Study On The Fatigue Life Of Turbine Shafts Based On The Time Domain Simulation

Any of the power system disturbances may result in changes of turbine shaft torques. The change process will cause the loss of shaft fatigue. The fatigue damage occurs, which leads to shaft fracture, motor outage or even more serious accidents, as the loss accumulated to a certain degree. Based on the electromagnetic transient simulation software PSCAD/EMTDC, the paper proposed some methods to predict the fatigue life of the turbine shafts. It contains:1) Describes the general characteristics of metal fatigue,.and the general theory and methods for fatigue life estimation in materials science.2) Introduces the modeling methods of the turbine shafts in the electromagnetic transient simulation and the conversion method of parameters in various units.3) Through the analysis of different damping components, the most concerned damping component is identified. Based on the complex modal analysis method widely used in the mechanical vibration engineering, the relationship between the damping coefficient matrix and the torsional mode damping is established, furthermore, an iterative method to compute the damping coefficient matrix is developed.4) Two methods were used to evaluate the damage accumulated based on the electromagnetic transient simulation. Through a simple system the methods were proved to be suitable. Then the impacts of some important factors on the damage are studied. Those important factors include the sequence of the load, the proceeding of half cycles in rain-flow counting method and the torsion modulus. At last the methods were compared.