Surface crack length, c (mm) 0 1 2 3 4 5 Surface crack growth rate, dc/dN (mm/cycle) 10-6 10-5 10-4 10-3 Experimental (left) Experimental (right) Finite element predictions 6 Figure 5: Measured fatigue crack growth rates for cold expanded specimens subjected to creep relaxation compared with averaged finite element results. CONCLUSIONS Residual stresses arising from cold expansion and after creep relaxation have been predicted using finite element simulations and measured using the Garcia-Sachs method. A generally good agreement was obtained between prediction and measurement except near the edge of the hole. Fatigue crack growth rates have been measured for cracks growing from non cold expanded and cold expanded holes with and without creep relaxation. Creep relaxation reduces the resistance to fatigue, but there is still a benefit of cold expansion. Finite element predictions of growth rates have been made but only partial agreement with measurement has been obtained. ACKNOWLEDGEMENTS The work described here was sponsored by DTi and managed by DERA. Their financial support and assistance is gratefully acknowledged. REFERENCES 1. Petrak, G.J. and Stewart, R.P. (1974) Eng. Fract. Mech., 6, 275 2. Pavier, M.J., Poussard, C.G.C., and Smith, D.J. (1997) J. Strain Analysis, 32, 287 3. Smith, D.J., Poussard, C.G.C. and Pavier, M.J. (1998) J. Strain Analysis, 33, 263 4. Garcia-Granada, A.A., Lacarac, V.D., Holdway, P., Smith, D.J. and Pavier, M.J. (2001) to appear in J. Eng. Mat. Tech. 5. Fatigue Technology Inc., 150 Andover Park West, Seattle, Washington, USA. 6. Garcia-Granada, A.A., Smith, D.J. and Pavier, M.J. (2000) Int. J. Mech. Sci., 42, 1027 7. Pavier, M.J., Poussard, C.G.C. and Smith, D.J. (1999) Eng. Fract. Mech., 63, 751 8. Lacarac, V.D., Smith, D.J., Pavier, M.J. and Priest, M. (2000) Int. J. Fatigue, 22, 189
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