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A mismatched welded component exists when the strength of the weld material is different than the strength of the base material. This research examined the effect of weld joint geometry and the mismatch level on the strength and fracture performance of high-strength steel weld components. Eleven different welded systems were constructed with the 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 tension tests were utilized to characterize weldment strength behavior, while single-edge 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 to determine the fracture performance of mismatched systems. The results indicate that more contact strengthening occurs in beveled, structural undermatched weldments compared to straight-sided welds. Flawed undermatched performance 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 hen the inherent toughness of the overmatching weld metal consumable is poor.
mismatching, mismatched welds, undermatched welds, elastic-plastic fracture, J-R, curve, cracking resistance, weld joint geometry, weldment strength
Mechanical engineer, Naval Surface Warfare Center, West Bethesda, MD