Effects of Preloading Level on a Warm Pre- Stressed Crack Speciman

The residual stress and the crack tip blunting are two major suggested mechanisms for justifying the improvement in the load bearing capacity of cracked specimens after warm pre-stressing. In this paper, the finite element method is used to simulate the warm pre-stressing in a three-point bend specimen. The specimen is preloaded and its effect on these two mechanisms is investigated. It is shown that in general both the residual stress and the crack tip blunting are important in warm pre-stre ssing. However, depending on the level of applied preload one of them can be considered as the main cause. It is shown that in low levels of preloading crack tip blunting is more influential and in contrast, it is compressive residual stress that plays more important role in high levels of preloading.