The stress and strength behavior of cylindrical tubular adhesive joints composed of dissimilar materials was explored. This was accomplished with the finite element method (FEM) and stress-based failure theories. Also, it was shown how a design of experiments (DOE) based method can be used to objectively organize the process of optimizing joint strength by using stress-based failure criteria. The finite element program used in this work was written in-house from scratch to implement the FEM for the purpose of solving both axisymmetric and three-dimensional linear elastic governing equations of static equilibrium. The formulation of the three-dimensional model is presented, and the required operations to arrive to the axisymmetric model are also presented. The axisymmetric model is two dimensional, capable of using four and eight node quadrilateral elements. However, only four node elements are used because a mesh of eight node elements requires more memory and increased mesh refinement. The three-dimensional model is capable of using eight and twenty node brick elements, but only eight node brick elements are used for the same reason. Both of the axisymmetric and three-dimensional models calculate the nodal displacements, strains, stress values for each material, and strength values for each material. The external static loads can be individually applied, or coupled together. The outputs seem to be most useful for interpretation when plotted through-the-thickness (TTT) and along-the-length (ATL) of the joint or tube. Outputs are valid only for materials that behave linearly elastic up to(or near) failure, and the stress-based failure criteria are used to define that limit. A small laboratory-sized joint was modeled to look at the theoretical stress and strength distributions plotted along-the-length of the joint at different radial locations. These stress and strength distributions can be correlated to the type of load being applied because of unique or prominent features seen in the stress and strength distributions. The load can be a uniform temperature change, axial load, torque load, internal and external pressure, and/or bending load. A variance in the stress or strength for different joint sizes and materials is not examined closely due to the many possible combinations of these parameters.

La mousse flexible de polyuréthane est couramment utilisée dans nombreuses applications telles que acoustiques, thermiques et de bâtiment grâce à sa faible densité et à son pouvoir d’isolation thermique et acoustique. Elle est également utilisée dans les applications de confort pour les sièges tels que véhicule, train, avion etc. grâce sa faible raideur et à son pouvoir à absorber l’énergie de déformation. Pour optimiser le confort des systèmes d’assise, il est nécessaire de modéliser le siège et en particulier la partie flexible, c’est-à-dire la mousse de polyuréthane. Les objectifs principaux de cette thèse consistent à identifier puis à modéliser le comportement quasi-statique de la mousse de polyuréthane sous différentes conditions d’essais sous grandes déformations. Des essais de compression/décompressions unidirectionnels monocycle et multicycle à différentes vitesses de déformations ont été réalisés sur trois types de mousse de polyuréthane, afin de comprendre le comportement du matériau. Ces essais ont permis de déduire que les mousses de polyuréthanes sous grandes déformations présentent à la fois un comportement hyperélastique et un comportement viscoélastique. Ils ont également montrés que les mousses de polyuréthanes présentent un phénomène d’assouplissement appelé ‘effet de Mullins’ lors que les essais de compression/décompressions multicycle, c’est-à-dire que les contraintes dans 1er cycle sont moins faibles que les contraintes dans les cycles suivants pour une même déformation. Sur la base des résultats d’expérimentaux et afin de modéliser le comportement quasi-statique de la mousse de polyuréthanne, nous avons développé trois modèles visco-hyperélastiques qui se composent de deux éléments à savoir la partie modèles énergétiques hyperélastiques, utilisés généralement pour des matériaux à comportement caoutchoutique, et la partie modèle à mémoire entier qui tient compte de l’historique et permettant de décrire le comportement viscoélastique. Les paramètres des modèles ont été identifiés en utilisant la méthode d’identification et la méthode d’optimisation appropriée. Les résultats des modélisations du comportement mécanique de la mousse sur les essais monocycles et multicycles ont été comparés aux résultats expérimentaux, monteront à la fois une très bonne capacité à simuler le 1er cycle de charge/décharge, ainsi que les cycles suivant. Nos modèles ont prouvé leur capacité à modéliser l’effet de Mullins sur les mousses de polyuréthane souple. Ces modèles ont été validés sur les trois types de mousse et pour trois vitesses de sollicitation, permettent de conclure leurs efficacités et de leurs représentativités. / Flexible polyurethane foam is widely used in numerous applications such as acoustic, thermal and building due to its low density and its ability to absorb thermal and acoustic energy. It is also used for the comfort of the seats such as the vehicle, train, plane due to its low stiffness and its ability to absorb deformation energy. In order to optimize the comfort of the car seat, it is necessary to model the behavior of seat system, particularly the flexible component - polyurethane foam. The main objective of this study is to identify and model the quasi-static behavior of polyurethane foam under different test conditions in large deformations. Compression / decompression uniaxial unicycle and multicycle tests were carried out on three types of polyurethane foam at different strain rates, which allows us to understand the behavior of the material. The results of the tests indicate that the polyurethane foams exhibit a hyperelastic behavior and a viscoelastic behavior under large deformations. They also showed that the polyurethane foams have a stress softening phenomenon which is called 'Mullins effect' during the compression / decompression multicycle tests. In other words, the stress in first cycle is lower than the stresses in the subsequent cycles in the same deformation. ‘Mullins effect’ for the polyurethane foam is also an important study in this dissertation. Based on the experimental results and the goal of modeling quasi-static behavior of the polyurethane foam, three visco-hyperelastic models were developed. These models consist in two elements: hyperelastic models, which is normally used for description the behavior of rubber materials, and entire memory model which takes into account the history and describing the viscoelastic behavior. Model parameters were identified using appropriate identification and optimization methods. The results of modeling the mechanical behavior of the foam on the unicycle and multicycle tests were compared with experimental results. The models showed a very good competence to simulate the first cycle and the following cycles during the charge / discharge tests. Our models have proven its ability to model Mullins effect on flexible polyurethane foams. These models have been validated on three types of foam in order to present a comparative study of their effectiveness and their representativeness.

<p>In this research paper, it evaluates the benefits achievable from static testing framework by analyzing and transforming the <em>JUnit3.8 </em>source code and static execution of transformed code. Static structure enables us to analyze the code statically during creation and execution of test cases. The concept of research is by now well established in static analysis and testing development. The research approach is also increasingly affecting the static testing process and such research oriented work has proved particularly valuable for those of us who want to understand the reflective behavior of <em>JUnit3.8 Framework</em>.</p><p><em> JUnit3.8 Framework</em> uses <em>Java Reflection API</em> to invoke core functionality (test cases creation and execution) dynamically. However, <em>Java Reflection API</em> allows developers to access and modify structure and behavior of a program.  Reflection provides flexible solution for creating test cases and controlling the execution of test cases. Java reflection helps to encapsulate test cases in a single object representing the test suite. It also helps to associate each test method with a test object. Where reflection is a powerful tool to perform potential operations, on the other hand, it limits static analysis. Static analysis tools often cannot work effectively with reflection.</p><p>In order to avoid the reflection, <em>Static Testing Framework</em> provides a static platform to analyze the <em>JUnit3.8</em> source code and transform it into non-reflective version that emulates the dynamic behavior of <em>JUnit3.8</em>. The transformed source code has possible leverage to replace reflection with static code and does same things in an execution environment of <em>Static Testing Framework</em> that reflection does in <em>JUnit3.8</em>. More besides, the transformed code also enables execution environment of <em>Static Testing Framework</em> to run test methods statically. In order to measure the degree of efficiency, the implemented tool is evaluated. The evaluation of <em>Static Testing Framework</em> draws results for different Java projects and these statistical data is compared with <em>JUnit3.8</em> results to measure the effectiveness of <em>Static Testing Framework</em>. As a result of evaluation, <em>STF</em> can be used for static creation and execution of test cases up to <em>JUnit3.8</em> where test cases are not creating within a test class and where real definition of constructors is not required. These problems can be dealt as future work by introducing a middle layer to execute test fixtures for each test method and by generating test classes as per real definition of constructors.</p>

In this research paper, it evaluates the benefits achievable from static testing framework by analyzing and transforming the JUnit3.8 source code and static execution of transformed code. Static structure enables us to analyze the code statically during creation and execution of test cases. The concept of research is by now well established in static analysis and testing development. The research approach is also increasingly affecting the static testing process and such research oriented work has proved particularly valuable for those of us who want to understand the reflective behavior of JUnit3.8 Framework. JUnit3.8 Framework uses Java Reflection API to invoke core functionality (test cases creation and execution) dynamically. However, Java Reflection API allows developers to access and modify structure and behavior of a program.  Reflection provides flexible solution for creating test cases and controlling the execution of test cases. Java reflection helps to encapsulate test cases in a single object representing the test suite. It also helps to associate each test method with a test object. Where reflection is a powerful tool to perform potential operations, on the other hand, it limits static analysis. Static analysis tools often cannot work effectively with reflection. In order to avoid the reflection, Static Testing Framework provides a static platform to analyze the JUnit3.8 source code and transform it into non-reflective version that emulates the dynamic behavior of JUnit3.8. The transformed source code has possible leverage to replace reflection with static code and does same things in an execution environment of Static Testing Framework that reflection does in JUnit3.8. More besides, the transformed code also enables execution environment of Static Testing Framework to run test methods statically. In order to measure the degree of efficiency, the implemented tool is evaluated. The evaluation of Static Testing Framework draws results for different Java projects and these statistical data is compared with JUnit3.8 results to measure the effectiveness of Static Testing Framework. As a result of evaluation, STF can be used for static creation and execution of test cases up to JUnit3.8 where test cases are not creating within a test class and where real definition of constructors is not required. These problems can be dealt as future work by introducing a middle layer to execute test fixtures for each test method and by generating test classes as per real definition of constructors.

Im Projekt wurde das Ermüdungsverhalten eines hochgefüllten, extrudierten Holz- Polymer- Werkstoffes (Wood Polymer-Composite, kurz: WPC) und dessen technisches Halbzeug (WPC-Systemprofil) im Anwendungsfeld der Fördertechnik erforscht. Kernsegment im Projekt ist das hochgefüllte WPC-Extrusionsprofil als Trag- und Gleitelement im Hängefördersystem (HFS). Im ersten Schritt wurde das Kriechverhalten (langzeitstatisch) und Ermüdungsverhalten unter dynamisch-schwingender Belastung (langzeitdynamisch) am produktspezifischen WPC-Material und am WPC-Systembauteil untersucht. Das Prüfregime bezieht sich dabei auf das reale Belastungskollektiv in der Anwendung des Hängefördersystems, welches vorrangig einer Dreipunktbiegebelastung im WPC-Systemprofil und einer Zugbelastung in der Verbindungsstelle entspricht. Aufbauend auf die Material- und Bauteiluntersuchung wurde der Dauerlauftest am Funktionsprototyp (Hängefördersystem) durchgeführt. Dabei wurden die Kriechneigung des WPC-Systemprofils und der Vorspannkraftverlust in der Verbindungsstelle im praxisrelevanten Fall überwacht. / In the research project the fatigue behavior of a high filled extruded Wood Polymer Composite (WPC) and its technical product were investigated in the application of material handling technology. The main focus of the project is the high filled WPC extrusion profile, which is applied as a sliding rail for the use in an overhead material handling system. In the first step the creep behavior (long-term static load) and fatigue behavior under dynamic-oscillating loads were studied on the product-specific WPC material and on the WPC component. The testing procedure refers to the real stress collection in the application of the overhead material handling system, which corresponds to a three-point bending load in the profile and a tensile load in the connection point. Furthermore, an endurance test was carried out under practical conditions on the overhead matrial handling system to oversee the long-term mechanical properties of the WPC sliding rail and the loss of the preloaded force in the connection point.