Influence of Constraint of Material on Shearing Characteristics

In shearing, the crack occurrence may be controlled by elevating a hydrostatic pressure of a material near tool cutting edges. Since hydrostatic pressure is affected by constraint of material, the influence of constraint on shearing characteristics was investigated by the experiments and FEM analysis. The results of this study clarified the followings. The smooth sheared surface of blanked product is increased by constraint of material. When the material is tightly constrained, crack earlier occurs at the material near punch cutting edge than that of die cutting edge. This tendency agrees with the magnitude of hydrostatic pressure at punch and die cutting edges. It is confirmed that the constraint of material prevents cracks by adequate controlling of material flow aiming the hydrostatic pressure rise. It is also confirmed that the dishing of product is affected by the condition of the constraint.