A ductile fracture criterion in sheet metal forming process

Abstract Forming limit curves at neck (FLCN) and forming limit curves at fracture (FLCF) for various steel sheets were determined from a hemispherical punch stretching. The measured FLCF of the sheets with higher ductility limit had approximately linear shape like one of the bulk forming process. Whereas, the FLCF of the sheets with relatively lower ductility limit had a rather complex shape approaching the FLCN towards the equi-biaxial strain paths. Some experimental FLCFs of aluminum sheets and steel sheets were compared with the fracture strains predicted from some ductile fracture criteria reported in the literature. To determine the constants in the various ductile fracture criteria, a numerical procedure, which is based on plane stress condition and Barlat’s nonquadratic anisotropic yield criterion, was used. To predict precisely the experimental FLCFs with both the linear shape and the complex shape approaching the FLCN towards the equi-biaxial strain paths, from a combination of the Cockroft–Latham ductile fracture criterion and the maximum shear stress criterion, an empirical ductile fracture criterion in sheet metal forming process was newly suggested. The empirical criterion could be used to predict the FLCFs with the rather complex shape as well as the linear shape.

[1]  Dong Nyung Lee,et al.  Analysis of forging limit for sintered porous metals , 1995 .

[2]  Hitoshi Fujimoto,et al.  Prediction of forming limit in bore-expanding of sheet metals using ductile fracture criterion , 1999 .

[3]  S. Shima,et al.  Criteria for ductile fracture and their applications , 1980 .

[4]  S. Clift,et al.  Fracture prediction in plastic deformation processes , 1990 .

[5]  Ken-ichiro Mori,et al.  The application of some criteria for ductile fracture to the prediction of the forming limit of sheet metals , 1999 .

[6]  H. Kuhn,et al.  Fracture in cold upset forging -a criterion and model , 1973 .

[7]  Ken-ichiro Mori,et al.  FINITE ELEMENT ANALYSIS OF LIMIT STRAINS IN BIAXIAL STRETCHING OF SHEET METALS ALLOWING FOR DUCTILE FRACTURE , 2000 .

[8]  Beom-Soo Kang,et al.  Prediction of the forming limit in hydroforming processes using the finite element method and a ductile fracture criterion , 2001 .

[9]  J. Mize.  Optimization Techniques With Fortran , 1973 .

[10]  D. Lloyd,et al.  Fracture limit prediction using ductile fracture criteria for forming of an automotive aluminum sheet , 1999 .

[11]  F. A. McClintock,et al.  A Criterion for Ductile Fracture by the Growth of Holes , 1968 .

[12]  John A. Williams,et al.  The use of a shear instability criterion to predict local necking in sheet metal deformation , 1983 .

[13]  Frédéric Barlat,et al.  Plastic behavior and stretchability of sheet metals. Part I: A yield function for orthotropic sheets under plane stress conditions , 1989 .