FRACTURE TOUGHNESS ANALYSIS OF ASTM A36 STEEL WELDED JOINTS: THE CRITICAL ROLE OF STRESS CONCENTRATORS

Abstract

The traditional criterion for designing structural elements relies on the material’s elastic limit, a practice that proved inadequate with the advent of welded structures susceptible to cracks. All materials contain imperfections like dislocations, pores, or inclusions, but cracks are the most critical as they act as stress concentrators, leading to catastrophic failure at loads below the design limit. This deficiency prompted the development of Fracture Mechanics, which introduces crack size as a third critical variable alongside load and material properties. Instead of mechanical strength, this field uses fracture toughness to quantify the critical combination of stress, crack size, and a material’s resistance to crack propagation. A key design criterion is to calculate the critical crack size for a given load and, by applying a safety factor, determine the maximum allowable crack size for safe operation. This study investigates the influence of stress concentrators on the fracture toughness of ASTM A36 steel joints welded via the SMAW process, hypothesizing that the heat-affected zone (HAZ) is the most critical area. The primary objective is to identify the most fracture-critical zone within the weldment by experimentally determining the J-integral in the elasto-plastic regime. The findings are crucial for enhancing the design, quality assessment, and structural integrity of welded joints.