Evaluation of stress field parameters in fracture mechanics by photoelasticity - Revisited

Multi-parameter stress field equations have been reported in the past two decades to model the elastic stress field in the neighbourhood of a crack lying in finite bodies. Notably among them are the generalised Westergaard equations proposed by Sanford, Williams' eigen function expansion and the recent one of Atluri and Kobayashi. The equivalence among these equations is brought out. Using the equations of Atluri and Kobayashi an over-deterministic least squares technique is proposed to evaluate the mixed-mode stress field parameters by the technique of photoelasticity. It is shown that the use of Atluri and Kobayashi's equations leads to a very simple software where one can independently increase the number of terms in Mode I or Mode II series depending on the specific problem requirement until the experimental fringes are correctly modelled. The software is validated by solving three example problems. The example problems emphasise that the use of multi-parameter stress field equations is not just an academic curiosity but a practical necessity to apply concepts of Fracture Mechanics to solve real life problems. Further, it is shown that the multi-parameter solution allows the collection of data from a larger zone which helps to simplify the data collection from experiments. Copyright (C) 1996 Elsevier Science Ltd