Engineering treatment model for creep crack driving force estimation: CTODin terms of delta(5)

Based on finite element analyses, a set of formulas for estimating the crac k driving force under creep conditions in terms of the crack tip opening di splacement (CTOD), delta (5), which measures the CTOD at the specimen side surface, spanning the original crack tip over a gauge length of 5 mm, is pr esented for three fracture specimens. These formulas are developed for stat ionary 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 cr eep delta (5) is a promising load parameter For creep ductile materials. Th e calculation of the creep delta (5) and the creep fracture analysis based on the creep delta (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 sectio n stress level. (C) 2000 Elsevier Science Ltd. All rights reserved.