THE INFLUENCE OF SOFT ROOT ON FRACTURE BEHAVIORS OF HIGH-STRENGTH, LOW-ALLOYED (HSLA) STEEL WELDMENTS

Abstract

The presence of different microstructures along the precrack fatigue front has an important effect on the critical crack tip opening displacement (CTOD). This value is the relevant parameter for safe service of a welded structure. For a specimen with a through-thickness notch partly in the weld metal, partly in the heat-affected zone, and partly in the base material (i.e., using the composite-notched specimen), fracture behavior strongly depends on the proportion of ductile base material, size, and distribution of the mismatching factor along the vicinity of the crack front.

Keywords:

• Crack growth
• Crack tip opening displacement (CTOD)
• CTOD fracture toughness testing
• CTOD-R resistance curve
• DC potential drop technique
• Direct CTOD measuring
• Fatigue precracking
• Fluxo cored arc welding process
• Heat-affected zone
• High-strength, low-alloyed steel (HSLA)
• Round tensile specimens
• Stepwise high ratio method procedure
• Single-edged, notched bend specimen
• Soft root layer
• Strength mismatch factor
• Undermatched welded joints

6.0 ACKNOWLEDGMENTS

The authors wish to acknowledge the financial support of the Japan Society for the Promotion of Science, and the Slovenian Foundation of Science and Technology. Kocevar & Thermotron d.o.o, Aga Gas d.o.o, and Arko d.o.o Slovenia are also noted for providing a financial support of this research program. We also express special thanks for many useful discussions and contributions of Prof. Dr. I. Rak, Prof. Dr. K.-H. Schwalbe, Prof. Dr. B. Petrovski, and Dr. M. Kocak.