Advanced self-compensated, high-accuracy optical extensometer based on field-of-view splitting and dual-reflector imaging techniques. (April 2021)

• Record Type: Journal Article
• Authors: Zhu, Feipeng; Tao, Jin; Lu, Runzhi; Bai, Pengxiang; Lei, Dong
• Is Part Of: Measurement. Volume 174(2021)
• Publication Date: 2021-04
• Subjects: Optical extensometer -- Field-of-view splitting -- Gauge length -- Digital image correlation -- Dual-reflector imaging; Weights and measures -- Periodicals; Measurement -- Periodicals; Measurement; Weights and measures; Periodicals; 530.8
• DOI: 10.1016/j.measurement.2021.109024
• Languages: English
• ISSNs: 0263-2241

Abstract

Highlights: A high-accuracy optical extensometer is proposed using a common imaging lens and FOV splitting technique. High-resolution strain measurement is feasible due to the use of the FOV splitting technique. Dual-reflector imaging technique is adopted in proposed extensometer to self-compensate the effect of out-of-plane motion. Experimental results indicate that the RMSE decreased from 20.5με to 5.64με when adopting the proposed extensometer. Abstract: Optical extensometers realized using a telecentric lens and field-of-view (FOV) splitting technique can achieve a high strain measurement accuracy. However, the telecentric lens has some disadvantages such as high cost, fixed FOV, and fixed working distance. In this study, we have developed an advanced optical extensometer using a low-cost imaging lens and FOV splitting device. Dual-reflector imaging technique is implemented in the proposed optical extensometer to reduce the strain errors induced by out-of-plane motion. With the FOV splitting device, the proposed extensometer exhibits a gauge length of 4659 pixels, while the initial gauge length is only 1700 pixels. The effectiveness of this extensometer is verified by static and tensile tests. The experimental results indicate that the values of axial strain obtained using the proposed extensometer in uniaxial tensile tests are in excellent agreement with those obtained using a strain gauge, and the standard deviation of corresponding strain errors is 4.6 microstrain, which validates the high accuracy of the extensometer.