Failure assessment diagram analysis of creep crack initiation in 316H stainless steel

Abstract

In this work the time dependent failure assessment diagram (TDFAD) approach is applied to the study of crack initiation in Type 316H stainless steel, a material commonly used in high temperature applications. A TDFAD has been constructed for the steel at a temperature of 550 o C, and was found to be relatively insensitive to time. The TDFAD procedure is then applied to predict initiation times, at increments of creep crack growth Δa = 0.2 mm and Δa = 0.5 mm, for tests on compact tension specimens and the results compared to experimentally determined values. It has been found that initiation time predictions are sensitive to the creep toughness values, and to the limit load (or reference stress) solution used. Conservative predictions of initiation times have been achieved through the use of the lower bound creep toughness values in conjunction with the plane strain limit load solution. The plane stress limit load solution has given conservative predictions for all bounds of creep toughness used.

Three-dimensional numerical analysis of out-of-plane creep crack-tip constraint in compact tension specimens

“…This is consistent with the experimental results in ultra-large CT specimens reported by Tabuchi et al [21]. Higher constraint will lead to shorter creep crack initiation (CCI) time, higher CCG rate and lower creep fracture toughness (which is the creep toughness corresponding to a given crack extension at a given time [40]). Hence the creep cracks will firstly initiate and propagate at the mid-plane region along the crack front, and which will lead to the crack tunneling.…”

Predicting creep crack initiation in austenitic and ferritic steels using the creep toughness parameter and time‐dependent failure assessment diagram

“…As can be seen in Fig. 12a and described in 9 the 316H TDFAD is insensitive to time and deviates little from the R6 option 1 curve. The P22 TDFAD however, is in relatively good agreement with the R6 Option 1 curve at time 0 h, but almost instantly deviates significantly from it.…”

High temperature crack initiation and defect assessment of P22 steel weldments using time dependent failure assessment method

“…Note that predicted loci depend also on plane stress and plane strain limit load solutions as discussed in detail in [28]. The lowest L r or K r locus corresponds to the lowest time of 10 hrs, where its value increases with time.…”