Metal Material Fatigue Failure Research Under Coupling Factors Of Load And Temperature

The turbine blades of the civil aviation engines work in high temperature environments for long term. Material's mechanical properties under high temperature is relatively complex,it can be affected by many factors, including temperature, corrosion, load and so on. Due to this complex work environment, fatigue fracture phenomenon often occurs on the turbine disks, turbine blades and other components. So there is huge significance to research the fatigue properties of the superalloy which is used in the engines, and this is important for the life prediction of the engine components.The mechanical property of materials is studied by the tensile test on the Instron 5982 testing machine, and the experimental data is recorded by the VIC-3D equipment. Low cycle fatigue properties under different frequency, temperature and load are investigated through the tension-compression fatigue testing by using the Instron 8803 servo-hydraulic fatigue testing system. The microscopic observation and EDS analysis of the fracture surface is studied by using the Hitachi S-3400 N scanning electron microscope. The fatigue life is predicted by the nominal stress method with the MSC.Fatigue simulation software, and it is compared with the experimental fatigue life.VIC-3D equipment can record the date intuitively during the tensile test on the nickel-base superalloy GH4033, it can measure the data with large range and predict the occurrence of cracks. The phenomenon of cyclic additional softening is observed for the fatigue under high temperature. The results show that the fatigue lives decrease with the increase of stress amplitude, the increase of the frequency and the increase of the temperature.The nominal stress method can predict more accurately for the fatigue life more than 104,but the prediction has a deviation for the life lower than 103. The fatigue fracture of GH4033 under high temperature consists of three parts: the crack initiation zone, the crack propagation zone and the short interruption area. With the increase of the load, the proportion of the crack initiation zone and the crack propagation zone decreases, and the quantity of the second crack initiation increases. Morphology of cracks under high temperature is composed of crack body, the oxide film and the diffusion region. The result of the EDS analysis shows that the well-distributed carbine particles are the second crack initiation sites.