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Estudo da direção de iniciação de fendas sob carregamentos biaxiais
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Abstract(s)
Os componentes mecânicos podem estar sujeitos a carregamentos complexos ao longo do tempo, desencadeando um processo de fadiga quando os carregamentos são dinâmicos. Muitos destes carregamentos são multiaxiais, podendo ser muitas vezes não-proporcionais, provocando uma resposta muito complexa no material.
Neste trabalho realizaram-se ensaios de fadiga biaxiais, usando-se provetes cruciformes, com diferentes cargas entre eixos e diferentes desfasamentos, com o objetivo de determinar a direção de iniciação de fissuras nestas condições. Recorreu-se a vários critérios de plano crítico para previsão da direção da propagação cujos resultados serão comparados com os ensaios experimentais.
Verificou-se que para carregamentos proporcionais, que os modelos de Smith, Watson e Topper e Liu I permitem obter boas previsões de iniciação de fissuras, enquanto para carregamentos não-proporcionais são os modelos de Findley, Brown-Miller, Fatemi-Socie e Liu II que estimam melhor a iniciação de fissuras, quando comparado com os resultados dos ensaios experimentais.
Mechanical components can be subject to complex loads over time, triggering a fatigue process when the loads are dynamic. Many of these loads are multiaxial, and can often be non- proportional, causing a very complex response in the material. In this work, biaxial fatigue tests were performed, using cruciform test pieces, with different loads between axes and different fase angles, in order to determine the direction of crack initiation in these conditions. Several critical plan criteria are used to predict the direction of propagation whose results will be compared with those of the experimental tests. It was found that for proportional loads, the models of Smith, Watson and Topper and Liu I allow to obtain good predictions of crack initiation, while for non-proportional loads are the models of Findley, Brown-Miller, Fatemi-Socie and Liu II that better estimate the initiation of cracks when compared with the results of the experimental tests.
Mechanical components can be subject to complex loads over time, triggering a fatigue process when the loads are dynamic. Many of these loads are multiaxial, and can often be non- proportional, causing a very complex response in the material. In this work, biaxial fatigue tests were performed, using cruciform test pieces, with different loads between axes and different fase angles, in order to determine the direction of crack initiation in these conditions. Several critical plan criteria are used to predict the direction of propagation whose results will be compared with those of the experimental tests. It was found that for proportional loads, the models of Smith, Watson and Topper and Liu I allow to obtain good predictions of crack initiation, while for non-proportional loads are the models of Findley, Brown-Miller, Fatemi-Socie and Liu II that better estimate the initiation of cracks when compared with the results of the experimental tests.
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Keywords
Componentes mecânicos Carregamento não-proporcional Fadiga Biaxial Direção de iniciação Critérios de plano crítico Mechanical components Non-proportional loading: Biaxial fatigue Initiation direction Critical plan criteria