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Progress in low-frequency vibration processing technology for metal welds in shipbuilding and mamachine engineering

Residual welding strains and stresses affect strength, lifetime and reliability of shipbuilding hull structures and a wide spectrum of welded metal structures applied in manufacturing of machine tools, machines and railroad cars, as well as in building industry. Welding strains also increase man-hours required for manufacturing. A traditional way of residual stress mitigation in shipbuilding and other industries is thermal processing which is known to be a costly and labour-intensive operation. An alternative process is low-frequency vibration processing that is relatively easy and highly cost-efficient. Low-frequency vibration processing basically means that metal structures are subjected to alternating-sign loads at resonant or near-resonant frequencies by means of an electromechanical vibration exciter. Size stabilization in this kind of processing is achieved through mitigation and re-distribution of the first-kind residual stresses, i.e. those equilibrating over the entire product or its large elements, so that material structure comes to a more stable equilibrium. This paper discusses SSTC experience in the induction of low-frequency vibration processing of welded metal structures to the practice of shipyards and machine manufacturing enterprises, as well as describes state-of-the-art equipment for its performance and the equipment used to assess and check its results.