Structural integrity of pipelines: T‐stress by line‐spring

The elastic T-stress is an important constraint parameter for characterizing elastic–plastic crack-tip fields and in fracture assessment procedures. However, many of the methods reported in the literature for estimating T-stress are not easily suited for surface-cracked pipes because these are three-dimensional in nature. Here, the line-spring method is demonstrated to be an efficient and accurate tool for the constraint estimation in surface-cracked pipes. Detailed three-dimensional analyses are performed to verify the line-spring results. Using the line-spring method, the effects of different crack geometries and diameter-to-thickness ratio on stress-intensity factor (SIF) and T-stress in circumferentially surface-cracked pipes are examined. Further, a compendium of normalised SIF and T-stress values for surface-cracked pipes in remote tension and bending, calculated from a total of 1000 analyses, is tabulated. Finally, the application of an ‘elastic–plastic’ T-stress under large-scale plasticity is explored.

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

[2]  Frank A. McClintock,et al.  PLASTICITY ASPECTS OF FRACTURE , 1971 .

[3]  J. Rice,et al.  The Part-Through Surface Crack in an Elastic Plate , 1972 .

[4]  A. J. Carlsson,et al.  Influence of non-singular stress terms and specimen geometry on small-scale yielding at crack tips in elastic-plastic materials , 1973 .

[5]  M. Shiratori.  EVALUATION OF CONSTRAINT FACTOR AND J-INTEGRAL FOR SINGLE-EDGE NOTCHED SPECIMEN , 1980 .

[6]  D. Parks,et al.  The Inelastic Line-Spring: Estimates of Elastic-Plastic Fracture Mechanics Parameters for Surface-Cracked Plates and Shells , 1981 .

[7]  C. S. White,et al.  Elastic-Plastic Line-Spring Finite Elements for Surface-Cracked Plates and Shells , 1982 .

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

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

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

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

[12]  D. Parks,et al.  Evaluation of the elastic T-stress in surface-cracked plates using the line-spring method , 1992 .

[13]  Nakamura Toshio,et al.  Determination of elastic T-stress along three-dimensional crack fronts using an interaction integral , 1992 .

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

[15]  Guandong Wang,et al.  Two Parameter Fracture Mechan-ics: Theory and Applications , 1993 .

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

[17]  Hyungyil Lee,et al.  Enhanced elastic-plastic line-spring finite element , 1995 .

[18]  Andrew H. Sherry,et al.  COMPENDIUM OF T‐STRESS SOLUTIONS FOR TWO AND THREE DIMENSIONAL CRACKED GEOMETRIES , 1995 .

[19]  Bjørn Skallerud,et al.  A mixed mode I/II inelastic line spring , 1996 .

[20]  R. Mohan.  Fracture analyses of surface-cracked pipes and elbows using the line-spring/shell model , 1998 .

[21]  Hyungyil Lee,et al.  Line-spring finite element for fully plastic crack growth—I. Formulation and one-dimensional results , 1998 .

[22]  Bjørn Skallerud,et al.  Collapse of thin shell structures—stress resultant plasticity modelling within a co-rotated ANDES finite element formulation , 1999 .

[23]  Hiroshi Tada,et al.  The stress analysis of cracks handbook , 2000 .

[24]  Matteo Chiesa,et al.  Closed form line spring yield surfaces for deep and shallow cracks: formulation and numerical performance , 2002 .

[25]  Xin Wang,et al.  Elastic T-stress solutions for semi-elliptical surface cracks in finite thickness plates , 2003 .

[26]  Erling Østby,et al.  Fracture response of pipelines subjected to large plastic deformation under tension , 2004 .

[27]  Bård Nyhus,et al.  Constraint correction of high strength steel Selection of test specimens and application of direct calculations , 2004 .

[28]  Bjørn Skallerud,et al.  Thin shell and surface crack finite elements for simulation of combined failure modes , 2005 .