Quantification of creep stresses within HAZ in welded branch junctions

Abstract

This paper quantifies the mismatch effect in creep properties on creep stresses in the heat‐affected zone of welded branches using systematic elastic‐creep finite element analysis. It is found that the section‐averaged normalized stresses in the heat‐affected zone can be uniquely characterized by the mismatch factor in creep. The relationship is almost linear and is not so sensitive to the loading condition. Implication to practical creep life assessment of welded branch components is discussed in the context of the R5 procedure.

Characterizations of material constraint effect for creep crack in center weldment under biaxial loading

“…For the convenience of analysis and calculation, it is assumed that the elastic properties of weld metal and base metal are identical, i.e., the nominal stress r 0 , Young's modulus E and Poisson ratio v for the weld metal and base metal are taken as 180 MPa, 125,000 MPa and 0.3, respectively. These materials are close to the 1/2CrMoV steel for base material and 2.25Cr1Mo steel for weld material, which have been used widely in high temperature pressure vessels (Han et al 2015). It implies that there is no elastic mismatch discussed in this paper so as to make the investigation be focused on creeping mismatch.…”

“…The critical challenge on quantifying the stress field of crack tip in those welded components is that the crack tip field can be influenced by many factors such as material mismatch (Kumar et al 2014), weldment geometry (Zhou et al 2014), residual stress (Ren et al 2009) and loading state, e.g., biaxial loading (Wang 2012;Shlyannikov et al 2011;Shlyannikov et al 2014;Wang et al 2014). Those factors can lead to the variations of microstructure (Kulkarni et al 2020), stress level (Han et al 2015), fracture toughness (Hemer et al 2020) as well as crack growth rate (Krishnan et al 2018;Alves et al 2020;Velu 2018) for the weldment, among which fracture toughness is an crucial fracture parameter to be determined as it can affect the border of failure assessment diagram which has been widely used as the evaluation tool by the industrial field (Dai et al 2020a). Note that the fracture toughness is always related to the so-called ''constraint effect.…”

Characteristics and implications of material mismatch on mode II creep crack tip field: Theoretical analysis and numerical investigation

“…Nine typical cases, shown in Table 1 numbered from C1 to C9, are selected to study the material mismatch effect with a fixed creep exponent of n=7. The data in Table 1 is available from [45]. Among those data in Table 1, there are two kinds of mismatch effect which are characterized by the weld mismatch factor, MFW, and the HAZ mismatch factor, MFHAZ, respectively.…”

Influences of T-Stress on Constraint Effect in Mismatched Modified Boundary Layer Model for Creep Crack

“…Lee et al [8] gave a study on the quantification of creeping stress of a welded branched pipe. Han et al [9] also presented the creeping stress distribution of a welded branched pipe junction with a heat affected zone (HAZ). There were also some other related works on creeping weldments [10][11][12].…”