Crack path stability in cracked panel

Abstract

The prediction of the crack growth path plays a significant role in the estimation of the final shape of broken solids and structures. Furthermore, the study of the crack path in broken specimens renders the loading conditions just before fracture. Experiments on brittle materials, pre‐cracked specimens of the same geometry, under similar loading conditions, occasionally result in different trajectories of the crack propagation. The already proposed theories for the prediction of the crack path (in) stability are based on the perturbation method in combination with analytical and finite elements methods; however, they require knowledge of the toughness equations. Therefore, they can only be applied in specimens with uncomplicated geometry and straightforward loadings. In the present paper the problem of the crack path (in) stability, is approached from a different viewpoint. Using a finite element program, the stres field is calculated, and consequently, a plotting program constructs the contours map of the strain energy density on the idealized geometry of the specimen or structure. For the determination of the predicted trajectory of the crack during unstable propagation, the minimum of the strain energy density criterion (SED) is used. The forecasted trajectory appears with the drawing of the “gorge” on the contours map of the strain energy density. Based on the estimation criterion, which claims that the degree of stability is a function of the distinctness of the gorge plot, we can predict the degree of the crack path stability. Therefore, this simple method offers good reliability in the prediction of the crack path stability for two as well as three‐dimensional problems with complex geometry structures and arbitrary loadings. In order to clarify the suggested prediction method, we apply it on the central cracked panel where a rich international practical experience exists. The results that are analysed in the present work, are in good agreement with equivalent published experimental results.