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Usage of Abrasive Grains with Controllable Shapes as Means of Grinding Wheels Operation Stabilization
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Procedia Engineering 206 (2017) 188–193
International Conference on Industrial Engineering, ICIE 2017 International Conference on Industrial Engineering, ICIE 2017
Usage of Abrasive Grains with Controllable Shapes as Means of Grinding Wheels Usage of Abrasive Grains with Controllable Shapes as Means of Grinding Wheels Operation Stabilization Operation Stabilization N.V. Baidakova, T.N. Orlova* N.V. Baidakova, T.N. Orlova* Volzhsky Polytechnic Institute (branch) Volgograd State Technical University, 42a, Engelsa Street, Volzhsky 404121, Russia Volzhsky Polytechnic Institute (branch) Volgograd State Technical University, 42a, Engelsa Street, Volzhsky 404121, Russia
Abstract Abstract In general the efficiency of the grinding process depends on the effectiveness of the cutting ability of each individual grain. The better eachthe grain works, of thethe higher the performance of grinding is. The grain of geometry which is favorable for a particular In general efficiency grinding process depends on the effectiveness the cutting ability of each individual grain. case The may provide for the most efficient work of the grain. In turn, the geometry of the grain is determined by two main factors: the better each grain works, the higher the performance of grinding is. The grain geometry which is favorable for a particular case shape and its for position in theefficient tool body (grinding wheel).InInturn, Volzhsky Polytechnic Institute of Volgograd Statefactors: Technical may provide the most work of the grain. the geometry of the grain is(branch) determined by two main the University in position the SECin “Volzhsky Scientific-Research Institution of Abrasive Grinding” the(branch) new technology of theState production of shape and its the tool body (grinding wheel). In Volzhsky Polytechnic Institute of Volgograd Technical an abrasiveintool It allows both stabilizing its operation managing its performance at the manufacturing stage by University thewas SECmade. “Volzhsky Scientific-Research Institution of and Abrasive Grinding” the new technology of the production of improving the was classification processboth of grinding grain, only byand its managing size but also its the shape. an abrasiveoftool made. It allows stabilizing its not operation its by performance at the manufacturing stage by © 2017 The Authors. Publishedprocess by Elsevier B.V. grain, not only by its size but also by its the shape. improving the classification of grinding © 2017 Theofunder Authors. Published by Elsevier Ltd. Peer-review responsibility of Elsevier the scientific of the International Conference on Industrial Engineering. © 2017 The Authors. Published by B.V. committee Peer-review under responsibility of the scientific committee of the International Conference on Industrial Engineering Keywords: abrasive; grinding; shape of a grain. Peer-review under responsibility of the scientific committee of the International Conference on Industrial Engineering. Keywords: abrasive; grinding; shape of a grain.
1. Introduction 1. Introduction Currently, grinding places about 20% of all kinds of mechanical processing. In general mechanical engineering about 10 ÷ 12% of machine tools 20% are grinding ones,ofinmechanical the car producing industry - 25%, and in engineering the bearing Currently, grinding places about of all kinds processing. In general mechanical industryto 55of÷machine 60%. Therefore, issuesones, related of grinding considered bebearing highly about 10 up ÷ 12% tools are the grinding in to thethe carmethod producing industry are - 25%, and intothe relevant industry-ones. up to 55 ÷ 60%. Therefore, the issues related to the method of grinding are considered to be highly relevant ones.
* Corresponding author. Tel.: +7-937-545-7602; fax: +7-844-327-5732. address:author. [email protected] * E-mail Corresponding Tel.: +7-937-545-7602; fax: +7-844-327-5732.
E-mail address: [email protected] 1877-7058 © 2017 The Authors. Published by Elsevier B.V. Peer-review the scientific committee 1877-7058 ©under 2017responsibility The Authors. of Published by Elsevier B.V.of the International Conference on Industrial Engineering . Peer-review under responsibility of the scientific committee of the International Conference on Industrial Engineering .
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the International Conference on Industrial Engineering. 10.1016/j.proeng.2017.10.458
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N.V. Baidakova et al. / Procedia Engineering 206 (2017) 188–193 N.V. Baidakova, T.N. Orlova / Procedia Engineering 00 (2017) 000–000
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2. Relevance Frequently any process of grinding is very unstable. It is due to changes in cutting characteristics of tool during its operation [1-23]. Therefore the grinding process becomes more complicated and requires the permanent correction of the tool and its operation modes. In this connection, the issues are related to the creation of a tool which composition would include grains with controlled shapes have the significant relevance. It would let us create the tool with regimented characteristics, the stable indicators of the grinding process and the possibility of its usage for the work with CNC machines. 3. The formulation of the problem One of the main reasons of the decreasing of the grinding efficiency is that the tool is made of grinding grains of an arbitrary shape. As a result many grains participate poorly or do not participate at all in the overall process of cutting because of unfavorable geometry of their cutting wedges. Some attempts were taken to solve this problem for grinding belts with the help of the orientations of long axis of a grain perpendicular to the basis with the help of electrostatics. In this research we study how the physico-mechanical properties of initial materials influence the production of abrasive grains, in particular - the material of the aluminothermic production of niobium [23]. As we can conclude from practice, the effect of this measure is quite good. However this approach may provide only a partial solution of the problem, as the second factor, forming of the geometry of the cutting grain wedge, i.e. its shape, remains unmanageable. If this factor is taken into consideration and is purposefully varied, it will become possible to achieve a better effect of the usage of each grain. Traditionally,the form of particles is divided into two classes: isometric and non isometric. The particles, having a ratio of geometric dimensions l/h2, where l - length, and h - width or height, are considered to be isometric. A medium-grained fraction (from 200 to 800 micrometers) in the white electrocorundum contains 50-65% of isometric particles; fine grained ones (50 to 160 microns) - 25-45%. This correlation is common for other types of abrasive materials as well. All isometric particles, that satisfy the condition l/h2, have the pretty same form and volumetric figure. Non isometric part of the material is represented by the set of the diverse shapes of particles: tubulars having a significant thickness, thin tubulars, acicular, etc. [1,2,5,6,8,9,12,13,17]. We created the computer program for the analysis of different shapes of grains. With the help of this program we investigated the abrasive materials produced at JSC “Boksitogorsk alumina”. The analysis of the results of the research let us make the following conclusions: grain distribution according to the shape depends on the brand, technology of manufacturing and abrasive grit; the bulk of the grain has so-called intermediate (2l/h3) shape, the rest of grains has isometric (l/h2) and tabulate (l/h3) shape. Such inequality of grain shapes influences on the production of each grain, because the difference in shapes leads to the difference in the geometry of their cutting edges, and, hence, influences on the ability to cut off the shavings. 4. The results of the experimental studies The research on the cutting ability and strength of individual abrasive grains with different shapes shows the following: The experiments which were made to determine the cutting ability of individual grains were implemented on the surface grinder 3G71 model where a disc with a grain was fixed on the spindle, the cutting conditions were following ones: the rotational speed of the disc V = 30 m / s; longitudinal feed S = 0,20 m / min; the depth of the cut t = 0,04 mm. To hold the experiments we selected grains 13A125 (JSC “Boksitogorsk alumina”) with isometric and intermediate tubular shapes (which were alternately and individually fixed on the metal disk, simulating a grinding tool). The orientation angle ( ) of abrasive grains of the disk was changed according to the cutting direction varied from 15° to + 90°.
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The rectangular samples with dimensions L×B×H = 20×20×10 mm made of steel St3 (HB 111) were used as the workpieces. The number of passes in all cases (to one side) was N = 20. The results of the experiments show the following: individual grains of tubular shape have the highest cutting ability, and the grains of isometric shape - the lowest one; the angle of orientation of individual abrasive grains, at which the cutting capacity is maximum ranges from 60° to 90°. The study of the picture of stresses in models of individual grains with different shapes obtained by finite element method with the help of the program «MSC / NASTRAN» let us conclude the following: grains that get the load by their sharpened parts have the maximum voltage near their peaks, it promotes the spalling of small particles and therefore the self-sharpening of the grains; grains that get the load by their flat parts, have the maximum voltage near the areas of their engagement into binder, that promotes their tearing of the binder; the feature of loading of isometric (near to spherical) particle model is a point character of load applications that can lead grains to be pulled out from the binder, by a sufficiently large force, and can provoke the destruction of the grain. Isometric grains, taken under the equal conditions, have a greater strength; for the completeness of study of this issue, a regenerated abrasive material was included in the list of the materials used for the creation of recipes. The research of this material proved the conclusions had been obtained before. Thus, the results of the modeling showed that the grain shape affects the level of the stress arising therein during the operation and therefore influences on the grain strength. For the practical assessment of the impact strength of individual abrasive grains with different shape the test method of swinging load was applied. To make the testing with the help of this equipment the normal electrocorundum of the brand 13A with the value of grit 125, 100, 80 of JSC “Boksitogorsk alumina”, as well as the normal electrocorundum of marks NK F24 (Germany) with the grit value of 80 were used. The grains had isometric, intermediate and tubular shapes. We took the angle of the inclination () of grains with the respect to the horizontal tubular as 75 ° in the direction of impact. The analysis of the obtained results showed that with the changes in the shape of the grains from tabulate to isometric one the impact index of an individual grinding grain is reduced. Currently, the grinding belts on elastic basis with the oriented grains of different shape are produced commercially in large quantities (Fig. 1).
Fig. 1. Abrasive particle shape:(а) isometric particles (b) non isometric (lamellar) particles.
The orientation of grains by large geometric axis with the respect to the treated surface leads to the reduction of grain sharpening angles and hence to the decrease in the radii of rounding of vertices (the larger grain axis corresponds to a smaller angle at the vertex and the smaller radius of rounding) (Fig. 2).
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Fig. 2. Schematic illustration of cross-section grinding skins: (a) entire coating with grains of different shapes; (b) with an ordered arrangement of single grains of different shapes; (c) with ordered arrangement of grains non-isometric forms (tubular and acicular) (1-abrasive grain; 2-binder; 3lastic-flexible base).
In comparison with the tools with randomly arranged grains, the tools with an ordered arrangement of the grains on the working surface have some advantages: the better cutting properties; the greater processing capacity; the best output of processing products; better conditions of lubricating coolant submission to the cutting area; lower cutting forces and temperature during grinding; greater flexibility; significant savings of an abrasive material. Due to its geometric orientation the abrasive grains of acicular and lamellar shapes are set to treated surface by their the most sharp peaks, that have smaller radii of rounding of vertices and thus it improves the cutting corners. The assessment of the influence of the shape and the orientation of grains on the performance of grinding belts demonstrates that the cutting ability of the experimental belts with lamellar grains and orientation angle = 75 is higher than the performance of other belts in all the cases. The cutting ability of this type of belt is better that the one of the standard belt (GOST) by 30÷40%. For belts that contain grains of isomentric shape, this parameter is lower, than the one of the standard belt by 25÷30%. In the process of the processing of steel grades 20H13 and ShH15 we got the similar pattern of results. The results of the research on belts wearout (by gravimetric method) show that the wear of the experimental belts with isometric grains is always lower than the wearout of the belts with other varieties of grain shapes. This type of belts has less wear in comparison with the wear of the standard belt (GOST) in 1,3÷1,4 times. Belts that contain grain with tubular shape and orientation = 75 has the increased wearout. In this case it is higher than the wearout of the standard belt (GOST) by 35% in average. The research of the roughness of the surfaces of the parts after their processing by belts with different shapes and orientation of the grains shows that the roughness of the surface obtained by the experimental belts with lamellar grains is higher than the roughness received by the usage of the standard belt (GOST) by 20 ÷ 30%, and lower by 15 ÷ 20% then the roughness received by isometric grains. The laboratory tests have shown that the use of grains with the controllable shape can significantly increase the efficiency of the tool in comparison with the efficiency of the standard tool. It is necessary to note, that the choice of the particular shape and orientation of the grains depends on the particular task. For example, if the high grinding performance is the main task, non-isometric grain will be expedient to be used in the grinding belts. This shape of grains provides the increase of the cutting ability of a tool by 30÷40%. If the main task is to decrease the roughness of the processing, it would be better to choose grains with isometric shape which when other conditions are equal, ensure the reduction of roughness by 15 ÷ 20%. At JSC «EPK-SHAR» production conditions the tests of grinding wheels made of conventional grains 24 A16 and grains 24 A16 with the controllable shape were conducted. All of the wheels were produced in the laboratory of Volzhsky Institute of Civil Engineering. The wheels were made of the grains taken from the same party of electrocorundum, based on the same binder and produced by the same technology (identical temperature, firing time, mixing time and so on.), which ensured the equal initial conditions for the testing implementation. The wheels were tested on the operations of final grinding of track and bottom of rings of bearings 205 on the machines DLZ-80. The produced wheels were 4086, 24А16СМ16К5grade. In the process of the production testing of the experimental grinding wheels the operating parameters of the parts machining process met the requirements of the technological processes used at the enterprise. For the testing we used the wheels with different shapes of abrasive grains: initial (unsorted), isometric (close to spherical), lamellar and acicular ones.
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As output parameters we controlled the dimensional wearout of wheel and the roughness of the tracks of the bearing. The wearout of wheels was controlled stepwise through each 10 rings at three different points and then was averaged. The results of the measuring of the experimental wheels’ dimensional wearout and the determination of the number of rings, produced by them without any defect are reflected in the Table 1. Table 1. The results of measuring of the size deterioration and the results of determining of the number of rings of the experimental wheels. Shape of a grain
Average dimensional wear of wheel, , mm
The number of rings produced by a wheel without any defect
Acicular
35,55 – 35,44
3
Lamellar
35,14 – 35,07
10
Initial
36,23 – 36,17
36
Isometric
35,89 – 35,86
38
Based on the Table 1 we may conclude that with the change of the shape of a grain from acicular to isometric the dimensional wear of a wheel decreases. (from 0,11 mm to 0,03 mm per 50rings) and the quantity of the parts produced without defect increases. (from 3 to 38). The results of the measurement of the roughness of the bearing traces of the rings of bearing, got by the method of taking of the impressions of the investigated surface (three-time measurements on each surface) and their study with the MIS-11 microscope are shown in Table 2. For the comparison there are also the results taken by a standard wheel 4088 25А12ПСМ16К5, that is usually used in such operations. From the Table 2 It may be concluded that the roughness of the treated surface is directly dependent on the predominant shape of grains in the disc. The roughness is less if the grains are isometric. With the change of grain shape from isometric to lamellar - the roughness increases in about 4 times. If we make the comparison with the wheel produces from initial (unsorted) grain, we will see that by the usage of the isometric shape of grains we may achieve the reduction of the roughness in 3 times. Table 2. The dependence of the roughness of the machined surface on grain shapes. Shape of grain
Seediness
Acicular
0,5-0,63
Lamellar
0,4-0,5
Initial
0,4-0,5
Isometric
0,125-0,16
Standard
0,2-0,25
5. Conclusion Thus, the implemented research let us conclude that the shape of a grain significantly influences on the performance characteristics of abrasive tools. The differentiated approach to the realization of benefits of grains classified by their shape significantly increases the efficiency of the grinding process, because the application of this approach let us get a new, high quality abrasive tool which is more homogeneous according to its sanding properties. Acknowledgement I am glad to have a chance to share my scientific ideas with colleagues from different countries. This opportunity was given to me by the team of International Conference on Industrial Engineering, ICIE 2017. I am thankful to all of you. As far as my personal scientific achievements are concerned I would like to express my sincere gratitude to
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my supervisor Dr. V.M. Shumiacher, who was helping me in the process of the creation of the thesis for the degree of candidate of science and who is still supporting me. With his help I started to work on my Doctoral thesis 3 years ago. If my article is published in Elsevier, it will encourage me and my colleague T.N. Orlova to continue working in this direction. References [1] N.V. Baidakova, Improving the efficiency of grinding by use of a tool made of classified by size and shape of the abrasive grain: thesis for the degree of Candidate of Technical Sciences, Saratov, 2006. [2] A.N. Korotkov, Operational properties of abrasive materials, Edition of Krasnoyarsk University, Krasnoyarsk, 1992. [3] A.N. Reznikov, Abrasive and diamond material processing, Mashinostroenie, Moscow, 1977. [4] S.A. Kryukov, A.V. Slavin, N.V. Baidakova, Predicting of the mechanical strength of the abrasive composites, Manufacturing Engineering. 10 (2013) 31–32. [5] N.V. Baidakova, S.A. Kryukov, A.V. Slavin, Effect of shape and grain of the abrasive grain on the efficiency of the grinding process, Heavy engineering. 3-4 (2016) 35–37. [6] N.V. Baidakova, S.A. Kryukov, The influence of the shape and grain of the abrasive grains on the grinding efficiency. In the Proceedings of the International Scientific and Technical Conference "Shlifabraziv 2014". (2014) 106–110. [7] N.V. Baidakova, S.A. Kryukov, System-integrated methodology for improving abrasive tools, In the Proceedings of International Scientific and Technical Conference "Shlifabraziv 2014". (2014) 110–114. [8] N.V. Baidakova, S.A. Kryukov, The effect of the form of the abrasive grains to the cutting tool's ability in the process of roughing operations In the Proceedings of Collection All-Russian youth scientific conference. (2014) 475–478. [9] N.V Baidakova, V.A. Nazarenko, Mathematical modeling of vibratory separation of the abrasive grain particles according to their size, In the Proceedings of International Scientific and Technical Conference hold by Volzhsky Institute of Construction and Technology (branch) of Volgograd State University of Architecture and Civil Engineering. (2012) 17–21. [10] S.A, Kryukov, V.M. Shumyacher, Improved stability and efficiency of abrasive tools, LAP LAMBERT Academic Publishing, Saarbrücken, 2013. [11] V.M. Shumyacher, A.V. Slavin, S.A. Kryukov, Basics of highly efficient abrasive tools, Edition of Volgograd State University of Architecture and Civil Engineering, 2015. [12] N.V. Baidakova, S.A. Kryukov, Study of the influence of abrasive grain on the quality of grinding tools, In the Proceedings of the International Conference dedicated to the 60th anniversary of the university education. (2012) 27–30. [13] N.V. Baidakova, S.A. Kryukov, The Influence of granularity and shape of abrasive grains on grinding efficiency, In the Proceedings of International Scientific and Technical Conference hold by Volzhsky Institute of Construction and Technology (branch) of Volgograd State University of Architecture and Civil Engineering. (2012) 96–99. [14] V.I. Kurdyukov, Scientific basis for the design, manufacture and operation of abrasive tool: thesis for the degree of doctor of technical sciences, Kurgan, 2000. [15] V.I. Ostrovsky, Theoretical bases of the grinding process, Leningrad State University, Leningrad, 1981. [16] A.V. Korolev, Yu.K. Novoselov, Theoretic probability foundations of abrasion. Status of working surface of the tool, Saratov University Press, Saratov, 1987. [17] S.G. Redko, A.V. Korolev, Location of abrasive grains on the working surface of the grinding wheel, Machines and tools. 5 (1970) 40–41. [18] A.K. Baikalov, The introduction to the theory of the grinding of materials, Naukova dumka, Kiev, 1978. [19] W. Konig, W. Lorts, Proherties of cutting edges related to chip formation in griding, CIRP. 24 (1975) 231–235. [20] P.E. Dyachenko, Study of the grinding process, Mashgiz, Moscow, 1941. [21] S.A. Kryukov, A.V. Slavin, Ways of improving of the structural and mechanical characteristics and efficiency of abrasive tools, Edition of Volgograd State University of Architecture and Civil Engineering, Volgograd, 2016. [22] I.Yu. Orlov, T.N. Orlova, V.M. Shumyacher, Improving of the efficiency of the operation grinding of butt of steels by a bakelite tool by selecting fillers that reduce the calorific process, Engineering journal. 6 (2015) 7–10. [23] T.N.Orlova, V.M. Shumyacher, I.Yu. Orlov, A.E. Zhumakanov, Slag aluminothermic production of niobium - a new abrasive material in the manufacture of abrasive tools XXI century: innovative technologies in metallurgy. Problems. Prospects, In the Proceedings of International scientific-practical conference dedicated to the 80th anniversary of the famous metallurgist Akhat Salemhatovich Kulenov. (2012) 143–146.
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Procedia Engineering 206 (2017) 188–193
International Conference on Industrial Engineering, ICIE 2017 International Conference on Industrial Engineering, ICIE 2017
Usage of Abrasive Grains with Controllable Shapes as Means of Grinding Wheels Usage of Abrasive Grains with Controllable Shapes as Means of Grinding Wheels Operation Stabilization Operation Stabilization N.V. Baidakova, T.N. Orlova* N.V. Baidakova, T.N. Orlova* Volzhsky Polytechnic Institute (branch) Volgograd State Technical University, 42a, Engelsa Street, Volzhsky 404121, Russia Volzhsky Polytechnic Institute (branch) Volgograd State Technical University, 42a, Engelsa Street, Volzhsky 404121, Russia
Abstract Abstract In general the efficiency of the grinding process depends on the effectiveness of the cutting ability of each individual grain. The better eachthe grain works, of thethe higher the performance of grinding is. The grain of geometry which is favorable for a particular In general efficiency grinding process depends on the effectiveness the cutting ability of each individual grain. case The may provide for the most efficient work of the grain. In turn, the geometry of the grain is determined by two main factors: the better each grain works, the higher the performance of grinding is. The grain geometry which is favorable for a particular case shape and its for position in theefficient tool body (grinding wheel).InInturn, Volzhsky Polytechnic Institute of Volgograd Statefactors: Technical may provide the most work of the grain. the geometry of the grain is(branch) determined by two main the University in position the SECin “Volzhsky Scientific-Research Institution of Abrasive Grinding” the(branch) new technology of theState production of shape and its the tool body (grinding wheel). In Volzhsky Polytechnic Institute of Volgograd Technical an abrasiveintool It allows both stabilizing its operation managing its performance at the manufacturing stage by University thewas SECmade. “Volzhsky Scientific-Research Institution of and Abrasive Grinding” the new technology of the production of improving the was classification processboth of grinding grain, only byand its managing size but also its the shape. an abrasiveoftool made. It allows stabilizing its not operation its by performance at the manufacturing stage by © 2017 The Authors. Publishedprocess by Elsevier B.V. grain, not only by its size but also by its the shape. improving the classification of grinding © 2017 Theofunder Authors. Published by Elsevier Ltd. Peer-review responsibility of Elsevier the scientific of the International Conference on Industrial Engineering. © 2017 The Authors. Published by B.V. committee Peer-review under responsibility of the scientific committee of the International Conference on Industrial Engineering Keywords: abrasive; grinding; shape of a grain. Peer-review under responsibility of the scientific committee of the International Conference on Industrial Engineering. Keywords: abrasive; grinding; shape of a grain.
1. Introduction 1. Introduction Currently, grinding places about 20% of all kinds of mechanical processing. In general mechanical engineering about 10 ÷ 12% of machine tools 20% are grinding ones,ofinmechanical the car producing industry - 25%, and in engineering the bearing Currently, grinding places about of all kinds processing. In general mechanical industryto 55of÷machine 60%. Therefore, issuesones, related of grinding considered bebearing highly about 10 up ÷ 12% tools are the grinding in to thethe carmethod producing industry are - 25%, and intothe relevant industry-ones. up to 55 ÷ 60%. Therefore, the issues related to the method of grinding are considered to be highly relevant ones.
* Corresponding author. Tel.: +7-937-545-7602; fax: +7-844-327-5732. address:author. [email protected] * E-mail Corresponding Tel.: +7-937-545-7602; fax: +7-844-327-5732.
E-mail address: [email protected] 1877-7058 © 2017 The Authors. Published by Elsevier B.V. Peer-review the scientific committee 1877-7058 ©under 2017responsibility The Authors. of Published by Elsevier B.V.of the International Conference on Industrial Engineering . Peer-review under responsibility of the scientific committee of the International Conference on Industrial Engineering .
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the International Conference on Industrial Engineering. 10.1016/j.proeng.2017.10.458
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N.V. Baidakova et al. / Procedia Engineering 206 (2017) 188–193 N.V. Baidakova, T.N. Orlova / Procedia Engineering 00 (2017) 000–000
189
2. Relevance Frequently any process of grinding is very unstable. It is due to changes in cutting characteristics of tool during its operation [1-23]. Therefore the grinding process becomes more complicated and requires the permanent correction of the tool and its operation modes. In this connection, the issues are related to the creation of a tool which composition would include grains with controlled shapes have the significant relevance. It would let us create the tool with regimented characteristics, the stable indicators of the grinding process and the possibility of its usage for the work with CNC machines. 3. The formulation of the problem One of the main reasons of the decreasing of the grinding efficiency is that the tool is made of grinding grains of an arbitrary shape. As a result many grains participate poorly or do not participate at all in the overall process of cutting because of unfavorable geometry of their cutting wedges. Some attempts were taken to solve this problem for grinding belts with the help of the orientations of long axis of a grain perpendicular to the basis with the help of electrostatics. In this research we study how the physico-mechanical properties of initial materials influence the production of abrasive grains, in particular - the material of the aluminothermic production of niobium [23]. As we can conclude from practice, the effect of this measure is quite good. However this approach may provide only a partial solution of the problem, as the second factor, forming of the geometry of the cutting grain wedge, i.e. its shape, remains unmanageable. If this factor is taken into consideration and is purposefully varied, it will become possible to achieve a better effect of the usage of each grain. Traditionally,the form of particles is divided into two classes: isometric and non isometric. The particles, having a ratio of geometric dimensions l/h2, where l - length, and h - width or height, are considered to be isometric. A medium-grained fraction (from 200 to 800 micrometers) in the white electrocorundum contains 50-65% of isometric particles; fine grained ones (50 to 160 microns) - 25-45%. This correlation is common for other types of abrasive materials as well. All isometric particles, that satisfy the condition l/h2, have the pretty same form and volumetric figure. Non isometric part of the material is represented by the set of the diverse shapes of particles: tubulars having a significant thickness, thin tubulars, acicular, etc. [1,2,5,6,8,9,12,13,17]. We created the computer program for the analysis of different shapes of grains. With the help of this program we investigated the abrasive materials produced at JSC “Boksitogorsk alumina”. The analysis of the results of the research let us make the following conclusions: grain distribution according to the shape depends on the brand, technology of manufacturing and abrasive grit; the bulk of the grain has so-called intermediate (2l/h3) shape, the rest of grains has isometric (l/h2) and tabulate (l/h3) shape. Such inequality of grain shapes influences on the production of each grain, because the difference in shapes leads to the difference in the geometry of their cutting edges, and, hence, influences on the ability to cut off the shavings. 4. The results of the experimental studies The research on the cutting ability and strength of individual abrasive grains with different shapes shows the following: The experiments which were made to determine the cutting ability of individual grains were implemented on the surface grinder 3G71 model where a disc with a grain was fixed on the spindle, the cutting conditions were following ones: the rotational speed of the disc V = 30 m / s; longitudinal feed S = 0,20 m / min; the depth of the cut t = 0,04 mm. To hold the experiments we selected grains 13A125 (JSC “Boksitogorsk alumina”) with isometric and intermediate tubular shapes (which were alternately and individually fixed on the metal disk, simulating a grinding tool). The orientation angle ( ) of abrasive grains of the disk was changed according to the cutting direction varied from 15° to + 90°.
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The rectangular samples with dimensions L×B×H = 20×20×10 mm made of steel St3 (HB 111) were used as the workpieces. The number of passes in all cases (to one side) was N = 20. The results of the experiments show the following: individual grains of tubular shape have the highest cutting ability, and the grains of isometric shape - the lowest one; the angle of orientation of individual abrasive grains, at which the cutting capacity is maximum ranges from 60° to 90°. The study of the picture of stresses in models of individual grains with different shapes obtained by finite element method with the help of the program «MSC / NASTRAN» let us conclude the following: grains that get the load by their sharpened parts have the maximum voltage near their peaks, it promotes the spalling of small particles and therefore the self-sharpening of the grains; grains that get the load by their flat parts, have the maximum voltage near the areas of their engagement into binder, that promotes their tearing of the binder; the feature of loading of isometric (near to spherical) particle model is a point character of load applications that can lead grains to be pulled out from the binder, by a sufficiently large force, and can provoke the destruction of the grain. Isometric grains, taken under the equal conditions, have a greater strength; for the completeness of study of this issue, a regenerated abrasive material was included in the list of the materials used for the creation of recipes. The research of this material proved the conclusions had been obtained before. Thus, the results of the modeling showed that the grain shape affects the level of the stress arising therein during the operation and therefore influences on the grain strength. For the practical assessment of the impact strength of individual abrasive grains with different shape the test method of swinging load was applied. To make the testing with the help of this equipment the normal electrocorundum of the brand 13A with the value of grit 125, 100, 80 of JSC “Boksitogorsk alumina”, as well as the normal electrocorundum of marks NK F24 (Germany) with the grit value of 80 were used. The grains had isometric, intermediate and tubular shapes. We took the angle of the inclination () of grains with the respect to the horizontal tubular as 75 ° in the direction of impact. The analysis of the obtained results showed that with the changes in the shape of the grains from tabulate to isometric one the impact index of an individual grinding grain is reduced. Currently, the grinding belts on elastic basis with the oriented grains of different shape are produced commercially in large quantities (Fig. 1).
Fig. 1. Abrasive particle shape:(а) isometric particles (b) non isometric (lamellar) particles.
The orientation of grains by large geometric axis with the respect to the treated surface leads to the reduction of grain sharpening angles and hence to the decrease in the radii of rounding of vertices (the larger grain axis corresponds to a smaller angle at the vertex and the smaller radius of rounding) (Fig. 2).
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Fig. 2. Schematic illustration of cross-section grinding skins: (a) entire coating with grains of different shapes; (b) with an ordered arrangement of single grains of different shapes; (c) with ordered arrangement of grains non-isometric forms (tubular and acicular) (1-abrasive grain; 2-binder; 3lastic-flexible base).
In comparison with the tools with randomly arranged grains, the tools with an ordered arrangement of the grains on the working surface have some advantages: the better cutting properties; the greater processing capacity; the best output of processing products; better conditions of lubricating coolant submission to the cutting area; lower cutting forces and temperature during grinding; greater flexibility; significant savings of an abrasive material. Due to its geometric orientation the abrasive grains of acicular and lamellar shapes are set to treated surface by their the most sharp peaks, that have smaller radii of rounding of vertices and thus it improves the cutting corners. The assessment of the influence of the shape and the orientation of grains on the performance of grinding belts demonstrates that the cutting ability of the experimental belts with lamellar grains and orientation angle = 75 is higher than the performance of other belts in all the cases. The cutting ability of this type of belt is better that the one of the standard belt (GOST) by 30÷40%. For belts that contain grains of isomentric shape, this parameter is lower, than the one of the standard belt by 25÷30%. In the process of the processing of steel grades 20H13 and ShH15 we got the similar pattern of results. The results of the research on belts wearout (by gravimetric method) show that the wear of the experimental belts with isometric grains is always lower than the wearout of the belts with other varieties of grain shapes. This type of belts has less wear in comparison with the wear of the standard belt (GOST) in 1,3÷1,4 times. Belts that contain grain with tubular shape and orientation = 75 has the increased wearout. In this case it is higher than the wearout of the standard belt (GOST) by 35% in average. The research of the roughness of the surfaces of the parts after their processing by belts with different shapes and orientation of the grains shows that the roughness of the surface obtained by the experimental belts with lamellar grains is higher than the roughness received by the usage of the standard belt (GOST) by 20 ÷ 30%, and lower by 15 ÷ 20% then the roughness received by isometric grains. The laboratory tests have shown that the use of grains with the controllable shape can significantly increase the efficiency of the tool in comparison with the efficiency of the standard tool. It is necessary to note, that the choice of the particular shape and orientation of the grains depends on the particular task. For example, if the high grinding performance is the main task, non-isometric grain will be expedient to be used in the grinding belts. This shape of grains provides the increase of the cutting ability of a tool by 30÷40%. If the main task is to decrease the roughness of the processing, it would be better to choose grains with isometric shape which when other conditions are equal, ensure the reduction of roughness by 15 ÷ 20%. At JSC «EPK-SHAR» production conditions the tests of grinding wheels made of conventional grains 24 A16 and grains 24 A16 with the controllable shape were conducted. All of the wheels were produced in the laboratory of Volzhsky Institute of Civil Engineering. The wheels were made of the grains taken from the same party of electrocorundum, based on the same binder and produced by the same technology (identical temperature, firing time, mixing time and so on.), which ensured the equal initial conditions for the testing implementation. The wheels were tested on the operations of final grinding of track and bottom of rings of bearings 205 on the machines DLZ-80. The produced wheels were 4086, 24А16СМ16К5grade. In the process of the production testing of the experimental grinding wheels the operating parameters of the parts machining process met the requirements of the technological processes used at the enterprise. For the testing we used the wheels with different shapes of abrasive grains: initial (unsorted), isometric (close to spherical), lamellar and acicular ones.
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As output parameters we controlled the dimensional wearout of wheel and the roughness of the tracks of the bearing. The wearout of wheels was controlled stepwise through each 10 rings at three different points and then was averaged. The results of the measuring of the experimental wheels’ dimensional wearout and the determination of the number of rings, produced by them without any defect are reflected in the Table 1. Table 1. The results of measuring of the size deterioration and the results of determining of the number of rings of the experimental wheels. Shape of a grain
Average dimensional wear of wheel, , mm
The number of rings produced by a wheel without any defect
Acicular
35,55 – 35,44
3
Lamellar
35,14 – 35,07
10
Initial
36,23 – 36,17
36
Isometric
35,89 – 35,86
38
Based on the Table 1 we may conclude that with the change of the shape of a grain from acicular to isometric the dimensional wear of a wheel decreases. (from 0,11 mm to 0,03 mm per 50rings) and the quantity of the parts produced without defect increases. (from 3 to 38). The results of the measurement of the roughness of the bearing traces of the rings of bearing, got by the method of taking of the impressions of the investigated surface (three-time measurements on each surface) and their study with the MIS-11 microscope are shown in Table 2. For the comparison there are also the results taken by a standard wheel 4088 25А12ПСМ16К5, that is usually used in such operations. From the Table 2 It may be concluded that the roughness of the treated surface is directly dependent on the predominant shape of grains in the disc. The roughness is less if the grains are isometric. With the change of grain shape from isometric to lamellar - the roughness increases in about 4 times. If we make the comparison with the wheel produces from initial (unsorted) grain, we will see that by the usage of the isometric shape of grains we may achieve the reduction of the roughness in 3 times. Table 2. The dependence of the roughness of the machined surface on grain shapes. Shape of grain
Seediness
Acicular
0,5-0,63
Lamellar
0,4-0,5
Initial
0,4-0,5
Isometric
0,125-0,16
Standard
0,2-0,25
5. Conclusion Thus, the implemented research let us conclude that the shape of a grain significantly influences on the performance characteristics of abrasive tools. The differentiated approach to the realization of benefits of grains classified by their shape significantly increases the efficiency of the grinding process, because the application of this approach let us get a new, high quality abrasive tool which is more homogeneous according to its sanding properties. Acknowledgement I am glad to have a chance to share my scientific ideas with colleagues from different countries. This opportunity was given to me by the team of International Conference on Industrial Engineering, ICIE 2017. I am thankful to all of you. As far as my personal scientific achievements are concerned I would like to express my sincere gratitude to
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my supervisor Dr. V.M. Shumiacher, who was helping me in the process of the creation of the thesis for the degree of candidate of science and who is still supporting me. With his help I started to work on my Doctoral thesis 3 years ago. If my article is published in Elsevier, it will encourage me and my colleague T.N. Orlova to continue working in this direction. References [1] N.V. Baidakova, Improving the efficiency of grinding by use of a tool made of classified by size and shape of the abrasive grain: thesis for the degree of Candidate of Technical Sciences, Saratov, 2006. [2] A.N. Korotkov, Operational properties of abrasive materials, Edition of Krasnoyarsk University, Krasnoyarsk, 1992. [3] A.N. Reznikov, Abrasive and diamond material processing, Mashinostroenie, Moscow, 1977. [4] S.A. Kryukov, A.V. Slavin, N.V. Baidakova, Predicting of the mechanical strength of the abrasive composites, Manufacturing Engineering. 10 (2013) 31–32. [5] N.V. Baidakova, S.A. Kryukov, A.V. Slavin, Effect of shape and grain of the abrasive grain on the efficiency of the grinding process, Heavy engineering. 3-4 (2016) 35–37. [6] N.V. Baidakova, S.A. Kryukov, The influence of the shape and grain of the abrasive grains on the grinding efficiency. In the Proceedings of the International Scientific and Technical Conference "Shlifabraziv 2014". (2014) 106–110. [7] N.V. Baidakova, S.A. Kryukov, System-integrated methodology for improving abrasive tools, In the Proceedings of International Scientific and Technical Conference "Shlifabraziv 2014". (2014) 110–114. [8] N.V. Baidakova, S.A. Kryukov, The effect of the form of the abrasive grains to the cutting tool's ability in the process of roughing operations In the Proceedings of Collection All-Russian youth scientific conference. (2014) 475–478. [9] N.V Baidakova, V.A. Nazarenko, Mathematical modeling of vibratory separation of the abrasive grain particles according to their size, In the Proceedings of International Scientific and Technical Conference hold by Volzhsky Institute of Construction and Technology (branch) of Volgograd State University of Architecture and Civil Engineering. (2012) 17–21. [10] S.A, Kryukov, V.M. Shumyacher, Improved stability and efficiency of abrasive tools, LAP LAMBERT Academic Publishing, Saarbrücken, 2013. [11] V.M. Shumyacher, A.V. Slavin, S.A. Kryukov, Basics of highly efficient abrasive tools, Edition of Volgograd State University of Architecture and Civil Engineering, 2015. [12] N.V. Baidakova, S.A. Kryukov, Study of the influence of abrasive grain on the quality of grinding tools, In the Proceedings of the International Conference dedicated to the 60th anniversary of the university education. (2012) 27–30. [13] N.V. Baidakova, S.A. Kryukov, The Influence of granularity and shape of abrasive grains on grinding efficiency, In the Proceedings of International Scientific and Technical Conference hold by Volzhsky Institute of Construction and Technology (branch) of Volgograd State University of Architecture and Civil Engineering. (2012) 96–99. [14] V.I. Kurdyukov, Scientific basis for the design, manufacture and operation of abrasive tool: thesis for the degree of doctor of technical sciences, Kurgan, 2000. [15] V.I. Ostrovsky, Theoretical bases of the grinding process, Leningrad State University, Leningrad, 1981. [16] A.V. Korolev, Yu.K. Novoselov, Theoretic probability foundations of abrasion. Status of working surface of the tool, Saratov University Press, Saratov, 1987. [17] S.G. Redko, A.V. Korolev, Location of abrasive grains on the working surface of the grinding wheel, Machines and tools. 5 (1970) 40–41. [18] A.K. Baikalov, The introduction to the theory of the grinding of materials, Naukova dumka, Kiev, 1978. [19] W. Konig, W. Lorts, Proherties of cutting edges related to chip formation in griding, CIRP. 24 (1975) 231–235. [20] P.E. Dyachenko, Study of the grinding process, Mashgiz, Moscow, 1941. [21] S.A. Kryukov, A.V. Slavin, Ways of improving of the structural and mechanical characteristics and efficiency of abrasive tools, Edition of Volgograd State University of Architecture and Civil Engineering, Volgograd, 2016. [22] I.Yu. Orlov, T.N. Orlova, V.M. Shumyacher, Improving of the efficiency of the operation grinding of butt of steels by a bakelite tool by selecting fillers that reduce the calorific process, Engineering journal. 6 (2015) 7–10. [23] T.N.Orlova, V.M. Shumyacher, I.Yu. Orlov, A.E. Zhumakanov, Slag aluminothermic production of niobium - a new abrasive material in the manufacture of abrasive tools XXI century: innovative technologies in metallurgy. Problems. Prospects, In the Proceedings of International scientific-practical conference dedicated to the 80th anniversary of the famous metallurgist Akhat Salemhatovich Kulenov. (2012) 143–146.