Experimental Mechanics

, Volume 18, Issue 12, pp 441–448 | Cite as

Classification of stress-intensity factors from isochromatic-fringe patterns

Isochromatic fringes corresponding to different combinations of KI, KII and σox have been constructed, and the unique characteristics of the isochromatics can be used to classify the state of stress (KI, KII and σox) at the crack tip
  • J. W. Dally
  • R. J. Sanford


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.


Mechanical Engineer Fluid Dynamics Stress Intensity Stress Field Local Neighborhood 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Kobayashi, A.S., ed., Experimental Techniques in Fracture Mechanics I, Iowa State Press (1973).Google Scholar
  2. 2.
    Kobayashi, A.S., ed., Experimental Techniques in Fracture Mechanics II, Iowa State Press (1975).Google Scholar
  3. 3.
    Post, D., “Photoelastic Stress Analysis for an Edge Crack in a Tensile Field,”Proc. SESA,12 (1),99–116 (1954).Google Scholar
  4. 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. 5.
    Irwin, G.R., Discussion of Ref. 4, Proc. SESA,16 (1),93–96 (1958).Google Scholar
  6. 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. 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. 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. 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. 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. 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. 12.
    Paris, P.C. and Sih, G.C., “Stress Analysis of Cracks,” ASTM Spec. Tech. Pub. 381, 30–83 (1964).Google Scholar
  13. 13.
    Sanford, R.J., “Computer-simulated Stress-Optic Patterns,”Experimental Mechanics,11 (9),418–420 (Sept.1971).Google Scholar
  14. 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

Copyright information

© Society for Experimental Mechanics, Inc. 1978

Authors and Affiliations

  • J. W. Dally
    • 1
  • R. J. Sanford
    • 2
  1. 1.University of MarylandCollege Park
  2. 2.Structural Reliability Section, Ocean Technology DivisionNoval Research LaboratoryWashington

Personalised recommendations