Applied Mechanics and Materials Vols. 249-250

Abstract: In the light of the structural features of the wind turbine tower and force characteristics, the mechanical model of the variable cross-section tube tower is established. Based on the elastic stability theory, the buckling of tower is studied, and the critical force formula of the tower under the concerted action of concentrated force and gravity is deduced. Calculation models are numerically simulated for the stability of the tower by using the finite element software ANSYS, and corresponding critical load is obtained. The results show that the finite element models are feasible in engineering application, and the analysis provides a theoretical basis for structural design of wind turbine.

Abstract: On the basis of the principles for diagnosing roller axles and personal practice with the theory on site for years, the writer has summarized the method for diagnosing roller axles to “Three Frequency Bands”and “Eight Confirmations”. This diagnosis method is suitable particularly for urgent conditions without complete data of the equipment .It’s practical use has proven that the method is not only feasible, but simple , convenient and ease to grasp as well.

Abstract: In the harmonic electromagnetic drive motor, the rotating magnetic field may deform gear as well as the shape of interaction electromagnetic fields, thereby resulting in the interaction between electromagnetic field and the structure field. By analyzing the electromagnetic-structural coupling relationship of the system and conducting discretization, this paper established the finite element coupling equilibrium equations of electromagnetic field and structure field and discussed the coupling conditions between two fields as well as the boundary conditions of various fields, thus deducing the expression of the force and displacement transmission on the interface of two physical fields. By finite element simulation of the system, the law of the radial displacement distribution of flexible gear changing with the system parameters, which has provided a basis for further study of electromagnetic harmonic drive motor.

Abstract: The turning load resistance torque of large wheeled vehicles is very big and these vehicles are all the multi-axle vehicles. It is important to select the suitable steering system. In the multi-axle vehicle steering system, EHPS is the most appreciate driving mode in all of them including MS, HPS, EHPS, EPS, etc. In order to improve the performance of the present EHPS with proportional valve, the new EHPS with servo solenoid valve was designed. The static and dynamic characteristics of servo solenoid valve are much better than proportional valve, such as dead band, hysteresis and frequency response. Firstly, the single-axle electro-hydraulic servo steering system was introduced including hydraulic system and electronic control system. Then multi-axle electro-hydraulic servo steering system with coordination control strategy was introduced. The designed multi-axle steering system with servo solenoid valve makes it possible to improve the steering performance significantly.

Abstract: Thermo-mechanical vibrations of functionally graded (FG) beams are developed. Governing equations of functionally graded beams are obtained based on higher-order variation of transverse shear strain through the depth of the beam. The material properties of the functionally graded beam are assumed to vary according to power law distribution of the volume fraction of the constituents. Equations of motion and boundary condition are derived from Hamilton’s principle. Beam is assumed under uniform thermal loading and simply supported boundary condition. Analytical solution is presented, and the obtained results are compared with the existing solutions to verify the validity of the developed theories. Numerical computations are performed for a functionally graded simply supported beam with a gradient index obeying power law and the results are displayed graphically and tabular to show the effects of the gradient index, temperature rise, and geometrical parameters on the fundamental natural frequency of FG beams, indicating that natural frequency is sensitive to the gradient variation of material properties, geometrical parameters, shear deformations and temperature rise.

Abstract: An algebraic multigrid by smoothed aggregation preconditioned conjugate gradient method is developed to solve the liner system arising from 3-D direct current finite element resistivity forward modeling. The algorithm combines the efficiency of algebraic multigrid method and the stability of conjugate gradient method. Algebraic multigrid by smoothed aggregation keep in high-efficiency while simulation using local quasi-uniform mesh and its convergence effect will reduce while numerical modeling using anisotropic stretched grids. However tensor product non-equidistant mesh, a kind of anisotropic stretched grids, is often used in 3-D direct current resistivity forward modeling. In order to improve this situation, a factor is added to guide correct aggregation. Consequently, a typical example is used to prove that the improvement is the right. Finally, it is natural to conclude that the algorithm suggested in this paper is efficient and robust whether simulation using local quasi-uniform mesh or tensor product non-equidistant mesh

Abstract: The breakage of conductor/ground wire seriously affects the secure operation of transmission line. According to the features of UHVDC power transmission lines, the broken conductor model for bundled conductors of continuous span is built and the broken conductor load is calculated; A simulating test was carried out the first time in China for a series of "broken conductor" events on one continuous span on the field to study the dynamic response of the transmission tower because of impact, then the dynamic strain and displacement were obtained. On the basis of the simulation and experiential research results, the paper discussed about the rational values of broken wire loads for the suspension towers of UHVDC.

Abstract: In this paper, early stage of granular materials flowing through the orifice of a cuboid hopper with flat bottom is investigated based on the results generated by using the discrete element method. The results show that in the start up stage of the flow, a switch curve is formed between static and flowing particles, and a force arch on which the forces are very small is generated below the switch curve. Both curves propagate into the granular bed with the discharge of particles, and reach the top of the bed when a steady state is achieved.

Abstract: Control problems for the stationary magnetohydrodynamics equations of viscous thermally conductive fluid are considered. Solvability of these problems with electromagnetic and thermal boundary controls and stability of solutions for some cost functionals are studied. We develop a numerical algorithm and discuss some computational results.

Abstract: As one new kind of 3D textile structural composite which has a strong potential in the application field of structural engineering, the mechanical behavior of 3D angle-interlock woven composite (3DAWC) needs to be extensively investigated. In this paper, a comparative experimental analysis of 3DAWC between quasi-static tension and three-point bending loading conditions were described, which has not been well studied so far. To evaluate the mechanical properties of the 3DAWC, the stress-strain/deflection curves were obtained under quasi-static tension and three-point bending loading, respectively. Furthermore, the Young’s modulus and peak values in stress were also compared. All of these results show that the 3DAWC has good integral performance.