AN EVALUATION OF THE STRIP-YIELD RETARDATION MODEL FOR CRACK GROWTH PREDICTION UNDER SPECTRUM LOADING

摘要

7475-T7351 and 7050-T7451 aluminum alloy coupons have been tested under a gust and maneuver spectrum, corresponding to a transport aircraft wing. The test coupons include two crack configurations: "center-cracked tension" (CCT) and "open hole" (OH). The test results were evaluated using the NASA developed "Strip-Yield Model" contained in NASGRO (version 5) software. The results of the testing, and the subsequent analysis, have shown that the Strip-Yield retardation model contained in version 5 of NASGRO has been significantly improved over the model that was used in version 4. It is suggested that Strip-Yield model contained in NASGRO version 5 be further refined. The study also concluded that empirical factors could be used to perform NASGRO crack growth analyses that include retardation. These factors would need to be determined by performing coupon tests for the appropriate spectrum and alloy.