High-accuracy optical extensometer realized by two parallel cameras and two-dimensional digital image correlation.

Area of Science:

• Materials Science
• Mechanical Engineering
• Optical Metrology

Background:

• Conventional optical extensometers using single cameras and 2D-DIC struggle with strain accuracy due to out-of-plane specimen motion.
• Out-of-plane translation and rotation significantly impact measurement reliability in traditional setups.

Purpose of the Study:

• To develop and validate an improved optical extensometer system for accurate strain measurement.
• To mitigate the adverse effects of out-of-plane motion and vibrations on extensometry results.
• To offer an easy-to-implement and highly accurate alternative to conventional methods.

Main Methods:

• Implementation of a novel optical extensometer utilizing two parallel cameras synchronized with 2D-DIC.
• Strategic selection of gauge points at the image centers of both cameras to minimize out-of-plane motion influence.
• Validation through rigid out-of-plane translation experiments and multiple uniaxial tensile tests.

Main Results:

• The proposed two-camera system demonstrates significant resistance to out-of-plane motion and experimental vibrations.
• Strain measurements from the improved extensometer show excellent agreement with traditional strain gauge data, with errors in the microstrain range.
• The method achieves high accuracy and reliability without requiring complex compensation techniques.

Conclusions:

• The dual-camera optical extensometer offers a robust and accurate solution for strain measurement, effectively addressing out-of-plane motion challenges.
• This method is easily integrated with 2D-DIC and adaptable to various specimen sizes by adjusting camera separation.
• The findings support the adoption of this improved technique for precise material characterization.