The achievement of constant strain rates in electromagnetic Hopkinson bar test

During the electromagnetic Hopkinson bar test, a sinusoidal shape of the stress wave could be generated and applied to the specimen. It is difficult to achieve a constant strain rate during the tests for the metal materials. This paper introduces a novel technique that can generate a bilinear shape of the stress wave based on the Fourier transform in which the multiple sinusoidal waves are superimposed. The mechanism of stress wave generation is analyzed theoretically and simulated numerically. On this basis, a new set of electromagnetic Hopkinson bar experimental equipment is set- up. The dynamic compression test of the material is carried out by the experimental device. The experimental results demonstrate that the specimens have a constant strain rate when subjected to bilinear stress wave impact. The regulation of stress wave shape can also be controlled by adjusting the electromagnetic emission parameters. Hence, the application scope of the ESHB technique in investigating dynamic properties can be expanded to various types of materials.