J integral evaluation of U-notched bainitic functionally graded steel plates in notch arrester and notch divider configuration

In the present research, a kind of Functionally Graded (FG) steel (ferritic-bainitic- austenitic) was produced using Electro Slag Remelting (ESR) process. The position of each layer was determined utilizing Metallography and Vickers Hardness tests. Then, three point bending test was used for the U notched specimens in the form of notch arrester and notch divider configuration and effect of the notch depth on the critical fracture load and Jcr under mode I loading were investigated. Also J values of the FG steel and homogeneous steel under constant loading was evaluated and in this case, effect of the notch depth on J value was studied. Then a comparison was made between J values of the FG steel and homogeneous steel. Results showed that in arrester configuration, maximum critical load in specimens was occurred in the beginning of Bainite phase and Jcr was depended on the material and notch depth. While in divider one, variation of the Jcr was negligible. The J value of Each of the studied configurations were then computed using finite element approach based on Rice theory and a good agreement was observed between numerical results with the experimental ones.