疲労き裂進展過程における不確定要因の相乗効果

抄録

There exist many well-known uncertainty factors associated with the fatigue crack propagation process, among which two major uncertainty factors, one due to material inhomogeneity and the other due to the randomness of applied loads, undoutedly play an inevitably important role. Uncertainties caused by these two factors must be clarified not only individually but also jointly, since the cross-effect of both factors may arise under random loading and this is often the case in engineering reality.
In this respect, the present paper deals with the case where crack propagation resistance and stress amplitude of applied load are both stochastic processes and, in addition, each correlation decays exponentially with the increase of time difference. Towards this case has first been constructed a theoretical stochastic model with the aid of a Markov approximation method. Then the aforementioned cross-effect has been evaluated and discussed in detail, and the distribution characteristics of the model have been investigated by utilizing numerical computation techniques. Finally, the wide applicability of the proposed model has been emphasized by exemplifying a useful application of this model towards the inspection period determination problem which is often encountered in the practical reliability-based design of machines and/or structures.