Classification of stress-intensity factors from isochromatic-fringe patterns
The stresses in the local neighborhood of a crack tip have been used to develop a relation between the isochromatic-fringe orderN, its position parametersr and θ and the stress field expressed in terms of stress intensities,K I ,K II , and a far-field stress σ ox . This relation was programmed and a plotting routine was developed to map isochromatic (σ1 − σ2) fields in the neighborhood of the crack tip.
The stress intensitiesK I andK II and the far-field stress σ ox were varied and isochromatic fields were constructed for each combination. As bothK II and σ ox influence the size, shape and orientation of the isochromatics loops in a systematic manner, the pictorial representation of the isochromatic fields can be used to classify the state of stress (K I ,K II and σ ox ) at the crack tip. Isochromatics which classify six different states of stress have been illustrated and methods used to determineK I ,K II , andσ ox in five of the six states are given.
KeywordsMechanical Engineer Fluid Dynamics Stress Intensity Stress Field Local Neighborhood
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- 1.Kobayashi, A.S., ed., Experimental Techniques in Fracture Mechanics I, Iowa State Press (1973).Google Scholar
- 2.Kobayashi, A.S., ed., Experimental Techniques in Fracture Mechanics II, Iowa State Press (1975).Google Scholar
- 3.Post, D., “Photoelastic Stress Analysis for an Edge Crack in a Tensile Field,”Proc. SESA,12 (1),99–116 (1954).Google Scholar
- 4.Wells, A.A. andPost, D., “The Dynamic Stress Distribution Surrounding a Running Crack—A Photoelastic Analysis,”Proc. SESA,16 (1),69–92 (1958).Google Scholar
- 5.Irwin, G.R., Discussion of Ref. 4, Proc. SESA,16 (1),93–96 (1958).Google Scholar
- 6.Schroedl, M.A., McGowan, J.J. andSmith, C.W., “An Assessment of Factors Influencing Data Obtained by the Photoelastic Stress Freezing Technique for Stress Fields Near Crack Tips,”J. Engrg. Fract. Mech.,4 (4),801–809 (1972).Google Scholar
- 7.Bradley, W.B. andKobayashi, A.S., “An Investigation of Propagating Cracks by Dynamic Photoelasticity,”Experimental Mechanics,10 (3),106–113 (Mar.1970).Google Scholar
- 8.Kobayashi, T. and Dally, J.W., “The Relation Between Crack Velocity and the Stress Intensity Factor in Birefringent Polymers,” ASTM Spec. Tech. Pub. 627, 257–273 (1977).Google Scholar
- 9.Smith, D.G. andSmith, C.W., “Photoelastic Determination of Mixed Mode Stress Intensity Factors,”J. Engrg. Fract. Mech.,4, (2),357–366 (1972).Google Scholar
- 10.Gdoutos, E.E. andTheocaris, P.S., “A Photoelastic Determination of Mixed-mode Stress-intensity Factors,”Experimental Mechanics,18 (3),87–96 (Mar.1978).Google Scholar
- 11.Liebowitz, H., Lee, J.D. andEftis, J., “Biaxial Load Effects in Fracture Mechanics,”Engrg. Fract. Mech.,10 (2),315–335 (1978).Google Scholar
- 12.Paris, P.C. and Sih, G.C., “Stress Analysis of Cracks,” ASTM Spec. Tech. Pub. 381, 30–83 (1964).Google Scholar
- 13.Sanford, R.J., “Computer-simulated Stress-Optic Patterns,”Experimental Mechanics,11 (9),418–420 (Sept.1971).Google Scholar
- 14.Etheridge, J.M. andDally, J.W., “A Critical Review of Methods for Determining Stress-intensity Factors from Isochromatic Fringes,”Experimental Mechanics,17 (7),248–254 (Jul.1977).Google Scholar