Applied Mechanics and Materials Vols. 55-57

Abstract: The forward displacement analysis of parallel mechanism is attributed to find the solutions of complicated nonlinear equations and it is a very difficult process. Taking chaotic sequences as the initial values of the damp least square method, we can find all the solutions of equations quickly. Making use of existing chaos system and discovering new chaos system to generate chaotic sequences with good properties is the key to the damp least square method based on Chaos sequences. Based on utilizing hyper-chaotic Hénon mapping to obtain initial points, a new method of finding all real number solutions of the nonlinear questions is proposed. Using cosine matrix method, the author established the mathematical model of forward displacement for the generalized 3SPS-3CCS parallel robot mechanism and a numerical example is given. Compared to the quaternion method building mathematical model, the result shows cosine matrix method building mathematical model and hyper-chaotic damp least square method to find solution is brief and high calculation efficiency as the calculation is done in real number range. The proposed method has universality which can be used in forward displacement of other parallel mechanism.

Abstract: The forward displacement analysis of the 6-SPS Stewart mechanism can be transformed into solving complicated nonlinear equations and it is a very difficult process. Taking chaotic sequences as the initial values of damp least square method, all the solutions of equations can be found quickly and making use of existing chaos system and discovering new chaos system to generate chaotic sequences with good properties is the key to the Chaos sequences-based damp least square method. Based on the connection topology of chaotic neural network composed of the four chaotic neurons, hyper-chaos exists in the chaotic neural network system. Combining hyper-chaos with damp least square method, a new method to find all solutions of nonlinear questions was proposed, in which initial points are generated by utilizing hyper-chaotic neural network. Based on direction cosine matrix and Euler parameters, the model of the forward displacements of 6-SPS parallel mechanism with seven variables is built up. The result is verified by a numerical example.

Abstract: This paper is concerned with the quantitative effect of design parameters on the stamping process of automobile crossbeam. The considered parameters in this paper are the friction coefficient, the die fillet radius and the blank holding force, which greatly affect the metal flow during stamping. Based on the finite element numerical simulation, the stamping shaped process of the automobile crossbeam is numerical simulated with the explicit finite element method with various parameters by dint of Dynaform software. According to the simulation results, the forming limit diagram(FLD) and the wall thickness distribution of cloud on the stamping processes are technologically analyzed, the reasons and control methods of wrinkling are also pointed out, and then the optimal parameter combination of the automobile crossbeam is obtained by orthogonal experiments. It is noted that the parametric study of design parameters such as µ , BHF and R_D are very important in the process design of the complicated member.

Abstract: A new type ultrasonic materiel transmission system is proposed in this study. In this new design, bending vibration traveling wave is generated in an elastic pipe by using two uniform sandwich type longitudinal vibration transducers. Thus, elliptical trajectory motions can be formed at particles on the pipe wall, which can drive the materiel by frictional force. The adopting of sandwich transducer in this device can gain large vibration amplitude and improve the electromechanical coupling efficiency. The structure and working principle of the proposed design are introduced. The transducer and the pipe are designed and analyzed by using FEM method. The longitudinal vibration mode of the transducer and the bending vibration mode of the pipe are analyzed, and the resonant frequencies of these two modes are tuned to be close. A prototype system is fabricated and measured.

Abstract: As the improve of voltage class in power system and the aggravation of industrial pollution, flashover of contaminated insulators in HV and UHV system is growing, imperiling the security of power system severely. The linchpin of enhancing the security of system is excavating ways of monitoring status of insulator’s surface by some eigenvalues. In this paper, distinctive spectrum features of leakage current(LC) are computed, including power spectrum and bispectrum. The results show that bispectrum depicts the information of arc discharge in LC more valid than power spectrum, which is a good eigenvalue for flashover identification and risk predictions.

Abstract: There is no a united formula about how to calculate the bearing capacity of a single gravelly pile yet. Recent years, the engineers had developed several theory or experience formulas through many experiments and much studying. But every one has its drawback in calculating. The writer of this paper expresses a new formula bases on Brauns theory to choose by designers.

Abstract: This paper assumes that a row of the frame, shear wall structure as affected by lateral bending and torsion modules coupling effect of thin-walled members, through the floor to work together to establish a collaborative analysis of structural bias of the Hamiltonian on the dual system, with precise integration method for the numerical solution of high-precision systems, analysis of bias is given a set of construction the structure of collaborative work. The results make the structure more in line with the actual deformation.

Abstract: AZ91D magnesium alloy used as the automotive cooling system’s pump impeller material, using the finite element analysis software ProCAST to numerical simulation for the temperature field and the flow field of die-casting process, analyzed the defects causes of magnesium alloy die-casting, and then determined the gating system. Based on the results of numerical simulation analysis, the design of ingate of the gating system set on central department is reasonable. It's benefit for smooth filling of liquid metal and uniforming the temperature field distribution, so as to reduce casting porosity, cold shut and shrinkage defects.

Abstract: At a switching point, the inconsistency can exist between subsystems switched before and after the point, resulting in the solutions of singular switched system with time delay there may be discontinuity. We consider the discontinuity of the solutions for a class of switched linear singular systems with time delay and the convergence of discontinuous solutions. Using Lyapunov-Krasovskii function and the LMI method, we establish some criteria to guarantee all solutions of the systems converge to zero. The criteria are expressed as LMI form and depended time delay. An example is given to illustrate the application of the presented results.

Abstract: In order to keep the temperature of Light emitting diode (LED) lamp below some limitation, a finned plain-plate heat-pipe was presented and numerically investigated to predict heat transfer performance under natural convection. Two kinds of fin configurations were studied. It is found that 30° is the worst orientation for the fin configuration with the tops of every other two channels covered, while the worst orientation is around 60° for the fin configuration with channel tops opened. The thermal conductivity of fin material only has mild effect on the cooling capacity with 7 % difference when its thermal conductivity varies from 50 to 200 W/(m·k). The latter configuration has better thermal performance than the former at the same orientation, especially at relatively low inclined angle.