Comparing Results of Plastic Strain Ratio Values of Metal Thin Sheets Measured by Three Methods

The plastic strain ratio r values of four different thickness sizes DC03 cold rolled thin steel sheets were tested by semi-auto, full-auto and video-extensometer three different methods respectively. Comparing the testing results of these three different methods, it was found that there was large difference among them, and then reasons for the large difference were analyzed. The results show that plastic strain ratio values tested by semi-auto method and video-extensometer method were nearly, and reliability and repeatability of these two methods were high. However, reliability and repeatability of full-auto method was low. It was mainly due to the measurement results of transverse extensometer automatic measurement system to the transverse deformation was uncertainty. So, when testing plastic strain ratio values of metallic material it should give priority to video-extensometer method, and in the case of manual handling extensometer, semi-auto method should be the preferred over full-auto method.