Papers by Author: Da Wei Jiang

Abstract: Fatigue tensile treatment was performed on 00Cr12 heat-resistant steel specimens which had been treated by laser shock processing (LSP). The unilateral tolerance factor statistical analysis method and the two-dimensional Weibull distribution method were used to predict the values of fatigue safe lives of the specimens respectively. The results indicate that the fatigue lives of 00Cr12 specimens were enhanced greatly after LSP, and improved by 62% compared with the specimens which were not treated by LSP. The unilateral tolerance factor method obtained an exact estimation value of the fatigue safe life; while the two-dimensional Weibull distribution method can get a range of values of fatigue safe lives, the fatigue safe lives of the specimens which after LSP were a range from 116570 to 150230, the average value was 132330. The two-dimensional Weibull distribution method has more engineering applicability and can be used to estimate the fatigue safe lives with fewer experiments.

Abstract: Cracks were prefabricated on compact tension specimen of 7050 Aluminum alloy, which was laser shock processing(LSP) once and three times. The whole crack initiation process, distribution and size evolution on aluminum alloy was studied with replica technique and through optical microscope. It was found that without LSP, small cracks initiated at the grain boundary and grew quickly. The cracks continued growing in depth. The growth of short cracks had the trend of stop-and-go oscillation, the crack data were relatively scattered, and short cracks had short average length and grew earlier. After LSP, surface residual compressive stress restrained to the trend of crack origins where crack origins would form most easily; after origination, cracks initiated towards the processed region, but stop temporarily if encountering great resistance, and might generate additional crack origins; Moreover, the higher the level of stress created by LSP was, the fewer cracks initiated.