On a Hybrid Method to Analyse Viscoelastic Problems

Abstract

To analyze problems of plane stress states when the material shows time-depending response, i.e. linear viscoelastic response, experimental procedures can be applied similar to photoelasticity. However, not only the mechanical, but also the optical rheological effects must be considered. Beside the isochromatic fringe pattern, the isoclinics are to be recorded over time. Obviously, recording the isoclinics is difficult and the reason of unavoidable incertainty and inaccuracy. On the other hand, the two different fringe patterns are to be evaluated separately by means of automatic digital image processing and the data to combine in order to determine the components of the stress-tensor according to algorithms, which are not appropriate to computer calculations. To avoid the difficulties, in order to obtain more reliable results and to save time for recording and evaluating the optical phenomena as well as computer capacity, a procedure will be described, which enables the principal stress components to be calculated, although the principal directions of the stress tensor, i.e. the isoclinics, are still unknown.