RESIDUAL STRENGTH PREDICTION FOR AIRCRAFT PANELS WITH MULTIPLE-SITE DAMAGE, USING THE EPFEAM FOR STABLE CRACK-GROWTH ANALYSIS

In this paper, a new analytical method for solving stable crack propag ation problems in a ductile panel with a row of cracks, is presented. The main purpose of the present study is to estimate the maximum load carrying capacity of such panels accurately. The so called Elastic Pla stic Finite Element Alternating Method (Pyo et al. (1994)) was extende d to account for the propagating cracks. The crack propagation algorit hm utilizes the analytic crack solution to release the stresses ahead the crack tip. The T-epsilon(star) integral is employed as the crack e xtension criterion. This integral parameter accounts for the near tip stress-strain singularity and its critical values for crack propagatio n can be extracted from the P-Delta a curve of single cracked specimen case. The present method can be applied to the problems of the fusela ge skin of aging airplanes, in which a row of cracks develop (MSD; Mul tiple Site Damage) from rivet holes. The load carrying capacity of suc h damaged structure reduces by a considerable amount. In order to pred ict the behavior near the critical load, one must account for plastic deformation, if the material is ductile. Furthermore,the maximum load carried by the structure is often reached after some amount of crack p ropagation. In this paper, a series of analyses have been conducted an d their results compare with the available experimental data.