Scattering in Fatigue Crack Growth of Thin Pure Copper Sheet for Smart Stress Memory Patch

Abstract

A new sensing method called “smart stress memory patch” has been developed. This patch can estimate the number of cycles and the stress amplitude using its crack length. In this study, the scattering in the fatigue crack growth of the thin copper specimen was investigated to evaluate the error of estimated number of cycles. The rolled and the electrodeposited (ED) Cu with thin thickness were prepared. The fatigue test was performed to obtain the fatigue crack growth of each sample and the fatigue crack growth behaviors of specimens with large grain size demonstrated large scatter. The observed crack path and fracture surface indicated that large grain size affects scattering in crack growth. The effect of thickness and grain size on the scattering was also evaluated by the stochastic model. Furthermore, the error of estimated number of cycles demonstrated that the accuracy of measurement for memorized stress is improved using a specimen with small grain size such as as-received ED Cu for smart stress memory patch.