Effect of longitudinal cracks on structural life of functionally graded beams exhibiting creep

Developing of approaches for evaluation of structural life of load-bearing functionally graded beam structures containing longitudinal cracks under creep is a current problem. This is due to the fact that in many cases longitudinal cracks are observed during routine maintenance check of such structures. The present paper novelty is that an approach for evaluating the effect of longitudinal cracks on structural life of functionally graded load-bearing beams which exhibit non-linear creep is developed. In this relation, general time-dependent solution of the strain energy release rate (SERR) is derived. The beams under consideration are functionally graded in the thickness direction. The crack is located arbitrary along the thickness. The creep behavior is described by non-linear stressstrain- time relationship written in general form. The solution of the SERR is derived by analyzing the time-dependent complementary strain energy. Two cases of behavior (beams with identical creep behavior in tension and compression and beams with asymmetrical creep behavior in tension and compression) are considered. The general solution is applied to evaluate the effect of a longitudinal crack on the structural life of a cantilever beam. The timedependent SERR in the cantilever beam is obtained also by considering the balance of the energy for check-up of the general solution. It is found that the structural life is extended with increasing thickness to width ratio of the beam. However, the life of the structure is shortened as the crack length to beam length ratio increases. Furthermore, a beam with asymmetric creep behavior in tension and compression has a shorter structural life than that of a beam with identical creep behavior.