塑性应变比(r值)是评价金属材料成形性能的重要指标之一，ISO 10113:2020标准规定：采用全自动方法测试时，应在试样平行长度部分至少均匀测试3处宽度。根据ISO 10113:2020标准的要求，采用视频引伸计同时测试了试样长度和宽度方向的实时应变。结果表明：视频引伸计采用非接触式测试，避免了与试样接触产生的人为不确定因素的影响，测试结果与人工测试结果也更为接近。

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.