Daw-Kwei Leu*
The Journal of Mechanical Science and Technology, vol. 25, no. 6, pp.1509-1517, 2011

Abstract : This work presents an indentation model of the Brinell hardness test, which is a rigid ball-deformable plane contact model (RB-DP model), to elucidate the sliding friction mechanism of sheet metal forming. In the proposed model, the friction force can be defined as a combination of shear (shearing effect) and plough (ploughing effect) forces. The real contact area ratio α is determined from the RBDP model under sliding condition. Moreover, the lateral contact area ratio / c r A A can be specified as a function of the real contact area ratio α . Based on Meyer’s law and Hertz contact problem, the maximum contact area ratio u α , a limiting condition of the real contact area ratio α , can be described as a function of the strain hardening exponent n. Additionally, a limiting condition applies: the strain hardening exponent n must be less than 0.64 in the present model. The present friction model reveals that the friction coefficient d μ is a function of strain hardening exponent n, the real contact area ratio α and the maximum contact area ratio u α . The calculated friction coefficient d μ agrees with the published experimental results.

Keyword : Sliding friction; Indentation; Strain hardening; Contact area; Sheet metal forming