Reliability Theory of Stochastic Fracture Processes in Sustained Loading: Part I

It is shown that the physical mechanism of thermally activated subcritical crack growth is always a stochastic process and leads, therefore, to probabilistic crack propagation. This process is the result of the random breaking of atomic bonds and has to be clearly distinguished f rom the well known Weibull distribution. A Markov chain analysis leads to the normal distribution of crack sizes. The results demonstrate that conventional deterministic finite life-time designs are unsatisfactory and can lead to early failure of machine or structure elements as the consequence of the probabilistic process of crack propagation. The conclusions lead to the reliability analysis of Part II.