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The vibroisolation properties of the lattices containing the lumped inclusions
Get PDFThe vibroisolation and wave properties of the lattice consisting from the beam elements and lumped masses located in the lattice nodes are studied. The finite element method is used to obtain the lattice dynamic model and its dispersion equation in analytical form. It is shown that such a lattice is a bandpass mechanical filter, and the opacity bands of the harmonic signal depending on the direction of the wave propagation is found. The limiting minimum and maximum frequencies for the harmonic signal transmission are also obtained. It is shown that the addition of discrete inclusions to the lattice increases its vibroisolation properties in low-frequency range
Computational fluid dynamics (CFD) modelling of hybrid photovoltaic thermal system
Get PDFIn this paper an attempt has been made to simulate and evaluate the distribution of temperature and heat flux for the hybrid photovoltaic thermal system with CFD (computational fluid dynamics) module in ANSYS 19.1 software. The simulation was carried to determine the temperature and heat flux across the different layers of HPVT (hybrid photovoltaic thermal) system. The temperature and heat flux were found to gradually decrease from the top glass layer to the bottom tedlar layer. The temperature varied from 36.4 °C (ambient) to 26.8 °C across the layers from top glass layer to bottom tedlar layer. The heat flux of (561.2 W/m2) at the glass layer due to solar insolation was also found to gradually decrease with the increasing thickness. The reduction in temperature and heat flux with increasing thickness is attributed to fluid flowing beneath the system. The water flowing beneath the tedlar layer takes the excess heat out of the photovoltaic layer, thereby increasing the efficiency of the hybrid photovoltaic thermal system
Numerical analysis of single grit grinding on aluminum workpiece
Get PDFGrinding is a finishing process used in almost every industry. The purpose of this research is to study the effects of grinding on aluminum. Finite Element Method (FEM) is used to numerically simulate grinding by using microscale modeling. It is found that though under grinding, stress mises developed do not exceed yield stress. The force variation and displacement parameters have been correspondingly discussed. The effects of grinding on the workpiece with and without lubrication
Design of vibration standard device based on random comparison method
Get PDFIn order to meet the needs for aircraft vibration transducer and measurement equipment to be calibrated at the job site, it is necessary to design a compact, dynamic and functional vibration standard device. This paper introduces a vibration standard device based on random comparison method. The structure and working principle of software and hardware are described in detail. Unlike the calibration requirements under laboratory conditions, on-site calibration requires that the calibration process be more consistent with the actual operating conditions. A random vibration comparison calibration method using random signals as excitation sources is designed. The vibration standard device can be maneuvered from the laboratory environment to the aircraft maintenance site. It has been proved measurement uncertainty of the system is 1.0 % (k= 2) by the method of control accuracy
Analysis of gearshift processes in an automatic transmission at low vehicle speeds
Get PDFThe increase in the number of speeds in automatic transmissions of vehicles leads to a convergence of gear speeds between adjacent gears. At low vehicle speeds, periodic changes in external driving conditions (for example, hilly or winding sections of roads) can lead to loop shifting between adjacent gears. To simulate this process, a dynamic transmission model is proposed, which can be used in the development of shift control systems and for calibration of the engine and automatic transmission at various operating modes and vehicle conditions
Simulation on metro railway induced vibration. Part II: effect of corrugated rail
Get PDFThe deterioration of running surface, including out-of-round wheels and corrugated rails. The effect of out-of-round wheels on simulation of rail dynamic behavior was presented in a companion paper [1]. In this paper, the effect of corrugated rails was discussed. Considering a perfect round wheels moving on different irregularities rail surface, including perfect smooth rail, irregularities generated from a US PSD, measurement data from corrugated rails. Calculation result indicated that (1) the traditional used irregularity generated from US-PSD would not satisfy the requirement simulation on rolling noise and vibration generation in high frequency range; (2) corrugated rail plays the dominant role on the vibration which obviously related to its typical wavelength
Research on vertical vibration of hot rolling mill under screw-down-strip combined excitation
Get PDFIn this paper, we find the violent vibration of the hot rolling mill is induced by the combination of the screw-down system and the strip, explain how the srew-down-strip combined excitation effects the rolling mill, and introduce an effective method to restrain the vibration. First, two experiments, stripless rolling and turning off the screw-down system, are conducted, the first experiment simulates the rolling process without strip and the second experiment simulates the rolling process without the screw-down system, the results indicate that the rolling mill vibration is induced by the srew-down-strip combined excitation. Then, to explain this phenomenon, the mathematical model of the rolling mill under screw-down-strip combined excitation is proposed, we find that few excitation frequency components can induce more response frequency components, therefore it’s more possible to approach the natural frequency of the rolling mill. Finally, a vibration suppression method is introduced by eliminating some specified frequency components of the screw-down system with a filter, and the result shows that the vibration decreased by 98.7 %
Optimization and analysis of novel thermoelectric module
Get PDFOptimization and analysis of novel thermoelectric module is proposed in this research paper. The simulation for four thermoelectric modules were performed in COMSOL Multiphysics 5.4 software and detailed analysis of these thermoelectric modules were carried out. The three thermoelectric modules showed the efficiency and power output above-average thermoelectric modules. It also indicated that lead telluride based thermoelectric modules could be used in isolated areas due to toxicity of lead whereas tetrahedrite based thermoelectric module could be used in non-isolated areas due to its non-toxic properties. The proposed thermoelectric modules can be utilized in applications such as industries, deep space explorations, automobiles, thermal power plants, renewable electricity generation, hybrid renewable systems, etc. in an economically viable manner
Unknown input reconstruction in non-linear dynamical systems using homotopy optimization
Get PDFIn this work, a homotopy optimization method is proposed for reconstructing unknown inputs in non-linear dynamical systems. The unknown inputs are parametrized using a B-spline basis. This parameterization of inputs converts the unknown input identification problem into a parameter identification problem. The unknown parameters are identified through an optimization process. The proposed homotopy-based optimization method is designed to converge to the global optimal solution instead of a local minimum. The unknown parameters are obtained through a series of iterations guided by a homotopy parameter and an optimization algorithm
Feasibility study on the application of carbon dioxide phase change fracturing technology in a foundation pit of an open cut tunnel
Get PDFCarbon dioxide phase change fracturing technology is a brand-new and efficient cracking and tunneling technology. Because the method utilizes the change of carbon dioxide state, it belongs to a pure physical process. By adjusting the release rate of gaseous substances, it can effectively control the pressure of the gas, and achieve micro vibration, zero flying stone, zero toxic gas emission, and no micro harmful effect of shock wave, but the application of carbon dioxide phase change cracking technology in urban foundation pit excavation is less. In this paper, through the analysis of three different cracking parameters of urban foundation pit excavation process, it is found that when the diameter of the cracked pipe is 85 mm, the construction safety can be guaranteed. In addition, according to the on-site cracking effect, the carbon dioxide phase change cracking technology is a safe, reliable, relatively economical and efficient excavation technology under urban complex environmental conditions, and will not affect the surrounding environment during use, but Its cracking efficiency has a great relationship with the air surface