Influence of Pulsed Electric Current on the Motion of Spontaneous Plastic-Deformation Waves in Steel-Plate Extension

Аннотация

Despite growing interest in the intensification of shape changes by means of current pulses, very limited experimental and theoretical information regarding plastic deformation is available, and the physics of plasticization in metals has not been adequately studied. That is delaying the application of promising techniques in practice. In studying electrically stimulated plastic deformation, it may be useful to regard plastic flow as a wave process. By infrared thermography and double-exposure speckle interferometry, the plastic deformation of low-carbon steel in the presence of pulsed electrical current is studied in the present work. Such treatment increases the velocity of the plasticity waves by 65%. Analysis shows that the velocity distribution corresponds to a impact-transition wave. At first, the velocity of the material is zero (motionless clamp), but on the right side of the graph the velocity of the material is equal to the extension rate specified by the test machine. When current pulses are applied, the distribution of displacement velocities is split at both the mobile and immobile ends of the sample. Thermal data show that a temperature gradient runs from the clamps to the center of the sample. That does not match the distribution of the displacement. In the initial treatment by powerful current pulses, the sample temperature reaches 351 K in the central region of the sample and 330 K at the clamps. In other words, the difference is 21 K. Subsequent treatment increases the temperature only slightly. According to literature data, such increase in temperature decreases the yield point by 10% for the given steel. That corresponds to the results of the present experiments. The present work confirms previous findings regarding the change in velocity of the slow wave on current transmission. The splitting of the velocity values at the mobile clamp has not previously been reported.