CHARACTERIZATION OF ELASTIC-PLASTIC FIELDS NEAR STATIONARY CRACK-TIP AND FRACTURE CRITERION

The effectiveness of the J-Q two parameter solution is clearly displayed in the cases of single-edge shallow cracked panel, double-edge cracked panel and center cracked panel from small scale yielding to large scale yielding. It is also suitable for the bend cracked panel specimen from small scale yielding to medium scale yielding. However, for bend cracked panel from medium scale yielding to large scale yielding, the J-Q two parameter solution will deviate gradually from finite element solution. Especially in large scale yielding, the deviation is remarkable. In this paper, we carry out the finite element calculations for two representative cases of the bend cracked panel and center cracked panel specimens from small scale yielding to large scale yielding. By considering a modified term on the basis of two parameter solution, and properly selecting the second term and modified term by matching with finite element solutions, we obtain a modified two parameter solution, which is very well in conformity with the finite element solutions in a wide range. The upper bound and lower bound fracture toughness curves predicted by the modified two parameter solution are given. These two curves have covered most experimental data and fully captured the trend of most experimental data.