Influence of contact extensometer abnormality on plastic strain ratio test

Based on the influence cases of extensometer jitter, poor clamping, droop and inaccurate positioning on the measurement of plastic strain ratio (r value), the reasons for the deviation of r value measurement results were analyzed by combining with the calculation formula. The results show that the abnormal measurement results of r value in the case were caused by the asynchronous measurement feedback of longitudinal and transverse extensometers. Methods and steps for finding measurement errors were provided,and reasonable suggestions were put forward.