Real‐Time and Quantitative Measurement of Crack‐Tip Stress Intensity Factors Using Digital Holographic Interferometry

Abstract

Detection of the crack in an object is a critical problem for the health monitoring of a transparent object. e real-time and quantitative measurement of the crack-tip stress intensity factor (SIF) remains an open issue. In this paper, an approach for realtime and quantitative measurement for the SIFs of a Mode I crack is presented based on digital holographic interferometry (DHI). A transmission digital holographic system is established to measure the phase difference of an object wave during loading. e expression to achieve the SIF from the phase difference is formulated. To enhance the accuracy of measurement, calibrated phase unwrapping based on least-squares and iteration and median filtering is applied to retrieve the actual phase from the noisy wrapped one. e SIFs of the Mode I crack in a transparent polymethyl methacrylate (PMMA) specimen are measured by this approach. e results are compared with the theoretical ones to demonstrate the feasibility of the proposed approach.

Advances in Digital Holographic Interferometry

“…Historically, digital holography began to receive its first practical applications in industry. High-precision analysis of mechanical vibrations, mechanical deformations, and stress tests—all these tasks were solved by holographic methods [ 75 , 76 , 77 ].…”

Near Crack Line Elastic‐Plastic Field for Mode I Cracks under Plane Stress Condition in Rectangular Coordinates

“…In the above analysis, the general solution of the plastic stress field near the crack line in rectangular coordinates (5a)-(5c) and the rectangular form of the elastic-plastic boundary near the crack line (7) have been obtained, respectively. By substituting equation 7into equations (5a)-(5c), the rectangular form of the plastic stress field at the elasticplastic boundary near the crack line can be obtained in this paper: Advances in Materials Science and Engineering…”

“…In linear elastic fracture mechanics [1][2][3], the stress intensity factor is the most critical parameter for the analysis of the elastic stress field near the crack tip [4][5][6][7][8]. However, in elastic-plastic fracture mechanics [1,2,9], the conventional crack tip asymptotic analysis method is widely used for the elastic-plastic analysis near the crack tip region [10][11][12][13][14][15][16][17]; such a method is confined by the small-scale yielding conditions.…”