Applied Mechanics and Materials Vols. 52-54

Abstract: Effects of deformation temperature and strain rate on deformation behavior of semi-solid 6061 alloy were investigated on Gleeble3800 thermal-mechanical simulator. On basis of the experimental data of semi-solid 6061, a model was established to describe the relationship between the processing parameters and flow stress, which showed that the experimental results and calculation ones fitted well. It would be beneficial to realize the distribution of stress and strain during the semi-solid forming on the basis of numerical simulation technology. This research paper presented the numerical simulation results of the 6061 alloy during the backward extrusion thixoforming process.

Abstract: The corrosion behaviors and mechanisms of 310S and AL-6XN stainless steels in MgCl2 molten salts were investigated at 800°C for 8-72h. The weight change kinetics, surface and cross-sectional morphologies as well as corrosion products and compositions were analyzed. The results showed that corrosion velocities of both steels were very high in the preliminary period, then diminished quickly and trended to zero afterward. The AL-6XN steels exhibited better corrosion resistance in MgCl2 molten salts than 310S. The predominant peaks of MgO were detected from both steels after corrosion in molten MgCl2 at 800°C, which could serve as the protective barriers between the alloy and the MgCl2 molten salts. The depletion of Cr was very serious throughout the corrosion layer for both steels due to their preferential oxidation for the formation of an outer corrosion layer. The other elements in alloy were corroded in succession through the outward diffusion with the progress of the corrosion. The outward migrations of the metal ions led to the coalescence of vacancies to form the voids. The two steels possessed the uniform corrosion behavior.

Abstract: In recent years, one dimensional nanostructure, nanofibers with unique properties have been subjected of intense research due to potential properties in many applications. This study presents synthesize of Perovskite-type Ba0.5Sr0.5Co0.2Fe0.8O3−δ (BSCF) nanofibers using sol-gel via electrospinning as a cathode for intermediate temperature solid oxide fuel cell. BSCF nanofibers are prepared by treating electrospun polyvinyl Pyrrolidon/ Ba0.5Sr0.5Co0.8Fe0.2O3−δ composite fibers at high temperature in an air atmosphere. BSCF nanofibers were characterized by x-ray diffraction (XRD) to observe desired structure, scanning electron microscopy (SEM) to investigated the morphology of fibers, and Brunauer, Emmett and Teller (BET) for measuring the surface area. To the best of our knowledge, investigation on Ba0.5Sr0.5 Co0.2 Fe 0.8O3−δ nanofibers has not been reported up to now.

Abstract: In consistent with sustaining development, recycled aggregate concrete (RAC)that is made from recycled concrete aggregates could be a perfect solution to resource and environment preservation. It is a kind of practical and economic material to reuse the great amount of construction and demolition wastes, which has received many discussions nowadays. But, its fatigue behavior is different from other concretes as a result of different property of the aggregate of recycled concrete and other concrete. In order to apply RAC more effectively, it is necessary to study its properties especially for those aggregates from earthquake-stricken area for post-earthquake reconstruction. Therefore, on the basis of experimental research, the fatigue behaviors and microstructure of recycled concrete are studied in this paper. The present paper deals with investigations on fatigue behavior of the axial and eccentric compression performance of recycled aggregate reinforcement concrete specimens with contain recycled aggregate proportion of 0%、50%、100%. Then micro-structural observations of the specimens by means of scanning electron microscopy (SEM) were obtained. Based on the analysis of experiment results, it can be proved that it is feasible to apply recycled concrete to practical engineering.

Abstract: The liquid-gas flow is proposed to accurately simulate the offshore environmental state. The aerodynamic feature is estimated using the three-dimensional model of horizontal-axis wind turbine with NRELS809 series aerofoil by means of the simulating software tool of FLUENT. The variable speed is implemented via the six different wind speeds. The calculated results show that the similarly evolutional tendency of velocity occurs in the wake region when operating at the six variable speeds. The stall speed is related to blade height and wind speed. The small blade height or large wind speed also leads to the serious stall phenomenon. The total force is conducted to estimate the potential capability for leeward and windward surface to capture wind power. The calculated results reveal that the larger wind speed facilitates generating the more magnitude of total force. However, the velocity and force feature for the wind turbine has the especially rapid change at the wind speed of 6 m/s, which perhaps results from the intrinsic geometry and configuration.

Abstract: Contact heat transfer are widely used in mechanical system and research on thermal contact resistance is a significant link in engineering application. In this article, main influencing factors of thermal contact resistance such as material characteristics, contact pressure, surface roughness, intermediate medium had been further researched by experimental methods, and the relations between pressure and thermal contact resistance had been taken under different materials, different suface processing quality and different medium. Several other problems related to thermal contact resistance had also been discussed. The research contents provide reference for the application of thermal contact resistance and reasonable design of mechanical structure.

Abstract: Based on the generalized thermoelastic theory postulated by Green and Lindsay(G-L), the dynamic response of an infinite rotating piezoelectric plate subject to thermal shocks on both up and bottom surfaces was investigated. To avoid the calculation precision loss caused by the integral transform technique, the so-called direct finite element method was used to solve the governing equations in time domain directly. The distributions of the dimensionless temperature, stress, displacement and electric potential were presented graphically. The results show that the direct finite element method provides an effective way for achieving high calculation precision in solving the generalized piezoelectric-thermoelastic problem. The results also show that the rotation effect tends to decrease the dimensionless displacement and electric potential and barely affects the dimensionless temperature and stress.

Abstract: A recurrent neuro-fuzzy based inferential sensor is applied to design an inferential control algorithm that can improve the operation of residential heating systems in which both energy efficiency and indoor environment quality are below expectation due to insufficient control. In current practice, the control of these heating systems is based on the measurement of air temperature at one point within the building. The inferential control strategy presented in this paper allows the control to be based on an estimate of the overall thermal performance, minimizing the chance of overheating (saving energy) and underheating (improving comfort) in the building. The performance of this control technology has been investigated through simulation study. The results show that the proposed control scheme can effectively maintain the temperature at set-point, and results in energy savings and improved thermal comfort.

Abstract: The purpose of this study is to provide a correct and timely diagnosis mechanism of shearer failures by knowledge acquisition through a fuzzy inference system which could approximate expert experience. Concerning a question of uncertain knowledge expression and reasoning in shearer malfunction, the fuzzy inference theory is used in shearer malfunction fault diagnosis. The fuzzy relation matrix of faults and signs is deduced based on deep research of failure mechanism and expert experience, which agrees with fault and fault symptoms non one-to-one relationship and human thinking. Fault characteristic parameter is calculated to corresponding subordinate degree, then is operated with fuzzy relation matrix and get fault fuzzy vector. Finally, the shearer malfunction fault is diagnosed according to certain diagnosis principle. The example proves that the method has less calculation, explicit conclusion and other merits.

Abstract: Expert system of full-mechanized face equipment fitting based on artificial neural network is researched and processing method is presented in this paper. On the basis of this, BP neural network models for the forecast of production capability of mining face and the parameters of equipment fitting of full-mechanized mining face are built up. Employing these models forecasts the output, work efficiency and main technical parameters of full-mechanized equipment of the test mining face in Ji'er Colliery.