Research On Low-cycle Fatigue Experiment And Life Prediction Of Turbine Rotor Steel12Cr

Under multi-axial proportional and non-proportional interactive cycle load, the stressand strain state of steam turbine rotor is very complicated. The complex stress state hasgreatly reduced the fatigue life of rotor and accumulated the fatigue damage, and so farseveral turbine shaft has been destroyed. So the fatigue life prediction method of turbinerotor is significant for the security operation of turbine. As the increasing of the steamtemperature and pressure, the steel Cr-Mo-V widely used in the past of China cannot meetthe strength requirement and the steel12Cr has been adopt. However, the research on thenew material is inadequate and few articles is published. This paper which concerns the lowcycle fatigue properties and fatigue life prediction method has a good reference value.To study the high temperature low-cycle fatigue properties and life fatigue models ofturbine rotor steels, total strain-controlled low-cycle fatigue tests were carried out to2kindsof domestic supercritical (ultra-supercritical) turbine rotor steels12Cr at540℃and593℃respectively. Fatigue properties of12Cr in cycle-steady stage were obtained from the testsdata, which is used to analyze superiority of two fatigue life models like Manson-Coffinmodel and total strain energy model. Results show that12Cr steels have an obvious cyclicsoftening behavior and high life in540℃, and the total strain energy model predicts thehigh temperature low-cycle fatigue life of12Cr better.With the test data of material properties, the article uses Fortran language and theincrement theory to write the elastic-plastic constitutive model of12Cr, which is proved bythe second development function of MSC.Marc. FEM and the total strain energy model areused to simulate the mechanics of a plate under torsion-bending load and estimate theresidual life of the pre-damage plate. Furthermore, the elastic-plastic constitutive model andFEM is use to simulate the stress-strain state of a thin-walled tube which under torsionaland tension-compression load. With different critical plane life prediction model, thefatigue life of the tube is predicted, and the result shows that the constitutive model andFEM is suitable for the prediction of fatigue life under multi-axial load.