Inhomogeneous deformation law in forming of multi-cavity parts under complex loading path

Taking a typical multi-cavity part, AISI-5140 tee valve, as object, the complicated inhomogeneous deformation law and related forming defect generation in multi-direction loading process were explored under four representative loading paths. It is found that four deformation modes, i.e., forward extrusion, forward-lateral combined extrusion, backward-lateral combined extrusion and backward extrusion, occur in different orders and times according to loading path. The cavum and folding defects are caused by metal's rapid flow to the vertical cavity in severe lateral extrusion when horizontal punch loads and subsequent loading of vertical punch. Vertical punch loading before the end of horizontal punch is beneficial to weakening backward-lateral combined extrusion and avoiding cavum and folding defects, but the vertical punch should not finish loading before the horizontal when load and offset load considered. By synthetically considering the deformation uniformity, metal flow, avoiding folding defect, forming load and offset load, the reasonable loading path is proposed.