Papers by Keyword: FVM

Abstract: Aiming at the aluminum profile extrusion process of a large caliber aluminum tube with porthole die, this paper established the simulation models by using finite element method and finite volume method, respectively. The extrusion process was simulated by using the above two models. The advantages and disadvantages and the applicability of the two simulation methods in simulating large aluminum profile extrusion processes were compared. It is concluded that finite volume method is more suitable than finite element method for simulating aluminum profile extrusion processes with a severe deformation. In addition, the distributions of stress and strain and the material flow patterns in the large caliber aluminum tube extrusion process with porthole die were given in detail. The results can provide useful theoretical guidelines for the process and die design as well as process parameter optimal selection for large aluminum profile extrusion processes with porthole die.

Abstract: The finite volume simulation of equal channel angular pressing (ECAP) was realized using 3D commercial code MSC.SuperForge. The knowledge of stress and temperature during ECAP process is very important for forming a hard-to-deform as Ti under optimal thermo-mechanical conditions to achieve desired mechanical properties. In this work, the strain, stress and temperature fields of both the die and workpiece are studied. The resulted stress and temperature distributions showed maximal values in the region of corner and channel angles of the die. Also, the temperature increased during the processing, as a consequence of the deformation. The heating of the deformation system was calculated and analyzed for three different ram speeds (v = 1, 10 and 20 mm/s) at 400 °C. Keywords: ECAP, SPD, FEM, FVM, heat transfer analysis, titanium

Abstract: Thehottest spot temperature (HST) of windings of oil-immersed transformer is animportant factor that affects load capacity and operation life of transformer,and is closely related to the transformer load, top oil and environmenttemperature. HST, when operating at high temperature and overload, may lead totransformer failure which will affect the normal operation of the power system.In order to calculate the transformer hot spot temperature accurately, we takea 33MVA-500KV transformer as an example, and establish a three dimensionalmodel, get its internal temperature distribution based on Fluent simulationsoftware. At last, we comparative and analysis the accuracy of FVM calculation andIEEE guidelines recommend model combined with online monitored values. Theresults show that the FVM method with higher accuracy relative to the IEEEguidelines model, proved that using the FVM can accurately calculate the HST ofoil-immersed transformer.

Abstract: When the large oil-immersed transformer start with heavy load in cold regions, due to the high viscosity of the oil at low temperatures, the flow of the oil is extremely slow in the early start of heavy load, resulting in a negative heat radiation. At the same time, the winding and the core are rapidly increasing heat in the early start of heavy load. Rapid increase in heat and the lack of heat dissipation caused a series of problems. In this paper, we study the process of heating and cooling when the large oil-immersed transformer start with heavy load in cold region and takes a transformer of 31.5MVA as example to build a three-dimensional model ,the model is based on the actual size of the transformer. We use the finite volume method to calculate three-dimensional temperature field distribution changing with time when the oil-immersed transformer startup with heavy load in - 35 °C,-30 °C and-25 °C three cases. The results show that the viscosity coefficient of transformer oil is very high at low temperatures. In the early start of the transformer, because of the poor fluidity of the oil, the heat cannot be dissipated in time and the transformer local overheating near the winding. Then we analyzes the damage of local overheating for a short period of time in the transformer, especially the damage of the oiled paper's insulation At last ,we analysis of the causes of transformer internal local overheating and give some measures to avoid local overheating when oil-immersed transformer start with heavy load in cold regions.KEYWORDS: oil-immersed transformer, cold regions, start with heavy load, FVM, three-dimensional temperature distribution

Abstract: To study the velocity and pressure distribution of the oil film in a heavy hydrostatic thrust bearing, a mathematical model of the velocity is proposed and the finite volume method (FVM) has been used to simulate the flow field under different working conditions. Some pressure experiments were carried out and the results verified the correctness of the simulation. It is concluded that the pressure distribution varies small under different rotation speed when the surface load on the workbench is constant. But the velocity of the oil film is influenced greatly by the rotation speed. When the rotation speed of the workbench is as quick as enough, the velocity of the oil film on one radial side of the pad will be zero, that is to say the lubrication oil will be drained from the other three sides of the recess.

Abstract: Hydrostatic vertical guideway is the key component of modern CNC equipments which is a common lubrication form of turret. In order to improve the cutting stiffness during processing, the hydrostatic vertical guideway in sliding seat during westbank ram processing. Take count different cutting force to analysis the thickness changing of hydrostatic oil film, and then the relation between cutting force and the thickness of oil film is obtained. Based on FVM, relation model between them is established and the limited condition including cutting force is T=100KN, flow flux of each inlet is 0.52L/min, pump of constant delivery type is applied, film thickness is 0.023mm and oil cavity depth is 2mm is numerical simulated. The Hydrostatic pressure field and film thickness under different condition of hydrostatic vertical guideway is obtained. The relation model between film thickness and custom forces is validated. Whats more, the regularity of cutting force influence that impacted on film thickness is revealed. The study is of vital theoretical significance for the improvement of machining accuracy of numerical control machine and the entire CNC equipment and provides valuable theoretical basis for the design of hydrostatic guide rail in engineering practice.

Abstract: A finite volume method for the numerical solution of viscoelastic flows is presented in this paper. The flow of a differential upper-convected Maxwell (UCM) model fluid through an abrupt expansion has been chosen as a prototype example. The equations are solved using the finite volume method (FVM) in a staggered grid. Stable solutions are found for high Weissenberg number (We), further extending the range of simulations with the FVM. Numerical results show the viscoelasticity of polymer solutions is the main factor influencing sweep efficiency.

Abstract: Today's, with the development of numerical analysis methods, simulation and analysis of processes of forging has witnessed a great deal of development and those methods one considered as one of the strongest ways of improving forge. In this research, the process of hub production with the finite volume method by means of superforge software is simulated and the required energy shaping of work piece was extracted. The considered work piece was produced in three stages by hot forging. The effect of coefficient of friction and temperature on process was examined. The result show that the effective stress will increase with rising of coefficient of friction and with increasing the temperature the press force decreases and effective plastic strain increases.

Abstract: The current research on the porthole-die aluminium alloy extrusion is presented here. The empirical method and simulation method are analyzed. Particularly, the Lagrangian Finite Element Method(FEM), Eulerian Finite Volume Method(FVM) and Arbitrary-Lagrangian Eulerian(ALE) algorithm are compared. The development of the porthole-die aluminium is educed.

Abstract: A body fitted based finite volume method (FVM) model of aluminum extrusion processes was established in this paper. The basic theories and rigid-plastic flow theories of this model were researched and built. Body fitted grids were used to match complex geometric boundaries and local refinement of grids was also realized. Plastic shear friction model was applied on body fitted grids. A typical then walled profile extrusion process was simulated using the program developed in this paper. The simulation results were also compared with that simulated by FEM software Deform in the same process, material and die conditions. The feasibility and efficiency of the mathematic model built in this paper was demonstrated by the simulation results and the comparison.