Effect of Distance of Loading Points on Long Brittle Crack Propagation/Arrest Behavior

Large-scale duplex ESSO tests were conducted to investigate the effect of distance of loading points on long brittle crack propagation/arrest behavior. The test results showed that the greater load drop was found to be easier to arrest a long brittle crack in the tests of a 5m loading-points distance, compared to the tests of a 10m loading-points distance. Traditional static equivalent spring model could roughly describe the differences in load drop phenomena, due to differences in loading-points distance. Dynamic FEM analyses showed that specimen length was needed to be expanded to about 20m in order to prevent a load drop in large-scale duplex ESSO test, when the brittle crack velocity was about 500∼800m/s. Also, if the distance of loading points was over 10m or the specimen length of large-scale duplex ESSO test was over 6.8m, the dynamic stress intensity factor of the long brittle crack were found to be almost equivalent to the actual conditions in which the effects of load drop and stress wave were small. In the large-scale duplex ESSO test to evaluate a long brittle crack propagation/arrest behavior, it was considered that setting the appropriate test conditions was important, so as not to cause significant load drop and unloading stress wave.