Effect of prestrain on material and single tensile overload cycles on crack closure

Abstract

Crack closure experiments were performed on 6063-T6 Al-alloy, using COD gauge for various overload ratios (1.67, 1.87 and 2.06) and different prestrains (0, 3 and 6%). On the basis of these experiments some relations are developed. The delay period after application of single overload is also increased as magnitude of overload is increased. The retardation is less as prestrain increased for the same overload ratio. After overload cycle the decrease in U value is less in prestrain material as compared to as received material. CGR is also decreased after application of overload cycle, it attains the CAL CGR after a certain number of cycles. In general crack closure load increased after overload cycle and after a certain number of cycles it tends to attain its CAL closure value.