Applied Mechanics and Materials Vols. 52-54

Abstract: In this paper,mathematical model of valve movement law was established after simultaneous equations (such as flow equations and differential equations of motion) .Simulation of the intake valve movement law was carried out by using Simulink in the Matlab.The valve displacement diagram ,the velocity curve and pressure ratio curve as well as volume change curves were got,which will help us to have a proper understanding on the working process and properties of valve and make the air compressor valve designs to become more theoretical and more in accord with practical.

Abstract: For improving the quick responses and instances quality in platform based product family design, a scalable platform reconfiguration method using sensitivity analysis and fuzzy clustering is proposed with robust design theory. The possible platform constants and scaling variables sets are divided by design variable sensitivity analysis firstly, during which multiple performances are aggregated by preference aggregation to ease the sensitivity for total product. Then the performance preference, robust deviation and constraint violation changes caused by constant sharing are clustered by fuzzy c-means algorithm (FCM) to reasonably plan the constant multiple platforms sharing strategy. A fuzzy percentage index is introduced in FCM to determine the optimal cluster number in fuzzy clustering. Finally the instances deviated from platform are optimized to set scaling variables. The efficiency and effectiveness of proposed method is illustrated by the optimization of scalable capacitor-run single-phase induction motor families, and the results are compared against previous work.

Abstract: The calculation model for torsion strength of prestressed concrete beams (PCs) under pure torsion is deduced theoretically based on Fixed-Angle Softened Truss Model (FA-STM) and an efficient algorithm for the model is proposed. The calculated values of torsion strength and the Torque-twist curves predicted by the proposed method agree well with these obtained from tests for the two specimens available in literature. These indicate that the proposed method can not only calculate the torsion strength efficiently but can also predict the load—deformation curve of the PCs.

Abstract: In order to increase the efficiency and reliability of dynamic and static force analysis for spatial multibody systems containing the coupling of multi-energy domains, a method based on gyrobondgraph is introduced. The procedure of modeling spacial multibody systems by bond graphs and its dynamic principle are described. The unified formulae of driving moment and constraint forces at joints are derived based on gyrobondgraph, they are easily generated on a computer in a complete form. As a result, the very difficult algebraic problem caused by differential causality and nonlinear junction structure can be overcome, and the automatic dynamic analysis of multibody systems on a computer is realized. By a practical example, the validity of this procedure is illustrated.

Abstract: This paper demonstrated a GIS system about Agricultural Production. Its main function is to show price transmission relations of agricultural production among the main markets. Using Silverlight and ArcGIS technology, the system has a strong user experience and abundant display effect. This paper mainly discussed the main technologies, structural framework and the main functions of the system.

Abstract: Inchworm-type wheeled mobile robot is a non-comprehensive, all-driven system. This paper establishes a kinematical model for such system. Based on the kinematical model, the motion of the system is analytically studied, and the simulation of the motion for this system is conducted with the means of Pro/E. The system in the dynamic motion presented make the collision avoidance and path seeking easier. It also provides a motion mould for the simulation, and proves the theoretical analysis is right.

Abstract: To obtain temperature distribution in regenerative-cooled liquid propellant rocket nozzle quickly and accurately, three-dimensional numerical simulation employed using empirical formulas. A reduced one-dimensional model is employed for the coolant flow and heat transfer, while three dimensional heat transfer model is used to calculate the coupling heat transfer through the wall. The geometrical model is subscale hot-firing chamber. The numerical results agree well with experimental data, while temperature field in nozzle obtained. In terms of computing time and accuracy of results, this method can provide a reference for optimization design and performance estimation.

Abstract: Numerical simulations for the Ahmed model with 25° slant angle are performed under three different turbulent parameters, intensity and length scale, intensity and viscosity ratio, k and epsilon. The external flow field of ahmed model with 25° slant angle is got, and all the velocity vectors, pressure distribution and the drag coefficient of the flow field are obtained as well. The comparison between the numerical simulations and the experimental statistics shows that intensity and viscosity and k and epsilon characterized by higher computation accuracy are more suitable for numerical simulation of automotive external flow field.

Abstract: Non-Linear Resonant Decay Method (NL-RDM) addresses the identification of multi-degree of freedom non-linear systems. This method offers a practical approach to the identification of lumped parameters and continuous systems by producing a non-linear extension of the classical linear modal model. This paper is concerned with the inclusion of residual modes, below any region of interest. Any structure that is not supported to earth will have rigid body modes, being modes that have a natural frequency at zero Hertz; a good example is an aircraft. These modes are sometimes ignored but for a complete mathematical model obtained from NL-RDM the effects of rigid body modes must be analysed. NL-RDM relies on a method of curve fitting to generate modal characteristics, in terms of force, displacement, velocity and acceleration in modal space. The lower residual region was observed to contain rigid body modes. Monitoring this effect was shown to be too difficult currently for the NL-RDM, given technological restrictions. A Mass Substitution method was generated to model the system response more accurately. Its accuracy was demonstrated through case studies.

Abstract: Compare with the Rayleigh wave method, ultrasonic creeping waves critically technique for surface and subsurface defects nondestructive measurement for has the prominent advantage, which not sensitive to surface roughness in coarse-grained materials such as austenitic steel, In this paper, the propagation characteristics and beam profiles of the creeping probe were investigated using finite difference method and measured experimentally. The finite difference numerical model for reflection arc part of the IIW block was established. Through the numerical analysis, wavefront snapshots of the creeping wave propagated in the IIW block are very clear to illustrate the mechanism, and the directivity characteristic of the main beam is obtained. The creeping wave sound characteristics were observed using the dynamical photoelastic experimental method. The beam profiles of the creeping wave probe was measured on the IIW block, the experimental measurement results and the numerical analysis are in good agreement. The results are really significant to design an efficient producer for the surface and sub-surface defects detection based on the ultrasonic creeping wave method.In this paper, a numerical modeling of contact conical transducers is discussed in conjunction with wave propagation analyses by a finite difference method (FDM). Although transducers are the devices to convert electrical energy into mechanical energy and vice versa, attention in this paper is paid mostly to the study of characteristics and parameters of cones and wedges influencing their performance. Cones and wedges inserted between an ultrasonic transducer and the specimen provide the transducer with enhanced capability for point or line contact with the specimen. We study the effect of the dimensions, shape and aperture on the frequency response and the angle of incidence of the wave. Through the testing transducer modeling, some conclusions have been drawn from the analysis, which is useful to as the guideline and criteria for an optimum conical wedge design.