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Abstract: The elastic stress field around a crack tip is fully defined through multiparameter equations such as the general relations of Westergaard proposed by Sanford or the most recent of Atluri and Kobayashi. Using the relations of Atluri and Kobayashi, a code was implemented to evaluate the characteristic parameters of the stress field around a crack tip by photoelastic analysis. The possibility to change the number of parameters makes it possible to adapt the study to different cases, increasing the extension of the analyzed area in order to have a correct modeling of the photoelastic fringes. The performed experimental tests allow emphasizing the importance of using multiparameter equations in the study of the stress field around the crack tip. [Copyright &y& Elsevier]

Abstract: The wheel–rail interface is fundamental for the comfort and the safety of the train. For this reason the wheel and the rail surface condition are checked with periodic non-destructive controls. The presence of a crack can be tolerated if we are able to predict its evolution by using fracture mechanics concepts. The problem is complicated by the fact that surface cracks propagate in mixed mode conditions. In this paper a photoelastic technique is presented to experimentally determine the stress intensity factors in a model of cracked rail under contact loads. The first results are critically discussed. [Copyright &y& Elsevier]

Abstract: The ever increasing research of performances and lightness leads engineers and manufactures toward the development of heavily loaded components, subjected to multiaxial fatigue loads, made of materials with improved surface mechanical properties. In these cases it is not rare the development of internal cracks, whose propagation involves mixed-mode conditions; where an accurate prediction of the growth rate and of the crack path requires the knowledge of the stress intensity factors concerning modes I, II and III. In this paper, an original method for the experimental determination of these quantities is described. It is based on the photoelastic technique and allows to obtain internal cracks with regular shape without using any cutting device. [Copyright &y& Elsevier]