“. Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-04062004-171807/unrestricted/gex%5Fdominique%5Fc%5F200405%5Fmast.pdf.
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Thesis (M.S.)--Mechanical Engineering, Georgia Institute of Technology, 2004.Berthelot, Committee Chair; Lynch, Committee Member; Jacobs, Committee Member. Includes bibliographical references (leaves 111-113).
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Moussiaux, Eric. „Bending of a bonded beam as a test method for adhesive properties“. Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/45759.
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A strength of materials type solution is obtained for the shear stress state in the adhesive layer of a bonded cantilever beam subjected to an end load.
The shear stress is constant through the thickness of the adhesive layer and varies from zero at the fixed end to a maximum value at the free end. This maximum value can, under certain conditions, be calculated from knowledge of the load and the beam geometry only. The adhesive's shear modulus can then be determined from a measurement of the shear strain in the adhesive layer.
An expression for the beam deflection is also obtained. It contains a coefficient of adhesion which is potentially useful to evaluate surface treatments or other factors leading to different states of adhesion.
Fracture mechanics application of the specimen, nonlinear and viscoelastic adhesive behavior are briefly mentioned.Master of Science
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Wallace, Robert James. „Effect of strain rate and bone quality on the bending behaviour of whole bone“. Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/9499.
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Forty ovine femurs were harvested and allocated into four testing groups; Fast-Normal, Fast- Decalcified, Slow-Normal, Slow-Decalcified. Contralateral pairings were used within these groups for closer comparison. Dynamic testing apparatus was designed and built allowing rates of strain similar to road traffic accidents to be investigated. These strain rates were achieved by using a pneumatic actuator to apply the load. Slow rate loading was achieved by testing with a commercially available mechanical testing machine at a rate of strain similar to that created by walking. Bone quality was altered by ultrasonically assisted decalcification in EDTA. Levels of mineral dissolution equivalent to the loss of bone mineral density (BMD) of a 75 year old woman were targeted. Whole bone was used for these experiments to facilitate comparison with real fracture radiographs obtained from NHS database. Fracture patterns and degree of comminution were similar between experimental and patient data. Bone is often analysed as a simple beam (engineers bending theory). This method of stress analysis was compared with a method that recognised the change in cross section over the length of the bone. Accounting for this had a highly significant effect on the calculated flexural modulus (p<0.0005).The length to depth ratio of whole bone indicates that shear forces cannot be ignored. The effect of the contribution from shear force on the deflection was investigated. After accounting for deflections due to shear, calculated normal strains agreed with literature values. Deflection due to shear was found to make a significant contribution to the deflection The effect of storage (freezing) on the mechanical properties at high strain rate was evaluated: no significant differences were found for force and deflection at failure. The main body of testing gave the following results: Normal quality bone, rate compared showed significant differences for Ultimate Stress, Ultimate Strain, Yield Strain, Flexural Modulus and Toughness. Demineralising bone resulted in no statistically significant differences between the loading rates for the Stress at failure. Yield Strain, Ultimate Strain, Flexural Modulus and Toughness did show significant differences. The fast loading tests showed significant differences when comparing quality for Stress at failure but not at Yield. Significant differences were found when comparing toughness. Slow loading tests showed significant differences between bone qualities for Stress at failure in contralateral pairs. No significant differences were found for strain or toughness. These results indicate that bone of normal quality can withstand higher than normal stresses for short durations. This ability is lost in demineralised bone. The high loading rate tests revealed closely matched strains at failure for both bone qualities, lending support to the strain based failure theory for bone at traumatic strain rates.
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King, Carin Palmer. „Methods development of multimodal loading under bending, compression and torsion for bench-top testing of cardiovascular stents“. Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83723.
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Thesis (S.B.)--Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (page 30).
This thesis describes a method for setting up, testing and analyzing cardiovascular stents in multiple deformation modes. Testing stents in multiple deformation modes, including bending, torsion and compression simultaneously is a novel technique. Specific details are provided on strategies for inserting a stent sample into the testing apparatus such that stent integrity is preserved. Using a dynamic feedback cycle for buffered video capture we have been able to document sequential fracture events during testing scenarios. Stereomicroscopy further allows us to detect and determine placement of stent fracture. This method will help stent designers to create stents that are more likely to stand up to the particular conditions they will face in the body and regulatory agencies to determine how well potential new stents will fair under physiologic conditions.
by Carin Palmer King.
S.B.
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Craig, Bruce A. „Comparison of creep/duration of load performance in bending of Parallam® parallel strand lumber to machine stress rated lumber“. Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26194.
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A comparison of the creep/duration of load (DOL) performance of a new structural wood composite material called Parallam® parallel strand lumber (PSL) to two grades of machine-stress-rated (HSR) Douglas-fir lumber is presented in this thesis. Evaluation of the creep/DOL performance was made on nominal 2x4 members under constant bending stress at three stress levels. A total of 306 test specimens were evaluated for a 15-1/2 month time period.
The analysis suggests that the duration of load effect for Parallam PSL was consistent with the Madison curve for the time period studied while the MSR Douglas-fir lumber was consistent with recent duration of load models developed for structural lumber. The analysis also indicates that the current duration of load adjustment factors can be applied to develop working stresses for Parallam.
The creep behaviour of the Parallam PSL was found to be equivalent or better than the two MSR lumber grades under dry-service conditions. Furthermore, evidence of linear viscoelastic behaviour was found for all test materials within the range of applied stresses evaluated. Two mathematical models of creep were fitted to the creep data and compared. A '4-parameter linear viscoelastic' model fitted the creep data better than an empirical 'power curve' model. The model parameters developed provide a basis for estimating the mean creep behaviour and variability in creep response for these materials under in-service load conditions for dry-service environments.Forestry, Faculty of
Graduate
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Areir, Milad. „Development of 3D printed flexible supercapacitors : design, manufacturing, and testing“. Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/16659.
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The development of energy storage devices has represented a significant technological challenge for the past few years. Electrochemical double-layer capacitors (EDLCs), also named as supercapacitors, are a likely competitor for alternative energy storage because of their low-cost, high power density, and high fast charge/discharge rate. The recent development of EDLCs requires them to be lightweight and flexible. There are many fabrication techniques used to manufacture flexible EDLCs, and these methods can include pre-treatment to ensure more efficient penetration of activated carbon (AC) patterns onto the substrate, or those that utilise masks for the definitions of patterns on substrates. However, these methods are inconvenient for building cost-effective devices. Therefore, it was necessary to find a suitable process to reduce the steps of manufacture and to be able to print multiple materials uniformly. This research work describes the first use of a 3D printing technology to produce flexible EDLCs for energy storage. In this research work, the four essential elements for the EDLCs substrate, current collector, activated electrode, and gel electrolyte were investigated. The AC powder was milled by ball milling to optimise the paste deposition and the electrochemical performance. A flexible composite EDLC was designed and manufactured by 3D printing. The electrochemical performance of the flexible composite EDLCs was then examined. Being highly flexible is one of the critical demands for the recent development of EDLCs. Therefore, highly flexible EDLCs were designed and manufactured by only one single extrusion process. The 3D highly flexible EDLC maintains significant electrochemical performance under a mechanical bending test. To meet the power and energy requirements, the EDLCs were connected and tested in series and parallel circuits. A supercapacitor based on printed AC material displays an area specific capacitance of 1.48 F/cm2 at the scan rate of 20 mV/s. The coulombic efficiency for the flexible EDLC was found to be 59.91%, and the cycling stability was achieved to be 56% after 500 cycles. These findings indicate that 3D printing technology may be increasingly used to develop more sophisticated flexible wearable electronic devices.
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Poggi, Francesco. „Bending properties of commercial wood-based panels by NDT methods“. Thesis, Linnéuniversitetet, Institutionen för skog och träteknik (SOT), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-66162.
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This thesis work focuses mainly on the application of non-destructive testing (NDT) methods on wood-based panels (WBP) in order to estimate the bending properties. To prove the accuracy and applicability of these methods on WBP, their results are correlated with results from a standardized static bending test. The behavior in different climate conditions and the application on panels of larger sizes is also questioned to provide an indication about strong points and boundaries of NDT methods applied on WBP.The bending properties are of major importance, especially for materials suited to bear loads. Bending stiffness, represented by the modulus of elasticity (MOE), is an expression of the deflection rate of a material under load. The bending strength, represented by the modulus of rupture (MOR), is an expression of the maximum load withstood by a material before rupture.Before testing, the material is acclimatized in three climate conditions: dry (20°C, 35% RH), standard (20°C, 65% RH) and wet (20°C, 85% RH), to understand the bending properties variation and how the NDT methods are affected by the variation in moisture content.The materials used are seven types of WBP, in particular four types of particleboards (PB), one type of high-density fiberboard (HDF), one type of dual density PB (with high and low density areas along the production direction) and one type of light-weight panel (Board-on-stiles, a composite panel of HDF, PB and paper honeycomb).To test the bending properties the following NDT methods are considered: transversal resonance vibration and longitudinal resonance vibration with the use of the BING system and the time-of-flight with the use of Fakopp Ultrasonic Timer and Silvatest Trio. The resonance vibration methods, transversal and longitudinal, are based on the relation between resonance vibration properties and bending properties of a material. The relation with bending properties also exists for the stress wave velocity (SWV) through a material, calculated with the time-of-flight method. The dynamic MOE resulting from these tests is then correlated with the static MOE and MOR from the static bending test.The NDT methods resulted to be reliable on WBP, with generally high levels of correlation between dynamic MOE and static MOE and MoR. The highest correlation value for MoE is with the transversal resonance vibration while the highest for MOR is with the longitudinal resonance vibration. The results of the dynamic MOE for all the NDT methods are higher than the static MOE, as confirmed also in the literature; the average ratio between the dynamic and the static MOE is, for example, up to 1,6 for WBP in standard climate condition, tested with Fakopp U.T.. These results are extremely higher than values suggested by previous studies. Moreover, the ratio increases with increasing relative humidity of the climate condition. The results from the tests on larger sizes suggest a possible application in this field. The time-of-flight method is suitable for in-plane uniform materials, like the PB and HDF, while the transversal resonance methods give also a good representation of the properties of the dual density PB and the light-weight panel.
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Thorne, Robert. „Mechanical Response Tissue Analysis: Inter- and Intra-trial Reliability in Assessing Bending Stiffness of the Human Tibia in College Aged Women“. Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/35568.
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Mechanical Response Tissue Analysis (MRTA) is an emerging technology for assessing maximal bending stiffness (EI) of human long bones in vivo. The MRTA variable, EI, is the product of Young's modulus of elasticity (E) and cross-sectional moment of inertia (I). EI quantifies material and architectural/geometric properties of bone. Published human research using MRTA to measure EI has been limited to the ulna; however, the tibia requires further investigation due to its central involvement in many human activities and exercise-related clinical problems, e.g. stress fracture of the lower leg. To evaluate the inter- and intra-reliability of tibial EI, 22 healthy women (X + SD: 20.8 + 1.8 yr) were assessed twice daily for three non-consecutive days. Each daily session consisted of five repeated trials. The ulnar EI protocol of McCabe et al. [J Bone and Mineral Res. 1991;6(1):53-59] was adapted to assess tibial EI via MRTA. A significant difference was not found in scores for five repeated trials taken consecutively on the same day. Mean scores for EI were higher on day 1 (59.1 ± 35.5 N·m2, p < 0.05), compared to day 2 (46.9 ± 22.3) and day 3 (49.9 ± 18.3). Individual trial mean scores for EI on each day (mean of 5 trials) were highly correlated, R2 = 0.84, 0.62, and 0.79 (set 1 vs. 2, for day 1,2,3, respectively) and the average percent change between sets 1 and 2 on each day was 5.3. The inter-test (between day) reproducibility was found to be low and unacceptable, 11.7, 18.3, and 1.3%, for day 1 vs. 2, 1 vs. 3, and 2 vs. 3. Poor inter-day reliability may be a result of the inability, at the time of this study, to apply the best computational EI model. It is concluded that tibial bone stiffness measurements with the MRTA are in the range of acceptability for same day inter- and intra-trial reliability when the 7-parameter analytic model of vibratory properties developed by McCabe et al. is used.Master of Science
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Rodomsky, Caitlyn Marie. „Surface Finish on A356-T6 Cast Parts using Additive Manufactured Sand Molds“. Youngstown State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1526030093287334.
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Robertson, Galen Charles. „Quantification of Skeletal Phenotype Using Micro-CT and Mechanical Testing“. Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4874.
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With the vast array of genetically altered (knockout) mice becoming available there is a need for quantitative, repeatable, and efficient methodologies to characterize the phenotypic consequences of knocking out specific genes. Since knockout animals often have the ability to compensate for a single missing gene, it is important to examine the structural, material and morphological properties to obtain a thorough understanding of the changes occurring. For this project, femurs of knockout mice were first scanned using microcomputed tomography (micro-CT) to obtain high-resolution images of the trabecular bone in the distal femur, as well as cortical bone in the mid-diaphysis. After scanning, the femurs were tested to destruction in four-point bending at the mid-diaphysis about the medial lateral axis of the femur. These methodologies allowed quantification of (1) morphologic properties such as bone volume fraction, trabecular properties and 2nd moment of the area (2) structural properties such as stiffness, maximum load at failure, and post yield deformation and (3) material properties such as bone mineral density, elastic modulus and yield strength.
As part of two independent studies, two different knockout mice, cyclooxygenase-2 (COX-2 -/-) and Apolipoprotein E (APOE -/-), were examined for structure-function relationships using these methodologies. COX-2 knockout mice were found to have decreased mineral content in their femurs, and increased post yield deformation. APOE knockout mice at 10 weeks of age had decreased bone mass and structural properties. However, by 40 weeks of age APOE deficient mice caught up to and exceeded the structural properties and bone mass of their wild type counterparts.
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Sim, Lay M. „Design, manufacturing and testing of smart beams with EFPI strain sensor for damage detection“. Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/13207.
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This thesis aimed at the development of a fibre optic strain sensor-based damage detection and evaluation system (FODDAS) based on the composite beams. EFPI strain sensors were used with their integrity being assessed. Their performance, either bonded on the surfaces or embedded was examined extensively. They were shown to be adequate and reliable for strain measurements. Through-the-width damages were simulated by artificially-embedded delaminations, which were located at several through-the-thickness locations, each with two different sizes. The overall design considerations were guided by ply stresses and strains which were estimated by using the modified classical lamination theory (CLT). Considerable efforts were devoted to assessing the through-the-thickness mechanical behaviours of the beams containing optical fibres in three-point bending and short beam shear (SBS). They involved various optical fibre orientations with respect to 00 plies / longitudinal axis and at various through-the-thickness locations, each with different number of optical fibres. The understanding of these behaviours paved the way for the evaluation of the beam-based FODDAS. Smart preconditioned beams were subjected to the quasi -static loads whose magnitudes and locations were required to be well controlled. The viability and effectiveness of the beam-based FODDAS was evaluated in terms of strength and strain obtained by the embedded sensor as well as the surface-bonded strain gauges via the cross comparison of ten cases. For the strength, each beam was incrementally loaded up to the ultimate failure either in three-point bending or SBS. After each increment, the beam was unloaded and inspected for damage. For the given locations of EFPI-SS and artificial delamination as well as the sizes of the latter, it was found that the embedded EFPI-SSs were capable of picking up the stiffness degradation when the 10- mm as well as the 20-mm delamination was located at the 29-30 ply interface in the tensile region of a 32-ply quasi-isotropic carbon/epoxy smart composite beam. It was speculated from single tests results that the propagation of the embedded delamination of the sufficient size was able not only to be detected but also to be monitored by the sensors.
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Drivas, Thanos. „Manufacturing Three-dimensional Carbon-fibre Preforms for Aerospace Composites“. Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31577.
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Carbon fibre reinforced polymer matrix composites (CF PMCs) are increasingly used in state-of-the-art aerospace applications. Aerospace manufacturers favour components made of CF PMCs over those made of traditional metallic alloys because of their light weight and corrosion resistance, which lead to significant improvements in fuel consump- tion, increased payload capability, and reduced maintenance and inspection costs. How- ever, manufacturing of CF PMC components is performed differently than traditional material in all stages – design, prototyping and production – and therefore, many com- mercial manufacturers have only recently begun producing components with CF PMCs.
The first half of this thesis was written as a contribution to the CRIAQ COMP-501 project, which focusses on investigating the cost-effective procurement of airframe com- ponents that are manufactured from final-thickness, net-shaped, and through-thickness reinforced CF preforms. Reinforcement preforms were assembled from commercial 2D woven fabric using stacks of various configurations of structural through-thickness CF stitch. The contribution herein provides the results obtained from investigations into the mechanical behaviour of the relevant reinforcements, when subjected to pre-infusion op- erations typical to RTM VARTM; mechanical behaviour in compaction, shear (draping) and bending (forming).
The second half of this thesis presents the major developments which were made to an alternative process for producing thick 3D preforms with great versatility, a process originally proposed as a candidate for supplying preforms to the COMP-501 project. This process interfaces a proprietary kinematic drape optimization (CAD) software with proprietary automated dry fibre placement assembly (CAM) machinery to produce vari- able or final-thickness reinforcements which are highly-drapable and can lay steered tow yarns.
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Abdullah, A. B. M. „Development of a Closed-loop Resonant Fatigue Testing Methodology and Experimental Life Test of Aluminum Alloy“. University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1289328504.
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Hausfeld, Gabrielle Christine. „Comparison of Cortical Porosity, Diameter, and Stiffness as Predictors of Ulna Bending Strength“. Ohio University Honors Tutorial College / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1429886070.
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Arnold, Patricia A. „Validation of Mechanical Response Tissue Analysis by Three-Point Mechanical Bending of Artificial Human Ulnas“. Ohio University Honors Tutorial College / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1366983271.
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Derrick, Nathan Lynn. „Shear and Bending Strength of Cold-Formed Steel Solid Wall Panels Using Corrugated Steel Sheets for Mobile Shelters“. Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1062814/.
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The objective of this thesis is to determine if the single sided resistance spot weld (RSW) can be used as a feasible connection method for cold formed steel (CFS) shear walls subject to lateral force of either seismic or wind loads on mobile shelters. The research consisted of three phases which include: a design as a 3D BIM model, connection tests of the resistance spot weld, and full-scale testing of the designed solid wall panels. The shear wall testing was conducted on specimens with both resistance spot weld and self-drilling screws and the results from tests gave a direct comparison of these connections when the solid wall panel was subjected to in-plane shear forces. The full-scale tests also included 4-point bending tests which was designed to investigate the wall panel's resistance to the lateral loads applied perpendicularly to the surface. The research discovered that the singled sided resistance spot weld achieved similar performance as the self-drilling screws in the applications of CFS wall panels for mobile shelters. The proposed single sided resistance spot weld has advantages of low cost, no added weight, fast fabrication, and it is a feasible connection method for CFS wall panels.
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Režnáková, Ema. „Příprava a charakterizace lehčených polymerních materiálů s hierarchickou celulární strukturou“. Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2020. http://www.nusl.cz/ntk/nusl-414127.
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The asymmetrical arrangement of cellular structure allows for an accurate functional adaptation at all levels of hierarchy, which derives excellent features for the development of new materials. The main objective of introducing a hierarchy into cellular structures is to improve the mechanical behaviour of the material while maintaining its elastic properties. A part of this work is devoted to the literature review related to the lightened cellular polymeric materials with hierarchical cellular structure. The rest is focused on the preparation of PLA based polymer structures using 3D printing, followed by a saturation in CO2 and a foaming in a silicon oil at elevated temperature. Samples were prepared from natural and white PLA filaments. Based on a series of experiments, optimal conditions for the saturation and foaming process were identified. Through 3D printing and foaming, a one-, two- and three-level hierarchy was introduced into the beam-shaped samples and the effect of the internal cell arrangement on the strain response of the material was examined by the means of a mechanical three-point bending test. Increasing the level of the hierarchy led to an increase in material resistance, which resulted in high values of strength and strain energy (toughness) based on the samples density. The best results were achieved by samples with “sandwich” structure with three levels of hierarchy and 30% filling. Despite the shorter plateau, there was a significant increase in strength and strain energy compared to gradient structures. At the same time, the contribution of the polymer structures prepared in this field of research was demonstrated by comparison with the theoretical model.
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Béjar, Luis Miguel. „CORROSION-FATIGUE TESTING ON STEEL GRADES WITH DIFFERENT HEAT AND SURFACE TREATMENTS USED IN ROCK-DRILLING APPLICATIONS“. Thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-194524.
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Corrosion fatigue is a common failure mechanism in rock drilling components and many othermechanical parts subjected to cyclic loads in corrosive environments. A crucial part in the design ofsuch components resides in the selection of the right materials for the application, which ideallyinvolves testing and comparison of their performance under working conditions. The present work was performed with the purpose of designing a corrosion-fatigue testing methodthat would allow the designer to compare the performance of different materials exposed to corrosionfatigue, permitting also the comparison with results from dry fatigue testing. The method was designedfor rotating-bending machines. Two different steel grades were used during the work, one throughhardened and one case hardened. The effect of these heat treatments and of shot peening overcorrosion-fatigue behaviour were studied using the proposed method. It was proven that the testing speed has a strong impact on the fatigue life of steel. It was found that,at a fixed stress level, the case hardened and shot peened steel reached 3X10^6 cycles at 2300 rpm,while it failed at only 5X10^5 cycles with a testing speed of 500 rpm. A large beneficial influence of theshot peening was demonstrated. It was also observed that, at fixed testing speed, the shot peening onthe through hardened steel can increase its fatigue strength from 190 MPa to 600 MPa under corrosionfatigue. Many cracks were found at the surface of the shot peened parts, which are arrested near thesurface by the compressive stress layer from the shot peening. It was also found that, for the non-shotpeened parts, case hardening had a slightly higher corrosion-fatigue strength than the throughhardened. This might be a result of the compressive stresses from carburization, or due to the highercore toughness of this steel grade.
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Lantz, Josephine. „Mechanical Properties of Calcium Phosphate and Additively Manufactured Titanium Alloy for Composite Spinal Implants“. Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-296636.
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One of the major health problems in western societies is back pain, with a prevalence rate of 49%–80%. In many cases, the back pain is due to degenerated discs. The gold standard to treat a severely degenerated disc is spinal fusion, where the vertebral disc is replaced with a cage structure. However, fusion cages have a failure rate of 30%, hence the need for further development. The focus of this thesis is to evaluate the combination of calcium phosphate cement with titanium, for a spinal application. Mechanical tests in the form of tensile, compression and 4-point-bending were performed to study the different material properties. The obtained results was applied as material parameters for isotropic linear elastic material models, using ANSYS. This was then used to develop a cage design through topology optimisation which was further evaluated by using Finite Element Analysis. From the tensile testing of the titanium, isotropic behaviour was found. It was also found that a longer mixing time of the cement resulted in poorer mechanical properties of the calcium phosphate, however, no conclusive results were obtained from the 4-point-bending tests. The final cage geometry filled with calcium phosphate was tested under compression to see whether the cage could protect the calcium phosphate or not. MicroCT after the test confirmed that no larger cracks developed during the testing, suggesting that the cage is strong enough to protect the calcium phosphate from mechanical failure.
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Běloch, Martin. „Optimalizace předúpravy povrchu oceli a hliníkové slitiny pro následnou aplikaci práškové barvy“. Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-444543.
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This diploma thesis deals with various procedures of surface pretreatment of steel and aluminum alloy for subsequent application of powder coating substance. The work begins with an overview of the general characteristics of the materials used. The core part of the work is then a summary of the individual methods of pretreatment that can be used to modify the material surface. A special chapter is devoted to methodologies for the application of powder substances. Before separate application, the sample must first be carefully pretreated to ensure removal of organic compounds (e.g. oils from primary processing - grinding, cutting), or dust impurities to ensure the correct barrier effect. After dividing the individual methods of surface preparation, a powder paint system with a total thickness of approximately 50 µm is applied to the test material. Samples with different surface pretreatments will be compared both in terms of mechanical properties and in terms of electrochemical properties.
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Pais, Luís Carlos da Rocha Carneiro. „Recuperação de máquina universal de ensaios para uma nova especialização em testes de fadiga“. Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/17001.
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Mestrado em Engenharia MecânicaAtualmente, o estudo do comportamento à fadiga dos materiais tem um importante papel no mundo da engenharia. O Departamento de Engenharia Mecânica da Universidade de Aveiro recebeu recentemente uma máquina universal de ensaios que estava inoperacional. O objetivo deste trabalho foi recuperar e adaptar a máquina à realização de ensaios de fadiga. Inicialmente, procedeu-se a uma revisão do estado do conhecimento relativamente aos tipos de carregamentos cíclicos e aos componentes e dispositivos usados nas máquinas de fadiga. Posteriormente, avaliou-se o estado dos componentes da máquina e realizaram-se algumas transformações e acrescentos às partes mecânica, elétrica e de controlo com a finalidade de tornar a máquina funcional. Finalmente, para efeitos de validação, realizou-se um ensaio à flexão que mostrou que a máquina está apta para realizar ensaios de fadiga.
Fatigue testing has nowadays an important role in engineering. The Department of Mechanical Engineering of the University of Aveiro was recently offered a non-operational universal testing machine. The objective of this work was to recover the machine and to adapt it to fatigue tests. Initially, a state-ofthe- art review was conducted focussing on the types of cyclic loadings and on components and fixtures used in fatigue testing machines. Then, after evaluating the functionality of the machine components, several modifications were made and new components were added to the mechanical, electrical and control parts. Finally, for assessment purposes, a flexural test was conducted which showed that the machine can be used to perform fatigue tests.
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Leite, Pinto Rodrigo. „Caractérisation physique et thermo-mécanique et analyse de fiabilité des fibres optiques à base de silice“. Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S125.
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Les fibres optiques sont de plus en plus utilisées aujourd’hui dans des installations dédiées aux réseaux de télécommunications. Un coût de production bas, faible atténuation (en db/km) et qualité de signal exceptionnel font des fibres optiques une solution privilégiée aujourd’hui pour les fournisseurs d’accès internet. Une fois installées, les fibres optiques peuvent être soumises à des contraintes mécaniques, thermiques et chimiques qui affectent leur intégrité structurelle et qui réduisent leur durée de vie. Cette thèse a été effectuée dans le cadre d’une convention CIFRE et est focalisée sur l’étude du comportement de fibres optiques à base de silice en fonction de leur environnement de pose, et du calcul de leur durée de vie. Des essais de fatigue statique ont été menés dans des environnements divers. Nous avons ainsi analysé le comportement de nos fibres optiques dans de l’eau à température variable, dans l’air libre, ainsi que dans des environnements où température et humidité ont été fixées. Nous avons également étudié en détail les paramètres de corrosion et distribution des défauts le long de nos fibres à l’aide d’outils de fatigue dynamiques tels que la flexion deux points et la traction courte longueur. Nos résultats nous ont finalement permis d’étudier en détail deux modèles théoriques de calcul de durée de vie : le modèle de Mitsunaga, et le modèle d’ArrheniusOptical fibers are being increasingly used today by internet providers in networks dedicated to telecommunications. By being low-cost, low attenuation and by providing an excellent quality of optical signal, optical fibers are quickly becoming the number one choice in data networks worldwide. Once installed in ducts or alongside power-lines, optical fibers might easily be subjected to thermal, mechanical or chemical strains that can damage their structural integrity and lower their reliability. This PhD is part of an academic-industrial cooperative project and is focused on studying the behavior of silica-based optical fibers once installed in networks, and defining an method for calculating their lifetime. Static fatigue test have been made in various environments. We thus analyzed the behavior of our optical fibers once subjected to distilled water heated at different temperatures, to environments where temperature and humidity were varied, and to plain air. We also looked into the corrosion parameter alongside the defects distribution in our fibers by dynamic fatigue testing using a two-point bending and a short-length tensile testing bench. Our results allowed us to study the reliability of our fibers using two theoretical models available in the literature: Mitsunaga’s reliability model and Arrhenius’ crack-growth model
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Müller, Christoph. „Untersuchung von Holzwerkstoffen unter Schlagbelastung zur Beurteilung der Werkstoffeignung für den Maschinenbau“. Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-184057.
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In der vorliegenden Arbeit werden Holzwerkstoffe im statischen Biegeversuch und im Schlagbiegeversuch vergleichend geprüft. Ausgewählte Holzwerkstoffe werden thermisch geschädigt, zudem wird eine relevante Kerbgeometrie geprüft. Ziel der Untersuchungen ist die Eignung verschiedenartiger Werkstoffe für den Einsatz in sicherheitsrelevanten Anwendungen mit Schlagbelastungen zu prüfen. Hierzu werden zunächst die Grundlagen der instrumentierten Schlagprüfung und der Holzwerkstoffe erarbeitet. Der Stand der Technik wird dargelegt und bereits durchgeführte Studien werden analysiert. Darauf aufbauend wird eine eigene Prüfeinrichtung zur zeitlich hoch aufgelösten Kraft-Beschleunigungs-Messung beim Schlagversuch entwickelt. Diese wird anhand verschiedener Methoden auf ihre Eignung und die Messwerte auf Plausibilität geprüft. Darüber hinaus wird ein statistisches Verfahren zur Überprüfung auf ausreichende Stichprobengröße entwickelt und auf die durchgeführten Messungen angewendet. Anhand der unter statischer und schlagartiger Biegebeanspruchung ermittelten charakteristischen Größen, wird ein Klassenmodell zum Werkstoffvergleich und zur Werkstoffauswahl vorgeschlagen. Dieses umfasst integral die mechanische Leistungsfähigkeit der geprüften Holzwerkstoffe und ist für weitere Holzwerkstoffe anwendbar. Abschließend wird, aufbauend auf den gewonnenen Erkenntnissen, ein Konzept für die Bauteilprüfung unter Schlagbelastung für weiterführende Untersuchungen vorgeschlagenIn the present work wood-based materials are compared under static bending load and impact bending load. Several thermal stress conditions are applied to selected materials, furthermore one relevant notch geometry is tested. The objective of these tests is to investigate the suitability of distinct wood materials for security relevant applications with the occurrence of impact loads. For this purpose the basics of instrumented impact testing and wood-based materials are acquired. The state of the technology and a comprehensive analysis of original studies are subsequently presented. On this basis an own impact pendulum was developed to allow force-acceleration measurement with high sample rates. The apparatus is validated by several methods and the achieved signals are tested for plausibility. A general approach of testing for adequate sample size is implemented and applied to the tested samples. Based on the characteristic values of the static bending and impact bending tests a classification model for material selection and comparison is proposed. The classification model is an integral approach for mechanical performance assessment of wood-based materials. In conclusion a method for impact testing of components (in future studies) is introduced
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Ornek, Cem. „Performance characterisation of duplex stainless steel in nuclear waste storage environment“. Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/performance-characterisation-of-duplex-stainless-steel-in-nuclear-waste-storage-environment(4db73e9b-c87c-40a6-9778-0b823b1c499f).html.
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The majority of UK’s intermediate level radioactive waste is currently stored in 316L and 304L austenitic stainless steel containers in interim storage facilities for permanent disposal until a geological disposal facility has become available. The structural integrity of stainless steel canisters is required to persevere against environmental degradation for up to 500 years to assure a safe storage and disposal scheme. Hitherto existing severe localised corrosion observances on real waste storage containers after 10 years of exposure to an ambient atmosphere in an in-land warehouse in Culham at Oxfordshire, however, questioned the likelihood occurrence of stress corrosion cracking that may harm the canister’s functionality during long-term storage. The more corrosion resistant duplex stainless steel grade 2205, therefore, has been started to be manufactured as a replacement for the austenitic grades. Over decades, the threshold stress corrosion cracking temperature of austenitic stainless steels has been believed to be 50-60°C, but lab- and field-based research has shown that 304L and 316L may suffer from atmospheric stress corrosion cracking at ambient temperatures. Such an issue has not been reported to occur for the 2205 duplex steel, and its atmospheric stress corrosion cracking behaviour at low temperatures (40-50°C) has been sparsely studied which requires detailed investigations in this respect. Low temperature atmospheric stress corrosion cracking investigations on 2205 duplex stainless steel formed the framework of this PhD thesis with respect to the waste storage context. Long-term surface magnesium chloride deposition exposures at 50°C and 30% relative humidity for up to 15 months exhibited the occurrence of stress corrosion cracks, showing stress corrosion susceptibility of 2205 duplex stainless steel at 50°C.The amount of cold work increased the cracking susceptibility, with bending deformation being the most critical type of deformation mode among tensile and rolling type of cold work. The orientation of the microstructure deformation direction, i.e. whether the deformation occurred in transverse or rolling direction, played vital role in corrosion and cracking behaviour, as such that bending in transverse direction showed almost 3-times larger corrosion and stress corrosion cracking propensity. Welding simulation treatments by ageing processes at 750°C and 475°C exhibited substantial influences on the corrosion properties. It was shown that sensitisation ageing at 750°C can render the material enhanced susceptible to stress corrosion cracking at even low chloride deposition densities of ≤145 µm/cm². However, it could be shown that short-term heat treatments at 475°C can decrease corrosion and stress corrosion cracking susceptibility which may be used to improve the materials performance. Mechanistic understanding of stress corrosion cracking phenomena in light of a comprehensive microstructure characterisation was the main focus of this thesis.
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Datsiou, Kyriaki Corinna. „Design and performance of cold bent glass“. Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/269408.
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The demand for flat glass is high and increasing significantly in the building industry as a direct result of architectural requirements for lightness, transparency and natural light. Current architectural trends require glass in curvilinear forms for smooth free-form façades. Two principal challenges arise from this: to cost-effectively produce the desired curvature and; to ensure its safe performance after exposure to ageing. The recent availability of high strength glass provides an opportunity to address the first challenge by developing cold bent glass. Cold bending involves the straining of relatively thin glass components, at ambient temperatures, and is a low energy and cost effective manner of creating curvilinear forms. However, cold bending is not yet widely established as a reliable method. The aim of this thesis is to develop the understanding of cold bent glass during the bending process and to evaluate its post-ageing performance. This thesis, firstly, investigates the mechanical response of monolithic glass plates during the cold bending process. The stability of cold bent glass is investigated experimentally by bending it in double curved anticlastic shapes. A parametric numerical analysis involves different boundary conditions, geometrical plate characteristics and bending parameters. The principal outcome is that a local instability, now termed cold bending distortion, occurs when certain displacement limits are exceeded and could degrade the optical quality of the glass. An evaluation procedure is also formulated to set limits and aid designers/manufacturers to predict the mechanical response and the optical quality of the glass. Cold bent glass is subjected to permanent bending stresses throughout its service life and therefore, its strength degradation after ageing needs to be quantified. Analytical, experimental and numerical investigations are undertaken in this thesis to identify the most effective method for estimating glass strength (evaluation of destructive tests, required number of specimens, statistical analysis methods and sub-critical crack growth). The limited availability of naturally aged toughened glass and the absence of a reliable ageing standard impede the evaluation of its aged performance. Therefore, a parametric experimental investigation of artificial ageing methods on glass is undertaken in this thesis. A procedure for the evaluation of the strength of aged glass is finally, formulated to allow the selection of artificial ageing parameters that correspond to a target level of erosion. The knowledge on artificial ageing and strength prediction acquired above is finally implemented on different types of glass to determine their strength after ageing and assess their safe use in cold bending / load bearing applications. The investigation showed that fully toughened glass has a superior performance to chemically toughened or annealed glass. Overall, the research presented in this thesis demonstrates that high quality cold bent toughened glass can be created when certain applied displacement limits are respected. These can be used as a safe, cost-effective and energy efficient replacement to the more conventional hot bent glass. However, cold bending / load bearing applications in which the stressed glass surface is exposed to ageing, require glass with a relatively high case depth such as fully toughened or bi-tempered glass.
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GALDINO, JÚNIOR Francisco. „Desenvolvimento de uma máquina de impacto por queda de peso para materiais compósitos“. Universidade Federal de Campina Grande, 2014. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/491.
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O crescente desenvolvimento de materiais compósitos reforçados nos últimos anos tem propiciado novas alternativas para solucionar diversos problemas acerca da necessidade de novos materiais com combinações de propriedades. Para utilizarmos tais materiais, devemos realizar vários ensaios mecânicos, como: tração, compressão, flexão e principalmente de impacto. Para isso, foram realizados estudos específicos sobre materiais compósitos e impactos em estruturas laminadas. Através desses estudos e de um levantamento do estado da arte acerca do projeto de diversas máquinas de impacto por queda de peso, foi projetada e fabricada uma máquina de impacto por queda de peso para materiais compósitos de simples concepção. A máquina desenvolvida possui um intervalo de energia de impacto entre 20J e 96J, obtida através de variação da massa de queda de impacto. Foi desenvolvido também um sistema instrumentação para aquisição da força de impacto e da energia absorvida pelo corpo de prova, além de um sistema anti rebote eletromecânico. Para a validação do equipamento foram realizados ensaios de impacto por queda de peso em placas compósitas de fibra de vidro com 8, 10, 12 e 14 camadas e analisado os danos causados nas mesmas, através de software de análise de imagem. A partir de um software de análise de vídeo foi possível calcular a velocidade de impacto e a energia de impacto nos ensaios e comparar com o método teórico e o instrumentado.
The increasing development of reinforced composite materials in recent years has provided new alternatives to solve various problems about the need for new materials with combinations of properties. For such materials we use, we conduct various mechanical tests, such as tensile, compression, bending and mainly impact. For this, specific studies on composite materials, and impact on laminate structures were performed. Through these studies and a survey of state of the art about the project in several of drop impact weight machines, is designed and manufactured a machine to drop impact weight for composites of simple design. The machine has developed a range of impact energy of 20J, and 96J, obtained by varying the mass of the drop impact. One instrumentation system for the acquisition of the impact force and energy absorbed by the specimen was also developed, and an anti rebound electromechanical system. To validate the equipment impact tests were performed by weight loss in composite plates with glass fiber 8, 10, 12 and 14 layers and analyzed the damage caused in the same via image analysis software. From a software video analysis it was possible to calculate the impact velocity and impact energy in the tests and compare with the theoretical method and instrumented.
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Liu, Pang-Ping, und 劉邦平. „Bending and Fatigue Testing of Bulk Si Micro-Cantilever Beams“. Thesis, 2004. http://ndltd.ncl.edu.tw/handle/85939282603758335087.
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碩士逢甲大學
機械工程學所
92
This thesis is aimed at studying flexural strength and fatigue life of single crystal silicon micro-cantilever beams. The bulk micro- machining technique is applied to fabricate the micro-cantilever beam on a silicon wafer. A MTS micro-force testing machine Tytron 250 with a probe is used to load on the beams. In the flexural test, flexural strength and failure strain decrease as the length (400-700�慆) of the beam increases, but increase with thickness (50-60�慆) of the beam. Maximum displacement increases with length but decreases with thickness. The beam with length of 400�慆 and thickness of 60�慆 has the maximum flexural strength 1.89 GPa, maximum failure strain 1.1x10-2, and Young’s modulus 164 GPa. In fatigue testing, the percentage (50-85%) failure strain �挲 is adopted as two times of the strain amplitude as well as the maximum strain. The results show that fatigue life increases with length of the beam. It is because that the compensator in the testing machine is unable to adjust output in order to meet the command value of strain amplitude at testing frequency of 40Hz. The error of strain amplitude thus raises up to 42.4% for the beam with length of 700�慆. For the beam with length of 400�慆, the cycle to failure N ranges from 7.05×106 to 5.35×108 cycles for maximum strain ranging from 50 to 85%�n�挲. The fatigue limit is expected at maximum strain in the range of 45 to 50 % �挲. Compared experimental results with theoretical ones for the flexural test, we can get a error factor L/bt2 and figure out a relationship L/bt2<0.0016μm2 which has smallest error. Both side and bottom surfaces of the micro cantilever beams are observed to have roughness after the MEMS fabrication. Roughness is calculated to be 684 at side and 248.7 at bottom. The results show that the roughness caused by mask at side surface is bigger than the surface at bottom etched by KOH. SEM is employed to observe the fracture surface of micro-cantilever beams under bending and fatigue tests. It is found that the bended fracture surface is quite smooth. On the other hand, the fatigued fracture surface is rougher and has kink bands due to slow crack growth. Both the fracture surfaces under bending and fatigue loadings are observed to occur predominantly in the (111) oriented surface.
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Heukelman, B. J., und Brandon Jay Heukelman. „Alternating torsion and bending moment testing of a vehicle rim“. Thesis, 2020. https://hdl.handle.net/10539/31229.
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A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in partial fulfillment of the requirements for the degree of Masters of Science in Engineering, 2020The automotive wheel is a fundamental vehicle component connecting the chassis to the road. Understanding the loading mechanism which leads to fatigue failure of a wheel is necessary to design light, safe wheels. This work characterised the strain along the length of spoke for various orientations with respect to the loading direction. Three wheel designs were tested according to the bending moment (cornering) and alternative torsion fatigue test specifications if the TUV and SAE. The results showed that the bending moment fatigue test (which reproduces the loading when cornering) is more critical than the alternating torsion fatigue test (which reproduces the loading when accelerating and decelerating). The bending moment load case produced strains that were on average 32 % higher than the torsion load case. The experimental results were compared to a finite element analysis (FEA) using commercial software (Ansys) and an analysis of the wheel which used Euler-Bernoulli beams and torsional elements of model spokes of the wheel. The FEA underestimated the peak strains 20 %, while the simplified model underestimated the peak strains by 30 %. Both the FEA and simplified model followed the same trend seen in the experimental results. The simplified model was further used to investigate the effect of spoke arrangement on the wheel's efficiency (i.e. the safety factor of the wheel normalised by the mass of the wheel). The model showed that increasing the number of spokes as well as increasing the angle of spoke to the radial increases the factor of safety (even after normalised with respect to mass)
CK2021
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Santa, Maria Raul Hernan. „Behavior of hollow, rectangular concrete piers subjected to biaxial bending“. Thesis, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3055241.
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39
Yap, Sze-Ting. „Evaluation of proposed methods to determine fracture parameters for concrete in bending“. 1986. http://hdl.handle.net/2097/22185.
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Wang, Leo, und 王聰榮. „Design and Testing of Measurement Device for Circular Tube Under Pure Bending“. Thesis, 1996. http://ndltd.ncl.edu.tw/handle/31115229717813541868.
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41
Pereira, da Silva Carlos Manuel Baptista. „Design and testing of an active aircraft wing spar with bending-torsion coupling“. Thesis, 2007. http://hdl.handle.net/1828/2228.
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An experimental investigation on active aeroelastic aircraft structures with bending-torsion coupling properties is presented. Two techniques for vibration and flutter alleviation are studied and tested. The passive approach is based on the use of carbon composite spars with misaligned fibres. The second technique involves an active spar with a multi-cross section embedded with PZT actuators. A wing was designed and manufactured for testing in a wind tunnel and subsequently implemented on a demonstrator platform for flight testing.
Results show that a carefully designed misalignment of the fibres can lead to significant performance increase. The active system based on PZT actuators with a linear controller exhibits significant improvements in aeroelastic performance compared to the passive system. The research findings lead to the conclusion that significant vibration reduction and flutter envelope extension can be achieved using the proposed strategies.
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Ren, Q.-X., L.-H. Han, Dennis Lam und W. Li. „Tests on elliptical concrete filled steel tubular (CFST) beams and columns“. 2014. http://hdl.handle.net/10454/10304.
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NoThis paper presents a series of test results of elliptical concrete filled steel tubular (CFST) beams and columns to explore their performance under bending and compression. A total of twenty-six specimens were tested, including eight beams under pure bending and eighteen columns under the combination of bending and compression. The main parameters were the shear span to depth ratio for beams, the slenderness ratio and the load eccentricity for columns. The test results showed that the CFST beams and columns with elliptical sections behaved in ductile manners and were similar to the CFST members with circular sections. Finally, simplified models for predicting the bending strength, the initial and serviceability-level section bending stiffness of the elliptical CFST beams, as well as the axial and eccentric compressive strength of the composite columns were discussed.
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Wright, Thomas J. (Thomas John). „Sensitivity of Hashin damage parameters for notched composite panels in tension and out-of-plane bending“. Thesis, 2012. http://hdl.handle.net/1957/35802.
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When using Finite Element Analysis (FEA) to model notched composite panels, the values of certain material properties can have a great effect on the outcome of the simulation. Progressive damage modeling is used to model how a composite structure will fail, and how that failure will affect the response of the structure. Many different progressive damage models exist, but the formulation known as Hashin damage is used to model failure in tension and out-of-plane bending in this study. This model has ten different material properties that are used to define the damage response of the material. Each of these material properties must be calculated experimentally in a time consuming and expensive process. A method of determining which properties will have the greatest effect on the model, and therefore, which to spend the most money on accurate tests, is a factorial analysis sensitivity study. Studies of this nature have been used in many different situations regarding material properties testing and optimization.
The work presented in this study uses several factorial analysis designs to perform a sensitivity study on the ten Hashin damage parameters in a variety of situations. Five different ply layups are used in modeling specimens that are loaded in tension and out-of-plane bending. The results of this study show that the significant factors depend on the ply layup and loading scenario, but there are generally less than three factors that play a significant role in modeling the failure of the panels. This means that in most cases, rather than spending substantial money on finding ten different material properties, the time and money can be focused on a small subset of the properties, and an accurate model can still be achieved. While the results of the scenarios presented may not apply to all scenarios, the methods presented can be used to perform a similar study in other specific scenarios to find the significant factors for that case.Graduation date: 2013
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hsu, hsiang-chin, und 徐祥進. „Strength Analysis of Ultra-Thin Wafers by Three-Point Bending Test and Thin Wafer Probe Testing Method with Temperature Effect“. Thesis, 2010. http://ndltd.ncl.edu.tw/handle/33759417392956658046.
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碩士國立中正大學
機械工程所
98
Light weight, small size, low voltage, and low cost are the mainly request of high performance IC product; on the other hand, it also means the spacing for IC system is very limited. Therefore newly development of 3D Stacked-Die Packaging (SDP) is the current important direction for advance packaging technique. SDP need to be supported with thin wafers so that the stacking dies could maintime the spacing limitation. However one failure die could cause whole packaging failure that could lead to lower the yield rate and increasing the manufacturing cost. Currently, one of the key technologies need to improve yield rate is the Thin Wafer Probing Technique. Researches focus on developing experimental methods and computer simulation skills to study the optimized probing parameters for ultra-thin wafer. In this thesis , we studied the fracture strength and failure stress of thin wafers with three-point bending method. We also set up temperature controlled system; Both probe and bonding pad could put in the temperature controlled system, observe the contact force and mark length and mark depth. The achievement from this research could reveal the limited stress index in thin wafer and also understand how temperature level could effect the scratch size and contact force under different probing overdrive conditions that help the engineer to select better parameter of probing process.
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Mikulak, James Kevin. „Size effects in out-of-plane bending in elastic honeycombs fabricated using additive manufacturing : modeling and experimental results“. Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-12-4565.
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Size effects in out-of-plane bending stiffness of honeycomb cellular materials were studied using analytical mechanics of solids modeling, fabrication of samples and mechanical testing. Analysis predicts a positive size-effect relative to continuum model predictions in the flexure stiffness of a honeycombed beam loaded in out-of-plane bending. A method of determining the magnitude of that effect for several different methods of constructing or assembling square-celled and hexagonal-celled materials, using both single-walled and doubled-walled construction methods is presented. Hexagonal and square-celled honeycombs, with varying volume fractions were fabricated in Nylon 12 using Selective Laser Sintering. The samples were mechanically tested in three-point and four point-bending to measure flexure stiffness. The results from standard three-point flexure tests, did not agree with predictions based on a mechanics of solids model for either square or hexagonal-celled samples. Results for four-point bending agreed with the mechanics of solids model for the square-celled geometries but not for the hexagonal-celled geometries. A closed form solution of an elasticity model for the response of the four-point bending configuration was developed, which allows interpretation of recorded displacement data at two points and allows separation the elastic bending from the localized, elastic/plastic deformation that occurs between the loading rollers and the specimen’s surface. This localized deformation was significant in the materials tested. With this analysis, the four-point bending data agreed well with the mechanics of solids predictions.text
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Santos, Rafael Alexandre Mota dos. „Effect of the Distance Between Impact Point and Hole Position and Non-Perpendicular Holes on the Impact Strength of Composite Laminates“. Master's thesis, 2016. http://hdl.handle.net/10400.6/7703.
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The effect of the distance between impact point and hole position and the angle of the hole with the vertical axis was studied. In order to understand this effect, flexural tests were also performed to evaluate the bending strength of CFRP. In terms of distance of the hole, a maximum reduction of 29.7% on the bending load for a distance of 0 mm was found. This reduction was 22.3% on the impact load. In terms of angle of the hole, a maximum load reduction of 15.6% on the bending strength was found and for the impact load this value was found to be 7% for 20º. The fatigue resistance was also studied. An average reduction of 68.5% on the fatigue resistance of GFRP was obtained for an impact energy of 12 J, in the presence of a hole.O efeito da distância entre o ponto de impacto e posição de um furo e o ângulo do mesmo com o eixo vertical foi estudado. Para avaliar este efeito, foram também realizados ensaios de flexão. Em termos de distância do furo, uma redução máxima da resistência à flexão de 29,7% foi verificada para uma distância do furo de 0 mm. Esta redução foi de 22,3% no carregamento de impacto. Em termos de ângulo do furo, a redução máxima do carregamento foi de 15,6% para a flexão e em relação ao impacto este valor foi de 7%, para um ângulo de 20º. A resistência à fadiga foi também estudada. Foi verificada uma redução média de 68,5% na resistência à fadiga em compósitos de fibra de vidro para uma energia de impacto de 12 J, na presença de um furo.