Testing Of Residual Stress For The Large-size Turbo Generator Shafts

The rotor is a core component of large-size turbo generator equipment, it is always keep high-speed rotation on its life cycle, rotor’s main parts contain shaft, coil winding, supporting rings and shaft is the most important carrier, so the mechanical properties of shaft determines the service life and operations of rotor. As a large-size forging, the shaft must been brought residual stress during its manufacturing process, and the residual stress is a main component of the mechanical properties.Now in domestic the main method to test the shaft’s residual stress is cutting-ring method, but abroad the main method is ring-core method, along with the technical and business cooperation between China and foreign counterparts are increasingly close and China’s manufacturing capability increase, domestic manufacturer also import the ring-core method in recent years, so now there are two parallel methods for shaft’s residual stress testing in domestic.The generator plant which the author worked in also import the ring-core method not long ago, but in the daily testing for the generator shaft’s residual stress, the data of the ring-core method larger than the data of the cutting-ring method. Through the comparison in theory and practical work of two methods, we found tangential and longitudinal residual stress from ring-core method have more practical value in engineering than radial residual stress from cutting-ring method in shaft, and the ring-core method’s testing depth and strain coefficient more scientific than the cutting-ring method; from the specific operations, the testing accuracy of the ring-core method which is 1μm/m is more accurate than the cutting-ring method which is 10μm/m, and the ring-core method will cost smaller materials, don’t take the traffic and large machine tool, these give a lower cost, at the same time, the time cost on each one testing in ring-core method is 30 min more efficient than the cutting-ring method which will cost about 12 h.So when testing the residual stress of the shaft in the future, suggest to use the ring-core method replace the cutting-ring method to gain a better comprehensive benefits.