Deflection measurement in low-blow Charpy impact tests

Abstract

Abstract The determination of velocity and displacement evolution of the specimen in a low-blow Charpy impact test was critically analyzed. To this end, a laser-based measurement of velocity and displacement was applied in addition to the standard integration procedure. The applicability of this non-contact method was investigated with respect to the measurement of velocity and detection of vibrations. It was shown that the velocity of the specimen could be determined in the case of unnotched specimens as well as of notched and precracked specimens. Utilizing the velocity evolution of the specimen determined by the laser, the dynamic force calibration was possible. The high sensitivity of the laser measurement to changes in velocity enabled the detection of pop-ins and, in some cases, the detection of stable crack initiation. The analysis of the specimen vibration frequency directly after the test could be utilized to estimate the final crack length.