The experiment is divided into two parts, the first part is the static tensile test of vermicular graphite cast iron, and the second part is the dynamic impact test of Hopkinson pressure bar. In the process of dynamic impact test, the end surface roughness and cylindricity of the sample are very important to the success of the experiment. The poor roughness of the end face will cause the stress-strain curve to wobble violently, so that the experimental data obtained can not be used.
The smaller the sample is, the more serious the jitter is, so for metal materials, larger samples are used to balance the errors that may occur in the experimental process. However, the smaller the sample is, the higher the strain rate is, and the larger sample can only reach 5000s-1 at most. In order to obtain high strain rate, the small sample is used in this experiment, and the quality of the sample is improved by reasonable process.
The static tensile test was carried out on the RSA250 electronic universal material testing machine at a temperature of 20 °C and a strain rate of 0.01s-1. According to the national standard GB/T228.1-2010 “tensile Test of Metallic Materials-part 1: room temperature Test method”, the cross section of the specimen is round and the diameter is 10mm. The neck of the specimen is polished with sandpaper to reduce the probability of stress concentration in the neck. When stretching, the testing machine itself will be deformed, in order to eliminate this error, there is no sample loading testing machine, and the deformation of the testing machine under different loads is recorded and eliminated in the subsequent experimental data processing.