Strain hardening rate dependency of deformation shape, strain distribution, and contact pressure during wire flat rolling

The effect of the strain hardening exponent (n) of a material on the changes in shape, strain inhomogeneity, and contact pressure was investigated during wire flat rolling to understand its effect on the deformation behavior of a flat-rolled wire and to determine the optimal working conditions with materials. The deformation behaviors of wires with various n values were systematically compared using finite element method. The shape of the deformed wire was found to depend on the n value of the material. Both the contact width and lateral spreading of the wire decrease with increasing n, resulting in a large reduction in area with the n value. The strain homogeneity of the wire increases with the n value of the wire. The improvement in the strain homogeneity with the n value is attributable to two factors: a lower strain concentration in the central region and a higher overall elongation as n increases. In addition, the average effective strain of the wire cross section decreases with the n value of a material during wire flat rolling. The contact pressure distribution on the surface of the wire differs significantly depending on the n value. In materials with a low n value, the contact pressure exhibits a higher value at the entry and edge zones of the contact surface. By contrast, materials with high n values exhibit a higher contact pressure at the exit zone. This behavior can be explained by the strain hardening behavior of the material during wire flat rolling.