Application of Finite Element Method to Analysis of Ductile Fracture Criteria for Punched Cutting Surfaces

Abstract

Many types of punching processes are utilized in the production of automobile parts and other components. In normal punching with a punch and a die, a sheared surface and a fractured one are usually formed on the cut surface. Here, to produce highly accurate parts, it is important to estimate the ratio of the sheared surface to the cut surface and to economically produce smooth cut surfaces, optimal tools and punching conditions must be selected within the limits of cost constraints. The finite element method (FEM) has been applied to the analysis of the ratio of the sheared surface to the fractured surface on the cut surfaces. For this, the ductile fracture criteria for the fracture initiation of the cut surface have been proposed by several researchers. It is difficult to determine the fracture criteria on the cut surface by tensile tests or bending tests because the punching process consists of many complicated steps. In this study, we apply the FEM to four punching arrangements to evaluate the ductile fracture criteria proposed by Oyane and by Cockcroft and Latham. We find that the morphology of the cut surface is affected by clearance between the punch and the die, by blank holding conditions and by ductile fracture criteria.

Hydrostatic Pressure Dependent Crystal Plasticity by Homogenization-based Finite Element Method

“…In contrast, at p = 552 MPa, the forming limit strain increases significantly near the equibiaxial tension, suggesting that higher hydrostatic pressure may increase sheet formability for hydrostatic pressure-dependent materials. Also, the hydrostatic pressure effect, i.e., shear deformation is enhanced during press forming when high hydrostatic pressure is imposed to a specimen, sometimes plays an important role in metal forming, 20,21) and the present result may relate to this effect. Further assessment and discussion of the effect of hydrostatic pressure on formability are left as future studies.…”

Optimum Clearance in the Microblanking of Thin Foil of Austenitic Stainless Steel JIS SUS304 Studied from Shear Cut Surface and Punch Load

“…As is known by the skilled persons in the shearing industry, in the deformation region around the tool edge, the deformation is concentrated in a very narrow range, and a large distortion occurs in the elements. Therefore, mesh size was determined by referring to the simulation results [25] in the previous FB study, which showed the relationship between the mesh size and the clearance CL. Specifically, the mesh size was set to about 1 µm, which is smaller than the clearance.…”

Elucidation of Shearing Mechanism of Finish-type FB and Extrusion-type FB for Thin Foil of JIS SUS304 by Numerical and EBSD Analyses

“…Since the deformation is concentrated in an extremely narrow range in the deformation area around the cutting edge of the tool, there is significant distortion in the elements [11]. The simulation result in a previous FB study, which revealed the relationship between the mesh size and the clearance Cl , was referred to for the determination of the mesh size [12]. Specifically, the mesh size in the analysis was set to about 1 μm, which is smaller than the clearance Cl .…”