Measurement system and measurement method for stress waves of Hopkinson bars by using flexoelectric effect

Abstract

The invention relates to a measurement system and measurement method for stress waves of Hopkinson bars by using a flexoelectric effect. The system comprises a bullet, a laser velocimeter, an input bar, an output bar, an absorbing bar, a damper, a first strain gradient sensor, a second strain gradient sensor, a speed measuring circuit and a two-way charge amplifier, wherein the first strain gradient sensor and the second strain gradient sensor are respectively attached to the input bar and the output bar, the speed measuring circuit is optically connected with the laser velocimeter, and the two-way charge amplifier is electrically connected with the first strain gradient sensor and the second strain gradient sensor; the speed measuring circuit and the output end of the two-way charge amplifier are electrically connected with signal processing, displaying and storing modules. During stress wave measurement, a test piece is fixed between the input bar and the output bar, the absorbing bar and the damper are sequentially arranged behind the output bar, and the bullet and the input bar are respectively arranged on the same horizontal plane on the two ends of the laser velocimeter. As the passive strain gradient sensors based on a flexoelectric principle are arranged, the measurement system can measure the first-order derivative of a real waveform, can directly carry out integral computation for the waveform, and can obtain the more real waveform of the stress waves, and the measurement precision is improved.

Description

technical field [0001] The invention relates to the technical field of testing based on Hopkinson rods, in particular to a Hopkinson rod stress wave measurement system and a measurement method utilizing the flexoelectric effect. Background technique [0002] In the field of military science such as shock and explosion, high strain rate, as a loading method to simulate the real environment, is widely used in the research of various materials. Due to the special loading method of high strain rate, various experimental platforms based on Hopkinson rods are currently the most widely used. In short, the material to be tested is fixed between two long straight metal rods, and the left end of the input rod is struck by a bullet (metal block) at a certain initial velocity, and a stress wave is generated on the input rod, and the strain on the input rod The chip detects the strain signal caused by the stress wave and sends it to the strain circuit; after the stress wave passes throu...

AI Technical Summary

Problems solved by technology

[0006] Taking the half-sine wave with a duration of 100μs as an example, its real waveform and measured waveform are as follows: figure 2 As shown: It can be clearly seen that there is a big difference between the actual waveform and the measured waveform at the beginning and end of the waveform, and the waveform maintenance time is elongated, and there is a certain waveform distortion

This phenomenon is more distorted in waveforms with steeper fronts and shorter durations

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