Synchronous measurement method of split Hopkinson pressure bar experiment based on digital images

Abstract

The invention discloses a synchronous measurement method of a split Hopkinson pressure bar experiment based on digital images. The method comprises the steps as follows: before the experiment, mark areas are made on the outer surface of one end where an incident bar and a tested piece are contacted as well as the outer surface of one end where a transmission bar and the tested piece are contacted; in the experiment process, moving images of the tested piece and the mark areas in the impact experiment process are obtained by a high-speed camera; through trace analysis of deformation of the mark area, strain of the tested piece as well as the incident bar and the transmission bar at the two ends of the tested piece is further obtained; and according to the principle of the Hopkinson pressure bar experiment, , stress of the two ends of the tested piece is calculated based on strain of the two bars; and further, through the novel experimental technology based on the digital images, the strain of a test piece and the stress of two ends of the test piece can be obtained synchronously.

Description

technical field [0001] The invention relates to a separate Hopkinson compression bar experiment, in particular to a digital image-based synchronous measurement method for the separate Hopkinson compression bar experiment. Background technique [0002] The split Hopkinson compression bar technique is an experimental method for testing the dynamic mechanical properties of materials. It has been widely used in the testing of mechanical properties of engineering materials under high strain rates. In the traditional separated Hopkinson compression rod experiment technique, strain gauges are first attached to the incident rod and the transmission rod, and then the stress-strain data of the specimen are converted according to the signals collected by the strain gauges during the experiment. Since the times for recording incident waves, reflected waves and transmitted waves are often different, the time starting points of these three waveforms are artificially selected in data proce...

AI Technical Summary

Problems solved by technology

Since the times for recording incident waves, reflected waves and transmitted waves are often different, the time starting points of these three waveforms are artificially selected in data processing. If the selected time starting points are inconsistent, it will lead to errors in stress-strain data, especially When testing some materials (such as soft materials, etc.) that require a long time to achieve uniform stress, it becomes more difficult to select the time starting point of the transmitted wave and the reflected wave, and the synchronization of the waveform cannot be guaranteed, so it is impossible to truly realize the Simultaneous measurement of specimen strain and stress at both ends

Some scholars have also proposed to embed quartz piezoelectric chips at the ends of the incident and transmission rods to obtain the stress at both ends of the specimen. Although the simultaneous measurement of the stress at both ends is realized, the strain data is still collected by the strain gauge, and its synchronization has not been improved.

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