| A component or structure may fail due to the fatigue damage that is caused by repeated application of some types of dynamic loading. Dynamic loading causes vibration motion in an elastic system, and the maximum response is, in general, greater than its equivalent static load. As a result, it is easier to initiate the fatigue failure of a structure under dynamic loading as compared to its static loading counterpart. Therefore, attempts have been made here to investigate some important features of the fatigue of a structure subjected to repeated dynamic loading.;An analytical procedure based on current engineering technology is developed to predict fatigue life, which is assumed to be the crack initiation life of the structure. The method employs a finite element dynamic analysis to determine the time-varying stress and strain responses due to the characteristics of dynamic loading. Once the dynamic stresses and strains at the critical point are known, a strain-based fatigue approach is used to conduct the fatigue damage analysis.;A thin beam which vibrates easily under dynamic loading is used to demonstrate the procedure and to investigate the fatigue behavior of the structure considered. The case studies include combinations of two types of boundary conditions of the beam and different levels of loads and damping ratios. The results of predicted fatigue lives are in agreement with the generally accepted values based on the traditional stress-life approach in the infinite-life region. Some general features of the problem are drawn for reference. It is believed that the results and methods presented in the dissertation give a good starting point for the study of this kind of problem. |
