Experimental and Numerical Study on Forming Limit Diagrams of 304 Stainless Steel Tubes in the Hydroforming Process

Tearing as a factor that restricts formability of sheets and tubes is determined by forming limit diagram (FLD). The aim of the current study is to present a novel approach to achieve FLD of a metallic tube using hydroforming process. Here, for 304 stainless steel tubes, various loading conditions, namely free loading, bulging with axial feeding and bulging with closed end, were considered. Along with loading condition, die geometries with different corner radius and deformation width were studied on the strain path and plastic instability. The effects of process parameters on the strain path have been evaluated and simulated using ABAQUS/Explicit. Meshed tubes were bulged under controlled loading, and the FLD was drawn after measuring the major and minor strains close to the tearing location. Finally, the evaluation of the current method has been investigated by using the obtained FLD in the forming of an industrial part (i.e., the cam-shaped tube). The results revealed that the proposed approach has the capability to predict the formability of industrial components.