Special Section on Optical Metrology in the Transportation Industry

Three-dimensional digital image correlation to quantify deformation and crack-opening displacement in ductile aluminum under mixed-mode I/III loading

[+] Author Affiliations
Michael A. Sutton

University of South Carolina, Department of Mechanical Engineering, Columbia, South Carolina 29208

Junhui Yan

University of South Carolina, Department of Mechanical Engineering, Columbia, South Carolina 29208

Xiaomin Deng

University of South Carolina, Department of Mechanical Engineering, Columbia, South Carolina 29208

Ching-Shan Cheng

GM R&D and Planning, Vehicle Development Research Lab, Warren, Michigan 48090

Pablo Zavattieri

GM R&D and Planning, Vehicle Development Research Lab, Warren, Michigan 48090

Opt. Eng. 46(5), 051003 (June 04, 2007). doi:10.1117/1.2741279
History: Received October 02, 2006; Revised December 26, 2006; Accepted January 05, 2007; Published June 04, 2007
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Fractures in ductile thin-sheet structures, such as a fuselage or automobile panels, often occur under complex loading conditions. In particular, under remote mixed-mode I/III loading conditions, a cracked structure is subjected to a combination of in-plane tension and large out-of-plane tearing deformation, which may lead to crack tip fields consisting of all three fracture modes (modes I, II, and III). Understanding such fracture events in ductile materials is an important component of the structural integrity analysis of load-bearing structures containing ductile, thin sheets. Due to the complex nature of mixed-mode I/III fracture in ductile thin-sheet materials, reports of experimental investigations are very limited in the literature. We configure three-dimensional digital image correlation (3D-DIC) systems to acquire full-field deformations during the loading and stable tearing processes. The full-field deformation measurements are used to characterize the stable crack extension behavior of an aluminum alloy undergoing quasistatic and dynamic mixed-mode I/III loading. Results confirm that 3D-DIC is an excellent methodology for measuring 3-D deformations in the presence of large out-of-plane warping and motion, both dynamically and statically. Data obtained during the fracture process indicate that the introduction of a mode III component into the loading process alters the crack tip displacement and strain fields relative to those measured in the nominally mode I loading. Furthermore, the measured crack-opening displacement (COD) values during quasistatic and impact mixed-mode I/III fracture show that (1) COD is nearly constant for crack extension beyond 2mm and (2) COD under combined-mode I/III loading is four times larger than observed during mixed-mode I/II or mode I fracture of the same material, indicating that the magnitude of the critical COD is a function of loading mode in highly ductile, thin-sheet materials.

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© 2007 Society of Photo-Optical Instrumentation Engineers

Citation

Michael A. Sutton ; Junhui Yan ; Xiaomin Deng ; Ching-Shan Cheng and Pablo Zavattieri
"Three-dimensional digital image correlation to quantify deformation and crack-opening displacement in ductile aluminum under mixed-mode I/III loading", Opt. Eng. 46(5), 051003 (June 04, 2007). ; http://dx.doi.org/10.1117/1.2741279


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