| Fatigue of notch component has been the concern matter of people. At present, uniaxial fatigue of the notch component in research has been a lot of ways, but there is no more mature approach about multiaxial loading fatigue life. In engineering practice, there is extremely rare in the uniaxial stress condition. Even if the outside is to be in the uniaxial stress state, multi-axial stress exit in the shaft notch. It is to be important theoretical significance and engineering application value to carry out the fatigue life prediction research. In this paper, through theoretical analysis and a large number of experiments, systematic research has to be carried out the fatigue life of annular gap axis.The main contents of this paper are as follows.(1) The impact factors of the gap-axis fatigue life are be summaried and its to be classified. Based on the traditional fatigue life model, the fatigue life prediction model of gap axis has been established. Several kinds of safety life prediction model and its influencing factors have been evaluated. The expression based on the stress field near the tip gap, dimensionless factor is be obtained. Using the establishment gap axis fatigue life model, through the computation, the relational expression between the gap radius, the gap open angle,the gap depth and the dimensionless factor has been established. The results show that the dimensionless factor can be as the unified parameter to describe the circumferential crack, circumferential blunt crack and ring-shaped crack.(2) In this paper, the fatigue experiments of gap axis have been carried out in the low cycle tension-compression, cantilever bending and cantilever blank tear load. A combined clamp has be designed to carry out the fatigue test in tension-compression, cantilever bending and cantilever blank tear load. The test equipment is a new electro-hydraulic fatigue testing machine made by Japan. The range of models are SHIMADZU EHF-EM100kN. Through experiments and analysis, the relation betwwen gap radius, gap depth, gap opening angle and its fatigue life in the three kinds of load conditions, has been obtained. The result indicated that the gap radius, gap depth and gap opening angle are a function of the dimensionless factor. As the notch radius increases gradually, the gap axis fatigue life show increasing trends.As the cutting diameter ratio increased gradually, fatigue life of the gap axis displayed downward trend. When the gap opening angle is less than 90°, its effect on fatigue life of notch shaft has been ignored. It proved that the model of axial fatigue life was effective and useful.(3) In view of many impact factors on fatigue life, and the interaction of various factors that exist, the author proposes a kind of fatigue life prediction method based on the Matlab BP artificial neural networks. The simulation results show that this method shows the advantage of high precision, good adaptive and self-learning intelligent characteristics to predict the gap shaft fatigue life on gap parameters (gap radius, gap depth and gap opening angle). The calculation method overcomes the traditional shortconging that relys on the mathematical model and a large quantity of calculation.(4) Through the analysis of typical fracture surface in cantilever blank tear load, the law of fatigue crack initiation and expansion has been obtained in multi-axial cyclic loading. Fatigue crack initiates the maximum equivalent stress at the specimen outer surface and presents the multi-origin fatigue crack. Fatigue crack formation of the outer surface of the sample expand to the inner showing radial. Along with load enlargement, tearing area in instantaneous fracture region increase gradually, and instantaneous fracture region is off-center. The analysis result has provided the theory basis for the multi-axial weary process and the fatigue failure mechanism. |
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