Study on the Duration of Impact in Elastic-Plastic Impact of Bodies.

点击翻译按钮获取中文摘要

1. Two kinds of methods for measuring an impulsive force generated at the impact end of a body subjected to impact loading were developed. The sensing circular plate and the sensing cylinder were produced by way of trial. Both methods using them were confirmed by calibration tests to be effective for directly measuring not only the impulsive force but also the duration of impact. The measurement was almost entirely free from disturbance caused by interference from reflected waves.2. The dynamic behavior of an elastic bar with a variable cross-section was studied theoretically and experimentally. Experiments of elastic impact were performed for two different truncated cones by impacting them against the sensing plate. The time variation of stress at the impact end of the truncated cones colliding with the sensing plate and the elastic response at several locations along the cones were measured. The theoretical predictions agreed well with the observed results.3. Plastic impact tests wer … More e made for pure copper and aluminum specimens with several different lengths by impacting them on the sensing plate or the sensing cylinder. The specimens bars were shot from a high-pressure air gun, built as a trial. The variations of stress vs. Time at the impact end of the specimens colliding the sensing cylinder and the duration of impact were measured at various impact velocities. The experimental results were compared with the theoretical predictions based on the strain-rate dependent theory of plastic wave propagation.Close agreement between the observed and the calculated values was obtained. The initial elevation of the impact end stress is strongly affected by the rise time of impact and its mode of rising, but the duration of impact is almost entirely uninfluenced by those impact conditions. The duration of impact is governed by the strain-rate sensitivity of materials and the impact velocity as well as the bar length.4. An electromagnetic transducer to record the particle velocities in longitudinal wave propagation in bars is made by way of trial. Less