Papers by Author: Yu Huai He

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Authors: Chang Kui Liu, Bing Zhang, Xing Chen, Ji Lin Ren, Chun Hu Tao, Yu Huai He
Abstract: Tension–tension fatigue tests of notched 18CrNi4A steel specimens were carried out under three different fatigue stresses, and metal magnetic memory (MMM) signals were detected. The effects of fatigue damage and fatigue stress on MMM signals were investigated. The results show that the absolute values of the feature parameters Hp(y)max, Hp(y)min and Hp(y)sub increase with the aggravation of the fatigue damage. There is an inherent relationship between the fatigue stress and the values of the Hp(y)sub; the larger the fatigue stress is, the larger the absolute values of the Hp(y)sub is. Fatigue-damaged locations can be effectively predicated according to the mutational character of the Hp(y) curve and the K curve, and zero-crossing points of the Hp(y) curve, respectively. Fatigue damage degree can be effectively predicated according to the value of the Kmax and the Hp(y)max, Hp(y)min and Hp(y)sub.
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Authors: Xue Qin Hou, Yu Huai He, Tao Jiang
Abstract: Fracture morphology analysis is an important way to understand material fracture process, find the reason of fracture and improve its performance. Nickel based powder metallurgy (P/M) superalloy is an important material which is widely used in the modern aeronautic and astronautic industry. In order to determine the fracture characteristic morpholgies and mechanisms of the P/M superalloy fractured at different conditions, the fracture surfaces of the high temperature low cycle fatigue,high cycle fatigue, high-low cycle complex fatigue, tension and creep specimens from the P/M superalloy were studied by scanning electron microscopy and stereo-microscopy. The mechanisms and influencing factors of high temperature fatigue crack initiation and propagation were emphatically analyzed, and creep and tension fracture mechanisms of the P/M superalloy were also discussed. The application of the fracture surface analysis for the fracture failure analysis of the P/M superalloy turbine disk were introduced finally.
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