Vibratory Stress Relief

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WHAT IS RESIDUAL STRESS ?

• Stresses remain in a body even after the removal of external forces and temperature gradients from the body.

• These stresses may prove to be detrimental to the service life of the body, affecting its fatigue life and dimensional stability.

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THERMAL METHOD• The part is heated under carefully controlled conditions to several hundred

degrees, maintaining this state till majority of the stresses have been relieved. It is then followed by controlled cooling to prevent introduction of new residual stresses.

• In many cases, this process is reiterated many times during the manufacturing process before the part is ready for use.

• During this process, the yield point of the material is substantially lowered, which allows for plastic flow in the material.

• This plastic flow in the material, consequently, causes redistribution and subsequent reduction of internal residual stresses.

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VIBRATORY STRESS RELIEF(VSR)

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

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VSR SETUP

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VSR is not yet accepted as the industrial standard for stress relief currently, there are many situations where VSR proves to be the better option with respect to other stress relief techniques. (ADVANTAGES)1.Energy consumption and fuel related costs related to

vibratory methods are much lesser 2. Treatment of large fabrications with vibratory methods can

be accomplished in smaller times compared to treatment with thermal methods, which translates into reduced costs for manufacturers.

3. In some cases with large size fabrications, stress relieving with TSR leads to Thermal Gradient Zones because of new stress patterns generated due to stress relieving in sections. Fortunately, in VSR, the entire fabrication can be stress relieved at once, precluding the possibility of such thermal gradient zones.

4. Compared to TSR, air pollution rates related with vibratory methods are lesser.

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DISADVANTAGE

• In cases where metallurgical changes are required to improve the properties of a component, vibratory methods are ineffective since they are solely mechanical methods

• There is little available theory to properly quantify the effectiveness of vibratory methods. Due to this, vibratory methods are difficult to use for stress relief of complex components

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CONCLUSION

• From its gradual increase in acceptance in many industries as a mainstream stress relief method, it is easy to surmise that the attitude towards VSR is on a rise. Its ubiquitous acceptance can be seen from its present day uses across continents.

• However, despite its many advantages, there is not a general consensus in favor of this method. This calls for continued work towards exploring the scope of this method and gaining acceptance for this method.

• For VSR to become a widespread practice in the industry, additional experimentation and research is required to produce a validated theory with the capacity to quantify the effectiveness of this method.

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THANKING YOU

REFERENCES1) Vibratory Stress Relief Techniques: A Review of Present Trends and Future Prospects Syed Askari Raza Baqar1, Yugal Raj Jain2, Pradeep Khanna3 1,2Student, 3Assistant Professor, Department of Manufacturing Processes and Automation Engineering, NSIT, New Delhi, India