THE COSSERAT CONTINUUM, A MODEL FOR GRAIN ROTATIONS IN METALS

Torsional experiments with aluminum cylinders and tubes were carried out, and the grain rotations were measured by means of the v. Laue method. Despite a large scattering of the results the tendency of the rotations relative to the mean rotation of the displacement field is unique. The average value of the grain rotations agrees in a satisfactory manner with the predictions made from the point of view of a rigid/plastic Cosserat model. This holds true for an isotropic initial state of the material. It is unknown whether a modification of the Cosserat model would become necessary or not, should a textural anisotropy exist. As a side result, the difference between the v. Mises and the Tresca yield criterion is illustrated at the basis of the cylindrical and tubular specimens used in the tests.