CRACK OPENING AREAS DURING HIGH TEMPERATURE OPERATION

摘要

This paper presents results from two-dimensional finite element analyses of a centre cracked plate under both plane stress and plane strain conditions. The plate has been loaded in tension and secondary creep conditions have been assumed. The variation of the crack opening area with time has been calculated. It has been shown that the rate of change of the crack opening areas reduces with time up to the redistribution time which approximates the time to achieve steady creep conditions. Thereafter, the rate of change of crack opening area is constant. From curve fits to finite element results, a simplified expression for the rate of change of crack opening area of a stationary crack has been derived in terms of the elastic crack opening area, the creep strain rate, the elastic strain and two characteristic crack lengths (one for a strain field dominated by elastic strains and one for a strain field dominated by creep strains). This expression predicts the rate of change of the crack opening area both during the transient period up to the redistribution time and at all times thereafter.