DESIGN-POINT EXCITATION FOR CRACK PROPAGATION UNDER NARROW-BAND RANDOM LOADING

Abstract

When cracks propagate under random loading, different realizations of the loading process lead to different histories of crack growth. Within all possible realizations of the random load process, the so-called design-point excitation represents that particular realization that most likely leads to failure (e.g. unstable crack growth). In this paper, the design-point excitation for random crack propagation is found under narrow-band load processes. The solution involves a spectral representation of the load process, rain-flow counting of the resulting stress ranges, crack growth computation by means of the Paris Law, and solution of a reliability problem by FORM (First Order Reliability Method). The FERUM software is used in the reliability analysis. The design-point excitation is shown to exist for narrow-band load processes. Some considerations are presented with respect to the form of this excitation. So far, no convergence has been obtained for broad-band processes.