engleski

Advanced computer - aided evaluation of caustics for cracks in mechanically anisotropic materials

In the past the method of caustics has been developed as a suitable tool for the evaluation of stress intensity factors in fracture mechanics. When investigating crack tip stress intensity factors the result is either one or a sequence of shadow spots, the shape and the diameter of which are indicative of the stress intensity. Previously, SIF-values have been determined from caustics diameter measurements. A new technique for the SIF’ s determination has been designed on the basis of interactive computer graphics and multi-point over-deterministic data reduction method. The squares of the distances between conjugated experimental data points and the best-fit theoretical caustic is minized on the basis of a least squares technique. For mechanically isotropic materials this method was shown to work very fast and reliable and the results converge very rapidly. The method is successfully applied to mechanically anisotropic materials of which the orthotropic materials form a very important special case where the theoretical solutions for the positions of the light beams and for the singular caustic curve are taken into the account. The large number of data points that are employed in the analysis make this method a much reliable one when compared to the classical-diameter measuring technique, which would fail to work in the case of general mixed-mode loading conditions or at bimaterial interfaces.

caustics; fracture mechanics; stress intensity factor

nije evidentirano