Life Time Estimation under Probabilistic Fatigue of Cracked Plates for Multiple Limits States

What is it about?

The fatigue failure is most critical factor in lifetime estimation of industrial elements. The failure of a device in fatigue is due to a crack growth becoming instable and leading to strength decreasing. Based on Paris equation and S-N curves of WhOler, the probabilistic fatigue crack growth is studied where each parameter can be considered as random variable. A reliability analysis was developed here for plates under fatigue crack; the failure event taken can be expressed by many performance functions called limits states depending on possible failure modes. We study 3 limit states, the first is the reaching of a critical value of crack width a^j, the second is the reaching of the capacity value of tenacity of materials Kjc, the third is the reaching of a critical number of cycles of applied stresses N^j. Between theses 3 modes, we choose the most critical one toward the reliability value. A model of crack growth with respect to time is chosen to evaluate the time-reliability variation and hence to estimate the life time corresponding to a desired level of reliability.

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