A Proposal on Quality Assessment of Weld Bond of Structural Steel Plate in Relation to Brittle Fracture Initiation

Abstract

In order to secure the safety of welded structures against brittle failure, a proposal on quality assessment of weld bond of structural steel plate is presented. This proposal is based on a general equation correlating the brittle fracture initiation characteristics under the reisdual stress of welded joints with Charpy impact characteristics, which is obtained as follows.
1) Bending COD test is available as a small size Kc Test. Good coincidence is found between the results of COD Test and Deep Notch Test, when the critical COD is translated to K_c value.
2) Ty-evaluation is proposed from the results of Cross Weld Notch Test. T_y is the safe-side estimation of the brittle fracture initiation temperature in the residual stress field of welded joints, which can simply be obtained from Bending COD Test or Deep Notch Test on weld bond using the equation K_c=σ_y√πC.
3) From the results of COD Test and Deep Notch Test, an equation correlating the brittle fracture initiation temperature T_y with Charpy transition temperature vTs is introduced as follows.
T_y = 234+1.5vTs+12√t-65lnσ_y0/F(σ_y0, C)
F(σ_y0, C) = 324+65lnσ_y0/273 + ln 3000/σ_y0√πC
where, Ty ; safe-side estimation of britlte fracture initiatilon temperature in the residual stress field of welded joints (°K),
vTs : Charpy 50% cyrstallinity transition temperature (°K),
t : plate thickness (mm),
σ_y0 : yield strength of material under room temperature (kg/mm²),
C : half crack length in infinite plate (mm).