Abstract
Composite materials have seen widespread use in the aerospace industry and are becoming increasingly popular in the automotive industry due to their high strength and low weight characteristics. The increasing usage of composite materials has resulted in the need for more effective techniques for nondestructive testing (NDT) of composite structures. Of these techniques, digital shearography is one the most sensitive and accurate methods for NDT. Digital shearography can directly measure strain with high sensitivity when combined with different optical setups, phase-shift techniques, and algorithms. Its simple setup and less sensitivity to environmental disturbances make it particularly well suited for practical NDT applications. This paper provides a review of the phase measurement technique and recent developments in digital shearographic NDT. The introduction of new techniques has expanded the range of digital shearography applications and made it possible to measure larger fields and detect more directional or deeper defects. At the same time, shearography for different materials is also under research, including specular surface materials, metallic materials, etc. Through the discussion of recent developments, the future development trend of digital shearography is analyzed, and the potentials and limitations are demonstrated.
Highlights
Composite materials have seen widespread use in the aerospace industry and are becoming increasingly popular in the automotive industry due to their high strength and low weight characteristics
Digital shearography is a laser-based optical interferometry technique that requires a shearing device to be placed in front of the camera to introduce image shearing, thereby allowing light reflected from two different object points to interfere at one point in the image plane
Spatial phase-shift digital shearography (SPS-DS), in which phase-shift interferograms are obtained in different spatial positions at the same time to realize dynamic shearography measurements, was proposed
Summary
Composite materials have seen widespread use in the aerospace industry and are becoming increasingly popular in the automotive industry due to their high strength and low weight characteristics. Optical NDT techniques such as holography [7], electronic speckle pattern interferometry (ESPI) [8], shearography [9], and digital image correlation (DIC) [10] all have the characteristics mentioned above. Shearography is insensitive to small rigid body movement because a rigid-body motion does not produce strain This means that shearography has a huge space for development in industrial operations. Digital shearography is the latest version and the mainstream of recent development It uses image sensors (charge-coupled device (CCD) or complementary metal-oxide semiconductor (CMOS)) to capture information and analyze data. After a brief introduction of the principles of digital shearography, the paper presents the development process of the phase measurement technique and discusses the advantages and disadvantages of the temporal phase-shift algorithm and spatial phase-shift algorithm in detail. The potentials and limitations of digital shearography are shown and demonstrated
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