Engineering treatment model for creep crack driving force estimation: CTOD in terms of δ5

Abstract Based on finite element analyses, a set of formulas for estimating the crack driving force under creep conditions in terms of the crack tip opening displacement (CTOD), δ 5 , which measures the CTOD at the specimen side surface, spanning the original crack tip over a gauge length of 5 mm, is presented for three fracture specimens. These formulas are developed for stationary and growing cracks for both plane stress and plane strain conditions, validated for different creep laws and loading conditions. These formulas are in closed form and accurately replicate finite element results. The creep δ 5 is a promising load parameter for creep ductile materials. The calculation of the creep δ 5 and the creep fracture analysis based on the creep δ 5 -concept are very convenient. They can be done by use of the nominal net section stress defined by the limit load of the cracked body and the original uniaxial creep curve at the corresponding net section stress level.

[1]  Karl-Heinz Schwalbe,et al.  Ductile crack growth under plane stress conditions: Size effects and structural assessment—II. Assessment of circumferential through-cracks in austenitic steel pipes using the δ5 technique and the engineering treatment model , 1992 .

[2]  Numerical fracture simulation of bend specimens using a CTOD criterion , 1989 .

[3]  A. Cornec,et al.  Engineering Treatment Model (ETM) for Crack Driving Force Estimation of Structures With Stress Concentration , 1993 .

[4]  G. G. Chell,et al.  CEGB ASSESSMENT PROCEDURE FOR DEFECTS IN PLANT OPERATING IN THE CREEP RANGE , 1987 .

[5]  K.-H. Schwalbe.  The Prediction of Failure Situations Using the CTOD Concept Based on the Engineering Treatment Model (ETM) , 1986 .

[6]  D. Smith,et al.  Characterizations of creep crack growth in 1 per cent Cr Mo V steel , 1981 .

[7]  Karl-Heinz Schwalbe,et al.  THE ENGINEERING TREATMENT MODEL (ETM) AND ITS PRACTICAL APPLICATION , 1991 .

[8]  E. Maas,et al.  Creep crack growth behavior of type 316L steel , 1985 .

[9]  A. Becker,et al.  An assessment of the crack tip opening displacement criterion for predicting creep crack growth , 1996 .

[10]  Robert A. Ainsworth,et al.  Some observations on creep crack growth , 1982 .

[11]  A. Pineau,et al.  COMPARISON BETWEEN TWO ASSESSMENT METHODS FOR DEFECTS IN THE CREEP RANGE , 1991 .

[12]  K.-H. Schwalbe,et al.  The engineering treatment model (ETM) for pure power law and non-power law hardening materials , 1998 .