CC BY
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The second group of cone channels, the loss of pressure medium in which the maximum. For the uniform treatment of such channels is recommended to change the flow regime of thecone to ring slit (№ 5...7) orto apply a one-way AFM (№ 6).
In the third group, consisting of a channel with the local resistance, AFM’s still rough surface, perpendicular to the flow (№ 10... 15). For processing to change the direction of flow through the leveling devices.
For a uniform treatment of channels with blades, which are the fourth group (№ 16...26), it is necessary to ensure an even flow environment in each of the channels, by forming the flow profile at the entrance of these channels.
In the fifth group included micro, requiring the use of working environments with low effective viscosity and low dispersion of abrasive filler (№ 27).
In analyzing the motion of individual abrasive grains in a flow is established that they move along the current lines. In steady flow the distance between neighboring grains is not changed. This confirms the supposition about the formation of elastic chains inthe flow [1]. Establishedthatthe grain, into contact withthe treated surface, the flow performs rotational motion. Studies education media vortices near walls orinthe flow with the flow in the channel was not observed.
Research has identified the nature of the flow in channels of different media configurations and taken into account in calculatingthe roughness of the surface finishandperformance of AFM on the previously developed technique [3].
Bibliography
1. Левко, В. А. Модель течения рабочей среды при абразивно-экс^узиожой обработке тонких осесимметричных каналов большой длины / В. А. Левко // Вестн. Чебоксар гое. пед. ун-та. Механика недельного состояния : сб. науч. тр. / под ред. акад. Д. И. ^вдева ; Ч^аш. гос. пед. ун-т. Чебоксары, 2008. № 2. С. 85-94.
2. Левко, В. А. Абразивно-экс^узионная обработка: современный уровень и теоретические основы процесса : монография / В. А. Левко ; Сиб. гос. аэрокосмич. ун-т. Красноярск, 2007.228 с.
3. Левко, В. А. Расчет шероховатости поверхности при абразивно-экструзионной обработке на основе модели контактных взаимодействий / В. А. Левко // Авиационная техника. Известия вузов / под ред. проф. В. А. Фирсова ; Казан. гос. техн. ун-т. 2009. № 1. С. 59-62.
© Levko V. A., Lubnin M. A., Snetkov P. A., Pshenko E. B., Turilov D. M., 2009
P A. Snetkov, V. A. Levko, E. B. Pshenko, M. A. Lubnin Siberian State Aerospace University named after academician M. F. Reshetnev, Russia, Krasnoyarsk
EXPERIMENTAL DETERMINATION FACTOR TO VISCOSITY, ELASTICITY AND PLASTICITY MEDIA FORABRASIVE FLOW MACHINING PROCESS*
Numerical values of factors of viscosity, elasticity and plasticity of a media are established. Experimental dependences of viscosity and elasticity of environment on degree of its filling and granularity of abrasive grains are revealed.
Keywords: abrasive flow machining, rheological characteristics, viscoelastic media, flowable abrasive particles, shear rate.
The one of the new types of such processing is abrasionextrusion processing (AFM), which is consist in removing the layer of material from the surface of the treated channel at extruding under pressure through it, working environment, consisting of a viscosity and elasticity foundation, filled of solid working elements (most often - abrasive or diamond grains).
AFM is difficult process. In its implementation there are a number of physical phenomena that influence for quality and productivity of processing. For the introduction of abrasive extrusion processing in the production of specific details must be made a sufficiently large volume of experimental studies, related with determining the optimum composition of the working environment and modes of its extrude, caused by physical-mechanical and geometrical characteristics of processed channels. Such researching
needs a lot of costs, which constituting up to 60 % of the total cost of implementing this technology in production.
The main parameters of technological process of abrasive extrusion processing is the volume of the working environment, pressure of the hydraulic system installation in burst and the host operating cylinder of installations for AFM, value (dispersion) and percentage (concentration) of abrasive grains in the working environment, its physical and mechanical characteristics, and also the numberof processing cycles. The geometric characteristics of the processed feed have great influence on the quality and productivity of the process - its radius and length, area and perimeter of the cross-sectional and also initial physical and chemical properties of the surface layer.
Cutting ability of the working environment as abrasive tools depends of flow’s conditions in the processed channel
* The work within the federal purpose program “Scientific, scientific-pedagogical cadres Innovative Russia”.
and its viscoelastic and plastic properties. Viscous and plastic properties determine its fluidity, the elastic properties -stiffness. For the theoretical calculations of the flow characteristics of working environment with AFM it needs to experimentally establish dependence of the effective viscosity ", Poisson’s ratio and Young’s modulus of working environment of the degree of its filling and dispersion of abrasive grains.
Characteristics of the working environment depends on the degree of filling of the polymer base (Ka concentration of abrasive grains inthe medium), of their size (Ba grits), and also of a pressure in filing cylinder Pin.
If the Ka and Ba are changed, changes are not only in the density c the medium and its viscosity, but also in its rheological characteristics - coefficients of tangential and normal stresses, flow velocity and shear rate, and also all the curves of the shearflow dependency of shear stress.
Because the nature of viscous flow abrasive medium at the extrusion processing a circular channel with big length the same to fluid flow in a capillary viscometer, for the researching of viscous properties a similar method was developed, based on the experimentally established values of maximum flow rate m and drop of pressures *P on the
max A A
section of a cylindrical channel L length and diameter d. Substituting the experimental values m and *P in in the
max
transformed Puayzel’s formula for known L and d value of the effective viscosity " is defined.
*P R2
" =-------------.
m 8 • L
max
For registration the parameters system of defined set of research was applied. Experiments were conducted on an experimental set UESH-25 with using a special device (fig. 1).
Device consists of a steel hull 1, which was subjected to heat treatment, with round channel 2 with 25 mm in diameter, coinciding with the diameter of working cylinders 3 and 4 UESH-25 - installation, with pressure sensors 5 and 6, and also a temperature sensor 7.
Onthe oscillogram (figure 2) pressure change inthe current moment in sections of sensor 5 (P1) and 6 (P2) recorded. Time is defined on the oscillogram for step cutoff tc = 0.2 c. On the line P1 the startpoint of deviationfromthe zero level of evidence 1 is revealed. Similarly, the beginnings of the emergence of the pressure’s environment at point 2 for the line P2 is found. Through found points 1 and 2 vertical lines to the lines P1 and P2 are held pursuant. The distance tc between the normals corresponds to the minimum duration of an environment from cross-section 1 to cross-section 2. By the known distance between cross-sections (L = 0.07 m) and tc maximum speed of flow m is calculated in this section. Then find the point 3,
max
a b
Fig. 1. Device for the study of viscous and plastic properties: a- scheme; b - the body of device with two adapters
cutoff
Fig. 2. Scheme of registration data on the oscillogram 100
which is intersection of the normal through the point 2, lying on P2 line, and point 4 by P1 line.
The exact values of physical quantities tc and *P were calculated taking into account the calibration of sensors and size of step cutoff tc. The pressure difference between the two cross-sections *P = P1 - P2 equal to the distance betweenpoints 3 and 4 onthe oscillogram, multipliedby the scale calibration. Six experiments with randomization of time and temperature controlled environment was conducted for each experimental conditions.
The researching of dependence the coefficient" of Ba and Pn was carried out according to Kono plan (m = 2, n = 3). For the mathematical processing the coding variables X = Ba; X2 = Pin; Y1 = " was produced. Granularity Ba and the pressure Pin were varied factors. Each experiment was repeated six times with randomization time. Terms of experiments onthe nine modes and experimental results are givenintable 1.
As a result of studies found that the higher the degree of filling polymer base working environment by abrasive, the higher its effective viscosity. Bigger factor 3 observed when lesser magnitude filled with abrasives at equal weight’s filling Ka abrasives of different grain Ba.
Increasing of Pin during extrusion of environment improves processing’s conditions by increasing shear stress and flow rate of the medium and the velocity gradient.
Young’s modulus and Poisson’s ratio is characterized elastic properties of the working environment. Elastic
characteristics of the medium depend of degree of filling Ka and dispersion of the filler Ba. The numerical values of these indicators are needed when calculating the contact working environment with workpiece and evaluated by change in length l - l' and diameter d - d of sample of environment during its compression load F (fig. 3).
Guides axle 5 installed in bronze bushings of base 2 devices with interference, and in the sleeve weight plates 3 - with sliding landing. The sample of working environment is forming in the working cylinder of the experimental setup UESH 25, determined in a certain position that ensures its dimensional stability. The nominal diameter of the specimen before the deformation d =25 mm, the nominal length of the specimenbefore deformation l = 50 mm. Cross-sectional area of the sample - S = 0.00049 m2. Measuring the size of the sample was held by using calipers and micrometers.
The mass of weight plates and additional cargo were chosen so, that specimen is deformed predominantly elastically and linear dependence of its size on the applied load was carried. Total weight was 150 g. Waiting time was 3...10 seconds.
It is possible to experimentally determine their values, based on the definitions ofYoung’s modulus and Poisson’s ratio [:
F = ■
S
l
(I' -l) /1
where mload - massoftheappliedload.
Fig. 3. Device and circuit measurement ofYoung’s modulus and Poisson’s ratio environment: 1 - sample of the working environment; 2 - base adjustment; 3 - weight bracket; 4 - extra weight; 5 - steered axles; 6 - micrometer
Table 1
Dependence the coefficient " of Ba and Pin
№ Ba, mkm Pin, Mna ti, Ila-c
1 300 9,0 36,892
2 400 9,0 36,093
3 500 9,0 29,215
4 300 7,5 32,368
5 400 7,5 30,402
6 500 7,5 23,204
7 300 6,0 27,283
8 400 6,0 24,166
9 500 6,0 16,223
Table 2 shows the results of studies of Young’s modulus depending on the degree of the working media content and size of abrasive filler.
Experimentally determined (fig. 4) that an increase of Ka for more than 80 %, fixed abrasive in polymer-based environment is significantly reduced. This phenomenon leads to loss of yield and environmental fallout of grains of the polymer base that significantly impairs the conditions of abrasive-extrusion processing. Therefore, this figure was adopted for the boundary condition for the maximum degree of filling. The value ofPoisson’s ratio [ of the polymerbase without abrasive filler - 1.34, for filling among its experimentally measuredvalue varies inthe range 0.4.. .0.42.
Fig. 4. Dependence ofYoung’s modulus of the working environment on the degree of filling of abrasive grains and the quantity of abrasive filler
Young’s modulus E increases with the degree of filling and reduced dispersion of abrasive grains. This effect is explained with the help of the transformed Kargin-Slonimsky-Rous model [1], which is describe the working
environmentas avisco-plastic mediumfull of elastic chains formedby abrasive grains and the polymerbase.
In polymer-based unfilled chain abrasive grains are absent. Reduction of dispersion of the filler with the same mass filling leads to an increase in the number of abrasive grains in the medium. The greater the number of abrasive grains in the medium to longer chains occurs in the environment, length of segments which, in turn, decreases. Shorter segments of the chain cause its high elasticity and viscosity. The plasticity of the medium reduced.
To assess the cutting properties of the studied working media used the method of simplices with the same initial data and constraints, composition of the medium and Pm. The results of experimental studies abrasive extrusionprocessing showed that the optimum cutting ability, measured by the value of surface roughness after treatment or change in processing ARa, value of the material removed layer Ah, is achieved using a composition of the working environment in which the elasticity of the medium is maximal. The coefficients of viscosity and plasticity at the same time used to setthe boundary conditions abrasive extrusionprocessing specific details. Numerical indicators of viscosity, elasticity and plasticity of the working environment depends on the geometric characteristics of the processed channel and the requirements of the surface layer of detail.
The developed technique allowed to determine experimentally the flow rate m and the coefficient of
A J max
effective viscosity 3 of media of different compositions with abrasive flow machinig process, which can be used to calculate the pressure-spending environment characteristics in the processed channels.
The degree of influence of filling abrasive Ka, Ba quantities of abrasive grains and the inlet pressure Pin of viscous, elastic and plastic properties of the medium were set. With increasing Pin and content of abrasive in the medium Ka environmental factors 3 increases. This is due to the fact that with increasing shear rate more intensively destroyed the spatial structure of the medium. The effective viscosity, shear and normal stresses become larger. So for a mediumgrit Ba = 400 microns with Pin= 6 MPa - " = 24,166 Pa; with P. =9MPa - " =36,093 Pa, i. e. is65...70%more.
Table 2
Elastic characteristics of working environments
Ba, mkm Ka, % Young’s modulus Poisson’s ratio
0 0 22,760 1.34
320 30 97,955 0.411
320 50 119,600 0.411
320 66 124,300 0.411
320 75 128,250 0.411
320 80 132,500 0.411
400 30 40,480 0.40
400 50 59,200 0.40
400 66 65,100 0.40
400 75 70,400 0.40
400 80 73,100 0.40
500 30 27,000 0.42
500 50 37,000 0.42
500 66 42,000 0.42
500 75 46,000 0.42
500 80 51,000 0.42
Experimental determination of the coefficients of viscosity, elasticity and plasticity allows for the theoretical calculations of accuracy, productivity and quality abrasive extrusion processing. Obtained numerical values of the elastic-visco-plastic medium allow the choice of contact of abrasive grains [2]. Having established contact on the proposed methods [3; 4] it possible to calculate the performance of AFM and the roughness of the treated surface details.
Bibliography
1. Левко, В. А. Модель течения рабочей среды при абразивно-экс^узиожой обработке тонких осесимметричных каналов большой длины / В. А. Левко // Вестн.
Чебоксар гое. пед. ун-та. Механика недельного состояния : сб. науч. тр. / под ред. акад. Д. И. ^вдева; Ч^аш. гос. пед. ун-т. Чебоксары, 2008. № 2.P. 85-94.
2. Левко, В. А. Контактные процессы при абразивноэкструзионной обработке / В. А. Левко // Металлообработка. 2008. № 3 (45). P. 19-23.
3. Левко, В. А. Расчет шероховатости поверхности при абразивно-экструзионной обработке на основе модели контактных взаимодействий / В. А. Левко // Авиационная техника. Известия вузов / под ред. проф. В. А. Фирсова; Казан. гос. техн. ун-т. 2009. № 1.P 59-62.
4. Levko, V. A. Calculation of surface roughness in abrasive-extrusion machining on the basis of contactinteractionmodel/VA. Levko //RussianAeronautics. N. Y., 2009. Vol. 52, № 1.P. 94-98.
© Snetkov P. A., Levko V. A., PshenkoE. B., LubninM. A., 2009
N. F. Orlovskaya, D. A. Shupranov, Yu. N. Bezborodov, I. V Nadeykin SiberianFederal University, Russia, Krasnoyarsk
MODEL-BASED STUDY OF OXIDATION PROCESSES IN A JET ENGINE FUEL LIQUID PHASE
The process of oxidation in hexadecane liquid phase as a conventional model of oil hydrocarbons is investigated. The oxidation product structure is defined by means of Chromatography/Mass Spectrometry.
Keywords: high-temperature oxidation, hexadecane, oxygen-containing organic compounds, jet fuel.
Aviation kerosene is utilized in aircraft engines as a fuel and also as a coolant. Therefore, it should have the property of strong stability against high-temperature oxidation.
It would be of interest to investigate the processes flowing in high-temperaturejet engine fuel oxidation liquid phase.
Hexadecane (HD) is a conventional model of oil hydrocarbons (fig. 1).
12
Fig. 1.Hexadecane
Hexadecane behavior in the process liquid phase oxidation was investigated by various authors and by differentways of reactorthermostatting [1].
The term “high-temperature” oxidation is usually applied to the processes flowing at the temperatures of150to170 °C in case ofhexadecane oxidation.
Previous research [1] has established that HD oxidation flowing at high temperature is an exothermal process.
At a certain moment, the so-called time-limited “thermal explosion” takes place in oxidation [1]. After the end of exothermal stage, the oxidation progresses at a lower speed.
Under the assumption [2] it occurs owing to formation of polar nanophase (inverted microemulsion, “water in oil” -type) on the basis of primary and secondary hydrocarbons oxidation products.
The nucleus of such reversed micellar aggregate under the assumption [2] contains a small amount of mono- and polycarboxylic acids and alcohols (polyols). The average sphere includes mainly fragments of ethers and esters. The external sphere consists mainly oflong hydrocarbonchains providing stabilization of micelle in the non-polar hydrocarbon environment (fig. 2).
Changes of the oxidized hydrocarbon phase structure has been experimentally studied [2] indirectly, through a method for water-stain solubilization, for example, methylorange (MeOr).
Judging by changes in MeOr band position taking place with a rising hexadecane oxidation degree, the authors [2] have assumed that the localization of stain molecules in the oxidized hexadecane polar nanophase corresponds to a moderately polar oxidation product layer containing chemical bonds of type C-O-C, or similar ones.
Shift ofMeOr absorptionband in the process of increasing hexadecane oxidation degree has been obtained [2].
At the stage of deep oxidation the mechanism of reaction is especially complex. The prime oxidation products are generated. The physical and chemical properties of system are developed and they determine the system operational performance.
