Fatigue Crack Propagation Properties of Welded Joints at 300°C

2003 ◽  
Vol 125 (2) ◽  
pp. 131-135
Author(s):  
Akihiko Ohta ◽  
Naoyuki Suzuki ◽  
Yoshio Maeda
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Welded Joints ◽  
Room Temperature ◽  
Welded Joint ◽  
Type Specimen ◽  
Pressure Vessels ◽  
Fatigue Threshold ◽  
Propagation Properties

Fatigue crack propagation properties of welded joints were investigated on steel plate for boilers and other pressure vessels. The fatigue crack propagation properties at 300°C became similar to those at room temperature when the thermal stress could be reduced down to −1 MPa by using center cracked type specimen with longitudinal slits and a specially designed furnace. The tensile residual stress was +152 MPa in the as-welded joint, and +12 MPa after PWHT. The fatigue threshold was about 2.7, 5.1 and 7.3 MN/m3/2 for weld metal in the as-welded condition, after PWHT and the base metal, respectively.

Pre-Strain Effects on Mixed-Mode Fatigue Crack Propagation Behaviour of the P355NL1 Pressure Vessels Steel

2018 ◽  
Author(s):  
João Ferreira ◽  
José A. F. O. Correia ◽  
Grzegorz Lesiuk ◽  
Sergio Blasón González ◽  
Maria Cristina R. Gonzalez ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Mixed Mode ◽  
Pressure Vessels ◽  
Mode I ◽  
Pure Mode

Pressure vessels and piping are commonly subjected to plastic deformation during manufacturing or installation. This pre-deformation history, usually called pre-strain, may have a significant influence on the resistance against fatigue crack growth of the material. Several studies have been performed to investigate the pre-strain effects on the pure mode I fatigue crack propagation, but less on mixed-mode (I+II) fatigue crack propagation conditions. The present study aims at investigating the effect of tensile plastic pre-strain on fatigue crack growth behavior (da/dN vs. ΔK) of the P355NL1 pressure vessel steel. For that purpose, fatigue crack propagation tests were conducted on specimens with two distinct degrees of pre-strain: 0% and 6%, under mixed mode (I+II) conditions using CTS specimens. Moreover, for comparison purposes, CT specimens were tested under pure mode I conditions for pre-strains of 0% and 3%. Contrary to the majority of previous studies, that applied plastic deformation directly on the machined specimen, in this work the pre-straining operation was carried out prior to the machining of the specimens with the objective to minimize residual stress effects and distortions. Results revealed that, for the P355NL1 steel, the tensile pre-strain increased fatigue crack initiation angle and reduced fatigue crack growth rates in the Paris region for mixed mode conditions. The pre-straining procedure had a clear impact on the Paris law constants, increasing the coefficient and decreasing the exponent. In the low ΔK region, results indicate that pre-strain causes a decrease in ΔKth.

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