Abstract
The design and capabilities of a computer-automated high-spatial-resolution displacement-measurement system are described. The system is used to determine the relative displacement fields generated by thermal or mechanical loads by comparing a pair of SEM or optical micrographs, one recorded before the load is applied and the other afterwards. The displacements are measured by cross-correlation analysis of the relative positions of visible surface texture on the micrographs. Displacement accuracy on a specimen surface is ±60 Ă for optical microscopy, and ±10 Ă for scanning electron microscopy. Both in-plane or out-of-plane deformation can be characterized depending on the angle at which the specimen is viewed. This instrument has the potential of quantifying surface deformation over submicron gage lengths and will be an invaluable tool in experimental micromechanics.
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References
Post, D., “Moiré Interferometry for Deformation and Strain Studies,”Opt. Eng.,24,663–667 (1985).
Sharpe, W.N., “Applications of the Interferometric Strain/Displacement Gauge,”Opt. Eng.,21,483–488 (1982).
Cox, B.N., Morris, W.L. and James, M.R., “High Sensitivity, High Spatial Resolution Strain Measurements in Composites and Alloys,” Proc. Nondestructive Testing and Evaluation of Advanced Materials and Composites, Colorado Springs, 25–39 (Aug. 1986).
Williams, D.R., Davidson, D.L. andLankford, J., “Fatigue Crack Tip Plastic Strains by the Stereoimaging Technique,”Experimental Mechanics,20,134–139 (1980).
Morris, W.L., Inman, R.V. andJames, M.R., “Measurement of Fatigue-Induced Plasticity,”J. Mat. Sci.,17,1413–1419 (1982).
Peters, W.H. andRanson, W.F., “Digital Imaging Techniques in Experimental Stress Analysis,”Opt. Eng.,21,427–431 (1982).
Metwalli, S.M., Ragab, A.R., Kamel, A.H. andAbdul Saheb, A., “Determination of Plastic Stress-Strain Behavior by Digital Image Processing Techniques,”Experimental Mechanics,27,414–427 (1987).
Lee, C., Peters, W.H., Sutton, M.A. andChao, Y.J., “A Study of Plastic Zone Formation by Digital Image Processing,”Int. J. Plasticity,3,129–142 (1987).
Peters, W.H., Ranson, W.F., Sutton, M.A., Chu, T.C. andAnderson, J., “Application of Digital Image Correlation Methods to Rigid Body Mechanics,”Opt. Eng.,27,738–742 (1983).
Chu, T.C., Ranson, W.F., Sutton, M.A. andPeters, W.H., “Application of Digital Image Correlation Techniques to Experimental Mechanics,”Experimental Mechanics,25,232–244 (1985).
Bruck, H.A., McNeill, S.R., Sutton, M.A., Chao, Y.J., and Peters, W.H., “Determination of Deformations using Digital Image Correlation with the Newton-Raphson Method of Partial Differential Corrections,” Proc. 6th Int. Cong. on Exp. Mech., SEM, 1152–1158 (1988).
Mostafavi, H. andSmith, F.W., “Image Correlation with Geometric Distortion,”IEEE Trans. on Aerospace and Electronic Systems,14,487–500 (1978).
Morris, W.L., James, M.R. andZurek, A.K., “The Extent of Crack Tip Plasticity for Short Fatigue Cracks,”Scripta Met.,14,149–153 (1985).
Morris, W.L., Inman, R.V. andCox, B.N., “Microscope Deformation in a Heated Unidirectional Graphite/Epoxy Composite,”J. Mat. Sci.,24,199–204 (1989).
Mastafavi, H., “Optimal Window Functions for Image Correlation in the Presence of Geometric Distortion,”IEEE Trans. on Acoustics, Speech and Signal Processing,27,163–169 (1979).
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James, M.R., Morris, W.L. & Cox, B.N. A high accuracy automated strain-field mapper. Experimental Mechanics 30, 60–67 (1990). https://doi.org/10.1007/BF02322704
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DOI: https://doi.org/10.1007/BF02322704