Papers by Keyword: Transient Analysis

Abstract: The study of amorphous semiconductors is of great interest because they find important applications in many electronic devices, like large area solar cells and photosensors. We have developed a methodology for the analysis of transient response of amorphous photodiodes when switched off from steady-state and when they are exposed to a δ pulse of light. For this purpose continuity equations and the transit time effect have been calculated. For the p-i-n photodiodes, characteristics of photo current decay have been analyzed for an ideal case in which the diode is assumed to have a unit current gain. It is found that characteristics either due to decay from steady-state or due to light pulse excitation is transit time dominated. The short-circuit performance of solar cells resembles to a p-i-n diode because a solar cell is essentially a p-i-n diode which is used as an energy converter. Thus short circuit current decay of solar cells behaves similar to the photocurrent decay of the diode and the same method of analysis can be applied.

Abstract: Partial differential equations such as models for flow in unsaturated porous media are difficult to be solved when space-time variable boundary conditions are included. A general solution to this problem is discussed in this contribution and is devised in such a way that the face with variable boundary condition can be subjected to Dirichlet, Neumann or the so-called Signorini/ambiguous boundary conditions, considering the transition from one type to another. A method based on the enrichment of finite elements that is able to accurately model seepage with these complex boundary conditions is discussed. Simulations are presented illustrating the capabilities of the new method in 2D and 3D, including cases where the free surface varies due to rain.

Abstract: A certain type of special computer was studied as the institute in this paper. Through researching on the structure of the special computer box, use the Pro/E software to create the simplified model of the case, including computer cabinet, PCB, power and fan etc. Model analysis is conducted in the FEA environment ANSYS, attains ten order natural frequency and vibration mode. Dynamic load in the model is applied with half sine impact acceleration, and the resistance performance of the PCB which is the important components of the model is researched by the acceleration, speed and displacement response results obtained. Verify the installation method of vibration isolator can effectively improve the shock resistance of special computer.

Abstract: In the present work, an experimental investigation has been made to analyze the performance of microchannel heat sink under transient operating conditions. The transient analysis has been made by estimating the response time for different input heat flux and coolant mass flow rate. Analysis has been made for rectangular cross-section microchannels fabricated on a copper block of size 25.7 × 12 × 10 mm³. Twelve (12) numbers of microchannels are fabricated in the copper block. The width and depth of individual channels are 400 μm and 750 μm respectively. Performance analysis has been made for both single phase and flow boiling conditions of the coolant flow using deionized water as coolant. Experiments have been performed for coolant mass flux (G) range of 90 - 250 kg/m²s and input heat flux (q) range of 20 - 300 kW/m² respectively. It has been observed that at constant input heat flux, response time decreases with the increase in coolant mass flux during single phase cooling. However this trend is not strongly followed during the two-phase or flow boiling cooling condition.

Abstract: In order to solve the vibration problems of car high-pressure cylindrical cylinders, Plate and Shell Vibration Theory is used for the calculation and analysis of the vibration characteristics. The vibration frequencies and modes of such cylinders are obtained. At the same time, the corresponding results are gotten through ANSYS12.0 simulation calculation. The similarities and differences of the both vibration frequencies and the changes of the respective modes are compared and analyzed to support the farther safety performance analysis of such cylinders in the vibration environment.

Abstract: Multi-Rotor Horizontal Axis Wind Turbine (MR-HAWT) system with three 2kW Horizontal Axis Wind Turbines (HAWTs) is the research object. After some appropriate simplifications, the finite element model is established and verified by experiments. The vibration characteristic of the tower under rotors’ periodic excitations is studied through transient analysis method and compared with 6kW single-rotor HAWT system. The result shows that the maximum stress of the 3-Rotor Horizontal Axis Wind Turbine (3R-HAWT) system is less than the single-rotor HAWT, so the safety of the 3R-HAWT system is superior to the single-rotor HAWT system.

Abstract: In this paper, based on the theory of ship-bridge collision, large-scale finite element software ANSYS is adopted to establish the calculation model of the bridge.According to the specification of our country, the calculation of bridge collision force then compares with the actual situation.Through the calculation of collision force, the ship-bridge collision is transformed into the problem of transient analysis of collision point.This article is mainly to analyze the change of bridge energy and the stress and displacement of main parts of the bridge. Finally, this article puts forward the personal vision.

Abstract: Abstract. The paper deals with the finite element modelling of acoustic waves propagation through a stone masonry specimen. In the last decades major efforts have been devoted to improve Sonic and Ultrasonic analysis of structural members and provide suitable correlations between acoustic wave features and the material parameters. This paper concerns the ultrasonic analysis and tomography of a masonry specimen made of trachyte blocks and cement mortar, including an inner void as an anomaly supposed to be detected by the analysis. The tests were performed with several equipments accordingly to the Direct Transmission Technique, transmitting an ultrasound signal by a piezoelectric transducer and detecting and analysing the signal received on the opposite side by another transducer. Basically the transmission time of the signal through an ideal path from the emitting and receiving transducers and the resulting wave speed are regarded as the main phenomenological measurements for non-homogeneity and anomalies detection.

Abstract: A field-circuit coupled finite element method has been applied on one induction machines for the transient analysis in case of inverter power supply and sinusoidal voltage supply in this paper. The focus is to build the time-stepping finite element method with external circuit coupled to the electromagnetic field equations and achieve voltage supply. The problem of the motion of rotor is solved through moving boundary by interpolation in the moving coordinate system. The induction machine starting transient simulation has been completed using Finite element equations indirect coupled with mechanical equation. The influence of the electromagnetic field and performance has been analyzed compared with sinusoidal condition. This method can be used for dynamic analysis of any power supply taking into account the magnetic nonlinearity of the core material. The established machine overall structure model is closer to the actual. Compared to the traditional analysis method, we can reduce the dependency of experience design. It can also be used for analysis and optimization of the new machine

Abstract: Friction Stud Welding is primarily used to bond different material. Joining of aluminum alloys, stainless steels and composites with any other materials is required in many underwater welding applications. In the present work, a mathematical model has been developed for underwater friction stud welding. A thick AA6061 plate is welded with steel stud in a modified drilling machine. Transient analysis of heat conduction in the plate has been calculated numerically including heat generation due to friction between the materials. The conduction, convective and surface boundary conditions have been considered as per the developed model. Comparison has been made between welding performed in normal atmospheric condition and underwater condition. The temperature distribution in the work piece has been predicted using the developed mathematical model. It is found that there is steep fall in a heat flow during underwater welding condition. High weld strength can be achieved due to less heat affected zone in underwater welding.