Analytical and numerical modelling of the Swift effect in elastoplastic torsion

Torsion tests are widely used to investigate the elastoplastic behaviour of metallic materials, particularly when large strains are involved, up to the specimen’s fracture. Such tests induce multiaxial inhomogeneous stress/strain and damage fields into the specimen. In this paper, elastoplastic torsion at room temperature of uniform isotropic circular solid and tubular metallic specimens is investigated in the finite strain range, both in analytical and numerical forms. The paper reports preliminary results of an on-going research project at the University of Bergamo [1]. Particular emphasis is given to the evaluation of the so-called Poynting (in the elastic domain) and Swift (in the plastic range) effects [2,3], i.e. the recorded axial length variation of the specimen that may appear under free-end torsion.