Constraint-based failure assessment diagrams

The loss of crack tip constraint leads to enhanced resistance to ductile tearing and cleavage. However, current defect assessment schemes use lower bound toughness obtained from highly constrained testpieces. Although this approach is safe, it is conservative, and may lead to the imposition of prohibitive repair and inspection policies when applied to defects which develop unconstrained flow fields. Recent theoretical developments indicate that geometry dependent fracture toughness effects can now be rationalised and united through a two-parameter characterisation of elastic-plastic crack tip fields. In this context a simple modification to existing failure assessment diagrams (FAD) is proposed, using a constraint matched toughness to modify one of the axes of the FAD. The procedure recovers the original failure assessment line and unifies the constraint dependent fracture toughness data.

[1]  Noel P. O’Dowd,et al.  A Framework for Quantifying Crack Tip Constraint , 1993 .

[2]  D. M. Parks,et al.  Advances in Characterization of Elastic-Plastic Crack-Tip Fields , 1992 .

[3]  J. Rice,et al.  Limitations to the small scale yielding approximation for crack tip plasticity , 1974 .

[4]  A. Kfouri.  Some evaluations of the elastic T-term using Eshelby's method , 1986 .

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

[6]  A. G. Varias,et al.  Quasi-static crack advance under a range of constraints—Steady-state fields based on a characteristic length , 1993 .

[7]  J. Willis,et al.  Matched asymptotic expansions in nonlinear fracture mechanics—III. In-plane loading of an elastic perfectly-plastic symmetric specimen , 1977 .

[8]  Michael G Dawes.  Shallow crack fracture mechanics toughness tests and applications , 1993 .

[9]  T. Sham.  The determination of the elastic T-term using higher order weight functions , 1991 .

[10]  C.H.A. Townley,et al.  The effect of defects on structural failure: A two-criteria approach , 1975 .

[11]  Ian C. Howard,et al.  Failure assessment diagrams. III. Mappings and failure assessment lines when the crack driving force is a functional , 1994, Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences.

[12]  Z. H. Li,et al.  Failure assessment diagrams. I. The tangency condition for ductile tearing instability , 1994, Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences.

[13]  P. Leevers,et al.  Inherent stress biaxiality in various fracture specimen geometries , 1982 .

[14]  C. Shih,et al.  Effect of Constraint on Specimen Dimensions Needed to Obtain Structurally Relevant Toughness Measures , 1993 .

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

[16]  J. W. Hancock,et al.  J-Dominance of short cracks in tension and bending , 1991 .

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

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

[19]  Viggo Tvergaard,et al.  Effect of T-Stress on mode I crack growth resistance in a ductile solid , 1994 .

[20]  Robert A. Ainsworth,et al.  Assessment of the integrity of structures containing defects , 1987 .

[21]  John W. Hutchinson,et al.  Singular behaviour at the end of a tensile crack in a hardening material , 1968 .

[22]  Noel P. O’Dowd,et al.  Constraint in the failure assessment diagram approach for fracture assessment , 1995 .

[23]  M. Williams,et al.  On the Stress Distribution at the Base of a Stationary Crack , 1956 .

[24]  G. Chell,et al.  A Procedure for Incorporating Thermal and Residual Stresses into the Concept of a Failure Assessment Diagram , 1979 .

[25]  Robert A. Ainsworth,et al.  The assessment of defects in structures of strain hardening material , 1984 .

[26]  Jdg Sumpter,et al.  An Experimental Investigation of the T Stress Approach , 1993 .

[27]  J. Willis,et al.  The influence of crack size on the ductile-brittle transition , 1988, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[28]  J. Rice,et al.  Plane strain deformation near a crack tip in a power-law hardening material , 1967 .

[29]  R. McMeeking,et al.  On criteria for J-dominance of crack-tip fields in large-scale yielding , 1979 .

[30]  Kumar,et al.  Engineering approach for elastic-plastic fracture analysis , 1981 .

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

[32]  Jm Bloom.  Validation of a Deformation Plasticity Failure Assessment Diagram Approach to Flaw Evaluation , 1983 .

[33]  John R. Rice,et al.  ON THE RELATIONSHIP BETWEEN CRITICAL TENSILE STRESS AND FRACTURE TOUGHNESS IN MILD STEEL , 1973 .

[34]  J. D. G. Sumpter,et al.  Jc determination for shallow notch welded bend specimens , 1987 .

[35]  Ian C. Howard,et al.  Failure assessment diagrams. II. The use of single failure assessment lines , 1994, Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences.