1989 Volume 38 Issue 429 Pages 675-681
Some difficulties inherent in the measurements by an instrumented Charpy impact testing apparatus have been studied by using aluminum alloy and mild carbon steel specimens in order to solve the disorderly oscillation of load and displacement observed during the measurement.
The measurements by the instrumented apparatus showed a remarkable oscillation of the measured load in the Charpy impact test under the condition of the standard initial tapping velocity. The load oscillation was effectively mitigated and a successful smoothing of the load-time records was obtained when the initial tapping velocity was lowered to about 75% of the standard value.
The load oscillation behavior was also effectively avoided by attaching a buffer material, such as a fat clay sheet, to the specimen tapping portion, and an effective smoothing of the load-time records was achieved simultaneously. The sensing error of the absorbed energy due to the attachment of the fat clay sheet was negligibly small.
It was confirmed that the cause of the displacement oscillation observed during the course of the impact test was the vibration of hammer shank of the testing apparatus due to the elastic deformation generated by tapping the specimen. It was also proposed that the increase in rigidity of the hammer shank is an effective procedure to reduce the displacement oscillation.
