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Stress-intensity factors in plates with a partially patched central crack

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Abstract

The fatigue and fracture performance of a cracked plate can be substantially improved by providing patches as reinforcements. The effectiveness of patches is related to the reduction they cause in the stress-intensity factor of the crack. Hence, an accurate evaluation of SIF in terms of various parameters is required for reliable patch design.

In this paper, the influence of patch parameters on the opening-mode stress-intensity factor for a plate with a central crack is studied by employing transmission photoelasticity. Cracked plates made of photoelastic material are patched on one side as well as both sides by epoxy, phenolic and E glass-epoxy composite materials. The patch is located on the crack in such a way that the crack tip is not covered. Magnified isochromatic fringes are obtained by using a projection microscope of 50 magnification, converted into a polariscope. Irwin's method with extrapolation is employed to compute the stress-intensity factor from photoelastic data. The reduction in the stress-intensity factor is presented in graphic form as a function of pathch parameters, namely stiffness, width and length.

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Abbreviations

a :

semi crack length (Fig. 1)

b :

semi width of plate (Fig. 1)

E :

Young's modulus of plate

E p :

Young's modulus of patch in the loading direction

f σ :

material fringe value

K AP :

apparent SIF

K I :

stress-intensity factor (SIF) of plate in opening mode

K IP :

SIF of plate with patch

\(\bar K\) :

K IP/KI

l :

semi length of plate (Fig. 1)

l p :

semi length of patch

N :

fringe order

t :

thickness of plate (Fig. 1)

t p :

thickness of patch (Fig 1)

w :

width of patch (Fig. 1)

σ:

uniformly distributed stress at cross section away from crack

α:

patch-stiffness parameter,E ptp/Et

β:

E p/E

η:

patch efficiency\((1 - \bar K)\)

τ m :

the maximum shear stress

References

  1. “Damage Tolerance and Fatigue Evaluation of Structure,” 14 FCR Part 25, 571 (1977).

  2. “Airplane Damage Tolerance Requirement,” MIL Spec., 83444, USAF (1974).

  3. Baker, A.A. and Hutchinson, M.M., “Fiber Composite Reinforcement of Cracked Aircraft Structures,” Tech. Memo. ARL/MAT., 366 (Aug. 1966).

  4. Baker, A.A., “A Summary of Work on Application of Advanced Fiber Composites at ARL Australia,”Composites,9 (1),11–16 (Aug.1978).

    Article  Google Scholar 

  5. Chandra, R., Murthy, M.V.V., Ramamurthy, T.S. andRao, A.K., “Analytical Estimation of Stress Intensity Factors in Patched Cracked Plates,”Eng. Fract. Mech.,21,479–494 (1985).

    Google Scholar 

  6. Subramanian, A., Chandra, R., Murthy, M.V.V. andRao, A.K., “Photoelastic Determination of Stress Intensity Factors in Patched Cracked Plates,”Eng. Fract. Mech.,18,305–313 (1983).

    Google Scholar 

  7. Chandra, R. andSunder, R., “Fatigue Crack Growth in Patched Plates under Constant Amplitude and Flight Simulation Loadings,” Advances in Fracture Research, Proc. 6th Int. Conf. on Fract., New Delhi, India,5,3523–3532 (1984).

    Google Scholar 

  8. Chandra, R., “A Study on Cracked Plates with Composite Patch Reinforcements,” PhD Thesis, Dept. of Aero. Eng., Indian Institute of Science (1986).

  9. Chandra, R. andGuruprasad, K., “Numerical Estimation of Stress Intensity Factors in Patched Cracked Plates,”Eng. Fract. Mech.,27 (5),559–569 (1987).

    Google Scholar 

  10. Post, D., “Photoelastic Stress Analysis for an Edge Crack in a Tensile Field,”Proc. SESA,12 (1),99–116 (1954).

    MathSciNet  Google Scholar 

  11. Wells, A. andPost, D., “The Dynamic Stress Distribution Surrounding a Running Crack—a Photoelastic Analysis,”Proc. SESA,16, (1),69–92 (1958).

    Google Scholar 

  12. Irwin, G.R., discussion of Ref. 11, Proc. SESA,16 (1),93–96 (1958).

    Google Scholar 

  13. Bradley, W.B., “A Photoelastic Investigation of Dynamic Brittle Fracture,” PhD Thesis, Univ. of Washington (1969).

  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 (1977).

    Article  Google Scholar 

  15. Smith, C.W., “Use of Three Dimensional Photoelasticity and Progress in Related Area,”Experimental Techniques in Fracture Mechanics, ed. A.S. Kobayashi,2,2–58 (1975).

    MATH  Google Scholar 

  16. Smith, D.B. andSmith, C.W., “Photoelastic Determination of Mixed Mode Stress Intensity Factors,”Eng. Fract. Mech.,4,357–366 (1972).

    Google Scholar 

  17. Smith, C.W., Peters III, W.H. andKriby, G.C., “Crack-tip Measurements in Photoelastic Models,”Experimental Mechanics,22 (12),448–453 (1982).

    Article  Google Scholar 

  18. Rooke, D.P. andCartwright, D.J., “Compendium of Stress Intensity Factors,”HMSO, London (1976).

    Google Scholar 

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Authors and Affiliations

  1. National Aeronautical Laboratory, 560 017, Bangalore, India

    R. Chandra (Research Associate)

  2. Department of Aerospace Engineering, University of Maryland, 20742, College Park, MD

    R. Chandra (Research Associate)

  3. Structures Division, National Aeronautical Laboratory, 560 017, Bangalore, India

    A. Subramania (Scientist)

Authors
  1. R. Chandra
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  2. A. Subramania
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Chandra, R., Subramania, A. Stress-intensity factors in plates with a partially patched central crack. Experimental Mechanics 29, 1–5 (1989). https://doi.org/10.1007/BF02327773

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  • DOI: https://doi.org/10.1007/BF02327773

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