Characterizing the buckling behavior of cylindrical hollow and hybrid specimens by experimental upsetting tests

Abstract

In the research of the compound forging of steel-aluminum parts mostly the upsetting test is used. In this paper the factors influencing the buckling behavior during the upsetting of mono hollow cylinders and hybrid steel-aluminum specimens are examined and characterized by two parameters. The buckle ratio is used as a measurement for the uniformity of the part geometry in radial direction and the buckle distance provides information about the part geometry in axial direction. The results gained by the upsetting of hollow cylinders show that the reproducibility depends on the wall thickness of the hollow steel cylinder. Above a forming temperature of T = 750 °C a transformation from mode II (double barrel profile) to mode I (single barrel profile) occurs. Furthermore, it could be shown, that the strain rate has no influence on the buckling behavior in both the upsetting of hollow cylinders as well as the upsetting of hybrid specimens. The results gained by the upsetting of hybrid steel aluminum specimens show that with increasing forming temperature the hybrid specimens with a wall thickness of the steel casing of s = 1 mm form more homogeneously in radial direction. In addition the scatter of the results decreases with increasing forming temperature.