Modeling the anisotropy and creep in orthotropic aluminum-silicon carbide composite rotating disc

Processing of composites containing whiskers and short fibers often result in anisotropy due to preferential alignment of reinforcing element during flow as in extrusion. Analysis of steady state creep in a rotating disc made of composites containing SiC whiskers has been carried out using Hill yield criterion. The results obtained have been compared with the results obtained using von Mises yield criterion for the isotropic composites. The material parameters characterizing anisotropy have been determined from yield stresses taken from experimental results of other studies. It is observed that the tangential stress distribution is lower in the middle of the disc but higher near the inner and the outer radius but the radial stress distribution does not get significantly affected due to anisotropy. In the disc following Hill yield criterion there is small lowering of the stress beyond the point of maxima in the middle of the disc. When one compares the consequences of these changes in the stress distribution on the creep behaviour, it is observed that anisotropy has helped to reduce the tangential strain rate significantly, more near inner radius and the strain rate distribution in the orthotropic disc is lower than that in the isotropic disc following von Mises criterion. It should be noted that the anisotropy constants have been taken from the experimental results of other studies and the lowering of tangential creep rate may be significant in the context of real life engineering. The compressive radial strain rate also reduces in the disc following Hill criterion of yield plasticity as compared to that in isotropic disc. Thus, anisotropy appears to help in restraining creep response both in the tangential and in the radial directions. (C) 2002 Elsevier Science Ltd. All rights reserved.