研究目的
To present a modified shearography setup that can be applied to workpieces with specular surface for non-destructive testing without requiring the surface to be sufficiently rough.
研究成果
The study demonstrates the feasibility of applying shearography to smooth surfaces without surface treatment, improving its usefulness in practical industrial applications. The specular surface under test is conjugated to the phase map, simplifying the positional correspondence between the interferogram and the internal defects.
研究不足
The method is difficult to quantitatively calculate the deformation gradient accurately due to defocus caused by the curvature and tilt of the surface, resulting in a decrease in spatial resolution. The location of the rough plate affects the measurement area and requires careful positioning.
1：Experimental Design and Method Selection:
A modified shearography setup based on a Michelson shearing interferometer is introduced for testing objects with specular surface. The setup involves illuminating the specular surface with light scattered from a rough plane to generate a speckle pattern.
2：Sample Selection and Data Sources:
A polished square metal plate and an acrylic plastic plate with a specular reflection film and an internal bubble are used as samples.
3：List of Experimental Equipment and Materials:
Industrial lens (focal length of 50 mm, relative aperture of 1/8), micro-head for applying deformation, and a rigid steel frame for clamping the samples.
4：Experimental Procedures and Operational Workflow:
The samples are edge clamped on a rigid steel frame, and a central concentrated loading is applied to generate deformation. The phase map is obtained using phase-shift technique and smoothed for quantitative evaluation.
5：Data Analysis Methods:
The phase map is analyzed using phase-shift technique and lowpass filtered for smoothing. The sensitivity factor is analyzed through ray tracing method based on geometric optics.
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