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

The effectiveness of the J-Q two parameter solution is clearly display ed in the cases of single-edge shallow cracked panel, double-edge crac ked panel and center cracked panel from small scale yielding to large scale yielding. It is also suitable for the bend cracked panel specime n from small scale yielding to medium scale yielding. However, for ben d cracked panel from medium scale yielding to large scale yielding, th e J-Q two parameter solution will deviate gradually from finite elemen t solution. Especially in large scale yielding, the deviation is remar kable. 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, a nd properly selecting the second term and modified term by matching wi th finite element solutions, we obtain a modified two parameter soluti on, which is very well in conformity with the finite element solutions in a wide range. The upper bound and lower bound fracture toughness c urves predicted by the modified two parameter solution are given. Thes e two curves have covered most experimental data and fully captured th e trend of most experimental data.