Assessment of Ductile Fracture Criteria Under Compressive Pre-strain With Digital Image Correlation

An object of this study is to assess ductile fracture criteria for compressively pre-strained material with digital image correlation (DIC) technique and to validate the criteria by performing finite element analyses (FEA). Uniaxial tension tests, uniaxial compression tests and tensile tests after pre-compression followed by reversed-tension were conducted with round bar and cylindrical specimens of A2024-T351 aluminum alloy. The radii of the minimum sections of the specimens at ductile crack initiation were measured with DIC technique in those tests. Stress triaxiality and equivalent plastic strain were obtained by substituting the radii into the Bridgman's equations. The relationship between the stress triaxiality and equivalent plastic strain under no pre-strain was evaluated using the Bao and Wierzbicki criteria. The fracture strain under compressive pre-strain was less than that of a material without compressive pre-strain. FEA implemented with the criteria was performed. The analytical results agree well with the experimental results of reversed tensile tests after compressive pre-strain.