Test analysis of metallic material´s elasto-plastic properties and macroscopic fracture criterion

Based on series of actual tests, such as tension-torsion tests on cast iron, compact tension-shear mixed mode fracture tests on aluminum alloy and routine failure tests on alloy steel, several different fracture modes have been summarized in this paper. For a kind of metallic material, under influences of the material itself, such as crystal boundary, inclusion and second phase participle, along with the descending of the stress triaxiality Rσ several different fracture modes may be emerged in order. These fracture modes are quasi-cleavage fracture, traction fracture with voids, shear fracture with voids and plastic shear fracture. For different fracture mechanisms, based on theoretical analysis and corresponding actual measurement, metallic material´s fracture criterion has been obtained separately. The fracture criterion can reflect macroscopic fracture phenomenon and microscopic fracture mechanism, and also comply with the fracture nature. It is a better supplement to the deficiency of fracture mechanics in explaining fracture test results of metallic materials. And it is also a better amendment to traditional strength theory for brittle fracture in solving materials´ fracture problems in complex stress states.