A Proposal on Creep Damage Analysis of Welded Joint of Low-Alloy Steel Considering Microscopic Damage Progress

Abstract

Creep damage analysis method of welded joint on the basis of the random fracture resistance model was proposed and was applied to the creep damage evaluation of welded joint of low alloy steel. Firstly a random fracture resistance of grain boundaries, an initiation and a growth driving forces of small defects, which were necessary in the above model, were determined considering the stress-dependent damage progress of the fine-grain HAZ material of 21/4Cr-1Mo steel. Secondly a procedure combining both the stress distribution in the welded joint and the random fracture resistance model was concretely proposed and was applied to the creep damage evaluation of the model test and the actual power piping. Experimental results of both the time history and the distribution of the number density of small defects in the welded joint were successfully reproduced by the proposed method.

OS12W0391 Advanced creep damage analysis of low-alloy steel welds considering the microscopic damage progress

“…Another perspective would be a method to predict the damage of actual operating piping, where the precise bead line is not known, but the time history of the inspection of the surface and the mid-wall thickness of the piping is known. A discussion on this subject is performed in the literature [13], where the characteristics of the stress distribution in the various pipe configurations with a bead line and with a thickness from 30mm to 100mm [8] is referred together with a method to modify the stress distribution on the basis of the inspection results of surfaces and mid-wall thickness of the piping. The compilation of the comparison between the damage simulation and the damage inspection is expected in the future.…”

Micro–macro creep damage simulation for welded joints

“…The results of parameter identification for FGHAZ are summarized as follows: the distribution of the grain boundary length [L] was determined as the normal distribution with a mean value of 10.5 mm and a standard deviation of 5 mm on the basis of the microscopic observation of the FGHAZ; the distribution of the initial value of fracture resistance [R 0 ] with a mean value of 0.5 and a standard deviation of 0.1607 was determined as shown in Figure 3(a) on the basis of the time history of the number density of small defects at a specific location of FGHAZ in the creep test of a welded joint; the stress dependence of F shown in Figure 3(b) was determined through a combination of the distribution [R 0 ] and the microscopic observation of a point with a prescribed stress; the parameter K is given in the literature [2,17].…”

“…(2) Creep damage simulation [2,17] of a power piping elbow with wall thickness of 108 mm taken from the power-piping used for 150,000 hours at 848 K.…”

Search for high-creep-strength welding conditions considering HAZ shape factors

“…Hongo et al [16] similarly performed finite element analysis to simulate experiments and compared the results with microstructural observations from a creep interruption test, noting that the areas where the creep strain and stress triaxiality are concentrated accumulate much creep damage. In addition, Kawashima et al [17] studied changing material properties in the vicinity of HAZ in a stepwise manner.…”