Beom-Cheol Hwang

An experimental study on forming characteristics of pre-coated sheet metals

To analyze the forming and friction characteristics of pre-coated metals (PCMs) that are widely used in household appliances, rectangular deep drawing and friction tests were performed. There were four types of die materials (STD11(TiCN), STD11(TD), STD11, AMPCO) used in the deep drawing tests, and the results show that STD11 and AMPCO are better than others in respect to forming load and surface roughness. The friction mechanism, the thickness of materials and the effect of the roller’s diameter on the friction coefficient and surface roughness were examined in the friction test. The PCMs used in the tests had low friction coefficients (μ=0.15–0.20) in non-lubricated condition due to the coating film acting as lubrication. The friction coefficient decreased as the radius of the roller increased and the surface of product became better as the thickness of the material decreased.

A UBET analysis of the non-axisymmetric combined extrusion process

Abstract In this paper, the upper bound element technique (UBET) method was used to analyze non-axisymmetric combined extrusion processes. New kinematically admissible velocity fields (KAVFs) were proposed to determine the forming load, the extruded length and the velocity distribution according to the stroke in the combined extrusion process of a socket wrench from solid cylindrical billets. Experiments were carried out with antimony–lead billets at room temperature without lubricants. In order to observe the flow pattern of a billet at each stroke, square grids were inscribed on the surface formed by cutting the billet longitudinally. The forming load and the extruded length were compared between theory and experiment. It was found that the theoretical predictions of forming load and extruded length were in good agreement with the experimental results.