Fatigue Crack Growth Research Of A GH4169 Power Turbine Disc

This paper investigates the fatigue crack growth (FCG) of critical locations on a GH4169 power turbine disc. The crack growth simulation by finite element analysis software ANSYS and three-dimensional crack propagation analysis software FRANC3D is compared with the results of low cycle fatigue (LCF) test. The main researches are as follows:(1) The research plan of crack propagation is performed by damage tolerance design method. The test parameters such as rotational speed and temperature are determined by the working conditions. By stress state analysis of the disc, center hole and eccentric holes are chosen as critical locations.(2) The crack growth rates of critical locations are calculated by FRANC3D, with the original crack length of 0.15 mm until the stress intensity factor is larger than fracture toughness. The crack growth rate are sorted as follows:eccentric radial direction (inward)> eccentric radial direction (outward)> center hole (inward)> eccentric hole (circumferential). By calculation, the α～N curve and K～α curve are drawn and the crack propagation is observed.(3) The low cycle fatigue test of the power turbine disc is conducted in a spin rig facility. Fourteen cracks are initiated by introducing EDM notches in predefined locations of the discs. Nondestructive inspection is made at every interval of a certain number of cycles. After the test, the crack is opened mechanically, with the fracture surfaces to be ovserved. The striation counts determined by the OEM from the test are compared with the simulation.The results show that the crack growth rates of eccentric radial direction (inward), center hole (inward) and eccentric hole (circumferential) gradually decrease. The crack growth rates, determined using crack length equivalent method, show good compliance with the results of the early growth period. The simulation can also predict the shape of the crack front extension accurately. The results of the simulation is somewhat conservative compared with the ones of the late growth period. The crack growth rates in different locations matched well with the simulation as well. The research on crack growth rate analysis which is conducted by initiating the cracks in high stress locations combining the numerical simulation with the low cycle fatigue test in a spin rig facility is in the leading position in China. It is hoped that this study can provide an effective means for further research on the damage tolerance design method of aero engine disc.