Analysis of material deformation response to dynamic tensile tests

Abstract

The material dynamic behaviour of components of rail vehicle subjected to impact loading is of great importance in terms of evaluating dynamic strength behaviour and stress-strain responses. It is also quite necessary objective to be able to understand the strengthening mechanisms depending on rate of loading during impact. For these purposes, it is mainly aimed to examine effects of stress distribution and dynamic peak forces corresponding each time step of the impact loading in this study. Besides, the position of strain gages incrementally placed over the surface of the specimens to analyse plastic deformations and impact forces. In order to perform experiments, a pendulum impact test method is proposed after making static calibrations of the strain gauges in a conventional tensile test machine. Therefore, eleven samples are prepared in which strain gauges are positioned at an equal interval from the fracture zone in order to measure time history plot of the dynamic forces. Throughout the study, the general principles and fundamentals about the dynamic strengthening mechanism, experimental procedure and preparation of samples including the all test equipment are sufficiently estimated in detail. Consequently, the signal values measured during the impact are converted into force-time plots and the results are tried to be investigated in terms of strengthening mechanism and material response in plastic region. In addition, an overview of the ability of material dynamic elongation response under crash process are presented for selected samples. It is certainly pointed out that for the regions near the fracture zone exhibits high plastic deformation and residual forces as a result of high amount of vibration and material heterogeneity. For the regions distant from the fracture zone, a more uniform and stable characteristics of material impact behaviour are observed.