Papers by Author: Dan Huang

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Authors: Dan Huang, Yan Li Wang, Ying Wang, Hong Bao Cui, Xue Feng Guo
Abstract: The thermodynamic analysis in Mg-SiO2 system was conducted for the determination of the priority reaction at experimental temperature. Then, Mg2Si reinforced Mg alloy was synthesized through reaction in Mg-SiO2 system at 730°C, whose Si mass fraction is up to approximately 10%. The thermodynamic analysis and microstructure investigation results show, that generation of reinforcing phase of Mg2Si in Mg alloy from the reaction in Mg-SiO2 system is feasible with lower free energy than that in Mg-Si at the same temperature; and under the experimental temperature and solidification condition, the microstructure of Mg-10Si alloy is composed of coarse primary Mg2Si dendrite crystal, Chinese script type eutectic Mg2Si, and α–Mg phase, the formation of α–Mg holes is resulted from the relatively high cooling rate leading to a deviation from the equilibrium diagram during solidification.
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Authors: Dan Huang, Wu Zhao, Wei Ping Chen
Abstract: A new model for energy-saving in cast irons production introduced technology contribution has been developed. According to the analysis model, in case of keeping same energy efficiency of device, the higher technological level increases, the easier the R increases; even if keep the same melting and heat treatment devices, significant reduction of production energy consumption would be implemented just depending on the production yield increase. A case study results show that technology measurements which has no direct effect on energy consumption play an important role in energy conservation, where the contribution rates of lost-foam casting and computer technology are 20% and 17%. The technological measurements play an important role in cast irons production which cannot be ignored.
2420
Authors: Dan Huang, Ying Wang
Abstract: The porous ceramic holds good potential as acoustic resistance and vibration reduction material during ultra-precision machining. Porous materials absorb acoustic energy by friction with the air that moves inside the pores, and in this paper, the motion is simplified as the incompressible fluid in a single cylindrical pore. The analysis and calculation results show that the acoustic coefficient of porous ceramic is a complicated wave function and the acoustic absorption coefficient calculation model is feasible based on fluid thermal viscous theory. The acoustic absorption coefficient of porous ceramic increases with the increase of thickness, and its period and amplitude decreases with the increase of porosity of ceramic.
140
Authors: Wu Zhao, Dan Huang
Abstract: An analytical method and model were investigated on torsional vibration of complex-branch transmission systems in high precision heavy machinery. In this study, application system dynamic theory, torsional vibration topology network model and its analysis technology were introduced for main driving system, including internal and external damping properties, in particularly considering small perturbation induced by microscale effect on the torsional damping and stiffness. Based on above methods, vibration response of input or output could be effeciently calculated and simulation, which was involved with each the rotation shaft as well as the internal torque response. The modal analysis included amplitude and phase response on reference change or load change, bode diagrams, and time domain simulations. Based on conclusion, the study acquired well consistency between the torsional vibration topology network methods and the other classical methods through the calculation example and simulation. Also the new representation could easy be input for the control system and exploit a new ways on real-time control or fault diagnosis monitor for heavy-duty machinery main transmission system.
59
Authors: Dan Huang, Wu Zhao
Abstract: The tribological behavior of continuous frame ceramic reinforced Al-based alloy against Cr12 steel has been studied with oscillating dry friction and wear tester under the testing conditions of 70°C, 270°C, and 30min, and the load range is from 40N to 100N. The analysis of experimental results show that it is characteristic of abrasive wear and oxidation wear mechanisms for continuous ceramic/Al-7075 composites. The friction resistance of comb ceramic reinforced composite is better than foam ceramic reinforced composite, since the former is with continuous ceramic frame on the worn surface while the latest is with discontinuous hard convex on the plane; and the metal matrix filling in comb ceramic is not continuous in 3-D space, which leads to the deterioration of thermal metal softening at high temperature. Therefore, the composite reinforced by 2-D comb ceramic exhibits better high-temperature friction resistance than the one reinforced by 3-D foam ceramic.
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Authors: Dan Huang, Wu Zhao
Abstract: The tribological behavior of two types of ceramic frames reinforced 7075 Al alloy against Cr12 steel have been studied with oscillating dry friction and wear tester, one is for 3-D continuous foam ceramic and the other is for 2-D continuous comb ceramic. The testing temperatures are 70°C and 270°C, for 30min under the load from 40N to 100N. The experimental results show that it is characteristic of abrasive wear and oxidation wear mechanisms for both continuous ceramic/Al-7075 composites. The friction resistance of comb ceramic reinforced composite is better than foam ceramic reinforced composite, since the former is with continuous ceramic frame on the worn surface while the latter is with discontinuous hard convex on the plane. In addition, the composite reinforced by 2-D comb ceramic exhibits better high-temperature friction resistance than the one reinforced by 3-D foam ceramic, for the metal matrix filling in comb ceramic is not continuous in 3-D space, which leads to the deterioration of thermal metal softening at high temperature.
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Authors: Wu Zhao, Dan Huang
Abstract: For suppressing torsional vibration on main driving system of the rolling mill, the paper studied modal control and control model of torsional vibration. Dynamic disturbance of the rolling mill main driving system were induced by small perturbation from torque fluctuation. Modal control analysis were investigated on include amplitude and phase response on reference change or load change, bode diagrams, and time domain simulations. Torque fluctuation reflects non-steady cyclical or quasi-cyclical characteristics on the torsional vibration system. Control model had been reconstructed from inversion of dynamic topology theory. The result of simulation showed that the established control model for suppressing torsional vibration was effectiveness. Feedback control experiment of nipping and throwing steel on the rolling mill’s main driving system using reaction control tactic was proved it could be easy input and output for controling to suppressing vibration.
509
Authors: Dan Huang, Ying Wang, Wu Zhao
Abstract: The continuously improving of the performance of ultra-precise machine bed is claimed for, including not only the better tolerance stiffness, strength, shock and wear resistance, but also the further shock-damping and acoustic-absorbing performance. In this paper, the acoustic absorption for continuous network SiC ceramic as the laying of ultra-precise machine bed is investigated. By way of the constitutive relation of the network SiC ceramic, the flexibility matrix of such structural body is obtained. In line with the virtual loading application, the balance equation of the unit cell of the network structure is constructed, as well as the effective stress and effective Yang’s modulus. While the elastic flexibility matrix of the structure body can be re-construct with the results above, the bulk strain of the material under the infinitesimal strain would be derived from the modified matrix. The mechanism induced the deformation of network SiC structure is revealed by means of the combination of the dynamic porosity model with the bulk strain. The sensitivities of all kinds of effective factors to the dynamic porosity is analyzed and the order of parameters’ sensitivities to the dynamic porosity of 3D triangle structure is: pressure < temperature < initial porosity < network rod length < network rod radius. The results lay the theoretical foundation of the micro-mesh structure design of the network ceramics as the ultra-precise machine beding.
267
Authors: Wu Zhao, Dan Huang
Abstract: A new mode of fault monitoring and controling methods on rotating speed fluctuation was proposed in this study. Torsional vibration model and identification equation of speed fluctuation of large-scale rotary machinery was established based on a two-mass motor driving model. Tachogenerator was adopted to measure speed fluctuation in torsional vibration experiment of large-scale rotary machinery. According to the short time fourier transforms method, the non-steady cyclical or quasi-cyclical characteristics signal of rotating speed fluctuation on elastic shafts were transformed into steady signal to study in a fixed time window function. The methods of monitoring rotating speed fluctuation developed nonlinear stable state signal processing into linear short time fourier transforms signal. The real rotating speed fluctuation solution could be obtained after the data of signal acquisition post-processing by the methods of frequency spectrum analysis and modal analysis. Based on data of signal acquisition, using the methods of fourier phase frequency spectrum, logarithm amplitude frequency spectrum, and self-power spectrum, the quantitative expression under the quantitative analysis stable state was obtained. Through the introduction of realtime signal on rotating speed fluctuation to feedback control system, it is easy to program to realize the real-time on-line torsional vibration monitor of the complex mechanism transmission system on the large scale rotating machinery.
501
Authors: Wu Zhao, Zhan Qi Hu, Dan Huang
Abstract: Cr, Ni, Mo, V exist in materials of high, medium and low pressure turbine rotor. Its composition contains higher carbon content, so leads to poor hardenability. Shear characteristics of martensite phase transformation is caused by a large number of micro defects inside crystal of microstructure in rotor during the service status. Martensite phase transformation is by strengthening because of plastic deformation in cutting process. Mechanical properties and phase transformation plasticity in cutting process show that rotor is hard machining material. Plastic deformation aggravates tool wear, and leads to an increased cutting force; hard points of uneven material internal organization lead to fluctuation of cutting force, and induced cutting chatter. During the course of machining critical or ultra-supercritical rotor, boring bar becomes a flexible system surrounded by rotating stirred vortex cutting fluid inside and outside it. BTA processing system is in a complicated hydraulic-solid coupling environment. Whether or not BTA deep hole boring processing system is stable, the essence is converted into estimating dynamic stability of BTA boring bar coupled fluid--solid with multi-physics environment. The system will be triggered cutting chatter, fluid flutter and self-excited vibration combination. This paper establishes nonlinear mathematical physics model on BTA deep hole processing system. The perturbation equation and Lyapunov function of BTA system are obtained, through introducing the stable Rumjantsev part variables analysis theory. Based on stability characteristic under the significance of Lyapunov, the constraint condition undisturbed stability is gotten and the global bifurcation analysis is finished. Hyperbolic periodic orbit and heteroclinic connection are found throughout the entire phase space of Hamiltonian system. The bifurcation condition on quadratic heteroclinic is acquired, by analyzing intersection relationship between hyperbolic stable manifold and its unstable manifold of Poincare mapping. The intersection critical conditions are shown on hyperbolic fixed stable manifold and its unstable manifold, by using computer numerical simulation to draw 3-D surface relationship among resonant frequency, cutting fluids flow velocity and the radius of free surface. The result could provide a reference on multi-machining parameters optimization for BTA deep hole boring process practical production.
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