Influence of geometric attributes on friction coefficient in sheet metal stamping

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.

Influence Of Geometric Attribute On Friction Coefficient In Sheet Metal Stamping

This paper presents a test device to explore the influence of geometric attribute of the contact surface on 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.

The Analysis on the Stamping Formability of High Strength Steel

Recently the high strength steel has been applied in the automotive more and more widely. In this study, the effect of blank shape on the formability of an automotive part was analyzed. The three kinds of blank shapes were chosen, including a rectangular shaped blank, a blank with two corners cut straightly and a blank with two corners cut in curve. The effect of the variable blank holder force on the formability was studied. The four kinds of variable blank holder force were applied. The blank shape in this part is the blank with two corners cut curve. The results show that the blank with two corners curve is the most suitable. And the blank holder force from 1000 kN to 1500 kN is the most useful for the formability.

Optimization and application of temperature field in rapid heat cycling molding

The rapid thermal cycle molding (RHCM) belongs to the injection mold temperature control system which is helpful to improve mold ability and enhance part quality. Despite many available literatures, RHCM does not represent a well-developed area of practice. The challenge is the uneven distribution of temperature in the cavity after heating, which mostly leads to defects on the surface of the products. In order to obtain uniform cavity surface temperature distribution of RHCM, the power of heating rods of the electric-heating system in an injection mold was optimized by the response surface method(RSM) in this work. The proposed optimization result was applied to design a complex RHCM injection mold with side core-pulling, holes and different thickness of an automotive part to verify its effectiveness by injection molding. Compared with initial design, the mold temperature uniformity was remarkably improvedby79%. Based on the optimization and injection molding numerical simulation results, the workable molding process to weaken the weld-lines effects on the quality was suggested and the practical injection molded parts were well produced.