Crack-tip constraint effects on creep fracture

Abstract A three-term expansion describing the crack tip fields in steady power-law creeping solids is used in a small-scale damage microstructural approach to study the initial stages of creep fracture under plane strain mode I loading conditions. These fields contain three important parameters. The first one is C∗, which sets the loading level, and the remaining, A ∗ 2 and σ∞, account for the constraint effect imposed by the specific geometry and loading configuration. The microstructural model incorporates a process window around the tip of the crack, which contains a large number of grains that are represented discretely by so-called grain elements. The grain boundaries are described by interface elements that incorporate the principal damage mechanisms, including cavity nucleation, diffusive-creeping cavity growth and grain boundary sliding. The process window is surrounded by a standard creeping continuum which is subject to remote boundary conditions corresponding to the crack tip fields in a steadily creeping material. Numerical results of the model are presented for a range of constraints using values of A ∗ 2 and σ∞ that correspond to typical test specimens. The effect of crack-tip constraints is demonstrated and explained for material parameter sets that give rise to either ductile or brittle creep fracture processes.

[1]  Viggo Tvergaard,et al.  On the creep constrained diffusive cavitation of grain boundary facets , 1984 .

[2]  Robert H. Dodds,et al.  Continuum and micromechanics treatment of constraint in fracture , 1993, International Journal of Fracture.

[3]  Yuh J. Chao,et al.  J-A2 Characterization of Crack-Tip Fields: Extent of J-A2 Dominance and Size Requirements , 1998 .

[4]  V. Tvergaard,et al.  University of Groningen Interaction of cavitating grain boundary facets in creeping polycrystals , 2002 .

[5]  David R Hayhurst,et al.  Creep in Structures , 1981 .

[6]  Patrick Onck,et al.  Growth of an initially sharp crack by grain boundary cavitation , 1998 .

[7]  Viggo Tvergaard,et al.  A creep rupture model accounting for cavitation at sliding grain boundaries , 1991 .

[8]  B. Dyson.  Constraints on diffusional cavity growth rates , 1976 .

[9]  Hermann Riedel,et al.  Fracture at high temperatures , 1987 .

[10]  John R. Rice,et al.  Plastic creep flow effects in the diffusive cavitation of grain boundaries , 1980 .

[11]  Y. Chao,et al.  Effects of Crack Depth, Specimen Size, and Out-of-Plane Stress on the Fracture Toughness of Reactor Vessel Steels , 1995 .

[12]  P. Onck,et al.  Micromechanics of creep fracture : simulation of intergranular crack growth , 1998 .

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

[14]  Noel P. O’Dowd.  Applications of two parameter approaches in elastic-plastic fracture mechanics , 1995 .

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

[16]  D. R. Hayhurst,et al.  The role of continuum damage in creep crack growth , 1984, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[17]  Yuh J. Chao,et al.  On the fracture of solids characterized by one or two parameters: Theory and practice , 1994 .

[18]  Patrick Onck,et al.  On Higher-Order Crack-Tip Fields in Creeping Solids , 2000 .

[19]  李尧臣,et al.  HIGH-ORDER ASYMPTOTIC FIELD OF TENSILE PLANE-STRAIN NONLINEAR CRACK PROBLEMS , 1986 .

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

[21]  D. Hayhurst,et al.  Creep Crack Growth , 1981 .

[22]  A. Needleman,et al.  Effects of triaxial stressing on creep cavitation of grain boundaries , 1982 .

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

[24]  P. Onck,et al.  Microstructural modelling of creep crack growth from a blunted crack , 1998 .

[25]  Robert A. Ainsworth,et al.  High Temperature Component Life Assessment , 1994 .

[26]  D. Parks,et al.  Growth modes of cracks in creeping type 304 stainless steel , 1991 .