Technique for two-dimensional displacement field determination using a reliability-guided spatial-gradient-based...

Area of Science:

• Experimental Mechanics
• Optical Measurement Techniques
• Digital Image Correlation

Background:

• Accurate measurement of in-plane displacement fields is crucial for understanding material behavior under stress.
• Existing optical methods often face challenges with accuracy and computational efficiency.

Purpose of the Study:

• To develop a novel algorithm for precise in-plane displacement field measurement.
• To enhance accuracy and computational efficiency in deformation analysis.

Main Methods:

• A linear illumination model was employed to ensure intensity invariance between images.
• Image upsampling and a reliability-guided strategy using zero-mean normalized cross-correlation identified matching points with 0.5-pixel accuracy.
• The brightness constancy and Lucas-Kanade optical flow constraints were combined to form an overdetermined linear equation, solved using a noniterative least-squares algorithm.
• Multithread calculation was utilized for efficient processing of cracking applications.

Main Results:

• The proposed method demonstrated sub-pixel accuracy in displacement measurement.
• Experimental results validated the algorithm's correctness, effectiveness, and robustness.
• High computing efficiency was achieved through multithread implementation.

Conclusions:

• The developed optical flow-based algorithm provides a robust and accurate solution for in-plane displacement measurement.
• The method is suitable for analyzing deformation, particularly in applications involving cracking.
• The combination of advanced image processing and efficient algorithms ensures reliable and fast deformation analysis.