Estimation of Constraint under Cyclic Loading on Cracked Components

The constraint plays an important role in the fatigue design of mechanicalcomponents. In particular, the global constraint factor αg is the most usedparameter in the field of fatigue to evaluate the level of constraint at the crackfront and it is a crucial parameter in wide spread algorithms.The present work aims to address how to obtain reliable values of constraint toemploy in fatigue crack growth simulations, in order to improve the predictions ofcrack propagation models such as the Strip-Yield model.A novel approach is presented for the calculation of the global constraint factor,based on the evaluation of local field parameters (J-integral, T-stress) and cyclicmaterial properties. The model was set up on typical fracture mechanics andfatigue test specimens, then applied to the evaluation of the constraint state aheadof cracks in a railway axle

[1]  C. Shih,et al.  Family of crack-tip fields characterized by a triaxiality parameter—II. Fracture applications , 1992 .

[2]  M. Madia,et al.  The Influence of Constraint on Fitting Fatigue Crack Growth Data , 2006 .

[3]  S. Beretta,et al.  Analysis of Crack Growth at R =−1 under Variable Amplitude Loading on a Steel for Railway Axles , 2008 .

[4]  J. Hancock,et al.  The effect of non-singular stresses on crack-tip constraint , 1991 .

[5]  Nikolaos Aravas,et al.  Determination of higher-order terms in asymptotic elastoplastic crack tip solutions , 1991 .

[6]  J. Newman.  A crack-closure model for predicting fatigue crack growth under aircraft spectrum loading , 1981 .

[7]  Wolfgang Brocks,et al.  Quantification of constraint effects in elastic-plastic crack front fields , 1998 .

[8]  Michele Carboni,et al.  Application of fatigue crack growth algorithms to railway axles and comparison of two steel grades , 2004 .

[9]  C. Shih,et al.  Family of crack-tip fields characterized by a triaxiality parameter—I. Structure of fields , 1991 .

[10]  Wanlin Guo.  Three-dimensional analyses of plastic constraint for through-thickness cracked bodies , 1999 .

[11]  Yuh J. Chao,et al.  Higher order asymptotic crack tip fields in a power-law hardening material , 1993 .

[12]  J. Newman,et al.  Three-dimensional elastic-plastic finite-element analyses of constraint variations in cracked bodies , 1993 .

[13]  J. W. Hancock,et al.  J-Dominance of short cracks in tension and bending , 1989 .

[14]  Fatigue Strength in Presence of Inhomogeneities: Influence of Constraint , 2006 .

[15]  J. Hancock,et al.  Two-Parameter Characterization of Elastic-Plastic Crack-Tip Fields , 1991 .

[16]  Yuh J. Chao,et al.  Quantification of constraint on elastic–plastic 3D crack front by the J–A2 three-term solution , 2001 .

[17]  J. C. NewmanJr..  A crack opening stress equation for fatigue crack growth , 1984 .