Analysis of the effects of compressive stresses on fatigue crack propagation rate

Abstract In this study, the effects of compressive stresses on the crack tip parameters and its implication on fatigue crack growth have been studied. Elastic–plastic finite element analysis has been used to analyse the change of crack tip parameters with the increase of the applied compressive stress level. The near crack tip opening displacements and the reverse plastic zone size around the crack tip have been obtained. The finite element analysis shows that when unloading from peak tensile applied stress to zero applied stress, the crack tip is still kept open and the crack tip opening displacement gradually decreases further with the applied compressive stress. It has been found that for a tension–compression stress cycle these crack tip parameters are determined mainly by two loading parameters, the maximum stress intensity Kmax in the tension part of the stress cycle and the maximum compressive stress σmaxcom in the compression part of the stress cycle. Based on the two parameters, Kmax, and σmaxcom, a fatigue crack propagation model for negative R ratios only has been developed to include the compressive stress effect on the fatigue crack propagation rate. Experimental fatigue crack propagation data sets were used for the verification of this model, good agreements have been obtained.

[1]  Daniel Kujawski,et al.  Analysis of crack propagation using ΔK and Kmax , 2005 .

[2]  A. K. Vasudevan,et al.  Critical parameters for fatigue damage , 2001 .

[3]  Shanyi Du,et al.  Analyses of the fatigue crack propagation process and stress ratio effects using the two parameter method , 2005 .

[4]  Filipe S. Silva,et al.  Crack closure inadequacy at negative stress ratios , 2004 .

[5]  K. Sadananda,et al.  A REVIEW OF CRACK CLOSURE, FATIGUE CRACK THRESHOLD AND RELATED PHENOMENA , 1994 .

[6]  S. Pommier,et al.  INFLUENCE OF A NEGATIVE R RATIO ON THE CREEP‐FATIGUE BEHAVIOUR OF THE N18 NICKEL BASE SUPERALLOY , 1997 .

[7]  K. Sadananda,et al.  Multiple mechanisms controlling fatigue crack growth , 2003 .

[8]  G. Glinka,et al.  A two parameter driving force for fatigue crack growth analysis , 2005 .

[9]  Jia-zhen Zhang,et al.  Elastic–plastic finite element analysis and experimental study of short and long fatigue crack growth , 2001 .

[10]  Paul Bowen,et al.  New perspective on slip band decohesion as unifying fracture event during fatigue crack growth in both small and long cracks , 1999 .

[11]  S. Dinda,et al.  Correlation and prediction of fatigue crack growth for different R-ratios using Kmax and ΔK+ parameters , 2004 .

[12]  J. Zhang,et al.  A shear band decohesion model for small fatigue carck growth in an ultra-fine grain aluminium alloy , 2000 .

[13]  M. de Freitas,et al.  The effect of microstructure and environment on fatigue crack growth in 7049 aluminium alloy at negative stress ratios , 2003 .

[14]  Filipe S. Silva,et al.  The importance of compressive stresses on fatigue crack propagation rate , 2005 .

[15]  S. Pommier.  Cyclic plasticity and variable amplitude fatigue , 2003 .

[16]  P. Bowen,et al.  In situ SEM observations of the contrasting effects of an overload on small fatigue crack growth at two different load ratios in 2024-T351 aluminium alloy , 1997 .