We’ve been using VSR for over 15 years to remove thermal stresses from large, A36 plate fabrications of welded components with reasonable results. We are trying to apply it toward removing residual stresses after shaft machining. I've been researching VSR for use in manufacturing 800 lb, AISI 4140, induction motor shaft assemblies.
Rotor construction has the motor core biased toward one end of the shaft. The core end has a duplex ball bearing set close to the core. At the opposite end, the shaft (and equipment) are overhung (cantilevered) almost half the shaft length past a journal bearing that is closest to the core.
The general shaft diameter is relatively uniform over its length; with the greater diametrical stock reductions located at the ends. The shaft size reductions are as great as 4¼" diametrical (stock removed) at the ends. We are using VSR on the shaft machining to relieve residual machining stresses. It is suspected that there are also additional mechanical stresses associated with shrink fitting of the laminated core to the shaft that are not being addressed.
It is preferred to use VSR over thermal stress relief to avoid any reduction in strength, unnecessary distortion and straightening, and surface oxidation of the rotor assembly. VSR also allows use to have in-house control of the stress relief process.
Modal analysis and critical speed predictions indicate that the mechanical design is stabile. When functioning purely as a motor, the unit operates as predicted. However, when operated in its integrated application, the shaft has been noted to develop as much as .004" eccentricity at the far end of the overhang. Considerable testing suggests that functional loading is probably not having an influence on stability.
To the best of our knowledge there is no known, proven evidence of what science is behind the VSR process. We are trying to better understand the mechanics and metallurgy behind VSR and what it can successfully accomplish. Also, we need to know what measurable (NDT) indicators there are to demonstrate that the rotors are effectively stress relieved. We are currently using TIR to demonstrate compliance.
Is there any suggests on how we can be successful with this method?
Rotor construction has the motor core biased toward one end of the shaft. The core end has a duplex ball bearing set close to the core. At the opposite end, the shaft (and equipment) are overhung (cantilevered) almost half the shaft length past a journal bearing that is closest to the core.
The general shaft diameter is relatively uniform over its length; with the greater diametrical stock reductions located at the ends. The shaft size reductions are as great as 4¼" diametrical (stock removed) at the ends. We are using VSR on the shaft machining to relieve residual machining stresses. It is suspected that there are also additional mechanical stresses associated with shrink fitting of the laminated core to the shaft that are not being addressed.
It is preferred to use VSR over thermal stress relief to avoid any reduction in strength, unnecessary distortion and straightening, and surface oxidation of the rotor assembly. VSR also allows use to have in-house control of the stress relief process.
Modal analysis and critical speed predictions indicate that the mechanical design is stabile. When functioning purely as a motor, the unit operates as predicted. However, when operated in its integrated application, the shaft has been noted to develop as much as .004" eccentricity at the far end of the overhang. Considerable testing suggests that functional loading is probably not having an influence on stability.
To the best of our knowledge there is no known, proven evidence of what science is behind the VSR process. We are trying to better understand the mechanics and metallurgy behind VSR and what it can successfully accomplish. Also, we need to know what measurable (NDT) indicators there are to demonstrate that the rotors are effectively stress relieved. We are currently using TIR to demonstrate compliance.
Is there any suggests on how we can be successful with this method?
