Applied Mechanics and Materials Vol. 344

Abstract: The vector form intrinsic finite element (V-5) method and the gap element method are combined to solve the static wheel/rail contact in two-dimensions in this paper to obtain the wheel/rail normal contact pressure, which would be compared with the normal contact pressure of ABAQUS and Hertz theory. The results showed that the contact pressure distribution of V-5 was consistent with ABAQUS and Hertzs, and the mechanical behavior of contact area was reasonable under the circumstance of different axle loads. Besides, it also verified the feasibility of adopting gap elements method to solve the static wheel/rail contact on the basis of vector form finite element method, which with the superiority of large rotation and large deformation, and laid the foundation of rolling wheel-rail contact behavior analysis.

Abstract: Taking the two-dimensional airfoil section model with two degrees of freedom as the object, this paper develops a multi-parameter optimization method, which regards the minimum system response under the given gust disturbances as the objective function and gives the expression describing the state space form of response sensitivity in which the matrix parameter sensitivity solution obtained by CVD method, further more, the Newton iteration method based on the sensitivity is adopted to realize the parameter optimization. By the simulated calculation of numerical examples and comparing with the conventional method, the optimization method has the advantage of better calculation efficiency and robustness and being used for aircraft design.

Abstract: It proves that steering wheel shimmy is a vibration of stable limit cycle occurring after Hopf bifurcation, which is elaborated by nonlinear dynamics theory, and the control objectives of shimmy are proposed according to its bifurcation properties. Numerical analysis of bifurcation characteristics has been conducted with a nonlinear shimmy model whose parameters come from a domestic automobile with independent suspension. The results indicate that when the speed reaches 49.98Km/h, supercritical Hopf bifurcation occurs to the system and stable limit cycle appears, i.e. wheels oscillate around the kingpin at the same amplitude; when the speed comes to 76.30 Km/h, Hopf bifurcation occurs again and limit cycle disappears. The bifurcation speed and amplitude of limit cycle match the shimmy speed and amplitude measured from road experiments very well, which confirms the conclusions that shimmy is a vibration of stable limit cycle occurring after Hopf bifurcation at critical speed.

Abstract: The global structural response of a four-leg jack-up wind turbine installation ship in the transit condition was analyzed in this paper. The finite element model of the hull and legs were established with the Software MSC. PATRAN. On the basis of long-term forecast of the wave loads, the corresponding designed wave parameters are determined with the vertical wave bending moment of the midship cross section served as the main load control parameter. Considering the gravity, hydrostatic pressure, the hydrodynamic loads induced by the wave, inertia force induced by the motion and acceleration of the ship and the wind force on the legs and hull, the direct calculated method was used to evaluate the global structural response of the vessel. The deformation and stress of the hull and legs were calculated and checked. The results showed that the strength of the hull and leg could meet the rules requirements. For the jack-up ship in the transit condition, the critical areas are mainly lower part of legs and the corresponding hull structure.

Abstract: Dynamics of the horizontal axis wind turbine is investigated in this paper. The wind turbine rotor modelling is based on the nonlinear Eular beam model, the generalized dynamic wake model and the Beddoes-Leishman dynamic stall model are used to predict the aerodynamic loads. The Newton-Rafson iteration is adopted to get the solution in each time step and the second-order backward difference is used in time marching. A horizontal axis wind turbine is analysed in fixed rotor speed and the structural responses in rated conditions and critical wind conditions are obtained. The critical wind velocity is acquired from simulation. The influences of the rotor speed and yaw angle on the critical wind velocity of the rotor are reserched.

Abstract: A plain-strain finite element (FE) model of the rail is developed by ABAQUS. The 1070 rail steel is considered in the model by Jiang and Sehitoglu's cyclic plastic constitutive equation. The wheel-rail rolling contact is represented by a moving load applied on the contact surface. Based on the FE results the initiation of rolling contact fatigue (RCF) crack is further evaluated by Jiang's fatigue model. Effects of the rail material inner defect and the friction coefficient are also investigated. The results show that the stress-strain state of the rail surface material becomes stable after about thirty passages. The maximum residual stress and strain are located in the subsurface. The life of a defected rail can be as low as 1/27~1/17 of a qualified rail, and the most probable location for crack initiation is highly dependent on the inner defect. The fatigue life is found to considerably decrease with the friction coefficient, while the location of crack initiation and its direction of propagation are less affected.

Abstract: Based on the 3D unsteady incompressible Navier-Stokes equation and the turbulent model of k-ε two equations, the processes of electric multiple units CRH380B passing by sound barriers installed on viaducts at the speed of 350 km/h were numerically simulated by finite volume method. The aerodynamic impulse pressure on sound barriers was analyzed. The distribution of impulse pressure on perforated sound barriers was compared with that on those with no holes. Effects of the shape, the size, the density, and tilt angle of the holes on deloading properties of perforated sound barriers were investigated. The numerical results show that the deloading properties of perforated sound barriers with circular holes are similar to those with square holes. The holistic distribution of impulse pressure on perforated sound barriers is similar to those with no holes. The density increases in two different directions has almost the same influence on the deloading properties. Deloading properties of perforated sound barriers become worse when tilt angle of holes increases.

Abstract: In this paper, a novel method for hulls three-dimensional angle measurement is presented. For the measurement of the transverse twist angle, a method based on moiré fringe is proposed, for the lengthways flexibility and course flexibility angle the conventional optical sensor method is applied. The principle of the measurement is discussed in detail. To verify the accuracy of the proposed method, both static and dynamic experiments are carried out. Results show that in the static states, the accuracy for them are smaller than 5'', in the dynamic states, the accuracy for them are smaller than 10''.

Abstract: The initial state of deflection sensor after replacement is not easy to be found. In order to overcome this disadvantage of the existing method,an improved deflection correction method is presented in this paper. The new method converts the problem into anglicizing the deviation of monitoring point. By using correlation analysis and SVM,the theoretical value can be obtained. The deflection deviation could be calculated by analyzing the theoretical value and the measured value. And then the deflection after correction is easy to be obtained. Numbers of experiments are done by using the real data of Caiyuanba Yangtze River Bridge. Results show that the mean square error of the new method is less than the existing method. The new method solves the problem of finding the initial state, and the precision is improved at the same time.

Abstract: Fault diagnosis accuracy is not high for traditional multivariate statistical methods ,in this paper , the deflection sensor fault diagnosis method based on independent component analysis was proposed .This method not only removed the relationship between process variables , but also make full use of higher order statistical properties of process variables ,establish the independent element model of the process information, finally ,simulation the multivariate process model in the system ，the simulation result shows that this method can quickly and accurately detect the abnomal occurred in the system ,verify the validity of this method and advantage compared with taditional PCA method.