Some experience in the use of damage mechanics to simulate crack behaviour in specimens and structures

Damage mechanics offers the possibility of representing the failure of components directly, without the use of characterising parameters such as the K or J of fracture mechanics. It does so by allowing the material to develop damage and fail at the level of the continuum mechanics description. Within the regime of ductile fracture, the method tries to encapsulate the loss of strength associated with void growth around the most significant second phase particles. Figure 1 illustrates diagramatically the process of void growth and the encapsulation of it in a ‘cell’ which represents at the continuum level the complex mechanics evolving within it as the cell softens and fails. Damage mechanics models these complex processes by building into the material constitutive equations the terms that represent the cell softening. The technique has been used successfully at SheffieldI to predict some of the spinning cylinder tests performed at AEA Risley.3 Figures 2 and 3 show the damage mechanics predictions for cylinders 1 and 3 in comparison with the experimental data and that from laboratory compact specimens. The enhancement of tearing resistance in the cylinders is correctly predicted directly from the computer simulation.