Premium
COMPARISON BETWEEN TWO ASSESSMENT METHODS FOR DEFECTS IN THE CREEP RANGE
Author(s) -
Piques R.,
Molinie E.,
Pineau A.
Publication year - 1991
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.1460-2695.1991.tb00721.x
Subject(s) - creep , materials science , pressure vessel , austenitic stainless steel , austenite , structural engineering , range (aeronautics) , metallurgy , stress (linguistics) , forensic engineering , composite material , engineering , microstructure , corrosion , philosophy , linguistics
In recent years considerable effort has been made to understand the behaviour of creep defects at elevated temperature. A large number of experimental studies have been devoted to creep crack growth behaviour. In Europe, both in U.K. (CEGB) and in France (EMP), attention is focussed not only on crack growth but also on creep crack initiation behaviour in the assessment of defects at high temperature. This paper describes and applies both methods, first to laboratory test results and then to a cracked component. The comparison with test data is made with three materials, a ferritic 1 Cr‐1Mo‐0.25 V steel and two austenitic stainless steels, while the application to a cracked pressure vessel deals with a ½ Cr‐Mo‐V steel. For these materials which are creep ductile, the relevant load‐geometer parameter for stationary creep cracks is the C * parameter, which relies on the concept of reference stress and reference length. The expressions used for these parameters in both procedures are compared. Then the methods used for calculating the time for incubation prior to crack extension, t 1 , the time for subsequent growth, t g , and the time to failure, t F = t i + t g are compared. This comparison is made not only for laboratory test data but also for a cracked pressure vessel. It is shown that, in spite of different approaches, especially in the assessment of t g , both methods provide comparable t 1 ‐ C * and t F = C * diagrams. The reasons for this situation are briefly discussed.