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18TECHNICAL SCIENCES
SURFACE ROUGHNESS AFTER A COMBINED FLAT PERIPHERAL GRINDING
Gusev V.
Doctor of Technical Science, professor, professor, Institute of Engineering and Automobile Transport, Vladimir State University
Abstract
In article the way of the combined grinding of materials is described, which is protected by the patent of the Russian Federation. The multiple-factor experiment is performed; the regression equations, connecting the surface microgeometry with elements of the combined grinding regime, are determind. The received data confirm a possibility of carrying out at the same time preliminary and final grinding of details on one machine tool with providing surface microgeometry, obtained as at traditional grinding, without replacement coarse-grained on the finegrained tool, what allows to increase a productivity of processing.
Keywords: combined grinding, machined surface, multifactor model, cutting regime, roughness, fine-grain wheel, coarse-grain wheel.
1. Introduction
Among processes of workpieces machining the important part in formation of quality of a processed surface layer is assigned to grinding, which is continuously improved by discretisation of the cutting surface [1-3], texturing of grinding wheels by laser radiation [4-8] and by an estimates of their influence on dynamics of the processes [9] etc. High-porous grinding wheels [10], the grinding wheels without a linking of abrasive grains [11] are developed and investigated. Use of the called tools allows to reduce considerably a temperature in a cutting zone, therefore they are effectively used at grinding materials, inclined to formation of thermal defects.
Together with it also scientific researches for increasing of efficiency of technological operations of grinding by standard abrasive wheels, which cheaper and find broad application in mechanical engineering, are conducted. The processes of metals and alloys grinding by standard abrasive wheels, depending on the cutting regime, of the technological requirements to the microgeometry of processed surfaces (to roughness), are divided into preliminary and final. The task of preliminary machining is a removing the main overmeas-ure with the maximum possible productivity, and the task of final machining - a shaping the required geometry and the physic-mechanical state of the superficial layer. Preliminary and final grinding depending on a release program of details, are carried out on one machine tool (on one technological operation) with the substitution of the coarse on the fine-grain grinding wheel or on two machine tools (on two technological operations).
In the first case after the preliminary machining by a coarse grinding wheel the final machining by the fine-grain grinding wheel is performed, what leads to a need of replacing the coarse by the fine-grained grinding wheel.
Is required an expending of a much main and auxiliary time on performance of technological operation, removing of the coarse grinding wheel, mounting and fixing the fine-grain grinding wheel on the machine tool spindle, and so on. After the installation on the machine tool spindle the fine-grain grinding wheel is subject to balancing, and correction by a diamond pencil during the several passes. After that the fine-grained grinding wheel is adjusted on a given size. When the machining is performed on two grinding machine tools (on two operations), the substitution of the coarse on the fine-grain grinding wheel is not required.
After the preliminary machining it is necessary to move the workpiece to the second machine tool and fix in a working position. The described methods require a lot of auxiliary time, during which expensive manufacturing equipment stands idle, what leads to increasing of the manufacturing cost of details. In addition, the machining with using two operations requires a more of a production area for machine tools and also of a workers number.
The reduction of the workers number, the production area and of an auxiliary time is possible to reach or significantly to reduce, if the preliminary and final machining will be performed simultaneously on one grinding machine tool in accordance with a new, so-called, by method of combined grinding which is protected by patent [12]. Elimination of shortcomings of the known grinding technology is possible on the base of the combined grinding.
2. Performance of the combined peripheral grinding of a flat surface
The machining process by the combined grinding wheel is perfomed as follows. The fine-grain 1 and coarse-grain 2 grinding wheels (Fig. 1, a, b) are mounted on the spindle 3 of the grinding machine tool so, that the coarse-grain grinding wheel 2 is situated between a front support 4 of the spindle and the fine-grain grinding wheel 1.
a b
Fig. 1. Initial disposition of grinding wheels and workpiece on the machine tool before the machining (a) and a start of the workpiece grinding by the coarse grinding wheel (b).
At such disposition of the grinding wheels the fine-grain grinding wheel 1 is the most distant from the front support 4 of the spindle. The annular gasket 5 eliminates contact of the abrasive material of both grinding wheels. The workpiece 6 is mounted on a magnetic plate 7 and disposed behind of the coarse-grain grinding wheel 2 (we are looking from an operator 8, which whorks on the machine tool). For the preliminary machining of the workpiece the machine tool
is adjusted to remove of the overmeasure Z , for this
a spindle
with both grinding wheels is moving downstairs for a contact of the workpiece with a coarse-grain grinding wheel 2. .As a result, the wheels 1, 2 and the workpiece 6 occupy the initial position for the machining start (Fig. 1, a).
At the machining the spindle 3 with the wheels 1
and 2 rotates in the direction of the arrow Dr (Fig. 1, b), the workpiece 6 moves in the direction of longitudinal Dspr and cross feed Dsp.
a b
Fig. 2. Simultaneous machining with coarse and fine-grain grinding wheel (a) and final machining with a fine-grain grinding wheel (b).
The workpiece 6 is periodically moved to the operator 8, whereby the coarse grinding wheel 2 begins to contact with the workpiece 6 along the entire height, and then the fine-grain grinding wheel 1 comes into a work.
The fine-grain grinding wheel 1 removes the over-measure Z for the final machining. In this position of
the wheels 1, 2 and of the workpiece 6 simultaneously occurs the preliminary and final machining, i.e. the combined grinding. At further discrete displacement of workpiece to the left along the arrow D the wheels 1
and 2 finish the preliminary and final machining of the workpiece.
At high requirements to microgeometry of processed surfaces, combined grinding is finished after an additional pass of a fine-grain grinding wheel. During the additional pass the coarse grinding wheel does not concern workpiece (Fig. 2, b). Due to this, the final
grinding pass occurs without deterioration of surface microgeometry by the coarse grinding wheel, which is characteristic for the known grinding methods. At performing of the additional pass the table with the work-piece moves in direction of the arrow Dsp from operator 8 (Fig. 2, b). Based on the foregoing, the hypothesis, that the combined grinding provides a surface geometry no worse, than the traditional grinding by a fine-grain grinding wheel, was proposed.
To verify this hypothesis experimental researches of the roughness of surfaces, processed by the proposed and traditional grinding method, were carried out.
2. Experimental research method of the surface roughness At the combined grinding during experimental research of the surface roughness two grinding wheels were used, which were fixed on the spindle of a machine tool 3G71M.
The preliminary grinding was performed by a coarse grinding wheel 250*76*20 25AF46L8V5A2 GOST R52381-2005, GOST R52587-2006, and the final grinding by a wheel 250*76*10 25AF90K8V5A2. The cutting speed equal 35 m/s. At the traditional machining, the same machine tool, the same cutting regimes and grinding wheels were used, but with the replacement of the coarse grinding wheel by the fine-grain wheel.
To compare the microgeometry of surfaces subjected to grinding by the traditional and proposed methods, experiments were conducted using the known
technology at the upper, main and low levels of independent factors (Tab).
The steel 30XGSA with a hardness HRC 29,0 ... 35,5 was processed with using a coolant LACTVCA WBA 5400. The mean arithmetic deviation of a profile of the processed surface was measured by a device SJ-201P (Japan). The planning matrix of the full multifactorial experiment N = 23 = 8 was performed.
Table
Characteristics of independent factors
Levels and variation intervals of factors Independent factors
Overmeasure t, mm Longitudinal feed Spr,, m/min Cross feed Sp, mm/pass
Code and values of factors
Code Х2 Хз
Top level 0,015 14 6
Variation interval 0,005 5 2
Main level 0,010 9 4
Lower level 0,005 4 2
The thickness t of the overmeasure, taken off as a result of a table pass, the longitudinal feed Spr and the cross feed Sp of the workpiece, as the independent factors, were chosen.
4. Multifactorial model of the processed surface roughness
The models of surface roughness in a function of independent factors were obtained as a rezult of statistical data processing of the multifactorial experiment and the regression equation verification on adequacy by using the Fisher criterion. The interactive influence of the overmeasure thickness t and the longitudinal feed
Spr on the parameter Ra is described by the equation:
Ra = 0,1885+1,75t+0,0222Spr . (1)
The graphical interpretation of the equation (1) is represented by a 3D-
XYZ surface-graph (Fig. 3), at the left of which there is a column with four rectangles with numerical values of the processed surface roughness. The surface-graph has the different colors, what allows using the named rectangles for determining of the mean arithmetic deviation of profile of the for determining of the mean arithmetic deviation of profile of the processed surface for an arbitrary combinations of overmeasure and longitudinal feed.
I I > 0,5
I I < 0,45
I I < 0,35
I I < 0,25
/
Fig. 3. 3D-XYZ surface-graph of the interactive influence of the overmeasure thickness and longitudinal feed on the surface roughness after combined grinding
The influence of the longitudinal feed Spr and the cross feed Sp on the roughness of surface, processed by the combined grinding, is described by the equation:
Ra = 0,0135 + 0,0222Spr + 0,0481Sp.
(2)
(Fig. 4), at the left of which there is a column of six rectangles with numerical values of the treated surface roughness. The interactive influence of the cross-feed Sp and the overmeasure t on the. surface roughness after combined grinding is described by the regression equation:
The graphical interpretation of the equation (2) is represented by a 3D-XYZ surface-graph
R = 0,1963 + 1,751 + 0,0481Sp
(3)
The graphical interpretation of equation (3) is rep- surfaces (Fig. 3) - (Fig. 5) testifies, that the greatest in-resented by 3D-XYZ surface-graph (Fig. 5). The anal- fluence on the ysis of equations (2) - (4), of the 3D-XYZ graphical
■
□ □
> 0,6
< 0,55
< 0,45
< 0,35
< 0,25
< 0,15
Fig. 4. 3D-XYZ surface-graph of the interactive influence of the longitudinal and cross feed on the surface roughness after combined grinding
microgeometry of surfaces, processed by the combined grinding method, does the longitudinal feed of
the workpiece. On extent of influence on surface roughness after longitudinal feed are situated a cross-feed, then an overmeasure.
□ > 0,5
□ < 0,5
□ < 0,4
□ < 0,3
Fig. 5. 3D-XYZ surface-graph of the interactive influence of the cross feed and overmeasure on the surface roughness after combined grinding.
On extent of influence on roughness after longitudinal feed are situated a cross-feed and the thickness of overmeasure, removed during each pass of the table. The increase in of independent factors t, Spr, Sp causes an growth of the roughness, what is explained by a rise in the external load on each cutting grain and on the
technological system as a whole. The 3D-XYZ contours-graphs (Fig. 6 a, b) are important, because on their basis a regime of combined grinding is assigned with ensuring of the requirements to a roughness and at providing the maximum process productivity.
■o
o
6,5 6,0 5,5 5,0 4,5 4,0 3,5 3,0 2,5 2,0 1,5
> 0,6 < 0,525
2 4 6 8 10 12 14 16 0 < 0,425
I I < 0,325
Longitudinal feed □ < 0,225
0,016
0,014
^ 0,012
s
cs
e0,010 QJ
q 0,008
0,006
0,004
1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6.
Cross feed
a b
Fig. 6. 3D-XYZ contour-graph of the interactive influence of the cross-feed and the overmeasure on the surface roughness.
■ > 0,5
5 □ < 0,475 □ < 0,375
■ < 0,275
5. Analysis of the obtained results
The obtained mathematical models of microgeom-etry and the information contained in the 3D-XYZ graphs present the scientific basis for development of efficient technological processes of the combined grinding. As a result it was found, that the roughness after the combined grinding is significantly smaller, than at the coarse grinding wheel machining according to the known method, what is explained by the using of a tool with a larger grain size. At the same time, the roughness of a surface, processed by the fine-grain grinding wheel at known method, is lower on (6-8)%, than at combined grinding, what is explained by the simultaneous work of coarse and fine-grain grinding wheel and by more dynamic activity of the technological system due to the working of the coarse grinding wheel. The using of the additional pass at the combined grinding, during which only a fine-grain grinding wheel works, leads to reduction in roughness till the values, typical for the final traditional grinding.
Thus, the proposed grinding method allows simultaneously to perform the preliminary and the final machining of details on one grinding machine tool without replacement of grinding wheels. The combined grinding provides the microgeometry of the processed surfaces, as at final traditional grinding and allows significant reduction of main and auxiliary time for performance of technological operation, what leads to increasing of the machining productivity. The proposed schemes of the combined grinding and the results of roughness research of the processed surfaces are recommended to use at engineering of effective technological grinding operations of responsible details.
6. Conclusion
1. A new method of combined grinding has been developed, allowing simultaneously to carry out the preliminary and the final surface machining on one grinding machine tool.
2. The multifactor experimental researches are carried out, the mathematical models, connecting the roughness of processed surface with independent factors, are obtained, which serve as the scientific basis of an effective processes engineering of combined grinding.
3. The combined grinding provides the microge-ometry of the processed surfaces as at the final traditional grinding and allows significantly to reduce a main and auxiliary time on performance of technological operation, what leads to increasing of the machining productivity.
REFERENCES:
1. V.G. Gusev, A.V. Morozov, Flat Peripheral Grinding with Discrete Wheels. RF, Yoshkar-Ola, 2012.
2. A.V. Morozov, V.G. Gusev, Discrete Plane Face Grinding, Moscow, Pen Publishing House, 2016.
3. V.G. Gusev, A.V. Morozov, P.S. Shvagirev, Discrete structure of the cutting surface of a grinding wheel, J. Sci. Russian Engineering Research. 29(9) (2009) 940-943.
4. Hao Nan Li and Dragos Axinte, Textured grinding wheels: A review, Int. J. of Machine Tools and Manufacture,
http://dx.doi.org/10.1016/j.ijmachtools.2016.07.001
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7. P.W. Butler-Smith, D.A. Axinte, M. Daine, Solid diamond micro-grinding tools: From innovative design and fabrication to preliminary performance evaluation in Ti-6Al-4V, Int. J. of Machine Tools and Manufacture, 59(0) (2012) 55-64.
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11. Ju.N. Poljanchikov, Scientific bases of creation and application of the unicomponent abrasive tool
formed by pulse pressing and high-temperature sintering, Saratov, 2002.
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УДК 159.9:656.61
THE PROBABILITY OF OCCURRENCE OF A FAILURE IN THE SHIP'S ORGANIZATIONAL SYSTEM, CAUSED BY THE EFFECT OF FATIGUE WHILE WATCH KEEPING
Kukui F.
candidate of technical sciences, leading engineer of the transport logistic department
LLC Gazprom neft shelf
ВЕРОЯТНОСТЬ ПОЯВЛЕНИЯ СБОЯ В РАБОТЕ ОРГАНИЗАЦИОННОЙ СУДОВОЙ СИСТЕМЫ, ВЫЗВАННОЙ ЭФФЕКТОМ УСТАЛОСТИ ПРИ НЕСЕНИИ ВАХТЫ
Кукуи Ф.Д.
кандидат технических наук, ведущий инженер управления по транспортному обеспечению
ООО «Газпром нефть шельф»
Abstract
The aim of the work is to identify the key components of the phenomena of "human factor" and to identify effective ways to reduce its negative impact on the safety of navigator. The article deals with the features of the functioning of modern automated control systems of the ship and the processes of interaction with them navigator. It is shown that the problem of reducing the negative impact of the human factor is complex and should be solved by simultaneously improving the technical capabilities of automated systems in combination with the training of the crew. Special attention is paid to the study of probabilistic failure caused by professional deformation of the "accumulated fatigue - effect" type during the watchkeeping. A mathematical model of the process of accumulation of fatigue in the ship's specialist in the work place. The estimation of probability of failure in the organizational system of Watch keeping is made and the working formula of calculation of coefficient of readiness of system to such failure is offered. It is proved that the most affordable means of dealing with organizational failures is to reduce the rate of arrival of the state of the ship's specialist in the limit "tired" state. In the organizational system of watchkeeping, to remove the problem of failures due to fatigue of individual specialists, it is possible, for example, through the constant coordination of the capabilities of the "human element" and the requirements of the workplace.
Аннотация
Целью работы является выявление ключевых составляющих явлений «человеческий фактор» и определение эффективных путей снижения его негативного влияния на безопасность мореплавания. В статье рассмотрены особенности процесса функционирования современных автоматизированных систем управления судном и процессов взаимодействия с ними судоводителя. Показано, что проблема снижения негативного влияния человеческого фактора является комплексной и должна решаться одновременным совершенствованием технических возможностей автоматизированных систем в сочетании с подготовкой плавсостава. Особое внимание в работе уделено исследование вероятностного сбоя, вызванного профессиональной деформацией вида «накопленная усталость - эффект» при несении вахты. Составлена математическая модель процесса накопления усталости у судового специалиста на рабочем месте. Произведена оценка вероятности сбоя в организационной системе несения вахты и предложена рабочая формула подсчета коэффициента готовности системы к такому сбою. Доказано, что наиболее доступным средством борьбы с организационными сбоями является снижение скорости прихода состояния судового специалиста в предельное «усталое» состояние. В организационной системе несения вахты снять проблему сбоев, обусловленных усталостью отдельных специалистов, можно, например, за счет постоянного согласования возможностей «человеческого элемента» и требований к нему рабочего места.
Keywords: human element, human factor, accumulated fatigue, extreme situation, management efficiency, accident, psychological factor, professional deformation, professional portrait, failure.
Ключевые слова: Человеческий элемент, человеческий фактор, накопленная усталость, экстремальная ситуация, эффективность управления, авария, психологический фактор, профессиональный потрет, рабочее место, профессиональная деформация, сбой.
