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摘要
Fracture is one of the main defects during metal deep drawing spinning(DDS). In order to accurately predict and control the fracture defects during DDS, a ductile fracture criterion for DDS is proposed by analysing the fracture form, stress characteristics and crack formation process. Ni-based superalloy of Haynes 230 is selected as the research object and its stress characteristics during DDS was analysed. It is pointed out that the maximum principal stress and the maximum shear stress are the main reasons for the formation of tangential and axial fracture in the middle and mouth of the cylinder wall respectively. The modified Lou criterion considering the two fracture forms of DDS is constructed. Uniaxial tensile tests with different stress triaxiality are designed to calibrate the damage parameters of ductile fracture criterion. The ductile fracture criterion for DDS is verified by the DDS experiments, and the fracture of Ni-based superalloy during DDS is predicted. The results show that the Lou criterion only considers the influence of the maximum shear stress, which leads to the axial fracture of the workpiece in advance. The modified Lou criterion takes into account the influence of both the maximum principal and shear stress, and can accurately predict the forming position and the forming time of fracture during the DDS. The relative error of the prediction of the fracture time is only 7%. The damage accumulates rapidly along the bulge area when the mouth bulge defect appears during DDS, which leads to the crack propagation along the axis direction from the bulge area and forms the axial fracture. Because of the compressive stress on the outer surface and the tensile stress on the inner surface of the contact area of the roller, the inner surface in the middle of the cylinder wall is more prone to form tangential fracture. ? 2023 Editorial Office of Chinese Journal of Mechanical Engineering.
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