Development of Two‑dimensional Video Extensometer Based on Target Recognition Algorithm

CHEN Junfu; WANG Zhentao; CHEN Fuyu; MA Binghui; LIU Yapi; WANG Jiangying

doi:10.3969/j.issn.1000-1158.2026.02.09

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Acta Metrologica Sinica ›› 2026, Vol. 47 ›› Issue (2) : 222-229. DOI: 10.3969/j.issn.1000-1158.2026.02.09

Development of Two‑dimensional Video Extensometer Based on Target Recognition Algorithm

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Abstract

In response to the requirement for precise measurement of deformation in uniaxial tension tests， a two-dimensional video extensometer capable of simultaneously measuring the longitudinal and transverse deformation of the specimen is developed. Firstly， the working principle of the two-dimensional video extensometer is clarified， and the imaging system is analyzed and hardware selection is also made. Secondly， the target recognition algorithm for synchronous measurement of longitudinal and transverse deformation is designed， and sub-algorithms such as image pre-processing based on grayscale morphology， template matching based on pyramids， straight-line feature detection based on edge tracking， and target recognition based on ROI are designed and tested. Finally， the two-dimensional video extensometer operation software with functions of image acquisition， graphic calibration， visual detection， and curve analysis is developed using LabVIEW and NI Vision platform， which is integrated with the test machine control software. Uniaxial tension tests are carried out on Q235 low carbon steel. The experimental results demonstrate that the video extensometer is capable of accurately monitoring both the longitudinal and transverse deformations within the gauge length of the specimens. Specifically， in the initial and fractured stage， the average relative error margin of longitudinal deformation measurements are less than 0.02%， while the average relative error margin of transverse deformation measurements are less than 0.2%.

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material deformation measurement / video extensometer / target recognition algorithm / two-dimensional deformation measurement / uniaxial tension tests

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CHEN Junfu , WANG Zhentao , CHEN Fuyu , et al . Development of Two‑dimensional Video Extensometer Based on Target Recognition Algorithm[J]. Acta Metrologica Sinica. 2026, 47(2): 222-229 https://doi.org/10.3969/j.issn.1000-1158.2026.02.09

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