Applied Mechanics and Materials Vols. 275-277

Abstract: According to theory of thermoelasticity, the paper deduces the formulas of the rolling bearing steel ball transient temperature, radial stress, tangential stress, radial displacement, and radial clearance, analyzes the influence of the temperature deformation on the radial clearance. The result shows that the radial displacement changes slowly on the surface, reaches the maximum when temperature becomes stable. The reduction value of the radial clearance is the linear function of the temperature and position. Fitness formula is adopted to calculate the radial clearance in the different temperature and radius. The error is less than 0.2% and 0.18%. The radial clearance formula is used to calculate the bearing’s maximum working temperature when the radial clearance reaches the standard radial clearance to ensure the reliable work of the bearing.

Abstract: It is assumed that hemp stalk, bast fibre and xylem are the geometrical model of hollow cylinder on the basis of getting the average size and the average elastic constants. The stress and strain distributions of hemp stalk under the transversely even-distributed load are analyzed through ANSYS software. According to the geometrical size and the material attributes of peeling roller, the dynamic simulation model of roller and hemp stalk is built.

Abstract: This article will perform the stress analysis of transmission system and tower of offshore wind power generator . It first utilizes the computer engineering software GH Bladed to get the load on the offshore wind power generator, then ANSYS software is used to get the stress distribution in the structure. From the analytical results, the stress distribution in the structure can be a basic data to perform a new design or strengthen the structure.

Abstract: During the cooling process of composites after curing, thermal residual stress will be produced due to mismatch of the coefficients of thermal expansion between matrix and reinforcement phases. Thermal residual stress is one of the most important factors that affect the mechanical properties of composite materials. The effect of fiber volume fraction on the distribution of thermal residual stress in unidirectional fiber reinforced composite has been investigated with finite element analysis. The results show an inhomogeneous distribution of thermal residual stress in different regions of composites. The longitudinal stress on the interface between matrix and fiber is the main factor resulting in debonding failure of composites. This numerical study can be of great significance in designing new composites with high performance.

Abstract: Ferromagnetic shape memory alloy (FSMA) is a new class of intelligent material, and has attracted the attention of researchers. This paper studied uniaxial compressive experiment along three different directions of single crystal Ni2MnGa. The experiment indicates that single crystal FSMA presents obvious anisotropy. Based on the experimental data, the mechanical constitutive model of single crystal FSMA under stress was established by using the theory of micromechanics and the thermodynamic principle. With the model, the mechanical behaviors of the material obtain a good description. The model provides theoretical evidence for the study on the mechanical behaviors of the material.

Abstract: Fracture surface of crept nickel-based single crystal superalloy specimen shows that voids play significant role in creep rupture. In this study, the unit cell model containing two voids was established to study the influence of void orientation on the stress and strain distribution for nickel-based single crystal superalloy under creep loading with the creep constitutive relationship based on the crystal slip theory. Three cases were considered with different angle between the line connecting the centers of two voids and loading axis. The distributions of equivalent Mises stress, maximal resolved shear stress and equivalent creep strain have been given for different creep stages. The results show that the void orientation has remarkable influence on the void growth and the stress and strain distribution during creep.

Abstract: With the development of the power grid, the proportion of large capacity unit is increasing rapidly. It requires a more in-depth study on the reliability of the unit, especially for the unit adjusting the peak. This paper concerned on the research of the surface heat transfer coefficient, which is the key factor affect the precision in thermal stress analysis. The surface heat transfer coefficient is obtained via the numerical calculation for the steam’s flow state and the transient heat transfer between rotor. This paper mainly describes the steam’s flow state and the transient heat transfer with the steam seal, and the results show that the direct numerical calculation is resultful in this subject.

Abstract: The simulation system on the thermal stress of the rotor during startup & shutdown for a domestic 300MW steam turbo unit, by the simulation, the surface of the shaft was suffered a crushing stress, but it was a pulling stress when a unit shutdown. The max thermal stress & the max combined stress produced on the rotor of a medium pressure cylinder was about 16% bigger than those on the rotor of the high pressure cylinder when they had the same increase rate of temperature. When thought from economics & safety, the optimal temperature-increase-rate of the rotor was 1.6°C/min when the unit startup at cold state, but it was 1. 8°C/min when started up and shut down the unit at hot state, it’s optimal for slipping-parameter and the optimal temperature-decease-rate of the rotor was 0.85°C/min.

Abstract: An aeroelastic model and its simulation method of a rotor system are presented. The aeroelastic mode of a rotor is deduced using the multibody system dynamics. The motion equations of the components of rotor system are independent by using Lagrange’s multiplier method, and the differential and algebraic equations are obtained. Equations of the component including joints are deduced to simplify constraint. The angular constraint equations, expressed by Rodriguez parameters, are modified by introducing a nominal motion to avoid singularities caused by large rotations. A large deformation blade component is incorporated. According to the nonlinear implicit expression and high stiffness ratio of the system equations, an implicit integration algorithm combined with the Broyden method is developed, which exhibits excellent numerical stability and good computational efficiency without calculating the Jacobian matrices and their inverse matrices. To verify the validity of the developed method, the transient analysis and aeroelastic analysis of model rotors are imple-mented. The influence of the stability analysis methods, blade structure models on computation is also studied. It demonstrates that the developed method is useful for improving the computation precision of aeroelastic analysis.

Abstract: A theory of general solutions of plane problem is developed for the coupled equations in plane elasticity of one-dimensional (1D) hexagonal quasicrystals (QCs), and three general solutions are presented by an operator method. These solutions are expressed in terms of a displacement function, which satisfies a sixth-order partial differential equation. By utilizing a theorem, a decomposition and superposition procedure is taken to replace the sixth-order function with three second-order displacement functions, and the general solution is simplified in terms of these functions. In consideration of different cases of three characteristic roots, the general solution possesses three cases, but all are in simple forms that are convenient to be used.