Dynamic uniaxial bidirectional compression experiment method for brittle materials

Abstract

A dynamic uniaxial bidirectional compression experiment method for brittle materials adopts an electromagnetic separation type Hopkinson pressure bar bidirectional loading device, and a sample to be tested is clamped between the end faces of two incident bars. When the device is used for carrying out dynamic synchronous bidirectional loading on a test sample, two electromagnetic stress wave generators with identical parameters need to be connected in parallel into a charging and discharging circuit composed of a capacitor, a crystal diode and other components and be attached to the two incident bar end faces which are equal in length and made of the same material. When the capacitor discharges to the stress wave generators, current can equally enter the two stress wave generators, and twoidentical stress waves are generated in the two incident rods, so that the internal stress balance state of the brittle test sample can be realized in a shorter time, and more accurate and effective dynamic mechanical property data can be obtained.

Description

technical field [0001] The invention relates to the field of material dynamics experiments, in particular to a separate Hopkinson pressure bar uniaxial bidirectional loading experimental method based on electromagnetic force loading for improving the test accuracy of dynamic compression mechanical properties of brittle materials Background technique [0002] At present, when testing the dynamic compressive mechanical properties of brittle materials in the high strain rate range, most of them use the traditional split Hopkinson pressure bar (SHPB). The SHPB device is mainly composed of an air cannon, a bullet, an incident rod, a transmission rod and a data acquisition system. The sample to be tested is sandwiched between the end faces of the incident rod and the transmission rod. When the SHPB experiment is carried out, the stress wave starts to load it from one end of the sample, so it takes a long time to realize the stress balance inside the sample. The literature (Parry D...

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Problems solved by technology

When the SHPB experiment is carried out, the stress wave starts to load it from one end of the sample, so it takes a long time to realize the stress balance inside the sample. The literature (Parry D J, Dixon P R, Hodson S, et al. Stress equilibrium effects within Hopkinson barspecimens[J].Journal de Physique IV,1994,04:107-112) pointed out that under certain conditions, it is generally believed that when the bullet hits the incident rod, the incident wave is reflected back and forth in the sample for 3 to 5 times. The stress at both ends of the sample will reach equilibrium. The test data before this are all invalid data. These invalid data will bring great difficulties to the later data interpretation. For the calculation of some parameters (such as elastic modulus, failure strain etc.) will also produce large errors

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