Applied Mechanics and Materials Vols. 66-68

Abstract: To control the inertial forces and moments, the new type of the reciprocating cam engine with counter-position placement has been invented. Such a thermodynamic model based on the kinematic and dynamic analysis is developed and the engine performance is simulated. Under the same structural design parameters, the counter-position placement cam engine would have the inadequate work due to the increase of throttle loss. Then effects of the gas distributions to the dynamic performance of the engine are researched. Six variables are selected to optimize maximum average indicated power and the minimum indicated specific consumption with the method of discrete variable gridding. The results indicate that: (a) The new engine structure design can present advantage of excitation forces balance. (b) The structural design parameters and the thermal efficiency of the engine should be optimized especially those of the valve actuating mechanism to achieved desired power. (c) The parameters optimized of valve train can conform to the requirements of speed and economy, and it is feasible and reasonable to put forward the scheme of cam engine with the counter-position placement.

Abstract: As the most dominative component under stress in an external combustion cam engine, the working condition of piston is very rigor. Once new design type and technical improvement is applied, it is necessary to analysis its thermal load and take secure steps. And the finite element model on each conditions of thermal is calculated, which is used to estimate the temperature field and provide a theoretical basis for further structural strength analysis and optimization design. Choosing analysis results of the piston as reference and taking five structural parameters of the piston as design variables, two objective functions including piston mass and maximal Von Mises stress are respectively considered. The optimum design of the piston is executed and the results indicate that it is feasible to improve temperature field and strength of the piston. These results enrich and develop the research on structural analysis and optimization of spatial engine, which are of guiding significance for analyzing engine strength and related problem in theoretically.

Abstract: This work studies the size effect on voltage-dependent resonant frequency of fixed-fixed carbon nanotubes (CNTs) resonator. Specifically, the effect of resonator length, diameter, and gap distance on the variation of the natural frequency under the DC bias voltage is investigated. The resonator is modeled as a cylindrical beam whose ends are ideally fixed on the substrate. Under the condition of neglecting the impact of van der force (gap larger than 100nm), both elastic forces and the electrostatic forces are considered in this study. The variation of frequency with the DC bias voltage is usually decreasing, because the mechanical stiffness is larger than the electrostatic stiffness. But in some case, the effect of the mid-plane stretching dominates that of the electrostatic forcing, and the variation is increasing. Our results shows that the trend of variation is much depend on the size effect of device, especially the size of CNTs diameter. This fact is useful for designers to optimal design of CNTs resonators, either for tunable or stable resonators within a certain range of DC bias voltage.

Abstract: A hydrodynamic model of towed system is studied. The model of towed cable in this paper is based on the Ablow and Schechter method. A basic problem in the design of towed system is presented by the choice of Euler angles and tension at ending point of cable. This paper proposes a new way to design an ideal towed system. And a code is written to assist in designing the towed system. The governing equation is solved using a 4th-order Runger-Kutta numerical method for stable cable. The computed results with the code are close to the measured ones.

Abstract: Software has been used more and more widely in CNC systems, the defects caused by soft­ware among all defects of a CNC device have been higher and higher as well. How to diagnose the defects caused by software in CNC device fast and effectively is the topic of this paper. This paper talks about the features of embedded soft­ware first, and then introduces a proved method used in software test and defect diagnosis by using software system test platform. We’ll use an instance to elaborate on it. We’ll make a general summary of this method at the end of the paper.

Abstract: Zeolite as a cheap mineral material in industry used in catalytic and environment protection, long time has passed for research on zeolite modification, synthesis and application. In the paper, several modifications for zeolite have been reviewed in detail such as the skeleton element modification, skeleton element modification and zeolite crystals surface modification, modified zeolite properties and application. The shortcomings of the modification methods were pointed out, development and zeolite modification suggestions in the future were put forward.

Abstract: High purity Al₂O₃ powder was used as raw material and MgO was used as additive to sinter alumina transparent ceramics in hydrogen atmosphere. EBSD image showed that, with the increase of the MgO content, the grain size decreased from 200μm (when no Mg was doped) to about 20μm (when the Mg doping amount was 1.0wt%), indicating that MgO had an inhibition effect on the grain growth. XRD analysis showed that the doping of MgO did not lead to the formation of new phases. A further refinement of cell parameters revealed that, when the doping amount reached 1.0wt%, lattice distortion occurred and the cell volume increased by about 80%, which was attributed to the formation and diffusion of oxygen vacancies. The E_g mode at ν=575cm-1 revealed by Laser Raman Spectroscopy suggested that AlO₆ octahedra were distorted with the increase of the MgO content. And the frequency change of the A_1g mode at ν=642cm^-1 reflected the combined effect of ion mass and mechanical constant. Measurement of the optical transmittance indicated that, after the doping of MgO, a small amount of MgAl₂O₄ phase formed at the grain boundary, causing the transmittance to increase first and then decrease with the increase of the MgO content. And analysis of the dielectric properties showed that the change of the dielectric constant and loss with the frequency at room temperature resulted from ion relaxation polarization induced by the weakly bound ions in the AlO₆ octahedron.

Abstract: Vibration and acoustic radiation of circular cylindrical shells are hot topics in the structural engineering field. However for a long period, this sort of problems is only limit to classical homogeneous boundary conditions. In this paper, the vibration of a circular cylindrical shell with elastic boundary supports is studied using modified Fourier series method, and the far-field pressure for a baffled shell is calculated by Helmholtz integral equation. Active control of vibration and acoustic radiation are carried out by minimizing structural kinetic energy and radiated acoustic power respectively. The influence of boundary conditions on the active control is investigated throughout several numerical examples. It is shown that the active control of vibration and acoustic for an elastically restrained shell can exhibit unexpected and complicated behaviors.

Abstract: The uncertainty of ship models and interferences can lead to reduce the effectiveness of conventional roll stabilization controller depending upon accurate mathematical model.This paper proposes the design of neuro-fuzzy controller for rudder roll stabilization. Learning ability of neural network is utilized to optimize the fuzzy controller. Hybrid learning rule which is a combination of backpropagation algorithm and least square estimator is utilized to realized parameter adjustment of fuzzy control rule and membership function in order to improve the adaptive capacity of controller. The simulation tests under various situations such as different navigational speed, sea conditions, wave-to-course angle and ship parameter perturbation are to check the performance of roll stabilizatin controller. Simulation results show that the neuro-fuzzy controller has better robustness and effectiveness for rudder roll stabilization in beam seas.

Abstract: With Third Wave AdvantEdge FEM software, an equivalent finite element model in tapping has been built, making a simulation study of the chip curling of titanium alloy TC4 and analyzing the influnce of a tap hook angle and chip flute shape on chip curling. Based on the simulation study above, the modified-tooth taps made of high-speed steel W9, which have two types of chip flute shape with a chamfer angle of 7°30´and respectively, were developed and the comparative tests of tapping TC4 have been done. The results indicates that the chip removal effects in hand tapping with the standard flute shape and respectively are on the same level, but the tapping torque has become smaller and more effective to a chamfer angle of .