Papers by Author: Zhu Feng Yue

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Authors: T. Li, Zhu Feng Yue
Abstract: The possibility of the life prediction model for nickel-base single crystal blades has been studied. The fatigue-creep (FC) and thermal fatigue-creep (TMFC) as well as creep experiments have been carried out with different hold time of DD3. The hold time and the frequency as well as the temperature range are the main factors influencing on the life. An emphasis has been put on the micro mechanism of the rupture of creep, FC and TMFC. Two main factors are the voiding and degeneration of the material for the creep, FC and TMFC experiments. There are voids in the fracture surfaces, and size of the voids is dependent on the loading condition. Generally, the rupture mechanism is the same for creep, FC and TMFC. If the loading can be simplified to the working conditions of the turbine blades, i.e. the hold time is at the top temperature and maximum stress, a linear life model is satisfactory to the life prediction of nickel-base single crystal superalloy from the experimental study in this paper. The temperature and the stress level of the nickel-base single crystal (SC)blades are not uniform. To predict the life of SC blades, one should consider the cycles of the temperature and stress as well as the oxidation simultaneously. In the past 30 years, there are many works on the mechanical behavior and description, such as the inelastic constitutive relationships, plastic, fracture, isothermal creep and fatigue and thermal fatigue as well as oxidation [1-3]. There are also special software (program) to analyze the deformation and life of nickel-base single crystal structures, such as blades. In order to apply to the engineering more conveniently, there should be a life prediction model for the blades. The model should not be too complex, but take more influential factors as possible into consideration.
Authors: Kua Hai Yu, Xi Yang, Zhi Xun Wen, Zhu Feng Yue
Abstract: This paper studies the aerodynamic and heat transfer influence of tip structures for cooling turbine blade. Four blades with different tip features are discussed, and coupling aerodynamic and heat transfer method is used to accomplish the simulation. The results show that squealer tip can greatly reduce the heat transfer between tip surface and high temperature gas, and also it reduces tip leakage, to some extent. That’s because it exists obviously eddy near the tip surface. Tip injection holes can cool the tip surface effectively, and it will greatly reduce the temperature of tip surface. However, injection holes improve tip leakage slightly.
Authors: Yong Shou Liu, Jun Liu, An Qiang Wang, Zhu Feng Yue
Abstract: In this paper, an amendment method for stress and strain of double-curved laminated composite is proposed and studied. According to finite element analysis results of the same model with two different mesh size (coarse mesh size 120mm× 300mm and refined mesh size 30mm× 30mm ), stress and strain have been amended with modified formula in user material subroutine (UMAT) subprogram so that the corrected results of model with coarse mesh is similar to the results of model with refined mesh. Using this method, with coarse mesh, a satisfied accuracy results still can be obtained without refining mesh. It’s efficient for design and analysis of complex structures.
Authors: Lei Li, Zhu Feng Yue
Abstract: The stress characterization around the hole in a composite plate under tensile stress has been studied by the analytical method in this paper. The distribution of the stress components has been presented. With the Hashin Failure Criterion, the failure characterization and different failure modes by the analytical method and finite element method are then studied. The possibility of the failure in different modes is compared. It is found that the fiber breakage, matrix failure and delamination are dominant. The place of the failure is between 70 degree and 90 degree to the loading direction in this paper. The results from analytical method and finite element method can agree with each other. And they are all confirmed by the experiment results.
Authors: Lie Zhang, Juan Zhang, Peng Fei Du, Zuo Jun Li, Zhu Feng Yue
Abstract: a Design Concept of Piecewise Variable Wall Thickness of Radome Is Proposed to Simulate the Radome which Has Variable Wall. the Paper Calculates the Far Field of a Medium-Size Radome in the Case of Piecewise Variable Thickness by Three Methods as Follows: Method of Moment (MOM), Multilevel Fast Multipole Method (MLFMM) and Physical Optics& the Method of Moments (PO/MOM) Respectively. after Comparing the Results, we Find that the PO/MOM Method Have the Superiority in Simulation of Radome’s Electromagnetic because it’s More Accuracy and Less Memory Consuming than the other Two Methods. Also it Proves the Feasibility of the Design Concept of Piecewise Variable Thickness for Radome.
Authors: Xiao Jun Shao, Zhu Feng Yue
Abstract: Compressive experiments and finite element method (FEM) have been used to study the mechanical behavior of composite laminate with plies drop-off. A user subroutine has been implemented to ABAQUS to simulate the damage development of the laminate plate. This user subroutine has taken consideration of the mechanical properties degradation according to development of three types of damage. The load-strain curves can agree with each other between experiments and FEM. The detail of damage development of the plies drop-off composite laminate under compressive loading can be described as followed. Matrix cracking damage and fiber-matrix shearing damage occur simultaneously at first, and then fiber buckling damage initiates. Matrix cracking and fiber-matrix shearing are very dangerous to the carrying capacity of laminate and fiber buckling intensifies further this effect. The initiation and development of fiber buckling indicates that laminate loses carrying capacity at all.
Authors: Zhi Xun Wen, Nai Xian Hou, Zhu Feng Yue
Abstract: Based on the microstructure change and damage characteristics of single crystal, a two-state-variable crystallographic creep damage constitutive model has been developed to investigate crack growth behaviors of single crystal compact tension specimen at 760 for two crack orientations: (001)[100] and (011)[100]. Numerical simulation results show the crack-tip stress fields are dependent on crack crystallographic orientation. Observations performed on the real single crystal specimens reveals that the macroscopic crack growth path appears as zigzag wave. The creep deformation at crack tip takes place in specific slip plane, and the deflection angles of crack initiation direction from the crack plane are 45º or 135 º and 53.7ºor 127.3º in the crack orientations (001)[100] and (011)[100]. A good agreement between experimental observations and numerical results is found.
Authors: Kun Rong Jia, Zhu Feng Yue
Abstract: The failure assessment for thick wall CrMoV steel pipes circumferentially welded at 640°C was studied using the Finite Element (FE) method under close-ended, open-ended and axial compression conditions, respectively. The life and position of failure, redistribution of stress on the welds and damage variations were obtained using damage modeling. Since there is a distinct mismatch of mechanical properties in parent material, weld material and heat affect zone, variations of damage with time, stress redistribution and failure life in each zone are different. The FEM results show that the weakness of the welds is the heat-affected zone (HAZ) where the hoop stresses increase sharply in the tertiary stage of creep. The maximum of damage of the welds lies on the inner surface of in the weld zone when failure occurs. The information is useful for assessing the performance of practical service welds in power plants pipe work.
Authors: Hai Long Zhao, Zong Zhan Gao, Zhu Feng Yue, Zhi Feng Jiang
Abstract: The stress distribution of adhesively-bonded single lap joints under tensile shear loading is analyzed using 2-dimensional elastic-plastic finite element method (FEM). Special attentions have been put on the influence of void in adhesive on the stress distribution of adhesively-bonded joints. The results show that the stress concentration of the void is less than that of the end part of the joints when adhesive layer’s deformation was in the range of elastic. Moreover, the influence of the void on the stress distribution becomes less when the void moving from the end-part to the middle. The stress concentration becomes larger and the stress distribution of adhesive’s mid-thickness region becomes flatter when adhesive layer has biggish plastic deformation. Finite element results show an agreement with the theoretical results.
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