Effect of Dissimilar Interfacial Roughness Properties on Deformation Characteristics of Plastic Compression

Abstract

A thermoelastic-plastic coupling formulation of large deformation combining with a hydrodynamic lubrication model is proposed to analyse the plastic upsetting of a cylinder, accounting for dissimilar interface conditions. The flow stress of the deforming workpiece is considered as a function of strain, strain rate and temperature; the lubrication model involves different lubrication regions from the thick film region at one extreme to the boundary lubrication region at the other. The effects of unequal interface frictional constraints, resulting from dissimilar interfacial roughness properties, at the top and bottom end surfaces on the temperature, strain component and effective strain distributions are investigated. The asymmetrical material flow inducing an uneven billet profile, together with the variations in the top and bottom die surface loads, are also predicted. The results obtained are consistent with the observations of upsetting experiments.