Vibration stress relief (VSR) is a technique used to achieve post manufacturing stress relief as well as dimensional stabilisation of castings, forgings and fabrications. The VSR process relieves residual stresses in components by vibrating the component at its resonant frequency.
Why Use VSR?
Residual stress in components can lead to failure, through stress corrosion cracking and fatigue mechanisms. Residual stress can also cause difficulties in achieving machining tolerances and may result in the lack of stability of finished components.
- VSR and thermal stress relief (TSR) both reduce residual stress and hence mitigate its consequences. As opposed to TSR:
- VSR can be used easily on components employing various material types in their construction,
- VSR can be used to treat components of any size (from 10 kg to 150 tons),
- VSR does not affect material properties, such as wear resistance, hardness and yield strength, specifically enhanced by heat treatment processes,
- VSR does not bring about the often undesirable metallurgical changes, such as grain growth and overageing, associated with thermal heat treatment,
- VSR does not, unlike thermal heat treatment, cause scaling or damage to coatings,
- VSR is a relatively rapid process and does not cause the delays that are frequently associated with TSR,
- VSR does not have any associated transport costs as the VSR system can normally be brought to the component.
VSR does, however, have limitations. For example, grain refinement associated with TSR cannot be achieved, and hence VSR cannot be used where this is one of the primary goals of the stress relief procedure. In addition the efficacy of VSR with regard to severely cold worked materials or those with exceptionally high yield strengths is still unclear and under investigation.
How To Get Access To VSR?
VSR equipment is expensive and the associated capital expenditure is only warranted by large production operations, VSR services are however available in all the major centres of South Africa and in Namibia. Origen offers an on site VSR service in the Cape and, by means of its contacts with the other VSR operations, throughout South Africa.