Abstract:Mechanical expanding is one of the finishing processes in cylindrical part forming. The distribution of stress and strain shows clearly regional features. FEA simulation and experiments show that the deformation process can be divided into three phases called as rounding phase, expanding phase and unloading phase in turn, in which the main types of deformation are wall bending, circumference elongating and thickness reducing, and spring back respectively. And the longitudinal section can be divided into three portions: expanding region, transition region and rigid region. The plastic deformation occurs regionally in suspended portion. A regional convex in transitional portion is inevitable.

Key words: mechanical expanding; deformation characteristic; numerical simulation