A Measurement Method for Tensile Strain Based on Machine Vision

The tensile strain of metal materials is measured by video extensometers features non-contact measurement, reducing the number of sensors and wide measurement range. However, the existing video extensometer stretching measurement technology has problems such as high measurement cost, complex structure, and low measurement efficiency. In response to above issues, a simple structured video extensometer is designed to realize the measurement of tensile strain by machine vision. The camera is calibrated by the static image of video extensometer firstly. Then the captured dynamic video of the extensometer is decomposed and image processed. Finally, tensile strain of the specimen is measured by the position of video extensometer on the image. The experimental results and analysis show that the method can realize visual measurement of the material tensile strain, and has good measurement accuracy and universality.