Global awareness and preservation have spurred increasing interest in utilizing environmentally friendly materials for high-performance structural applications. Biocomposites pose an appealing solution to this issue and are characterized by their sustainable lifecycles, biodegradable qualities, light weight, remarkable strength, and exceptional stiffness. Many of these structural qualities are found in applications that exhibit flexural loading conditions, and this study focuses on improving the bending performance of engineered biocomposite structures. The current application of biocomposites is increasing rapidly, so this expanding research explores other natural constituent materials for biocomposite structures under flexural loading. The renewable material investigated in this study was experimentally and numerically validated by optimizing the mechanical characteristics of bamboo fibers in biocomposite structures under flexural loading conditions through various thermal and organic chemical treatment methods. Therefore, bending performance of a biocomposite truss and I-beam are analyzed to demonstrate the benefits of utilizing optimally treated bamboos in their design. To accomplish this goal, the first task consisted of treating bamboos by thermal and chemical means to determine the resulting effects on the compressive and tensile mechanical properties through experimental testing. Results indicated a significant improvement in strength, stiffness, and weight reduction. An extensive analysis determined the optimal treatment method that was utilized for flexural loading conditions. The second task entailed studying the flexural behavior of the optimally treated bamboo in two geometric configurations, a hollow cylinder and veneer strip, to determine the resultant properties for the truss and I-beam structure. The effect of node location on flexural performance was also studied to establish design guidelines for the applied structures. Bending tests indicated that node location affects the strength and stiffness of the hollow cylindrical configuration but has minimal effects on the veneer strip. Observations discovered by this study were employed into the designs of the applied structures that yielded excellent mechanical performance through flexural testing. The final task required conducting a finite element analysis in Abaqus/CAE on the performance of each structural application to validate experimental results. A conclusive analysis revealed good agreement between the numerical method and experimental result.

A study was undertaken to create a finite element model of a cooled throat converging/diverging rocket nozzle to be used as a tool in designing a cooled aerospike nozzle. Using ABAQUS, a simplified 2D axisymmetric model was created featuring only the copper throat and stainless steel support ring, which were brazed together for the experimental test firings. This analysis was a sequentially coupled thermal/mechanical model. The steady state thermal data matched closely to experimental data. The subsequent mechanical model predicted a life of over 300 cycles using the Manson-Halford fatigue life criteria. A mesh convergence study was performed to establish solution mesh independence. This model was expanded by adding the remainder of the parts of the nozzle aft of the rocket motor so as to attempt to match the transient nature of the experimental data. This model included variable hot gas side coefficients in the nozzle calculated using the Bartz coefficients and mapped onto the surface of the model using a FORTRAN subroutine. Additionally, contact resistances were accounted for between the additional parts. The results from the preliminary run suggested the need for a parameter re-evaluation for cold side gas conditions. Parametric studies were performed on contact resistance and cold side film coefficient. This data led to the final thermal contact conductance of k=0.005 BTU/s•in.•°R for contact between metals, k=0.001 BTU/s•in.•°R for contact between graphite and metal, and h=0.03235 BTU/s2•in.•°R for the cold side film coefficient. The transient curves matched closely and the results were judged acceptable. Finally, a 3D sector model was created using identical parameters as the 2D model except that a variable cold side film condition was added. Instead of modeling a symmetric one or two inlet/one or two outlet cooling channel, this modeled a one inlet/one outlet nozzle in which the coolant traveled almost the full 360° around the cooling annulus. To simplify the initial simulation, the model was cut at the barrier between inlet and outlet to form one large sector, rather than account for thermal gradients across this barrier. This simplified nozzle produced expected data, and a 3D full nozzle model was created. The cold side film coefficients were calculated from previous experimental data using a simplified 2D finite difference approach. The full nozzle model was created in the same manner as the 2D full nozzle model. A mesh convergence study was performed to establish solution mesh independence. The 3D model results matched well to experimental data, and the model was considered a useful tool for the design of an oxidizer cooled aerospike nozzle.

Firearms are present in two-thirds of United States households. As of 2003, roughly 500,000 projectile wounds occur annually in the United States. This costs an estimated 2.3 billion dollars of medical spending. The best treatment of gunshot wounds relies heavily on experience, but even with experience the unpredictable nature of ballistics can make treatment difficult. Wound ballistics studies the injury pattern of a particular bullet. Ballistic gelatin tests are used to analyze this pattern. A block of 10 or 20% ballistic gelatin is set and a bullet is fired through the block. Key characteristics of the wound profile seen in this test include: depth penetration, permanent cavity, and temporary cavity. Even with ballistic gelatin tests, there is still confusion and many unknowns throughout wound ballistic literature. Finite element analysis (FEA) can be used to reproduce the wound profile of a ballistic gelatin test. A .38 lead round nose was chosen to model. The bullet was assigned as an elastic plastic material and the ballistic gelatin block was assigned as an elastic plastic and viscoelastic material. SolidWorks®, TrueGrid®, and LS-DYNA® were used to create the models. Two elastic plastic and two viscoelastic simulations were developed from these models. Elastic Plastic 2 and Viscoelastic 1 were able to reproduce a depth penetration, temporary cavity, and permanent cavity. Elastic Plastic 1 and Viscoelastic 2 were unable to reproduce the temporary cavity. These simulations provided hopeful results, but further investigation is needed for contribution to the advancement of bullet wound treatment.

Structural engineering is heavily dependent on the use of computers. When creating a building model using structural analysis software, it is required that the designer have an understanding of the system behavior and the modeling program capabilities. Some engineers in the Southern California region are taking steps towards incorporating the Dywidag ductile connector (DDC) and super hybrid systems into building practice due to the advantages found in these systems’ construction methods and seismic performance. As the DDC and super hybrid systems reach industry, the design engineer will need to model these systems using structural analysis programs. This report describes two DDC specimens that were each modeled two ways: (1) using elastic members in conjunction with nonlinear rotational hinges (lumped plasticity model), and (2) using finite elements (fiber model). The experimental pushover curve for each test specimen was compared to the corresponding analytical backbone curves. The fiber modeling focuses on providing a means to study the joint behavior as the parameters of the system change. The lumped plasticity model provides the design engineer with a means for modeling a three-dimensional DDC building in order to get acceptable global demand values. This project offers modeling suggestions for both the fiber models and the lumped plasticity models used to predict the seismic behavior of the DDC precast concrete system.

The purpose of this study was to investigate the influence of tibial stem geometry on stress shielding of the tibia for patients with a total knee replacement. Finite element analysis was used to study different tibial stem geometry types, as well as a vast array of different geometric sizes. Both a peg and stem type geometry were analyzed and compared in order to determine what type geometry causes the least amount of stress shielding. A static loading condition with a dynamic loading factor of three was used for the system and the stress responses were analyzed at regions of interest at various depths. Regions of interest include the posterior and medial regions, at depths ranging from the resurfaced tibial surface to 100 mm below the surface. It was found that the smallest stem/peg sizes produced the least amount of stress shielding, indicating that the less amount of foreign material within the tibia, the more natural the bending and stress response of the tibia. It was also concluded that for the loading conditions used in this study, peg type geometry yields a decreased amount of stress shielding when compared to stem type geometry. This is due to the fact that the peg type geometry allowed for more natural bending and a distributed loading transfer between two pegs rather than one long central stem. Further studies should be completed on other geometry types in order to understand how to best replicate the natural bending of the tibia.

A Comparison Study of Composite Laminated Plates with Holes under Tension A study was conducted to quantify the accuracy of numerical approximations to deem sufficiency in validating structural composite design, thus minimizing, or even eliminating the need for experimental test. Error values for stress and strain were compared between Finite Element Analysis (FEA) and analytical (Classical Laminated Plate Theory), and FEA and experimental tensile test for two composite plate designs under tension: a cross-ply composite plate design of [(0/90)4]s, and a quasi-isotropic layup design of [02/+45/-45/902]s, each with a single, centered hole of 1/8” diameter, and 1/4" diameter (four sets total). The intent of adding variability to the ply sequences and hole configurations was to gauge the sensitivity and confidence of the FEA results and to study whether introducing enough variability would, indeed, produce greater discrepancies between numerical and experimental results, thus necessitating a physical test. A shell element numerical approximation method through ABAQUS was used for the FEA. Mitsubishi Rayon Carbon Fiber and Composites (formerly Newport Composites) unidirectional pre-preg NCT301-2G150/108 was utilized for manufacturing—which was conducted and tested to conform to ASTM D3039/D3039M standards. A global seed size of 0.020, or a node count on the order of magnitude of 30,000 nodes per substrate, was utilized for its sub-3% error with efficiency in run-time. The average error rate for FEA strain from analytical strain at a point load of 1000lbf was 2%, while the FEA-to-experimental strains averaged an error of 4%; FEA-to-analytical and FEA-to-tensile test stress values at 1000lbf point load both averaged an error value of 6%. Suffice to say, many of these strain values were accurate up to ten-thousandths and hundred-thousandths of an in/in, and the larger stress/strain errors between FEA and test may have been attributed to the natural variables introduced from conducting a tensile test: strain gauge application methods, tolerance stacks from load cells and strain gauge readings. Despite the variables, it was determined that numerical analysis could, indeed, replace experimental testing. It was observed through this thesis that a denser, more intricate mesh design could provide a greater level of accuracy for numerical solutions, which proves the notion that if lower error rates were necessitated, continued research with a more powerful processor should be able to provide the granularity and accuracy in output that would further minimize error rates between FEA and experimental. Additionally, design margins and factors of safety would generally cover the error rates expected from numerical analysis. Future work may involve utilizing different types of pre-preg and further varied hole dimensions to better understand how the FEA correlates with analytical and tensile test results. Other load types, such as bending, may also provide insight into how these materials behave under loading, thus furthering the conversation of whether numerical approximations may one day replace testing all together.

The objective of this thesis is to determine the feasibility of a novel axial flux variable reluctance machine design. The design aims to compete with prevalent rare-earth permanent magnet machines while also implementing an innovative torque ripple minimization strategy. Given the fundamental operating principles, a selection of dimensions, materials, and excitations are prepared for the machine. Special attention is given to the rotor profile which is crucial to operation. Finite element analysis software is used to evaluate a three-dimensional model in terms of inductance and torque. The ultimate potential of the machine is discussed and recommendations for improvement are proposed.

Although highly underutilized by the medical device industry, Finite Element Analysis (FEA) in the development of new technologies is gaining popularity as regulatory bodies such as the Food and Drug Administration (FDA) begin to require additional proof of safety through scientific methods. Non-linear FEA allows engineers to realistically simulate the mechanical behavior of implants as seen in the in-vitro, or in some cases, the in-vivo configurations. The work presented in this report investigates how computational methods can be used to simulate the interaction of a St. Jude Medical silicone soft-tip as it passes through a Peel-Away Sheath (i.e. introducer). In this analysis the soft-tips were modeled as axisymmetric with hyperelastic material properties assigned to the soft-tips. An Ogden, second order hyperelastic material model was used to describe the non-linear stress-strain behavior of silicone soft-tips. The finite element program, ABAQUS/Standard was used to simulate the soft-tip/introducer interactions. The reaction forces obtained through these simulations represent the force required to push a lead through an introducer, and were then compared to experimental data.

Yes / The current UK rail network is managed by Network Rail, which requires an investment of £5.2bn per year to cover operational costs [1]. These expenses include the maintenance and repairs of the railway rails. This paper aims to create a proof of concept for an autonomous health monitoring system of the rails using an integrated finite element analysis (FEA) and artificial neural network (ANN) approach. The FEA is used to model worn profiles of a standard rail and predict the stress field considering the material of the rail and the loading condition representing a train travelling on a straight line. The generated FEA data is used to train an ANN model which is utilised to predict the stress field of a worn rail using optically scanned data. The results showed that the stress levels in a rail predicted with the ANN model are in an agreement with the FEA predictions for a worn rail profile. These initial results indicate that the ANN can be used for the rapid prediction of stresses in worn rails and the FEA-ANN based approach has the potential to be applied to autonomous health monitoring of rails using fast scanners and validated ANN models. However, further development of this technology would be required before it could be used in the railway industry, including: real time data processing of scanned rails; improved scanning rates to enhance the inspection efficiency; development of fast computational methods for the ANN model; and training the ANN model with a large set of representative data representing application specific scenarios.

Yes / Extensive experimental and theoretical studies have been conducted on the compressive strength of concrete-filled steel tubular (CFST) columns, but little attention has been paid to their compressive stiffness and deformation capacity. Despite this, strength prediction approaches in existing design codes still have various limitations. A finite element model, which was previously proposed by the authors and verified using a large amount of experimental data, is used in this paper to generate simulation data covering a wide range of parameters for circular and rectangular CFST stub columns under axial compression. Regression analysis is conducted to propose simplified models to predict the compressive strength, the compressive stiffness, and the compressive strain corresponding to the compressive strength (ductility) for the composite columns. Based on the new strength prediction model, the capacity reduction factors for the steel and concrete materials are recalibrated to achieve a target reliability index of 3.04 when considering resistance effect only.