The cold upsetting and free surface ductility of some commercial steels

Free Surface Fracture in Three Upsetting Tests

“…It has been found in many studies (e.g., [1][2][3][4]) that the failure curve in the Baxial straincircumferential strain^diagram is a straight line with a slope of approximately j0.5, though different experimental results have been also reported (e.g., [5][6][7]). In particular, in [7] it has been found that the failure curves are in most cases straight lines but their slope is not j0.5.…”

“…This approach has been adopted in [1,[4][5][6]8] among others and appropriate fracture criteria have been reviewed in [8,9]. To apply the approach, it is necessary to either experimentally determine the strain path at the fracture site [1,[5][6][7] or solve the problem numerically [4,5]. In the former case, experimental data for the axial strain as a function of the circumferential strain at the fracture site are usually approximated by either a linear polynomial [1,6,10], or a quadratic polynomial [3], or a cubic polynomial [8], or a cubic spline function [5,6].…”

“…To apply the approach, it is necessary to either experimentally determine the strain path at the fracture site [1,[5][6][7] or solve the problem numerically [4,5]. In the former case, experimental data for the axial strain as a function of the circumferential strain at the fracture site are usually approximated by either a linear polynomial [1,6,10], or a quadratic polynomial [3], or a cubic polynomial [8], or a cubic spline function [5,6]. Combining these approximate equations and a stress -strain curve for the material it is possible to find the state of stress at the fracture site and to assess empirical ductile fracture criteria.…”

“…Another approach is to combine experimental data on free surface fracture and empirical fracture criteria which are assumed to be applicable at any state of stress. This approach has been adopted in [1,[4][5][6]8] among others and appropriate fracture criteria have been reviewed in [8,9]. To apply the approach, it is necessary to either experimentally determine the strain path at the fracture site [1,[5][6][7] or solve the problem numerically [4,5].…”

Fracture Phenomenon in Simulation of Bimetallic Rods Extrusion Process

“…FEM may be applied to model and control metal forming process or predict possible negative phenomena. There are numerous papers concerning such problem [5][6][7][8][9] but up to now there is no enough good solution taking into account the real behaviour of various materials or choice of proper criterion of fracture.…”