Advanced Materials Research Vols. 335-336

Abstract: Abstract: On the basis of Reddy’s higher order shear deformation plate theory and the von Kármán’s geometry nonlinear theory, governing equations for nonlinear thermal buckling and post-buckling of cross-ply laminated composite beam subjected to a temperature rise are derived, in which the stretching-bending coupling terms produced by the non-homogenous distribution of the material properties are included. By using the shooting method to solve the corresponding nonlinear boundary value problem, numerical solutions for thermal post-buckling of cross-ply shear deformation laminated composite beam with its both ends immovably simply supported under uniform temperature rise are obtained. As an example, equilibrium paths and configurations for laminated composite beam paved in term of 0/90/0 are presented and characteristic curves of the nonlinear deformation changing with the thermal load were plotted. The effects of the geometric and physical parameters on the deformation of the beam are also examined. The theoretical analysis and numerical results show that different thermal expansion coefficient ratio, elastic moduli ratio, shear stiffness ratio will influence of the non-dimension critical buckling temperature.

Abstract: The dislocations in electron-irradiated c-plane n-GaN epitaxial layers grown on c-plane sapphire substrates by MOCVD were revealed by several different wet chemical etching methods. And the defect-selective etching method combined with SEM was carried out to study the mechanism of dislocations generation of GaN. SEM images of GaN epilayers with several individual methods are in good agreement with each other. Among all the defects, threading dislocations (TDs) dominated in the GaN epilayers and these defects could be divided into three types. In addition, the EPDs after annealing at various temperatures were studied. The experimental results showed that suitable thermal annealing can eliminate some dislocations.

Abstract: The prediction of optimal machining conditions for required surface roughness and material removal rate (MRR) plays a very significant role in process planning of wire electrical discharge machining (WEDM). Artificial neural networks (ANN) are widely applied to predict the performance characteristics of complex machining process like WEDM very accurately. This present work deals with the features of cutting operation by WEDM of tungsten carbide- cobalt composite(WC – Co) and an artificial neural networks(ANN) model in terms of machining parameters, developed to predict surface roughness(Ra) and material removal rate (MRR).The experiment was planned as per Taguchi’s L 27 orthogonal array. The predictive capacity of the models was validated. The test results indicate that the proposed models could adequately describe the performance indicators with the limits of the factors that are being investigated. Finally the accuracy of the developed ANN model was compared to the experimental values. It was observed that the proposed ANN model is good.

Abstract: The relationships between dynamics response and preload of bolted joint were studied. By using finite element analysis method, nonlinear model of flange structure with bolted joint was established. The transient analysis for different preload condition of bolted joint was employed to obtain steady state response. The energy of the difference signals between up and down mating surfaces was computed. The energy of the difference signals increased as preload of bolted joint decreased, and nonlinearity of bolted joint increased. The numerical results were compared with experimental measurements. The similarity was found to be satisfactory.

Abstract: Engineering ceramic is the ideal material for high-speed and high precision motorized spindle due to perfect characteristics of light weight, wear resistance, high temperature, high strength, and so on. The air-gap is changed due to the influence from various factors not only the tolerance of the manufacture and assembly of motorized spindle but also different working condition. The change of air-gap impacts on vibration performance of motorized spindle. The effects of rotating speed and air-gap between the rotator and stator on these characteristic parameters of the motorized spindle are analyzed. This paper analyses the effect change of air-gap on vibration performance of motorized spindle by the simulation analysis and experimental. The results show that vibration increase with the decrease of air-gap. Meanwhile, electromagnetic vibration increase with the increase of eccentricity of motorized spindle. These results are very helpful to the structure optimization and application of the ceramic motorized spindle.

Abstract: Microstructure and properties of Forging high Cr cast iron were investigated according to the requirements for production and application of engine valve seat. It is found that the microstructure of Forging high Cr cast iron consists of tempering martensite, M7C3 carbide and austenite. The strength ,and plasticity and hardness of Forging high Cr cast iron after heat treating is higher than that of centrifugal casting high Cr cast iron. So the Forging high Cr cast iron can meet the application demand of the engine valve seat.

Abstract: In order to solve the problem of long melting time and low yield rate of carbon while blind coal is used to recarburize, a new carburant is developed to replace blind coal. Experiment results show that compared with the blind coal, the new carbon-manganese alloy carburant obtains a high smelting velocity, and the average carbon yield rate is 92.95%, which increase by 7.67%, the yield rate of manganese is 93.31%, which a little higher than other normal manganese alloys. After carbon-manganese alloy is used to recarburize, logistics time and power consumption are saved and the cost of steel-making is reduced by 1.05 ¥/t. In addition, there is little effect on the quality of steel.

Abstract: The general rule that the modal parameters of linear system change with the structural parameters was discussed. The calculational method of the change of modal parameters was given on the basis of the current modal parameters and the change pattern variation of structural parameters. An example indicated that this method can greatly save computational time than repeated modal analysis. Withal, the qualitative conclusions of the change of modal parameters can be expediently gained. These results are important to amelioration and optimization design of systems.

Abstract: Effect of solid solution treatment on corrosive behavior of 00Cr26Ni5Mo2Cu3Re Duplex Stainless Steel in static stage of HNO₃+HF acid solution is studied in the paper.The results show that the corrosion between phases and pitting corrosion on ferrite are serious at low temperature ,the phenomenon gradually disappear with the solid solution temperature rising ; the corrosive resistance of 00Cr26Ni5Mo2Cu3Re is getting better first and then decrease with solution temperature at high temperature, the best corrosive resistance temperature is at 1050°C.

Abstract: A novel ADRC scheme is proposed for permanent magnet linear synchronous motor without sensor, which has nonlinear, multi-load disturbance and parameter time-varying characteristics. Extended states observer (ESO) in ADRC can real-time estimate speed, location and uncertain disturbance, and the parameters artificial is used to optimize by fish swarm algorithm. Finally, simulation results confirm the proposed strategy has better tracking performance and robustness than the traditional one.