Influence of metal forming parameters on surface roughness and establishment of surface roughness prediction model

Abstract

This paper aims to establish a prediction model of surface roughness for metal forming parts on the basis of analyzing the influence of metal forming parameters on surface roughness. Firstly, by W-M fractal function, a two-dimensional finite element model of upsetting with a rough surface was constructed and then the roughness evolution on contact surface of the formed part was numerically simulated during the upsetting process. The effects of multiple factors, including the contact normal pressure, the initial surface roughness of the workpiece, the sliding distance between the workpiece and the die and the surface area enlargement, on the surface roughness were analyzed thoroughly. It was found that the surface roughness of the formed part depends approximately linearly on the contact normal pressure applied by the die and the initial surface roughness of the workpiece, and exponential on the surface area enlargement rate. The effect of the sliding distance on surface roughness is related to the normal pressure. Based on the above analysis results, a surface roughness prediction model with consideration of multiple factors related to the metal forming process was proposed and verified via the upsetting experiments of pure copper at room temperature. The prediction results exhibit good agreement with experimental measurements. The surface roughness prediction model established in this paper can be applied to the metal formed parts which are difficult to improve the surface quality by machining, such as the parts with high precision requirements, complex shapes or ones with micro size by micro-forming.