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Vibratory Stress Relief, often abbreviated … Vibratory Stress Relief, often abbreviated VSR, is a non-thermal stress relief method used by the metal working industry to enhance the dimensional stability and mechanical integrity of castings, forgings, and welded components, chiefly for two categories of these metal workpieces:
* Precision components, which are machined or aligned to tight dimensional or geometric tolerances. Examples include machine tool bases or columns, components of paper mill, mining equipment, or other large-scale processing machinery, and centrifuge rotors.
* Heavily loaded metal workpieces, which are components designed and built with the ability to withstand heavy loads. Examples include lifting yokes, clamshell buckets, crane bases, vibratory screening system frames, ingot processing equipment, and rolling mill equipment. This stress is called residual stress, because it remains in a solid material after the original cause of the stress has been removed. Residual stresses can occur through a variety of mechanisms including inelastic (plastic) deformations, temperature gradients (during thermal cycle), or structural changes (phase transformation). For example, heat from welding may cause localized expansion, which is taken up during welding by either the molten metal or the placement of parts being welded. When the finished weldment cools, some areas cool and contract more than others, leaving residual stresses. These stresses often lead to distortion or warping of the structure during machining, assembly, testing, transport, field-use or over time. In extreme cases, residual stress can cause structural failure. Almost all vibratory stress relief equipment manufacturers and procedures use the workpiece's own resonant frequency to boost the loading experienced by induced vibration, so to maximize the degree of stress relief achieved. Some equipment and procedures are designed to operate near, but not at, workpiece resonances (perhaps to extend equipment life) example WIAP research, but independent research has consistently shown resonant frequency vibration to be more effective. See references 4, 6, and 9. The effectiveness of vibratory stress relief is highly questionable. In general, the strain amplitudes achieved during vibratory stress relief are too low to exceed the critical stress required to activate mechanical relaxation during the induced low amplitude high cycle fatigue excitation of the transducer vibrations. If the strain amplitudes were increased to a level sufficient to cause instability in the residual stresses, fatigue damage would occur. For most applications, conventional stress relief methodologies should be applied to components that require the reduction of residual stresses.equire the reduction of residual stresses.
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Vibratory Stress Relief, often abbreviated … Vibratory Stress Relief, often abbreviated VSR, is a non-thermal stress relief method used by the metal working industry to enhance the dimensional stability and mechanical integrity of castings, forgings, and welded components, chiefly for two categories of these metal workpieces: two categories of these metal workpieces:
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