Abstract
In this paper, the effect of strain hardening on the elastic-plastic contact of steel sheets is considered using experiments. The effect of normal load and the effect of prestrain of the sheets on the change of surface roughness parameter values and real area of contact are analysed. Continuous indentation tests were performed on 2 mm thick DC04 steel sheets. The mechanical properties of the sheet metal were determined using uniaxial tensile tests along three directions concerning the rolling direction. Two cylindrical and spherical indenters were used in the investigations. It can be concluded that the real area of contact between a tool and a workpiece depends on the degree of sample prestrain, normal load and different flattening and roughening mechanisms of the deforming asperities. The effect of normal force on real contact area depends on the load value. The penetration depth value increases proportionally to the normal load.

Key words
elastic-plastic contact, contact mechanics, flattening, indentation test, surface roughness

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