Effects of Geometric Variables on Stress Intensity Factors for Crack Gages.

摘要

A cracked metallic coupon, called crack gage, is being considered as a device for monitoring crack growth in aircraft structures. For this purpose, a stress intensity factor solution for the gage has to be known. This study provides stress intensity factor solutions for two basic geometric configurations subjected to prescribed displacements: 1. Edge cracked, trapezoidal shaped gages of uniform thickness. 2. Center cracked gages with varying or stepped thickness. For the trapezoid, the influences of changing the length of the cracked edge, while other edge remains constant, and vice-versa, were investigated. The results obtained do not show significant beneficial changes in stress intensity factor for the range of parameters considered over those of rectangular gages. Stress intensity factors were determined for stepped gages of various geometries. Various thickness ratios, length ratios and aspect ratios were considered, including the specific geometries of two gages now under development. In each case, the stress intensity factor was determined as a function of crack length.