Orientador: Prof. Dr. Wesley Góis / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Mecânica, 2015. / O objetivo deste trabalho é realizar uma revisão sobre a metodologia clássica de previsão de falha por fadiga, Método S-N (Método Vida sob Tensão) para o desenvolvimento de uma ferramenta computacional com fins acadêmicos, cujo propósito é auxiliar docentes e discentes durante o ensino dessa metodologia em disciplinas da graduação. O algoritmo foi implementado em linguagem MatLab® e utiliza como dados de entrada a variação temporal do tensor de tensões para determinada região de um componente estrutural, bem como suas propriedades mecânicas. Durante todo processo interativo, a ferramenta apresenta em forma de "passo-a-passo" os fundamentos teóricos de previsão de falha por fadiga (Teoria da Elasticidade, Equação de Basquin, Critérios de Falha, Contagem de Ciclos, Regra de Dano Acumulativo, etc.). Essa é a grande vantagem do programa, pois proporciona dinamicamente a base teórica para a sua utilização, ao contrário de ferramentas puramente comerciais, que normalmente já pressupõem que o usuário tenha o conhecimento teórico para sua utilização. Por fim, como forma de validação da ferramenta, foram simulados, com auxílio da ferramenta desenvolvida neste trabalho, exercícios clássicos da literatura. alternativa, que mais recentemente vem sendo explorada, como solução para as limitações da formulação clássica do Método dos Elementos Finitos (MEF) ¿ de modo a estudar o impacto da mesma numa possível redução dos problemas de instabilidade numérica previamente citada. O algoritmo desenvolvido ao longo do trabalho é baseado no algoritmo apresentado em SIGMUND (2001), assim como alguns exemplos utilizados como referência. Por fim, exemplos numéricos apresentados ao longo do trabalho comprovam a redução parcial, ou em certos casos, completa do problema de instabilidade de tabuleiro de xadrez, demonstrando a viabilidade da utilização do MEFG como uma alternativa para obtenção da distribuição ótima de material no interior do domínio de projeto da estrutura. / The objective of this paper is to perform a revision of the classical methodology for fatigue life prediction, the Stress-Life Approach, to proceed with the development of a computational tool for academic purposes, for the use of masters and scholars during the teaching of this methodology. The algorithm was developed in Matlab® and it uses as input the temporal variation of stress tensor for a region of a structural component and its mechanical properties. During all of the interactive process, the tool shows "step-by-step" all the theoretical fundaments related to the methodology (Elasticity Theory, Basquin¿s Equation, Failure Criteria, Cycle Counting Methods, Palmgren-Miner¿s Linear Damage Rule, etc.). This is the main advantage of the software, since it offers dynamically the theoretical concepts to be used, unlike purely commercial tools, which normally consider that the users have a previous knowledge. Finally, the validation step of the tool considers the resolution of classical exercises.

The suspension system in vehicles supports the vehicle's road stability and ride quality by scaling down the vibration responses resulting from road surface's roughness. This research focuses on fatigue life analysis of coil spring component. Static linear analysis is conducted on the 3D model of helical coil spring to investigate deformation and stress responses. Modal analysis evaluates the characteristics of vibration, i.e. natural resonance frequencies and corresponding mode shapes. The stress frequency response is generated after performing the harmonic analysis on the spring. Dynamics and performance of spring are analyzed over practical frequency range of 0 Hz to 200 Hz. Fatigue life estimation of vehicle suspension spring is performed using the stress data obtained from frequency response analysis. The stress-life (S-N) approach is utilized for fatigue life assessment of suspension spring. This durability analysis technique can be utilized in the automotive industry to improve reliability of vehicles. The outcome of this research can contribute in analysis and design of modern smart vehicles. / Master of Science / The suspension system in vehicles supports the vehicle's road stability and ride quality by scaling down the vibration responses resulting from road surface's roughness. This research focuses on the fatigue life analysis of suspension spring component. Initial phase of analysis is conducted to investigate the deformation and stress in 3D model of spring. Dynamics and performance of spring are analyzed over applicable frequency range of 0 Hz to 200 Hz. Fatigue life of vehicle suspension spring is evaluated using stress data from frequency response analysis. This durability analysis technique can be utilized in the automotive industry to improve reliability of vehicles. The outcome of this research can contribute in analysis and design of modern smart vehicles.

This study addresses the fatigue life of the head–to–skirt welds of tall distillation columns. Fatigue tests were done on two types of weld geometries which approximate the head–toskirt configurations. From the fatigue tests it was determined that the fatigue life of the experimental samples can be substantially improved by applying weld build–up between the head and the skirt. The expected fatigue life of the test samples was determined by way of calculation employing the so called Nominal–Stress–Approach, the Effective–Notch–Stress–Approach and the Stress–Life–Approach. For both the Nominal–Stress–Approach and the Effective–Notch–Stress–Approach the predicted fatigue life was found to be overly conservative compared to the experimental results. The Stress–Life–Approach predicted the fatigue life to within a factor of 1.3 for both the geometries under investigation when displacements due to welding are taken into account. If displacements due to welding is omitted this factor is increased, for the geometry without weld build–up, to 2. For the geometry with weld build–up the factor remains 1.3. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2011.

This study addresses the fatigue life of the head–to–skirt welds of tall distillation columns. Fatigue tests were done on two types of weld geometries which approximate the head–toskirt configurations. From the fatigue tests it was determined that the fatigue life of the experimental samples can be substantially improved by applying weld build–up between the head and the skirt. The expected fatigue life of the test samples was determined by way of calculation employing the so called Nominal–Stress–Approach, the Effective–Notch–Stress–Approach and the Stress–Life–Approach. For both the Nominal–Stress–Approach and the Effective–Notch–Stress–Approach the predicted fatigue life was found to be overly conservative compared to the experimental results. The Stress–Life–Approach predicted the fatigue life to within a factor of 1.3 for both the geometries under investigation when displacements due to welding are taken into account. If displacements due to welding is omitted this factor is increased, for the geometry without weld build–up, to 2. For the geometry with weld build–up the factor remains 1.3. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2011.