Strength and Crack Resistance Behavior of Mismatched Welded Joints

摘要

A mismatched welded component exists when the strength of the weld material isdifferent than the strength of the base material. This research has examined the effect of weld joint geometry and mismatch level on the strength and fracture performance of high strength steel weld components. Fracture performance was studied only for applied three-point bending loading. Eleven different welded systems were constructed with mismatch ranging between -36% to +47% and various weld joint profiles to sculpt fusion zone widths between 2 and 13 mm at the crack tip. Instrumented tensile tests were utilized to characterize weldment strength behavior while single edge notch bend J-R curve testing of short (a/W = 0.15) and deeply (a/W = 0.5) cracked specimens was conducted to measure both baseline weld metal toughness properties and determine the fracture performance of mismatched systems. The results indicate that contact strengthening in unflawed specimens occurs to a greater degree and at lower constraint in conventional undermatched weldments. Flawed undermatched performance under bending loads is highly dependent on the fusion zone width as well while the degree of mismatching is a secondary effect. As the zone width decreases, the apparent tearing resistance also decreases. The overall performance of undermatched systems, however, can still be better than overmatched systems when the inherent toughness of the overmatching weld metal consumable is poor. (MM).