13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Research on Fatigue Damage and Crack Propagation of GH4133B Superalloy Used in Turbine Disk of Aero-engine Rongguo Zhao1,*, Dunhou Tan1, Xiyan Luo2, Hongchao Li1, Junfei Li1, Wei Li1, Xuehui Liu3 1 College of Civil Engineering and Mechanics, Xiangtan University, Xiangtan 411105, China 2 College of Resources and Environmental Science, Chongqing University, Chongqing 401331, China 3 Liyang Aero-Engine Corporation, Aviation Industry Corporation of China, Anshun 561102, China * Corresponding author: zhaorongguo@163.com Abstract The fatigue damage and fracture of GH4133B superalloy used in turbine disk of aero-engine are studied. Firstly, the fatigue limit is measured, and the relation between electric resistance change ratio and number of fatigue loading cycles is investigated for smooth samples. Then, the fatigue crack propagation tests are carried out at various stress ratios, and the fatigue crack propagation threshold values are measured for standard compact tension samples. The research results indicate that the theoretical fatigue limit agrees well with experimental one, the modified Chaboche model can predict the fatigue damage preciously, and the Paris formula considering fatigue threshold can describe the crack propagation behavior accurately. Finally, the crack propagation equations and loads are derived using the inverse deducing method based on the fractography of smaples. It is suggested that the inverse deduced equations can predict the crack propagation behavior, and the predict results can effectively prevent the occurrence of fatigue fracture. Keywords Fatigue, Damage, Crack propagation, Fractrography, GH4133B superalloy 1. Introduction In the fracture accidents of engineering components and structures, the fracture caused by fatigue accounted for about 70% to 80% of all the fracture accidents [1]. In the field of aviation industry, the damage tolerance design criterion has been introduced into the structural design of the aircraft and aero-engine, instead of the traditional minimum safe life design criterion [2, 3]. As far as the fatigue damage mechanism is concerned, from the point of view of damage mechanics, the process of crack growth in material from initiation to propagation to ultimate failure is a one of continuous damage evolution. The damage evolution equation is stated by the relationship between the change of damage variable and the number of loading cycles. Therefore, constructing a suitable damage evolution equation becomes a key issue of the damage tolerance design. Many damage theories for various metals and their alloys under different conditions had been devoloped, and these models were reviewed, and they were grouped into six categories: linear damage rules; nonlinear damage curve and two-stage linearization approaches; life curve modification methods; approaches based on crack growth concepts; continuum damage mechanics models; and energy-based theories [4]. In general, the elastic modulus, fatigue cycles, microhardness, interface shrinkage, as well as electric resistance, etc., can be used to describe the fatigue damage of material. For most of the metals and their alloys, the electric resistance change method can be adopted to charaterize the fatigue damage evolution, which has better accuracy and sensitivity [5–7]. Fatigue crack growth in metals and alloys is a process controlled by many variables, which includes both external factors such as temperature, frequency, loading rate, stress ratio, mean stress, and internal factors such as content, microstructure, and inclusion. GH4133B is a nickel-based superalloy. Such alloy is selected to manufacture components operated at high temperature, such as turbine disk of aero-engine, for its resistance to sensitization, adaquate high temperature tensile strength and creep resistance. Hu [8] investigated the creep-fatigue interaction and the effect of loading history on the creep-fatigue damage of GH4133B superalloy at 600ºC in three cases of loading as continuous cyclic loading (CF), prior fatigue followed by creep loading (F+C), and prior
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