Ductile tearing in part-through cracks: experiments and cell-model predictions

Abstract This study describes an application of the computational cell model to predict ductile crack growth measured in experiments performed on surface-cracked, thick plates fabricated from a ferritic pressure vessel steel. The cell model limits void growth and coalescence to within a thin layer of material over the crack plane. Outside this layer, the material deforms plastically but remains void free. The Gurson–Tvergaard dilatant plasticity model describes the evolution of void growth and the associated macroscopic softening within the cells. Material-specific, cell parameters readily separate into two categories: those describing the micromechanics of void growth rate and those describing the local fracture process of the cell. Calibration of these parameters utilizes both discrete (3-D) cell models and R-curves measured using standard deep-notch bend or compact tension specimens. The cell model is applied here to surface-cracked plates subjected to different loading histories of tension and bending. The calibrated cell model reproduces accurately full details of the load-deformation records and the crack growth profiles for all the cases. These numerical studies suggest that the computational approach based on the cell model provides an engineering tool to predict ductile crack growth behavior in flawed structural components.

[1]  J. Faleskog.  An experimental and numerical investigation of ductile crack growth characteristics in surface cracked specimens under combined loading , 1994 .

[2]  John W. Hutchinson,et al.  A computational approach to ductile crack growth under large scale yielding conditions , 1995 .

[3]  C. Shih,et al.  Ductile crack growth-I. A numerical study using computational cells with microstructurally-based length scales , 1995 .

[4]  C. Shih,et al.  Ductile crack growth—II. Void nucleation and geometry effects on macroscopic fracture behavior , 1995 .

[5]  Claudio Ruggieri,et al.  Numerical modeling of ductile crack growth in 3-D using computational cell elements , 1996 .

[6]  Xiaosheng Gao,et al.  Cell model for nonlinear fracture analysis – I. Micromechanics calibration , 1998 .

[7]  Jonas Faleskog,et al.  Micromechanics of coalescence—I. Synergistic effects of elasticity, plastic yielding and multi-size-scale voids , 1997 .

[8]  Sj Garwood.  Effect of Specimen Geometry on Crack Growth Resistance , 1979 .

[9]  Claudio Ruggieri,et al.  A transferability model for brittle fracture including constraint and ductile tearing effects: a probabilistic approach , 1996 .

[10]  B. Moran,et al.  A general treatment of crack tip contour integrals , 1987 .

[11]  N. Aravas.  On the numerical integration of a class of pressure-dependent plasticity models , 1987 .

[12]  John G. Merkle.  Patterns and perspectives in applied fracture mechanics , 1994 .

[13]  A. Needleman,et al.  Void Nucleation Effects in Biaxially Stretched Sheets , 1980 .

[14]  Y. Wang.  On the Two-Parameter Characterization of Elastic-Plastic Crack-Front Fields in Surface-Cracked Plates , 1993 .

[15]  W Schmitt,et al.  Quantitative Assessment of the Role of Crack Tip Constraint on Ductile Tearing , 1993 .

[16]  James A. Joyce,et al.  Effects of constraint on upper shelf fracture toughness , 1995 .

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

[18]  Jonas Faleskog,et al.  Effects of local constraint along three-dimensional crack fronts—a numerical and experimental investigation , 1995 .

[19]  T. Hughes.  Generalization of selective integration procedures to anisotropic and nonlinear media , 1980 .

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

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

[22]  H. Andersson,et al.  Analysis of a model for void growth and coalescence ahead of a moving crack tip , 1977 .

[23]  Arne S. Gullerud,et al.  WARP3D-Release 10.8: Dynamic Nonlinear Analysis of Solids using a Preconditioned Conjugate Gradient Software Architecture , 1998 .

[24]  C. Shih,et al.  Ductile crack growth−III. Transition to cleavage fracture incorporating statistics , 1996 .

[25]  Z. Zhang,et al.  A class of generalized mid‐point algorithms for the Gurson–Tvergaard material model , 1995 .

[26]  A. Gurson.  Continuum Theory of Ductile Rupture by Void Nucleation and Growth: Part I—Yield Criteria and Flow Rules for Porous Ductile Media , 1977 .

[27]  R. H. Van Stone,et al.  Microstructural aspects of fracture by dimpled rupture , 1985 .

[28]  Brian Moran,et al.  Crack tip and associated domain integrals from momentum and energy balance , 1987 .

[29]  V. Tvergaard.  Material Failure by Void Growth to Coalescence , 1989 .

[30]  Viggo Tvergaard,et al.  Constraint effects on the ductile-brittle transition in small scale yielding , 1996 .

[31]  Xiaosheng Gao,et al.  Cell model for nonlinear fracture analysis – II. Fracture- process calibration and verification , 1998 .