Because of their high strength-to-weight ratio, Fiber Reinforced Composite (FRC) materials are well suited for use in high performance racing applications where weight must be kept to a minimum. Formula SAE (FSAE) race cars are designed and built by college students, roughly following the model of a scaled down Formula One car. Strict regulations are placed on specific components of the car in the interest of equalizing competition and ensuring the safety of the drivers. Students are required to construct a survival cell (the chassis), which can resist large amounts of energy in the event of a crash, with an energy absorbing device at the front of the vehicle. The nose cone of the Cal Poly FSAE car is constructed as a carbon fiber shell designed to act as this sacrificial energy absorbing device. One difficulty associated with using FRC materials is that the anisotropic properties can lead to a variety of complex failure modes such as buckling, delamination, matrix cracking, and fiber breakage, all of which absorb different amounts of energy. In order to accurately predict the behavior of the nose cone so that it meets the requirements set forth by SAE, an initial finite element model has been constructed. This model uses the test results from another paper to construct an explicit non-linear dynamic analysis in Abaqus which simulates the axial crushing of a thin walled composite tube between two rigid plates. The modeling techniques discussed in this paper will be used as the basis for a future thesis dedicated to designing the nose cone for the Cal Poly FSAE car.

The usage of welding in the process of manufacturing has become very widespread, mainly due to its low cost, versatility and the possibility of its automation. With its expansion comes higher demand for the possibilities of weld evaluation during the phase of design. Nowadays its possible to use tools based on finite element method for such evaluation. But the most commonly used tools are often very expensive. Therefore, the possibility of using Open-Source tool such as Salome-Meca to simulate the welding process as an alternative to commercial software was investigated. The first part of the work deals with the welding process and a description of the formation of residual stresses and deformations. It also deals with the description of the Salome-Meca software environment and the Code-Aster solver. In the next part the capabilities of the software in relation to problem of welding simulation are discussed. Furthermore, the goemetry of solved weldment, welding conditions, material properties and boundary conditions of the calculation are described. And finally, the individual solutions, their results and disadvantages of used approaches.

Investment casting is a complex manufacturing method with many challenges that must be solved before components of the right quality can be produced. TPC is a company that utilizes investment casting to produce a variety of products, lately the company has higher ambition in wanting to cast higher technical demanding component like heat resistant gas turbine blades. This requires a sprue that can control the filling process, by allowing the fallen stream of molten metal to enter the moulds cavity in a laminar manner. This study has implemented the product development process by (Ulrich, 2012) to develop the requested sprue. The primary support for this study is study material given by the company also known as "PMG running spreadsheet TPC" base on theory and equations from (Jolly, 2002), which is believed to have origin in sand casting manufacturing process. The project began with recreating the textbook model after establishing a number of control parameter such as critical velocity. Then simulation software Nova flow was used to evaluate the velocity and FEM in Solidworks to study if the dimension of the model can be directly use for investment casting process. The results show that it was not possible, therefore in the concept generating phase only theory of casting was used to create new concept. Then 3 existing sprues were chosen for benchmarking to gain deeper understanding about their design intension. One of the concepts was inspired by the CEO Mark Irwin “concentric pipe design” and in total 10 concepts were created of which 6 were tested for both flow and FEM analysis. 2 concepts were chosen for further development which also became 2 final concepts, after 3 iterations of improvement. These concepts show that many improve in terms of laminar filling and higher yield than the existing benchmark sprues. Although further development is required.   The analysis shows that every step in the project has its own flaws, but that is the nature of being an engineer, as long as the problem encountered can be viewed with critical and analytical eyes. A well-considered and balanced solution can be provided, although nothing of this can be certain before a trail of test can provided to confirm any assumptions which is not included in this work.   The discussion section processes the thoughts, experience, and doubts about the project in general and the decision making leading to this report and what could have been done differently. The most significant lesson learn from this is that section is when solving a complex issue there must be very clear delimitations and well-defined goals to every specific solution. Otherwise the workload will be extensive and cause more harm than necessary.   The conclusion of this project shows that two concepts generated with the help from the product development process work better than the case study, which can be found in section 4.3, that was based on “PMG running spreadsheet TPC” calculation model, from the velocity perspective. To achieve this, the sprue uses its own geometry constrain and constricts the flow by collecting the molten metal in a “well” before the calmer stream could be distributed throughout the whole cavity. Indirectly this means that the studied material given from TPC AB could not be directly implemented into the investment production process. The given material should be seen as a complement and guidance when creating new sprues. Concerning the FEM analysis tool, it was helpful in this project in evaluating the sprues geometry expose to the assumed force in the production process to avoid unnecessary failure and therefore waste. Although if the company do not intend further work with the development of other sprues then this method is not necessary and would not have significant value to their current manufacturing process.

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Any machining operation induces significant deformation and associated stress states within the component being machined. Once the component has been finished and is removed from the machining tool, a portion of these stresses remain within the finished component, and are termed residual stresses. These stresses have a significant effect upon the performance of the final component. However, despite their importance there is no accurate and cost effective method for measuring residual stresses. For this reason predicting these stresses without the need for measurement is highly desirable. The focus of this thesis is on advancing the development and implementation of finite element models aimed at predicting residual stresses induced by metal cutting operations. There are three main focus areas within this research, the first of which is concerned with predicting residual stresses when small feed rates are used. It is shown that in the existing cutting models residual stress prediction accuracy suffers when feed rates are small. A sequential cut module is developed, which greatly increases the accuracy of the predicted residual stress depth profiles. A second area of focus concerns the influence of friction models on predicted residual stresses. A detailed set of simulations is used to elucidate the effect of friction not only for sharp tools, but also for tools which have accrued wear. It is shown that whilst friction is not of critical importance for new tools, as tools continue to wear the choice of friction model becomes significantly more important. The third area of focus is on phase transformations, induced by the cutting process. A decoupled phase transformation module is developed in order to predict the depth, if any, of a phase transformed layer beneath the newly machined surface. Furthermore, the effect of this layer on the residual stress depth profile was also studied. All three focus areas present new and novel contributions to the field of metal cutting simulations, and serve to significantly increase the capabilities of predictive models for machining. / Thesis / Doctor of Philosophy (PhD)

The research in this master's thesis examines the mechanics of primate and early hominid feeding within the context of hypotheses about australopithecine diets. Specifically, this work will be helpful in testing the hypothesis that derived craniodental features in australopithecines are adaptations for feeding on hard, brittle, seasonally available foods. These foods may have been “fallback” items that could be fed upon during periods of scarcity, and thus their consumption may have been ecologically important to survival of early humans. In order to test the fallback theory, accurate estimates of bite force to initiate a crack in a hard food source using different tooth shapes is essential. These estimates help test the theory in two ways. First, the estimation of bite force for different tooth profiles helps in explaining effect of tooth morphology on fracture of hard food sources. This will test the premise that some species have more efficient tooth shapes for fracturing hard food than other species. Second, the obtained bite force will be used as an input to full scale finite element skull model of different species. Stress and strain distributions in critical regions of the skull will be helpful in understanding feeding adaptations of the different species during evolution. In this work a fast and accurate finite element analysis method was developed to estimate bite force required to initiate crack in a hard food source like the macadamia nut with different tooth morphologies. The proposed research will help in understanding the effect of tooth shape on the bite force required to initiate a crack in a hard food source In first experiment we simulated nut biting behavior found in ancient hominid by indenting macadamia nuts with aluminum alloy replicas of primate teeth. Finite element analysis simulation of the biting behavior provided insight into stress profile in the nut at the time of fracture. The results were statistically inconclusive due to huge variation in thickness, diameter and material properties of macadamia nut. In order to study effect of teeth shape on bite force, another study was performed in this work where four different hominoid species namely A.afransis, A.africanus, A.boisei and A.robustus of similar age level, were considered. Cast iron replicas of these hominoid teeth were created. In order to eliminate variability in thickness, diameter and material properties, we used acrylic hemispheres as a macadamia nut substitute. Statistical significance testing and FEA revealed that flatter teeth produces significantly lower force required to fracture acrylic hemisphere as compared to pointed and sharp teeth with comparable fracture stress. Results suggest that pointed teeth produces higher stresses in the food resulting in lower force required to fracture but at the same time stresses in teeth is also high increasing the probability of enamel failure. During the evolution teeth might have evolved to obtain optimum shape which provides tread off between minimum force required to fracture hard food items and minimum stress in enamel to reduce probability of enamel fracture Past work in estimating bite force is limited to experimental testing. Physical testing of bite force is tedious and time consuming. The proposed combination of physical testing and supporting finite element analysis will be helpful in reducing lengthy physical testing. The main advantage of this method is the comparatively low computational cost and the ability to estimate full field stresses and strains, as opposed to measuring surface strain at specific points. As our modeling and experimental methods become more refined, we anticipate being able to assess the degree to which tooth morphology affects the force needed to fracture hard food items, thereby providing insights into the dietary adaptations of living and extinct primates, including fossil humans.

An estimated 27 million Americans suffer from osteoarthritis (OA). Symptomatic OA is often treated with total knee replacement, a procedure which is expected to increase in number by 673% from 2005 to 2030, and costs to perform total knee replacement surgeries exceeded $11 billion in 2005. Subject-specific modeling and finite element (FE) predictions are state-of-the-art computational methods for anatomically accurate predictions of joint tissue loads in surgical-planning and rehabilitation. Knee joint FE models have been used to predict in-vivo joint kinematics, loads, stresses and strains, and joint contact area and pressure. Abnormal cartilage contact pressure is considered a risk factor for incidence and progression of OA. For this study, three subject-specific tibiofemoral knee FE models containing accurate geometry were developed from magnetic resonance images (MRIs). Linear (LIN), Neo-Hookean (NH), and poroelastic (PE) cartilage material models were implemented in each FE model for each subject under three loading cases to compare cartilage contact pressure predictions at each load case. An additional objective was to compare FE predictions of cartilage contact pressure for LIN, NH, and PE material models with experimental measurements of cartilage contact pressure. Because past studies on FE predictions of cartilage contact pressure using different material models and material property values have found differences in cartilage contact pressure, it was hypothesized that different FE predictions of cartilage contact pressure using LIN, NH, and PE material models for three subjects at three different loading cases would find statistically significant differences in cartilage contact pressure between the material models. It was further hypothesized that FE predictions of cartilage contact pressure for the PE cartilage material model would be statistically similar to experimental data, while the LIN and NH cartilage material models would be significantly different for all three loading cases. This study found FE and experimental measurements of cartilage contact pressure only showed significant statistical differences for LIN, NH, and PE predictions in the medial compartment at 1000N applied at 30 degrees, and for the PE prediction in the medial compartment at 500N applied at 0 degrees. FE predictions of cartilage contact pressure using the PE cartilage material model were considered less similar to experimental data than the LIN and NH cartilage material models. This is the first study to use LIN, NH, and PE material models to examine knee cartilage contact pressure predictions using FE methods for multiple subjects and multiple load cases. The results demonstrated that future subject specific knee joint FE studies would be advised to select LIN and NH cartilage material models for the purpose of making FE predictions of cartilage contact pressure.

A simulation was created using LS-DYNA® to determine the acoustical properties of a golf ball and golf driver head impact. LS-DYNA® has a coupled finite element analysis (FEA) and boundary element method (BEM) solver that uses the integral form of Helmholtz’s acoustic wave equation to deliver predicted sound pressure levels at predetermined acoustic points. Validation of the modeling was done on a simple plate donated by Titleist Golf. The plate was modeled and meshed using TrueGrid and impacted by a three layer golf ball model derived from “Tanka’s” paper on multilayered golf balls. The final converging model consisted of 10,900 solid fully integrated elements between the ball, plate, and plate support structure. The result was compared to experimental data taken by an air cannon and anechoic chamber that housed strain and acoustical measurement equipment. The sound level predictions from the model showed a promising correlation with experimental data and the focus switched to a golf driver head response during impact. The same ball developed from Tanaka’s paper was used to impact a 350cc generic golf driver head. The driver head consisted of 3300 fully integrated shell elements throughout the model. The top of the hosel was fixed during the simulation to simulate the connection to the golf shaft. The ball was fired at the center of the driver’s face and the predicted sound was determined for a point two feet behind the driver head. The BEM prediction of the driver head model showed little correlation with actual recorded impact sounds provided by Cleveland Golf when comparing frequency response functions. These differences could arise from assumptions and simplifications made to speed up the impact simulation. The sound produced from the golf ball after impact was one such factor was not included. Due to the complex shape of the driver head and the total number of elements involved, the numerical solution took upwards of 100 hours to finish. Adding the golf ball sound would greatly increase computational time and not contribute significantly to the overall predicted sound. Although the BEM solution can be used to characterize different driver heads, the impact is too complicated to efficiently and accurately predict the true impact sounds.

The nanoscale dimension known as D-spacing describes the staggering of collagen molecules, which are fundamental to the biphasic makeup of bone tissue. This dimension was long assumed to be constant, but recent studies have shown that the periodicity of collagen is variable. Given that the arrangement of collagen molecules is closely related to the degree of bone mineralization, recent studies have begun to look at D-spacing as a potential factor in the ongoing effort to battle postmenopausal osteoporosis. The theoretical models presented by previous studies have only opted to model a single collagen-hydroxyapatite period, so the creation of an intricate computational approach that more exhaustively models a network of collagen and mineral is well-warranted. Sheep present an excellent opportunity to examine metabolic disorders, as their bone structure similar to that of the human skeleton. Six Rambouillet-cross ewes were used for the purpose of gathering experimental data. Three ewes underwent a sham surgery (controls), while an ovariectomy (OVX) was performed on the remaining three sheep. Each sheep was sacrificed after 12 months and their radius and ulna were harvested for atomic force microscopy and mechanical testing. Each sheep bone produced up to 25 beam samples that were available for analysis, and two were randomly selected from each test sheep. The cranial anatomical sector was selected for testing as it replicates the tensile loading condition characteristically experienced by collagen molecules and its exclusive examination removes any unintended variation due to bone section. Experimental D-spacing measurements were used in a finite element software, Abaqus, to create the ``Complex Model'': a large-scale, 2-D staggered array representation of collagen and hydroxyapatite periodicity. D-spacings intrinsic variability was mimicked through a Gaussian distribution that randomly determined periodic lengths based on provided experimental data. The model was generated with these random conditions for 2 x 100 units. Safeguards were implemented to ensure appropriate ratios of collagen to hydroxyapatite throughout the randomization. Collagen was assigned viscoelastic material properties originally developed by Dr. Frank Richter and modified by Miguel Mendoza. Hydroxyapatite was modeled as an elastic isotropic material. Four models were created using randomized D-spacings from control sheep and four separate models were created based on OVX sheep. Tangent delta--a damping characteristic--was recorded to evaluate bone viscoelasticity across four test frequencies: 1, 3, 9, and 15 Hz. Results strongly suggest that the Complex Model matches experimental findings more accurately than previous computational approaches. These results indicate the complicated network of many collagen units is an essential parameter of adequate modeling. A repeated measures analysis of variance was performed to examine the differences between control and OVX sheep. After adjusting for all other predictors, at the 1% significance level, after adjusting for all other variables, there is not enough evidence to convince this study that the Surgical Treatment alone has a significant impact on output tangent delta. This finding leads this study to conclude that OVX is fully accounted for within the Complex Model through the inclusion of its D-spacing, and the answers to bone's complicated mechanical properties during estrogen loss may lie in how OVX changes collagen viscoelasticity. Significant interactions were found between the Model Type and the Test Frequency. A Tukey-Kramer pairwise comparison was performed between Complex and Experimental data, which determined the Complex Model did not behave statistically differently from experimental findings at 15 Hz. This result suggests the Complex Model may begin to be validated to experimental results in a statistically meaningfully way that is a first for this style of FEA approach. The flexibility implemented in the randomization of the Complex Model welcomes refinement primarily in modeling viscoelasticity and fine-tuning the representation of mineralization. Through adjusting these material characteristics, the Complex Model may become an even more powerful tool in examining bone viscoelasticity and metabolic disorders.

Finite element is used to predict the torsional stiffness and natural frequency response of a FSAE vehicle hybrid chassis, utilizing a carbon fiber reinforced polymer sandwich structure monocoque and a tubular steel spaceframe. To accurately model the stiffness response of the sandwich structure, a series of material tests for different fiber types has been performed and the material properties have been validated by modeling a simple three-point-bend test panel and comparing the results with a physical test. The torsional stiffness model of the chassis was validated with a physical test, too. The stiffness prediction matches the test results within 6%. The model was then used to model the natural frequency response by adding and adjusting the materials’ densities in order to match physical mass properties. A hypothesis is made to explain the failure of the engine mounts under the dynamic response of the frame.