| Dynamic fracture toughness of a structural steel has been estimated by employing instrumented impact testing method with small size specimens. One of the pendulum type impact testing machines equipped with semiconductor strain gage block in the tup, was used in this study. Signal from the dynamic transducer was multiplied by a dynamic strain amplifier and then stored in a digital memory before analyzing. Experimental results demonstrated that the toughness obtained from the instrumented impact testing agreed well with theoretical value, but several factors were appeared to play an important role when converting the test results into dynamic fracture toughness based on linear elastic theory. They were (1) the crack initiation point which would occur prior to maximum impact load, Pm, on the load-deflection curve, (2) compliance correction and (3) elastic inertial wave effect which had nothing to do with the specimen toughness. |
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