ANALYSIS OF THE ASYMMETRIC UPSETTING TEST WITH EXTREMELY HIGH-STRAIN RATE AS TOOL FOR FRICTION MEASUREMENT

The upsetting of flat plates offers a way to analyse friction conditio ns in the interface area between tool and workpiece with regard to sur face microstructure, lubrication, and material properties. If a plate is compressed between two punches and the friction conditions at both interfaces are different, the billet bends over at both sides of the p unches. The final angle is a measure for the friction difference. In t raditional friction tests the forming speed is too low or the specimen is deformed only at the surface. In most metal forming processes, e.g . rolling, friction conditions cannot be described precisely because o f the unknown behaviour of the lubricant at high pressure or high defo rmation speed. The advantages of the test proposed here are simplicity , full deformation, and feasibility with high speed. The process is co st effective and does not require large scale equipment. (C) 1998 Else vier Science S.A. All rights reserved.