For understanding the importance of the Stress relieving equipments, we should know about the concept of stress. For metallurgical purpose the stress is described as the force experienced between any parts of the body of continuous material in a state of equilibrium which is balanced internally. This stress causes distortion which is severe enough to destroy the whole component. Different processes involved in manufacturing like welding, casting, forging, machining, forming may introduce residual stress in the job. The stresses developed to developed in component may cause distortion in the job, which may result in . dimensional instability over a period of time. If the distortion is very severe, it may cause total destruction of the component.
Residual stresses can be relieved by many methods some of which were hammering the work piece with a wooden mallet and dropping a casting or welding from a height to pile of sand. This may have created vibrations which caused the elimination of some of the residual stresses developed during manufacturing process. Aging and annealing are the most recent methods. These earlier methods which were use for relieving stresses constituted the initial step towards the most effective and efficient method known as vibratory stress relief. The vibratory stress relief process can be explained as a 'method of applying controlled low amplitude, low frequency vibrations in metal components to obtain dimensional stability and control for machining tolerances'. This method has now become the most accepted way of stress relieving as it is a cost-effective, rapid and suitable way of reducing stresses and finds its utility during process to achieve the dimensional stability.
The methodology of the stress relieving involves “the micro plastic deformation of atoms which is achieved by injecting additional energy in the form of thermal or mechanical”. This method simply works on the 'theory of exerting a controlled range of low amplitude, low frequency vibrations in metal components to obtain dimensional stability and control for machining tolerances. Any stress reduction is associated with micro-plastic deformation of atom. This can be achieved by injecting the extra energy in the job.
During the process of thermal stress relieving, the value of residual stress gets higher than the yield stress value at relieving temperature which makes the material to immediately undergo plastic deformation so as to reduce the residual stress value. By mechanically means, the vibration energy is exerted into the work piece to make the applied stress superimposed on the existing residual stress. The resultant stress value passes through the yield point of the material and will endure plastic deformation resulting in the reduction of residual stress value. The energy injected should have enough magnitude to activate the stress atom to cross the yield point. To achieve this mark, the vibration energy is injected at natural frequency of the work piece.
VSR is a very vital and utmost useful technique to relieve the residual stress in a component which is an extremely efficient way of saving the component from destruction due to distortion resulting from residual stress. VSR helps in maintaining a perfect dimensional stability to ensure that the component does not experience the stress due to poor equilibrium problems. VSR is widely used technique for relieving residual stresses to achieve dimensional stability of the job and enhancing life of the components.
The various areas of application of VSR Include:
It really gets difficult to display the instant effect of VSR technique because it is not feasible to calculate the residual stress in a component unless some source of destructive test is put into application. With this, it is also difficult to obtain total stress reduction by making use of any commercial process. The improvement in the dimensional stability of a work piece is comparatively an easy way to demonstrate the success of VSR is and this way has proven its applicability with positive results.
VSR has proven its importance as a major technique for stress reduction in the component. We have conducted some stringent test on our VSR equipments to prove their effectiveness in worst of the situations. Our experts make these equipments to perform their task of establishing equilibrium in the component for continuously hour after hour and come up with positive and impressive results. Vibratory stress relieving of press brake body fabrication.
Vibratory Stress Relieving of Marine Shaft being carried out at site for dimensional stability and better machining tolerance.