Failure predictions for nuclear graphite using a continuum damage mechanics model

A failure model for nuclear graphite is presented in the context of continuum damage mechanics. It relates tractions to the relative displacements at an interface where cracking may occur. Both the stress-based and fracture-mechanics-based failure criteria are included in the model to construct a damage surface which shrinks in the stress space as damage develops. Damage initiation is governed by the stress criterion and full formation of a crack by the fracture-mechanics criterion. The unified failure model can deal with failure under both regular and singular stress concentration conditions. Numerical predictions for tension of L-shape and channel-section graphite specimens of different corner radius, including sharp corner, have been performed. The predicted failure loads are in good agreement with available experimental data. This indicates that the present failure model is suitable for graphite material.