Application of video extensometer in r value measurement of metal plate

Plastic strain ratio (r value) is one of the important indexes to evaluate the forming performance of metal materials. ISO 10113: 2020 standard stipulates that when using automatic method to measure, at least three widths should be uniformly measured in the parallel length part of the sample. According to the requirements of ISO 10113 : 2020 standard, the real-time strain in the length and width direction of the sample was measured by video extensometer. The results show that the non-contact test of video extensometer avoided the influence of human uncertainty caused by sample contact, and the test results were closer to the manual test results.