Effect of reverse cyclic loading on the fracture resistance curve in C(T) specimen

Fracture resistance (J-R) curves, which are used for elastic-plastic fractu re mechanics analyses, are known to be dependent on the cyclic loading hist ory. The objective of this paper is to investigate the effect of reverse cy clic loading on the J-R curves in C(T) specimens. The effect of two paramet ers was observed on the J-R curves during the reverse cyclic loading. One w as the minimum-to-maximum load ratio (R) and the other was the incremental plastic displacement (delta(cycle)/delta(i)), which is related to the amoun t of crack growth that occurs in a cycle. Fracture resistance tests on C(T) specimens with varying the load ratio and the incremental plastic displace ment were performed, and the test results showed that the J-R curves were d ecreased with decreasing the load ratio and decreasing the incremental plas tic displacement. Direct current potential drop (DCPD) method was used for the detection of crack initiation and crack growth in typical laboratory J- R tests. The values of crack initiation J-integral (J(l)) and crack initiat ion displacement (delta(i)) were also obtained by using the DCPD method. (C ) 1999 Elsevier Science S.A. All rights reserved.