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Clarification of magnetic abrasive finishing mechanism
Journal of Materials Processing Technology 143–144 (2003) 682–686
Clarification of magnetic abrasive finishing mechanism T. Mori∗ , K. Hirota, Y. Kawashima Department of Mechanical Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku Room 253, Nagoya 464-8603, Japan
Abstract In order to clarify the mechanism of magnetic abrasive polishing, a planar type process for a non-magnetic material, stainless steel, was examined. A magnetic abrasive brush was formed between a magnetic pole and a workpiece material, in which the summation of three kinds of energy necessary for magnetization of abrasives, i.e. repulsion between bundles (Faraday effect) and line tension of outer curved bundle was considered to be minimum. A normal force that pushes the abrasives on the brush end to be indented into the material surface is generated by the magnetic field. The magnetic abrasive brush will then be an extension of the magnetic pole. In this process, the tangential force acts to be the returning force created when the abrasive deviates from the magnetic balance point. Thus, the magnetic abrasives are expected to polish the material surface softly. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Magnetic abrasive finishing; Polishing mechanism; Magnetic abrasive brush
1. Introduction A magnetic abrasive finishing process is defined as a process by which material is removed, in such a way that the surface finishing and deburring is performed with the presence of a magnetic field in the machining zone. The method was originally introduced in the Soviet Union [1], with further fundamental research in various countries including Japan [2]. Nowadays, the study of the magnetic field assisted finishing processes is being conducted at industrial levels around the world. Most of the previous research work has been focussed on the finishing characteristics and mechanism from a macroscopic point of view using the surface roughness profiles as the measure. However, those approaches do not adequately characterize the behavior of abrasive cutting edges acting against the surface during the removal process. This paper examines the magnetic field, acting forces and provides a fundamental understanding of the process mechanism.
with one m accuracy. N and S poles were separated 5 mm, and within the gap a workpiece vessel was placed. The vessel was supported by a thrust and radial bearing and rotated by a motor through a belt–pulley system. All components except the magnet were of non-magnetic material in order to suppress the influence of the magnetic field. Table 1 shows experimental conditions. The workpiece, SUS 304 stainless steel disk of 80 mm diameter and 1 mm thickness was held inside the vessel. The abrasive was dispersed on the workpiece and magnetically attracted by the pole, hence forming the brush. This was then pushed downward against the workpiece surface. When the vessel carrying the workpiece is rotated at lower speed, the abrasives move circumferentially removing the surface material. The amplitude of the vertical run-out of the workpiece is less than 0.002 mm which is much smaller than the clearance between the upper pole tip and the workpiece surface. Fig. 2 shows the magnetic abrasive that was sintered from an aggregate of iron and alumina particles. The diameter of the magnetic abrasive was 70–170 m, but that of the alumina particle which cut and removed the material was about 5 m.
2. Experimental procedure Fig. 1 shows a schematic diagram of a plenary magnetic abrasive polishing apparatus. An electromagnet core with a diameter of 10 mm was wound 3000 turns using 1 mm diameter copper wire. This was mounted on an X–Y–Z table ∗ Corresponding author. Tel.: +81-52-789-2785; fax: +81-52-789-3107. E-mail address: [email protected] (T. Mori).
3. Results and considerations The magnetic properties of the abrasives and hardness and roughness of the polished material mainly influence the polishing mechanism of the magnetic abrasive particles. The stainless steel workpiece is non-magnetic with hard and smooth surface as shown in Table 1.
0924-0136/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0924-0136(03)00410-2
T. Mori et al. / Journal of Materials Processing Technology 143–144 (2003) 682–686
683
Fig. 1. Schematic diagram of a plenary magnetic abrasive polishing apparatus.
Table 1 Experimental conditions Workpiece
Non-magnetic stainless SUS 304 (t = 1 mm, d = 80 mm, Ra = 0.1 mm)
Coil currency Vessel revolution Abrasive (weight)
I = 0.5–5 A 250 rpm Iron, alumina (w = 0.1–1 g)
Provided that an average number of indented particles per an abrasive is n, the normal force, fn , and tangential force, fh , acting on the abrasive are represented as follows: fn = npn ,
fh = nph
(2)
Considered the volume, Vm , occupied by magnetized abrasives as an extension of the magnet from N pole, abrasives at its edge are magnetically attracted along magnetic field line by S opposite pole. By the way, the polishing abrasive at edge is not pushed but attracted upward by the neighboring abrasives and then fn is the force due to the field. The fh is also considered as the force due to the field. It is generated when the interested abrasive deviated from a balancing point. This mechanism is discussed next section: 3.2. Mechanism of forming magnetic abrasive polishing brush
Fig. 2. Magnetic abrasive.
3.1. Kinematics of the magnetic abrasive polishing Fig. 3 shows the configuration of the magnetic abrasive polishing in the case of non-magnetic material. Tips of alumina particles that are indented into the surface of the SUS 304 stainless steel, remove and polish it with the action of the relative tangential motion. A normal force, pn , and a tangential force, ph , presumed from a slip-line analysis are presented by the following equations: pn = kπ(1 + θ)tan2 θh2 ,
ph = kπ(1 + θ)tan θh2
(1)
Fig. 4 shows the configuration of magnetic abrasive brushes in which the magnetized abrasives stretch in a row from the pole to the material. In considering only the magnetic field, a continuous function, it is expected that the magnetized particles aggregate into bundles. However, the interaction of the magnetized particles must be taken into account. 3.2.1. Energy required to produce magnetic abrasive brush Energy requirements in the production of magnetic abrasive brush using magnetic abrasives that are added little by little into the magnetic field are discussed as follows:
where h and θ are the indenting depth and angle.
Fig. 3. Configuration of magnetic abrasive polishing in the case of non-magnetic material.
Fig. 4. Configuration of magnetic abrasive brushes.
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T. Mori et al. / Journal of Materials Processing Technology 143–144 (2003) 682–686
the tension energy acting on the outer side of the curved bundles is smaller than the magnetization energy: dWm > dWt
Fig. 5. Observation method of structures of magnetic abrasive brush.
On the other hand, when the increase of the curvature of the outmost bundle becomes too large or the separation of bundles becomes too short, the diameter of the bundle becomes large even though the magnetization energy is large: dWf > dWm ,
(i) Magnetization energy, Wm , required to magnetize the abrasives to form bundles. (ii) Repulsion energy, Wf , due to Faraday effect causes the bundles to repel from each other. (iii) Tension energy, Wt , needed to counter act the curved bundles due to repelling particles. Therefore, in order to form the magnetic abrasive brush sum of these energies, W, is necessary: W = Wm + Wf + Wt
dWt > dWm
(5)
However, the diameter of the bundle is limited because the differential factor of energy to diameter is assumed to increase abruptly. The tangential component of the tension in the outer curved bundles is directed inward and repulsion between bundles adds up in the inner side. Thus, the abrasives of the brush edge are held firm by these tangential forces. The holding force is thus strong at the inner side of the abrasive brush.
(3)
The brush is formed in a stable state when W is minimum, that is, dW = 0. 3.2.2. Formation of magnetic abrasive brush The structure of the magnetic abrasive brush was certified by a method shown in Fig. 5. After forming the magnetic abrasive brush from a lower pole to an acrylic plate, which was placed instead of a workpiece, it was observed from upper side by a CCD camera. A forming mechanism of a magnetic abrasive brush can be clarified from observations made on in various abrasive volumes; mass of abrasive was varied from 0.1 to 1.0 g by 0.1 g. Fig. 6 shows typical cases of 0.1, 0.2 and 0.6 g. The characteristics of the observed brush are as follows: (i) At an abrasive small volume, the diameter of each bundle is in the order of a few hundred micrometer that are separated from each other. (ii) With an increase of volume, the bundles get closer to other and the diameter of the bundles increase to several hundred micrometer, corresponding to several abrades. (iii) At large abrasive volume, the maximum diameter of a bundle dose not increase but the number of bundles of several diameter increase. These phenomena can be explained from the viewpoint of the brush forming energy. At a smaller volume of abrades,
Fig. 6. Typical cases of structures of magnetic abrasive brush.
(4)
3.3. Normal force 3.3.1. Theoretical equation of normal force generated by magnetic field When a workpiece is non-magnetic and a magnetic brush is assumed as the magnetized body, normal force Fn is represented by Eq. (6): B2 1 Fn = mfn = 1− S (6) 2µ0 µm Here m is the number of abrasives at the brush edge, µ0 the permeability in vacuum, µm the specific permeability of the magnetic brush, B the magnetic flux density and S the virtual contact area. The specific permeability of the magnetic brush is expressed approximately by Eq. (7), using µF of the specific permeability of iron and Vi of a volume ratio of iron: 2 + µF − 2(1 − µF )Vi µm = (7) 2 + µF + (1 − µF )Vi S was obtained by observation of CCD camera, Vi was calculated from S and specific weights of iron and alumina and B was measured by a flux-measuring instrument. (a) Change of normal force to electric current and abrasive mass. Figs. 7 and 8 show changes of normal force to electric current in a coil and abrasive mass. Calculated values agree well with measured ones in both cases, though the former are a little larger than the latter. The magnetic flux density, B, increases with electric current, and the virtual contact area, S, and the specific permeability of the magnetic brush, µm , increase with abrasive mass and thus the normal force increase. (b) Normal pressure distribution. Fig. 9 shows the method employed to obtain normal pressure distribution. The workpiece was prepared with a hole at the center and
T. Mori et al. / Journal of Materials Processing Technology 143–144 (2003) 682–686
685
Fig. 11. Magnetic flux density distribution. Fig. 7. Normal force to electric current.
magnetic flux density distribution, shown in Fig. 11. One of reasons seems to be that the concentration of µm superposes. 3.4. Generation of tangential force
Fig. 8. Normal force to abrasive mass.
In order to perform polishing, the mechanism of generating the tangential force that is the polishing resistance must be explained. The concept until now is that tangential force generated by a magnetic field gradient cannot interpret the force generation in half of the contact area. In this report the force generation was considered as follows. It is assumed that the magnetic abrasive moves by a small distance dx from the balanced point, the force acts on the abrasive such as it returns at that point: Fh =
dW dx
Fig. 12 shows change of tangential force to abrasive mass. 3.5. Mechanism of magnetic abrasive polishing Characteristics of magnetic abrasive polishing are summed as follows: Fig. 9. Method employed to obtain normal pressure distribution.
the normal force acting on workpiece was measured. The diameters of the holes are 2, 4, 6 and 8 mm, and then the measured normal force values were subtracted to give the net force around the ring. Fig. 10 shows the normal pressure distribution. Most of the normal force concentrates within the area of 1 mm radius and the degree of concentration is larger than that of the
Fig. 10. Normal pressure distribution.
(i) A normal and tangential forces, acting on the magnetic abrasive at brush edge, are generated by magnetic field. (ii) Each bundle is separated from each other. By taking into account these characteristics, a polishing mechanism peculiar to this process can be explained, as shown in Fig. 13. At the beginning of process abrasives at the brush edge are indented into various parts of the surface. When the material moves, the abrasives repulses each other and is distanced from the balancing point and thus a return
Fig. 12. Change of tangential force to abrasive mass.
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T. Mori et al. / Journal of Materials Processing Technology 143–144 (2003) 682–686
exceeds the cutting resistance of the material, the abrasive cuts off the material. An abrasive after using a process in 30 min, shown in Fig. 14, is round, and this certifies that it rotates.
4. Conclusions The following facts are clarified: Fig. 13. Mechanism of magnetic abrasive polishing.
force Fh is generated. If the abrasive indenting point is near to a hill of surface roughness, material removes by Fh . On the other hand, when the abrasive stands in a valley of surface roughness it cannot cut a material. In this case, the return force Fh acts at the center of the abrasive but a reaction Fh does at the edge of indenting alumina particle. Therefore, a moment acts on the abrasive and it climbs a hill with rotating. As a volume to be removed becomes smaller at the top of the hill due to climbing and the return force Fh , growing large,
(1) Formation of magnetic abrasive brush was explained from the viewpoint of the brush forming energy. (2) Calculated values of a normal force agree well with measured ones in both cases, though the former are a little larger than the latter. (3) Most of the normal force concentrates within the area of 1 mm radius and the degree of concentration is larger than that of the magnetic flux density distribution. (4) When the magnetic abrasive moves by a small distance dx from the balanced point, the tangential force acts on the abrasive such as it returns at that point. (5) A polishing mechanism peculiar to this process was explained.
References
Fig. 14. Comparison of abrasives before and after polishing.
[1] H.-J. Ruben, in: A. Niku-Lari (Ed.), Advances in Surface Treatments, vol. 5, Pergamon Press, Oxford, 1987, pp. 239–256. [2] H. Yamaguchi, T. Shinmura, Study of the surface modification resulting from an internal magnetic abrasive finishing process, Wear 225 (229) (1999) 246–255.
Clarification of magnetic abrasive finishing mechanism T. Mori∗ , K. Hirota, Y. Kawashima Department of Mechanical Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku Room 253, Nagoya 464-8603, Japan
Abstract In order to clarify the mechanism of magnetic abrasive polishing, a planar type process for a non-magnetic material, stainless steel, was examined. A magnetic abrasive brush was formed between a magnetic pole and a workpiece material, in which the summation of three kinds of energy necessary for magnetization of abrasives, i.e. repulsion between bundles (Faraday effect) and line tension of outer curved bundle was considered to be minimum. A normal force that pushes the abrasives on the brush end to be indented into the material surface is generated by the magnetic field. The magnetic abrasive brush will then be an extension of the magnetic pole. In this process, the tangential force acts to be the returning force created when the abrasive deviates from the magnetic balance point. Thus, the magnetic abrasives are expected to polish the material surface softly. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Magnetic abrasive finishing; Polishing mechanism; Magnetic abrasive brush
1. Introduction A magnetic abrasive finishing process is defined as a process by which material is removed, in such a way that the surface finishing and deburring is performed with the presence of a magnetic field in the machining zone. The method was originally introduced in the Soviet Union [1], with further fundamental research in various countries including Japan [2]. Nowadays, the study of the magnetic field assisted finishing processes is being conducted at industrial levels around the world. Most of the previous research work has been focussed on the finishing characteristics and mechanism from a macroscopic point of view using the surface roughness profiles as the measure. However, those approaches do not adequately characterize the behavior of abrasive cutting edges acting against the surface during the removal process. This paper examines the magnetic field, acting forces and provides a fundamental understanding of the process mechanism.
with one m accuracy. N and S poles were separated 5 mm, and within the gap a workpiece vessel was placed. The vessel was supported by a thrust and radial bearing and rotated by a motor through a belt–pulley system. All components except the magnet were of non-magnetic material in order to suppress the influence of the magnetic field. Table 1 shows experimental conditions. The workpiece, SUS 304 stainless steel disk of 80 mm diameter and 1 mm thickness was held inside the vessel. The abrasive was dispersed on the workpiece and magnetically attracted by the pole, hence forming the brush. This was then pushed downward against the workpiece surface. When the vessel carrying the workpiece is rotated at lower speed, the abrasives move circumferentially removing the surface material. The amplitude of the vertical run-out of the workpiece is less than 0.002 mm which is much smaller than the clearance between the upper pole tip and the workpiece surface. Fig. 2 shows the magnetic abrasive that was sintered from an aggregate of iron and alumina particles. The diameter of the magnetic abrasive was 70–170 m, but that of the alumina particle which cut and removed the material was about 5 m.
2. Experimental procedure Fig. 1 shows a schematic diagram of a plenary magnetic abrasive polishing apparatus. An electromagnet core with a diameter of 10 mm was wound 3000 turns using 1 mm diameter copper wire. This was mounted on an X–Y–Z table ∗ Corresponding author. Tel.: +81-52-789-2785; fax: +81-52-789-3107. E-mail address: [email protected] (T. Mori).
3. Results and considerations The magnetic properties of the abrasives and hardness and roughness of the polished material mainly influence the polishing mechanism of the magnetic abrasive particles. The stainless steel workpiece is non-magnetic with hard and smooth surface as shown in Table 1.
0924-0136/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0924-0136(03)00410-2
T. Mori et al. / Journal of Materials Processing Technology 143–144 (2003) 682–686
683
Fig. 1. Schematic diagram of a plenary magnetic abrasive polishing apparatus.
Table 1 Experimental conditions Workpiece
Non-magnetic stainless SUS 304 (t = 1 mm, d = 80 mm, Ra = 0.1 mm)
Coil currency Vessel revolution Abrasive (weight)
I = 0.5–5 A 250 rpm Iron, alumina (w = 0.1–1 g)
Provided that an average number of indented particles per an abrasive is n, the normal force, fn , and tangential force, fh , acting on the abrasive are represented as follows: fn = npn ,
fh = nph
(2)
Considered the volume, Vm , occupied by magnetized abrasives as an extension of the magnet from N pole, abrasives at its edge are magnetically attracted along magnetic field line by S opposite pole. By the way, the polishing abrasive at edge is not pushed but attracted upward by the neighboring abrasives and then fn is the force due to the field. The fh is also considered as the force due to the field. It is generated when the interested abrasive deviated from a balancing point. This mechanism is discussed next section: 3.2. Mechanism of forming magnetic abrasive polishing brush
Fig. 2. Magnetic abrasive.
3.1. Kinematics of the magnetic abrasive polishing Fig. 3 shows the configuration of the magnetic abrasive polishing in the case of non-magnetic material. Tips of alumina particles that are indented into the surface of the SUS 304 stainless steel, remove and polish it with the action of the relative tangential motion. A normal force, pn , and a tangential force, ph , presumed from a slip-line analysis are presented by the following equations: pn = kπ(1 + θ)tan2 θh2 ,
ph = kπ(1 + θ)tan θh2
(1)
Fig. 4 shows the configuration of magnetic abrasive brushes in which the magnetized abrasives stretch in a row from the pole to the material. In considering only the magnetic field, a continuous function, it is expected that the magnetized particles aggregate into bundles. However, the interaction of the magnetized particles must be taken into account. 3.2.1. Energy required to produce magnetic abrasive brush Energy requirements in the production of magnetic abrasive brush using magnetic abrasives that are added little by little into the magnetic field are discussed as follows:
where h and θ are the indenting depth and angle.
Fig. 3. Configuration of magnetic abrasive polishing in the case of non-magnetic material.
Fig. 4. Configuration of magnetic abrasive brushes.
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T. Mori et al. / Journal of Materials Processing Technology 143–144 (2003) 682–686
the tension energy acting on the outer side of the curved bundles is smaller than the magnetization energy: dWm > dWt
Fig. 5. Observation method of structures of magnetic abrasive brush.
On the other hand, when the increase of the curvature of the outmost bundle becomes too large or the separation of bundles becomes too short, the diameter of the bundle becomes large even though the magnetization energy is large: dWf > dWm ,
(i) Magnetization energy, Wm , required to magnetize the abrasives to form bundles. (ii) Repulsion energy, Wf , due to Faraday effect causes the bundles to repel from each other. (iii) Tension energy, Wt , needed to counter act the curved bundles due to repelling particles. Therefore, in order to form the magnetic abrasive brush sum of these energies, W, is necessary: W = Wm + Wf + Wt
dWt > dWm
(5)
However, the diameter of the bundle is limited because the differential factor of energy to diameter is assumed to increase abruptly. The tangential component of the tension in the outer curved bundles is directed inward and repulsion between bundles adds up in the inner side. Thus, the abrasives of the brush edge are held firm by these tangential forces. The holding force is thus strong at the inner side of the abrasive brush.
(3)
The brush is formed in a stable state when W is minimum, that is, dW = 0. 3.2.2. Formation of magnetic abrasive brush The structure of the magnetic abrasive brush was certified by a method shown in Fig. 5. After forming the magnetic abrasive brush from a lower pole to an acrylic plate, which was placed instead of a workpiece, it was observed from upper side by a CCD camera. A forming mechanism of a magnetic abrasive brush can be clarified from observations made on in various abrasive volumes; mass of abrasive was varied from 0.1 to 1.0 g by 0.1 g. Fig. 6 shows typical cases of 0.1, 0.2 and 0.6 g. The characteristics of the observed brush are as follows: (i) At an abrasive small volume, the diameter of each bundle is in the order of a few hundred micrometer that are separated from each other. (ii) With an increase of volume, the bundles get closer to other and the diameter of the bundles increase to several hundred micrometer, corresponding to several abrades. (iii) At large abrasive volume, the maximum diameter of a bundle dose not increase but the number of bundles of several diameter increase. These phenomena can be explained from the viewpoint of the brush forming energy. At a smaller volume of abrades,
Fig. 6. Typical cases of structures of magnetic abrasive brush.
(4)
3.3. Normal force 3.3.1. Theoretical equation of normal force generated by magnetic field When a workpiece is non-magnetic and a magnetic brush is assumed as the magnetized body, normal force Fn is represented by Eq. (6): B2 1 Fn = mfn = 1− S (6) 2µ0 µm Here m is the number of abrasives at the brush edge, µ0 the permeability in vacuum, µm the specific permeability of the magnetic brush, B the magnetic flux density and S the virtual contact area. The specific permeability of the magnetic brush is expressed approximately by Eq. (7), using µF of the specific permeability of iron and Vi of a volume ratio of iron: 2 + µF − 2(1 − µF )Vi µm = (7) 2 + µF + (1 − µF )Vi S was obtained by observation of CCD camera, Vi was calculated from S and specific weights of iron and alumina and B was measured by a flux-measuring instrument. (a) Change of normal force to electric current and abrasive mass. Figs. 7 and 8 show changes of normal force to electric current in a coil and abrasive mass. Calculated values agree well with measured ones in both cases, though the former are a little larger than the latter. The magnetic flux density, B, increases with electric current, and the virtual contact area, S, and the specific permeability of the magnetic brush, µm , increase with abrasive mass and thus the normal force increase. (b) Normal pressure distribution. Fig. 9 shows the method employed to obtain normal pressure distribution. The workpiece was prepared with a hole at the center and
T. Mori et al. / Journal of Materials Processing Technology 143–144 (2003) 682–686
685
Fig. 11. Magnetic flux density distribution. Fig. 7. Normal force to electric current.
magnetic flux density distribution, shown in Fig. 11. One of reasons seems to be that the concentration of µm superposes. 3.4. Generation of tangential force
Fig. 8. Normal force to abrasive mass.
In order to perform polishing, the mechanism of generating the tangential force that is the polishing resistance must be explained. The concept until now is that tangential force generated by a magnetic field gradient cannot interpret the force generation in half of the contact area. In this report the force generation was considered as follows. It is assumed that the magnetic abrasive moves by a small distance dx from the balanced point, the force acts on the abrasive such as it returns at that point: Fh =
dW dx
Fig. 12 shows change of tangential force to abrasive mass. 3.5. Mechanism of magnetic abrasive polishing Characteristics of magnetic abrasive polishing are summed as follows: Fig. 9. Method employed to obtain normal pressure distribution.
the normal force acting on workpiece was measured. The diameters of the holes are 2, 4, 6 and 8 mm, and then the measured normal force values were subtracted to give the net force around the ring. Fig. 10 shows the normal pressure distribution. Most of the normal force concentrates within the area of 1 mm radius and the degree of concentration is larger than that of the
Fig. 10. Normal pressure distribution.
(i) A normal and tangential forces, acting on the magnetic abrasive at brush edge, are generated by magnetic field. (ii) Each bundle is separated from each other. By taking into account these characteristics, a polishing mechanism peculiar to this process can be explained, as shown in Fig. 13. At the beginning of process abrasives at the brush edge are indented into various parts of the surface. When the material moves, the abrasives repulses each other and is distanced from the balancing point and thus a return
Fig. 12. Change of tangential force to abrasive mass.
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T. Mori et al. / Journal of Materials Processing Technology 143–144 (2003) 682–686
exceeds the cutting resistance of the material, the abrasive cuts off the material. An abrasive after using a process in 30 min, shown in Fig. 14, is round, and this certifies that it rotates.
4. Conclusions The following facts are clarified: Fig. 13. Mechanism of magnetic abrasive polishing.
force Fh is generated. If the abrasive indenting point is near to a hill of surface roughness, material removes by Fh . On the other hand, when the abrasive stands in a valley of surface roughness it cannot cut a material. In this case, the return force Fh acts at the center of the abrasive but a reaction Fh does at the edge of indenting alumina particle. Therefore, a moment acts on the abrasive and it climbs a hill with rotating. As a volume to be removed becomes smaller at the top of the hill due to climbing and the return force Fh , growing large,
(1) Formation of magnetic abrasive brush was explained from the viewpoint of the brush forming energy. (2) Calculated values of a normal force agree well with measured ones in both cases, though the former are a little larger than the latter. (3) Most of the normal force concentrates within the area of 1 mm radius and the degree of concentration is larger than that of the magnetic flux density distribution. (4) When the magnetic abrasive moves by a small distance dx from the balanced point, the tangential force acts on the abrasive such as it returns at that point. (5) A polishing mechanism peculiar to this process was explained.
References
Fig. 14. Comparison of abrasives before and after polishing.
[1] H.-J. Ruben, in: A. Niku-Lari (Ed.), Advances in Surface Treatments, vol. 5, Pergamon Press, Oxford, 1987, pp. 239–256. [2] H. Yamaguchi, T. Shinmura, Study of the surface modification resulting from an internal magnetic abrasive finishing process, Wear 225 (229) (1999) 246–255.