Some thoughts about the application of the Master Curve methodology to ferritic steels containing notches

Sergio Cicero,Sergio Arrieta

doi:10.1016/j.prostr.2021.10.012

Abstract

The Master Curve (MC) is an engineering tool that allows the fracture toughness of ferritic steels operating within their ductile-to-brittle transition zone to be estimated. It is based on statistical considerations, related to the distribution of cleavage-promoting particles around the crack tip, and assumes that: a) fracture is controlled by weakest link statistics; b) it follows a three parameter Weibull distribution. The authors have previously provided two different approaches for applying the MC in notched conditions. The first one consists of determining the reference temperature (T0) in cracked conditions and applying a subsequent notch correction to estimate the fracture toughness at a given temperature; the second one proposes obtaining directly a notch reference temperature (T0N) for a given notch radius by testing notched specimens. This second approach assumes that both the Weibull parameters (Kmin=20 MPam1/2 and b=4) and the censoring criteria used in cracked conditions are applicable in notched conditions. This paper provides some thoughts about these assumptions with the aim of analysing the applicability of the MC in ferritic steels containing notches, and includes specific validation on steels S460M and S690Q.

Highlights

SSeerrggiioo CCiicceerrooaa, SSeerrggiioo AArrrriieettaaaa aaLLAADDIICCIIMM ((LLaabboorraattoorryy ooff MMaatteerriiaallss SScciieennccee aanndd EEnnggiinneeeerriinngg)), UU44nn44ii,vvSSeeaarrssnniittttaayynnooddffeeCCrr aa33nn99tt00aa00bb55rr,iiaaSS,ppEEaa..iiTTnn..SS.. ddee IInnggeenniieerrooss ddee CCaammiinnooss, CCaannaalleess yy PPuueerrttooss, AAvv//LLooss CCaassttrrooss
The ductile-to-brittle transition zone (DBTZ) of ferritic steels has been successfully modelled through the Master Curve, which provides a description of the fracture toughness scatter, size effect and temperature dependence (Wallin (1984), Wallin et al (1984), Wallin (1985), ASTM E1921 (2020))
The Master Curve (MC) (Wallin (1984), Wallin et al (1984), Wallin (1985), ASTM E1921 (2020)) is a fracture characterisation tool for ferritic steels operating within their ductile-to-brittle transition zone (DBTZ)

Summary

The Master Curve

The Master Curve (MC) (Wallin (1984), Wallin et al (1984), Wallin (1985), ASTM E1921 (2020)) is a fracture characterisation tool for ferritic steels operating within their ductile-to-brittle transition zone (DBTZ). It is built on statistical considerations, associated with the distribution of cleavage promoting particles around the crack tip. Where KJc is the fracture toughness for the selected failure probability (Pf) (in stress intensity factor units), B is the specimen thickness and B0 is the reference specimen thickness assumed in this methodology (B0 = 1T = 25 mm). Where KJc(x) is the fracture toughness for a component size Bx, and KJc(0) is the fracture toughness for the reference thickness (B0=1T=25 mm)

The use of the Master Curve in notched conditions

Conclusions