Effects of Fixture Configurations and Weld Strength Mismatch on J-Integral Calculation Procedure for SE(B) Specimens

Area of Science:

• Materials Science
• Mechanical Engineering
• Fracture Mechanics

Background:

• Accurate fracture toughness evaluation is critical for high strength low alloyed steels.
• Standard J-integral estimation methods may not fully account for weld complexities.
• Bend specimens are commonly used to assess material fracture resistance.

Purpose of the Study:

• To develop an improved J-integral estimation procedure for cracked bend specimens with butt welds.
• To calibrate plastic factors (η, γ) and geometry factors (λ) using finite element analysis.
• To evaluate the impact of modified factors on J-R curve computation and fracture toughness assessment.

Main Methods:

• Tensile and fracture testing of S690 QL steel specimens (base and weld metal).
• Single specimen J-integral estimation using plastic work and normalization data reduction.
• Parametric finite element analysis to determine modified η, γ, and λ factors.
• Comparison of J-R curves computed using modified and standard ASTM E1820 factors.

Main Results:

• Modified η and γ factors were incorporated into the ASTM E1820 J-integral computation.
• Variations in specimen fixtures led to ≈10% overestimation of fracture toughness for base material.
• Standard factors overestimated fracture toughness by >10% for overmatched and ≈5% for undermatched idealized welds.

Conclusions:

• The developed J-integral estimation procedure enhances accuracy for high strength steel welds.
• Modified plastic factors are essential for reliable fracture toughness assessment in welded components.
• Standard J-integral methods can lead to significant overestimation of fracture toughness in certain weld configurations.