This paper presents a test device to explore the influence of geometric attributes of the contact surface on a friction coefficient along with sliding speed and contact pressure. Friction tests were conducted on a third-generation high-strength steel QP980. The friction coefficients for different surface curvatures, contact pressures, and sliding speeds were calculated, and the influences of these factors were analyzed. The formula for calculating the friction coefficients between curved contact surfaces was derived. The relationship between bending-induced surface roughness increase and friction coefficient was established. An enhanced friction coefficient model with pressure, velocity, and curvature dependence was proposed. The enhanced friction model was applied to simulate the stamping of an automotive part, and a better correlation was achieved.

Skid lines on the outer panels of automobiles seriously affects their appearance and are a common surface manufacturing defect. In the die and process design stages, numerical simulation is needed to predict skid lines to take prevention measures. However, it is still a challenge to predict skid lines accurately. The simulation-based skid line criteria need further verification and improvement. Therefore, this paper takes a lightweight aluminum alloy AL6061-T6 sheet as its research object, uses a set of U-shaped dies to explore the influence of process parameters on skid lines, and establishes the correlation between skid lines and surface roughness based on visual and microscopic measurements. The relationships between contact pressure/inverse bending strain and surface roughness are established through simulation. Thus, a contact pressure and inverse bending strain dependent skid line criterion is constructed. The skid line criterion based on the simulation results has theoretical, guiding significance for the practice of engineering.