SYMMETRY CLASSES AND HARMONIC DECOMPOSITION FOR PHOTOELASTICITY TENSORS

Two different definitions of symmetries for photoelasticity tensors ar e compared. A count of such symmetries based on an equivalence relatio n induced on the set of subgroups of SO(3) was presented by Huo and De l Piero, who proved the existence of exactly 12 classes. Here, another viewpoint is chosen, and photoelasticity tensors themselves are divid ed into symmetry classes, according to a different definition. By use of group theoretical techniques such as harmonic and Cartan decomposit ion, it is shown that this approach again leads to 12 classes. (C) 199 7 Elsevier Science Ltd.