Abstract
In steel structures, brittle crack propagates very fast and easily makes fatal damage on whole of the structures, so it has been studied from both aspects of numerical methods and experiments. However, there has been no valid equations governing brittle crack propagation. Nowadays, the local critical stress model is said to be able to explain brittle crack propagation behavior including the long brittle crack problem. Even though the model focuses on the stress field near the tip of crack, conventional models developed from the model does not evaluate stress precisely and it is needed to study the stress and other parameters near the crack tip to construct the more precise model.
This paper implements fundamental study on the simulation of the crack propagation by the nodal force release FEM in which crack velocity is an input variable. First, we compare error of dynamic stress intensity factor derived from the method releasing counterforce and find Linear counterforce releasing method is better than Jump counterforce releasing method. Second, we consider the effect of the crack acceleration and temperature gradient against stress, equivalent plastic strain and other parameters near the crack tip and these results show crack acceleration and temperature gradient does not affect the parameters when the material has strain-rate dependency. Generally, steel has strain-rate dependency and this result means we do not need to consider the temperature gradient and crack acceleration for simulating brittle crack propagation in steel structures.
