Stress relaxation due to ultrasonic impact treatment on multi-pass welds

Abstract

Ultrasonic impact treatment (UIT) is a relatively novel technique applied to the toe of welded joints to improve the fatigue life by changing the weld geometry and the residual stress state. In this study, the stress relaxation due to ultrasonic impact treatment is investigated on a six pass welded high strength quenched and tempered steel section. Stress measurements in two orthogonal directions were conducted by energy dispersive synchrotron X-ray diffraction. Results show that the application of only ultrasound to a welded component re-distributes the residual stresses more uniformly, while mechanical impacts in combination with ultrasound is an effective way to release the residual stresses. After welding, diffraction peak broadening due to the lattice distortion, characterised by the full width at half maximum (FWHM), is observed in the region of the weld toes. Ultrasonic impact treatment reduces the FWHM at these locations.

Effects of ultrasonic impact treatment on weld microstructure, hardness, and residual stress

“…Earlier work by Statnikov et al [14] and Kudryavtsev et al [15] reported that UIT produces a nanocrystalline layer up to 100 μm thick at the treated surface, due to rapid heating and cooling combined with severe plastic deformation. These findings were verified by Gao et al [16], who found a nanocrystalline layer up to 75 μm thick after applying UIT at the toe of a multi-pass welded joint in high-strength steel. Mordyuk et al [17,18] also found that UIT induced a nanocrystalline layer on the surface of an AISI-321 stainless steel.…”

Residual Stress, Defects and Grain Morphology of Ti-6Al-4V Alloy Produced by Ultrasonic Impact Treatment Assisted Selective Laser Melting

“…Sci. 2016, 6, 304 2 of 7 deformation methods (see Figure 1a), which was originally developed to relax residual stress and improve the fatigue performance of welded structures [10,11]. It is usually used for welded processing to eliminate residual tensile stress, and is also used for the surface treatment of bulk material to implant compressive stress and form fine grain zone.…”

Residual Stress, Mechanical Properties, and Grain Morphology of Ti-6Al-4V Alloy Produced by Ultrasonic Impact Treatment Assisted Wire and Arc Additive Manufacturing

“…UIT is an effective technique for reducing residual stress and improving the fatigue performance of welded structures. Gao et al applied UIT to the toe of welded joints, and determined that the fatigue life improved with a change in the weld geometry and the residual stress state [11]. Mordyuk et al determined that UIT-treated specimens experience an increase in a microhardness and fatigue relative to annealed alloys, while the surface roughness of the former in terms of the stress concentration factor did not exceed ~10% [12].…”