Numerical investigation of creep crack growth in cross‐weld CT specimens. Part I: influence of mismatch in creep deformation properties and notch tip location

Abstract

Creep crack growth (CCG) in cross‐weld CT specimens is investigated using two‐dimensional finite element simulations. A creep ductility‐based damage model describes the accumulation of creep damage ahead of the crack tip where a constraint parameter and the creep strain rate perpendicular to the crack plane are used as characterizing parameters. The numerical results reveal that, not only the material properties of the region in which the crack is propagating, but also the deformation properties of the surrounding material influence the CCG behaviour. For the specimen configurations investigated, the location of the starter notch in the HAZ of the cross‐weld CT specimen has, however, a minor influence on the CCG rate and the value of C *. This applies as long as the crack is propagating within a sufficiently narrow region that has material properties which can be regarded as homogeneous.

Mismatch effect in creep properties on creep crack growth behavior in welded joints

“…Experiences showed that both the deformation properties of materials containing crack and surrounding materials influence the creep crack growth (CCG) behavior in welded joints [5][6][7]. Such as, the type IV crack is the most severe form of cracks due to the high creep strain of type IV region where the crack is propagating and the high constraint given from hard BM of surrounding materials [4].…”

Creep damage analysis of simulated-HAZ notched bar specimens of modified 9Cr-1Mo steel

“…Nondestructive inspection of the Takashi HONDA*, Takuya FUKAHORI*, Toshihide IGARI*, Yasuharu CHUMAN*, Takumi TOKIYOSHI* and Alan CF COCKS** surface and subsurface of pipe welds is carried out to examine the current damage, such as the cavity density, and the results are employed to guide simulation-based predictions. Several approaches can be taken in terms of damage simulation for Type IV failure, such as: continuum mechanics together with the stress-based time fraction or the ductility fraction of the material; creep fracture mechanics using the C* parameter (Yatomi et al, 2003, Segle et al, 2000; creep cavitation mechanics assuming diffusion (Rice, 1981); use of a grain boundary-resistance model (Fukahori, et al, 2013; and/or damage mechanics (Hyde et al, 2003, Yao et al, 2007. It remains difficult, however, to determine an optimal method for expressing both the microscopic and macroscopic phenomena of actual Type IV damage.…”

Creep damage and fracture of weldments at high temperature

“…Segle et al [53] have performed numerical simulations of CCG in cross-weld CT specimens. A three materials model of parent metal, weld metal and HAZ is used in the computation.…”