Large sync belt-wheel is one of the most important parts in CT machine, material is ZL111, now usually using sand casting. Due to Al alloy castings have serious tendencies of oxidization and air-breathing, in the meanwhile, the alloy is hypoeutectic alloy,has obvious tendency of shrinkage porosity in the process of freezing. These defects can seriously influence Al alloy castings’ properties, so products have low percent of pass.In order to resolve the difficult problem of producing , the subject regards , as subject investigated. adopts metal-model foundry, according to flowing features of permanent casting filling, it uses Z-Cast foundry numerical simulation software to study casting filling and freezing processes of , and realizes optimization of casting filling by simulation. Its purpose is to improve castings’ percent of pass, inherence and appearance quality and comprehensive property.At first, in order to guarantee filling process smoothly and preventing Al alloy from generating defects of oxidization and air-breathing, and so on, bottom gate and setting separately three runners has been adopted. In the meanwhile, adopting vertical gate to fill casting body has been adopted. It is difficult to feeding through feeder, due to the edge of casting top is far from vertical gate, therefore, setting three feeding heads on casting top.Filling and freezing simulation results show that casting is filled well and has no flaws such as under priming, serious slay and so on, vertical gate and feeder heads have a good effect on feeding in process of cooling and freezing.According to simulation results, analyzing reasons of flows in freezing process and raising predicted methods of flaws, in order to define reasonable processing parameters: Tmold=240℃, Tsand=25℃, Tpour=710℃,tpour=25s.Adopting technology after optimization in this subject to produce Sync Belt-Wheel, 535（±5℃）×5h+170℃（±5℃）×6h, after cooling treatment in the air,σb=295MPa,δ=2% and HB=86 in ZL111 alloy large sync belt-wheel, products have no obvious flaws, and meet requirements of property. It shows that the technology after simulation optimization meets actual production; it can be used to direct exploitation process of large shape of annulus aluminum casting.
Post about "Numerical simulation"
Stirred tanks are typical process equipment and are widely used in. When the fluid in stirred tanks is turbulent, the fluid can mix well rapidly. But in the cases that the fluid viscosity is large or the fluid material is sensitive to shear force, the fluid in stirred tanks has to be in laminar. In these cases there are isolated mixing regions (IMRs) which are the worst obstacle to mixing existing in stirred tanks. With the rapid development of chaotic and nonlinear theories, can be utilized to destroy the IMRs and improve the mixing effect.According to the theory, aperiodic flow perturbations can be used to destroy the IMRs. So the blades of the 6-blade turbine were upper and lower dislocated respectively to generate the aperiodic flow field. The effect of the dislocated baldes on destroying the IMRs was investigated both experimentally and computationally. The main research contents and results are as followings.Firstly, Multi-reference frame(MRF) method was used for simulating the flow field of the standard 6-blade turbine. The positions of the IMRs were accord with the foreign experimental results. So the simulation method is feasible. Through the reliable FLUENT simulation method the velocity fields of different blades can be obtained. The results show that mixing effect of the dislocated blades are better than the standard blades and the improvements of the field depend on the dislocated scope and Re. The lager the blades dislocated, the better the mixing effect is. On the basis of the steady velocity field within the stirred tanks, the simulation of unsteady flow field were carried out by adding tracer. The results show that there are two IMRs whose tracer concentration are low in the standard 6-blade turbine stirred tank, however there aren’t IMRs existing in the dislocated 6-blade stirred tanks. So the dislocated blades can destroy the isolated mixing regions.The acid-base neutralization experiments were used to validate the mixing effect on the basis of the former simulations. The experimental results validate the simulation conclusions. There are two IMRs existing above and below the impeller respectively. The dislocated blades can destroy the IMRs and the mixing effect are better. But whether the dislocated blades can destroy the IMRs completely depend on the impeller speed and the dislocated scope of blade.
Mine water disaster is one of the biggest obstacles affecting and restricting China’s coal production. Only the floor karstic water threats about 42 percent China’s coal base. Therefore, the research on water invasion regularity of coal floor has an important practical and theoretical significance for the coal mine safety production.In this paper,finite difference software is used to simulate the in different working face length, mining depth, exploiting thickness, water pressure and floor lithology. Then, simulation results are calculated by variance analysis method. On the basis of that the sensitivity of main controlling factors is determined. Firstly, according to the actual production experience and results of previous studies, main influence factors of floor water invasion and action principles of these factors are discussed. Then, combining geological conditions of this study, the controlling factors are determined. On the basis of “down three zone” theory, using rock fracture mechanics theory, the formation mechanism and calculation formula of the down three zone are analysis, and dynamic mechanism of floor water invasion is revealed. All of that provides a theoretical basis for sensitivity analysis of floor controlling factors. Then, according to the actual conditions, simulation geological condition is set. Meanwhile, combination experimental conditions, level values of controlling factors are determined. In order to reduce workload, author identified test plan using orthogonal test, and did the numerical simulation by . Through the work of before, the under different controlling factors are determined. Eventually, using orthogonal analysis, charts and linear regression method, further discussed floor water invasion regularity and the sensitivity of main controlling factors. ’s useful for preventing water invasion. And provides a theoretical guidance for coal mine safety production.Water-inrush is the result of many factors working together. So water-inrush mechanism is very complicated. This paper presents a simple water-inrush law under the ideal geological conditions. In the actual production, coal mines should be based on the specific circumstances of water-inrush simulation to determine water control measures.
Mine tailings dam is an important production facilities, a large number of dams memory tailing sand and water, once the dam break, the tailing dam and water on the debris flow will be in the form of emission, the consequences would be disastrous. Their predecessors do a lot of theoretical research andexample statistics show that the impact of the tailings dam safety and stability of various factors, the location of the dam seepage infiltration is extremely important factor. The need for more stability in the evaluation of the tailings dam dam seepage field study to determine the location of infiltration and analysis of its impact, and propose alternatives.This article study on the rule of tailings dam changes of the seepage. Xi Ye Shan-tailing dam in several decades of operation has shown a lot of failures, and considering raising its 100 m to the situation, is need to study the stability of its seepage. Following are the mainly completion of work:(1) Through on-site inspection, testing analysis, master-Ye Shan tailings dam dam operation in the history and present situation and geotechnical ;(2) For the tailings dam material characteristics, the introduction of seepage theory, the seepage field two-dimensional finite element model, simulate, the dam of the changes of seepage;(3) Calculation of the rule-of-tailings dam specific types of damage and stability of the dam evaluation analysis and treatment measures;(4) Xi Ye Shan-tailing raise the tailings dam 100 m to conduct a feasibility analysis, methods of expansion dam design and analysis of the dam heightening the flow stability;(5) For this study the contents and methods, put the text of inadequate light industry and the development of future work in areas for improvement.
Photochemical smog is composed of ozone,Peroxyacetyl nitrates (PAN) and nitric acid (HNO3) pollutants which are formed by some photochemical reactions of nitrogen oxides and hydrocarbons under ultraviolet ray radiation.In order to understand the impact ofon photochemical smog in city and the relationships among the pollutant concentrations during photochemical fog formation reaction, the photochemical smog formation mechanism is explored firstly, and the current pollution levels and developing trends of exhaust pollution in big city are discussed. Then the simplified set of photochemistry dynamic equations is established, and a numerical simulation of photochemical smog formation at different initial conditions is carried out. We can summarize the prevention and cure measure of photochemical smog pollution . Finally the Empirical Kinetics Modeling Approach graphs of ozone and PAN are plotted, and the mitigation measures of photochemical smog pollution in different kinds of cities are proposed. The conclusions are summarized as follows:1.The index of photochemical smog pollution grade in city is established. Using the ratio of NOX to SO2, is concluded that the urban air pollution characteristic in this country is being transformed to the exhaust type of motor vehicle (photochemical smog type) from the soot type.2.The formation process of photochemical smog is numerically simulated using the explicit Runge-Kutta method and the MATLAB tool, the numerical simulation of photochemical smog formation process is carried out based on the simplified photochemistry dynamic model. can also be seen from the simulation results that under the condition of low concentration ratio of NMHC/NOX, when the initial concentration of NOX is fixed, increasing NMHC leads to increasing O3 and PAN. While initial concentration of NMHC is fixed, increasing NOX results in increasing both O3 and PAN. However the time of achieving the maximum of ozone value is retarded. When the initial concentration of NMHC and NOX increase, the yields of O3 and PAN are increased rapidly, the time of achieving the maximum of ozone concentration is postponed. from the simulation of CO, it can be seen that the yield of CO relates to the initial concentrations of NMHC and NOx, and CO level depends on the levels of NMHC and NOx, but do not have a simple linear relation between them. 3.The contour of ozone and PAN concentrations is plotted by using the Empirical Kinetics Modeling Approach( ). The results reveal that the relationships between the maximum and formed rate of O3 and the ratio of NMHC to NOX are not a linear. Using the ridged line of , the type of photochemical smog pollution in city can be classified into A and B. Finally the mitigation measures of photochemical smog pollution in different kinds of city are proposed.
Based on thebackground of liquid-propellant rocket engines, the characteristics of with have been researched in this paper. The main points are stated as following:Firstly, an ignition experiment equipment is designed which is used to heat single droplet of liquid-propellant with electricity. The propellant used in these experiments is LP1846. Time series photographs of the process what the droplet undergoes in all kinds of experimental conditions and characteristic parameters have been obtained. Some preliminary analyses about the experiment phenomena and mechanism are proposed. When the largest load voltage is increased, the effect of delayed ignition with droplet has been discussed.Secondly, a discharge experiment equipment of pulsed power source and a spray device with are designed in this paper. Under the conditions of single-pulse discharge, the disquisition of ignition characteristics with LP1846 spray has been investigated. On the basis of experiments, a simple calculation model of intense burning period of delay with LP1846 spray has been developed. The calculated theoretical results are in good agreement with experimental data.Thirdly, a sequence-pulse discharge device is designed. Discharge frequency is 50Hz. With this device, the of characteristics with LP1846 spray has been investigated. Results indicate that the droplets between two electrodes can combust in instantaneous moment, under the conditions which the discharge power is 50W, these LP1846 droplets are about tens of microns.
In this paper, the high-speed water entry load characteristics and Splashing water status of rocket sled’s water brake structure were introduced by using LS-DYNA software. In the first part, the water-entry research history and development of structure at home and abroad were reviewed, and the significance was emphasized. According to solid-fluid interaction’s algorithm offinite element computational procedures, a simulation analysis was made, which chiefly analyzes the high-speed water entry characteristics of rocket sled. Based on the analysis, water splash and pressure-wave emission, the resistance characteristics, the speed curve and acceleration curve are all obtained. Especially, a very clear physical image about splashing water phenomenon was given, which was caused under conditions of high-speed impact. Splash water has a great impact on the upper blade of water brake, and also poses greater influence on the water funnel device. However, the issue about was seldom considered in the previous studies. In short, a new methodology and technical reference for the design of rocket sled water brake structure were offered by the result of this study. The above numerical simulation results provided certain reference value for the design of high-speed water entry rocket sled water brake structure.
For more than a hundred years, the method of plastic deformation for measuring pressures has been the main mean to test the chamber pressure of conventional weapons because of its advantages that is reliability, convenience and low price. Aimed at a series of theory problem in the staticcharacteristic and the dynamic characteristic, a large amount of work has been done in dissertation. The main work consists of the following parts:a) The frictional coefficient between copper cylinder and the interface is one of the most important factor in the copper cylinder process. According to the diameter height ratio difference, the interface was divided into three parts : sliding area, restraint area, stagnant area. Bases on the difference of the touch,we get the formula between the pressure and distortion. At last, a comparatively satisfactory result based on the performed static formula of mathmatics and physics was obtained, and is testified by the tests.b) Regarding Rigid-Viscoplastic (the Finite Element Method) as theoretical foundation, an axial symmetry model of ring was built up through ANSYS software, the copper cylinder has been simulated by the . Information about the deformed sample, such as mesh distortion, displacement and pressure has been achieved. The deformation patterns were revealed. In order to verify the simulation results, various experiments about copper cylinder pressure measuring were designed and completed. The experiment results indicated that the simulation results are reliable.c) The mathematical model of copper cylinder pressure-measuring system was established according to the pressure-measuring mechanism of copper cylinders and the numerical solution program was made using the Matlab. The simulation of this model has been done and the simulation results comply with the measuring results quite well. According to the simulating calculation, the regularity of copper cylinder deformation under different pressure is obtained.
Sheet metal stampmg is a sheet metal forming process by using molds to get products that fit the requirement of design in shape, dimension and performance. As sheet metal stamping can provide the advantages such as saving materials, high efficiency and low cost,is one of the important machining processes in manufacturing industries, i.e., machinery, electron, instruments and aerospace, etc. Drawing is one of the most typical sheet metal stamping processes, which is also widely used in practical production of many work pieces. Although existing researches on have already developed to a relatively high level as well as abundant correlative literatures focus on , there are still some fields need to be studied. Therefore, thorough and further research on process is quite necessary.Based on the development history and status quo of process, this paper is focused on the drawing process which has not been studied well. For example, the influence of material thickness variety and material work hardening were omitted in the calculation to the drawing deformation pressure, etc. The main research contents and results are listed as follows:(1) Technologic experimentsWith utilization of s being designed, deformation characteristic and technological parameters are comprehended, as well as can be measured. The instance of can provide foundation and validation for theoretical study.(2) With utilization of FEM software DEFORM, Simulation and analysis on deformation course of drawing was carried out. Effective stress and effective strain are analyzed, the state and condition of fracture in drawing process are simulated, and is analyzed, which can provide foundation and validation for theoretical study. (3) Theoretical studyBase on al results and numerical simulation results, with utilization of slab method of plastic mechanics and material work-hardening theory, a new calculational formula of cylinder drawing force was deduced, and compared with different calculational formulas of drawing force.The studies of this paper enriched the contents and the theories of drawing process, which brought both academic and practical significance as well as its research method can be validated. can provide references for the technicians who are engaged in sheet metal stamping field.
Spur gears are important parts used widely for mechnical transmission. If can use the plasticity to form gear teeth,is very theoretic and practical significance to improve their quality, improve the production efficiency and lower their costs.In view of the diffculty of the filling of the corner when the spur gear is forming, This paper proposes one kind of method- according to the thought of the teacher. And process of forming has been researched based on numerical simulation and physical simulation.1. First, has been reasonable simplified based on main parameter of the gear and characteristics of . Developing 3-D geometric modeling by software UG. This parametric design will make modifying conveniently. Furthermore, is the base of the following simulation.2. Designed the mould for experiment. The key point is the design of splitting including the choice of the mold parameter, simple localization method and so on.3. Applying software DEFORM,the process of extrusion has been analyzed for spur gear. Obtained the metal flowing rule of the forming process, the stress and the strain distribution. Analyzed the possible flaw of the forming process and proposed the corresponding solution measure.4.The physical simulation of the forming process. Machined the mould for experiment. Carried on the physical experiment with the lead, the discussed the influence for forming of the different blank diameter and the shape.This research promoted the development for the continuous partial plastic forming theory, and it can provide the experience and reference for subsequent research on .