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THE USE OF A FAILURE ASSESSMENT DIAGRAM FOR INITIATION AND PROPAGATION OF DEFECTS AT HIGH TEMPERATURES
Author(s) -
Ainsworth R. A.
Publication year - 1993
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.1993.tb00080.x
Subject(s) - creep , failure assessment , materials science , fracture toughness , stress intensity factor , fracture mechanics , diagram , composite material , structural engineering , toughness , stress (linguistics) , forensic engineering , engineering , mathematics , linguistics , statistics , philosophy
The use of a failure assessment diagram, of the type in the R 6 defect assessment procedure, is investigated for creep crack growth under steady loading. While a detailed approach based on C * remains attractive for appreciable creep crack growth, it is shown that a simplified approach can be formulated for limited crack extension. A failure assessment diagram is derived based on the option 2 curve of R 6 using isochronous stress‐strain data. The inclusion of elastic strains in the isochronous data covers stress redistribution effects. Equations are given which enable a toughness, K mat , for assessments at temperatures in the creep range to be evaluated from creep crack incubation and growth data presented in terms of C *. The toughness, K mat , replaces the fracture toughness used in low temperature R 6 assessments. Thermal stresses can be included in assessments by evaluating the stress intensity factor for the combined thermal and mechanical loading. A formula is given which enables the effect of thermal stresses to be reduced when creep strains are sufficient to relax out part or all of the thermal stress.