Internal finishing process for alumina ceramic components by a magnetic field assisted finishing process

Precision Engineering 28 (2004) 135–142

Internal finishing process for alumina ceramic components by a magnetic field assisted finishing process Hitomi Yamaguchi a,∗ , Takeo Shinmura b a

b

Faculty of Engineering, Utsunomiya University, Utsunomiya, Tochigi 321-8585, Japan Graduate School of Engineering, Utsunomiya University, Utsunomiya, Tochigi 321-8585, Japan Received 14 January 2003; received in revised form 1 July 2003; accepted 25 July 2003

Abstract This study presents the application of a new technique, magnetic field assisted finishing, for finishing of the inner surfaces of alumina ceramic components. The experiments performed on alumina ceramic tubes examine the effects of volume of lubricant, ferrous particle size, and abrasive grain size on the finishing characteristics. The finished surface is highly dependent on the volume of lubricant, which affects the abrasive contact against the surface; on the ferrous particle size, which changes the finishing force acting on the abrasive; and on the abrasive grain size, which controls the depth of cut. By altering these conditions, this process achieves surface finishes as fine as 0.02 ␮m in surface roughness (Ra ) and imparts minimal additional residual stress to the surface. This study also reveals the mechanism to smooth the inner surface of alumina ceramic tube and to improve the form accuracy, i.e. the roundness of inside the alumina ceramic tube. © 2003 Elsevier Inc. All rights reserved. Keywords: Magnetic field assisted finishing; Internal finishing; Alumina ceramics; Finishing characteristics; Surface roughness; Roundness; Residual stress

1. Introduction Alumina ceramics have a wide range of structural and functional applications. The main advantages of alumina ceramics usually cited are their relatively high dielectric constant. Their main usefulness in fact arises mostly from their high strength and resistance to thermal stresses [1]. Consequently, alumina ceramics are widely used as substrates for electronic-device applications. The surface resistivity and dielectric losses dictate the use of a material containing 99% or more Al2 O3 . Strength and other properties generally improve as the percentage of alumina is raised, but the production cost rises because of difficulty in processing high aluminas [2]. This is one of the major challenges for their application despite their excellent material properties. The difficulty of internal finishing is incredibly complicated in the case of high alumina ceramic components, e.g. load-bearing components, translucent aluminum discharged lamps. The sliding surfaces between inner and outer races of bearings require highly smoothed surfaces and form accuracy to reduce wear and extend their effective life. In the case of discharged lamps, smoothly finished inner surfaces inhibit the light from scattering, improving the translucency ∗ Corresponding

author. Tel.: +81-28-689-6077; fax: +81-28-689-6077. E-mail address: [email protected] (H. Yamaguchi).

0141-6359/$ – see front matter © 2003 Elsevier Inc. All rights reserved. doi:10.1016/j.precisioneng.2003.07.001

[3]. The complex configurations of bearings and lamps, however, cause considerable difficulty in even introducing conventional tools inside the workpieces. Etching processes are commonly used for internal finishing, but they have drawbacks associated with the control of the surface quality and the treatment of chemical waste. It is, therefore, desirable to provide a new internal finishing process to replace chemical finishing process. A magnetic field assisted finishing process was proposed for producing highly-finished surfaces by removing material by magnetic abrasive in the presence of a magnetic field [4,5]. The process relies on the use of a magnetic field to direct the magnetic abrasive chains connected by magnetic force and takes advantage of the flexibility of the abrasive chain configuration for internal finishing of parts where conventional tools are hardly applicable, e.g. inside of flexible pipes or complexly bent tubes, in practical use [6,7]. This process is also practically used for edge finishing of components, such as razor blades and access arms of magnetic disk units [8,9]. Regarding the internal finishing of alumina ceramic components, a previous report presented the development of a magnetic abrasive consisting of diamond abrasive electroless-plated on ferrous material, and tested the performance of the newly-developed abrasive on internal finishing of alumina ceramic components [3]. Since the report concentrated on the unique method used to produce the

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magnetic abrasive, neither the finishing characteristics nor the mechanism of the internal finishing of alumina ceramic components has been clearly detailed. This study presents application of a new technique using magnetic field assisted finishing for the inner surfaces of alumina ceramic components. The use of a simple mixture of conventional abrasive with ferrous particles, which is favorable in terms of cost and process capability, is applied for this study. An experimental setup is developed to test the processing principle. The internal surface finishing experiments of alumina ceramic tubes examine the effects of lubricant volume, ferromagnetic particle size, and abrasive grain size on the finishing characteristics. The experiments also investigate the effects of the process on the form accuracy, i.e. the internal roundness of alumina ceramic tube. It is significant for alumina ceramic components used for critical geometric conditions such as air bearings, and they must exhibit precise form accuracy in addition to fine surface roughness. A series of the experiments reveals the generating mechanism to finished surface of alumina ceramic tube. Another index for evaluating the finishing characteristics is the residual stress of the finished surface. It affects the fatigue structural integrity of the components and is particularly important for components used in high-pressure or high-stress applications. Thus, the residual stress of the finished surface imparted by the process is also examined.

2. Processing principle Fig. 1 shows a schematic of the internal finishing process using a work rotation system for alumina ceramic tubes. The poles, consisting of small permanent magnets, generate the magnetic field needed for attracting the ferrous particles to the finishing area and generating the magnetic force needed for pressing the diamond abrasive against the inner surface of the tube. The magnetic force acting on the ferrous particles is a function of the volume and magnetic susceptibility of the ferrous particles in the magnetic field, and more specifically, the magnetic field intensity and the gradients at the finishing area [7]. The ferrous particles are conglomerated by magnetic force at the finishing area and mix with

Fig. 1. Schematic of magnetic field assisted finishing process for alumina ceramic tubes.

the diamond abrasive, and the diamond abrasive is sandwiched between the inner surface of the tube and the ferrous particles. If the tangential component of the magnetic force acting on the ferrous particles is larger than the friction force between the mixture of ferrous particles and abrasive and the inner surface of the tube, the mixture held at the finishing area shows smooth relative motion against the inner surface of the tube when the tube is rotated at high speed. Material is removed from the surface by the abrasive as a result of this relative motion, and the surface is smoothed. The finishing force of the abrasive is controlled by the magnetic force acting on the ferrous particles. Additional vibration of the poles in the direction of the tube axis causes the vibration of the mixture of abrasive and ferrous particles. This increases the rate of material removal, leading to efficient surface finishing. Moreover, manipulating the poles along the tube axis causes the mixture to move in the direction of the tube axis following the poles’ motion, thereby finishing the entire inner surface of the slender tube.

3. Experimental setup Fig. 2 shows an external view of the experimental setup, which embodies the processing principle described in the previous chapter. The finishing unit, equipped with poles installed on a circular yoke, is set on the carriage of a computer numerically-controlled (CNC) lathe. The poles consist of Nd–Fe–B permanent magnets (12 mm×18 mm×10 mm), and the pole arrangement is flexible to accommodate various tube diameters. The distance between the pole tips is minimized to obtain a stronger magnetic field. In this study, four poles are installed on a yoke in the finishing unit, and the distance between the pole tips was set at 22 mm with 1 mm clearance between the pole tip and the tube, to avoid the collision between the tube and pole tips. This finishing unit can be vibrated in the direction of the tube axis with 5 mm amplitude at a frequency of 0.8 Hz to give the mixture of ferrous particles and abrasive vibratory motion in the direction of the tube axis.

Fig. 2. External photograph of experimental setup.

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The alumina ceramic tube is chucked in the CNC lathe and rotated at high speed (1800 min−1 ). This gives the relative motion between the mixture of ferrous particles and abrasive and the inner surface of the tube in the circumferential direction of the tube. The combination of the tube rotation with the vibratory motion of the finishing unit in the direction of the tube axis results in a cross hatch pattern of the finishing loci of the abrasive cutting edges for efficient surface finishing. The finishing experiments of inner surface of alumina ceramic tubes were performed to observe the finishing characteristics using this experimental setup.

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Table 2 Material properties of alumina ceramics [12] Color

Ivory

Al2 O3 content (%) Bulk density (g/cm3 ) Water absorption (%) Vickers hardness (HV) Flexural strength (MPa) Young’s modulus (GPa) Poisson’s ratio Thermal conductivity (W/m K) Dielectric strength (V/m) Dielectric loss Volume resistivity (Ohm cm)

99.5 3.8 0 17.6 (load 500 g) 323 (three points bending) 363 0.23 25 1.5 × 106 0.001 >1014 (20 ◦ C)

4. Experimental conditions In general, lubricant is used to reduce the friction between the abrasive and inner surface of the tube as well as to cool the finishing area and eject chips from the finishing area. Previous research reported that the lack of lubricant caused iron oxide to be deposited on the surface due to excess frictional heat between the magnetic abrasive and the inner surface of the tube, in case of the internal finishing of SUS304 stainless steel tube using a magnetic field assisted finishing [10]. Other research into the internal finishing of Si3 N4 ceramic tubes using the simply-mixed the ferrous particles and Cr2 O3 abrasive under dry conditions found a similar deposit on the inner surface of the tube [11]. These deposits disturbed the surface finishing. The lubricant is, therefore, considered significant in this finishing process, and the required amount is dependent on the workpiece material. In this study, the lubricant is introduced with simply-mixed diamond abrasive and ferrous particles. The lubricant binds the diamond abrasive to the surfaces of the ferrous particles in addition to the general roles mentioned above. The volume of lubricant is considered critical for the abrasive contact against the inner surface of the tube, which in turn controls the finishing characteristics. The ferrous particle size is one of the major parameters determining the magnetic force acting on the ferrous particles, which affects the surface finishes in the case of the simply-mixed abrasive with ferrous particles. The depth of cut depends on the abrasive grain size; this must change the finished surface quality. Accordingly, the internal surface finishing experiments of alumina ceramic tubes demonstrated

the effects of ferromagnetic particle size and abrasive particle size, in addition to the volume of the lubricant, on the finishing characteristics. The experimental conditions are shown in Table 1. Alumina ceramic tubes (∅ 20 mm × ∅ 15 mm × 150 mm) were used for the experiments as workpieces. This alumina ceramic possesses superior wear and corrosion resistance and high rigidity; and the material properties are shown in Table 2 [12]. Electrolytic iron particles, which have high iron content (Fe: 99.5%), have surface unevenness made in the production process, and the pockets on this surface may play a roll in holding the abrasive during the finishing process. Electrolytic iron particles with a variety of three different mean diameters, 150, 330, 510 ␮m, were applied as ferrous particles for the experiments. The experiments used diamond abrasive with four different grain distributions: 0–1, 2–4, 4–8, and 8–12 ␮m. Soluble-type barrel finishing compound [10], which is commonly supplied for magnetic field assisted finishing of SUS304 stainless steel tube, was used as lubricant. The kinematic viscosity is 7.59 × 10−6 m2 /s at 30 ◦ C. The finishing experiments were halted every 5 min to measure the surface roughness and material removal. The mixture of the diamond abrasive, ferrous particles, and lubricant was renewed every 5 min. The surface roughness measurement was performed with a surface roughness profile tester. The surface roughness was measured at the closest points available more than three times, and the arithmetic mean of the measured value was defined as surface roughness in this study. The material removal was measured on an electronic force balance with 0.1 mg resolution.

Table 1 Experimental condition Workpiece

Alumina (Al2 O3 ) ceramic tube: 20 mm × 15 mm × 150 mm

Workpiece rotation Ferrous particles Abrasive Pole Pole vibration Lubricant Clearance Maximum magnetic flux density

1800 min−1 Electrolytic iron particles: 1.08 g (150, 330, 510 ␮m in mean diameter) Diamond abrasive: 0.12 g (0–1, 2–4, 4–8, 10–12 ␮m in diameter) Nd–Fe–B rare-earth permanent magnet: 18 mm × 12 mm × 10 mm Amplitude: 5 mm; frequency: 0.8 Hz Soluble type barrel finishing compound: 0.1, 0.2, 0.25, 0.3, 0.35 ml 1 mm 0.37 T

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face roughness and material removal with finishing time after 5 min. When the amount of lubricant was increased from 0.3 to 0.35 ml, the material removal rate and the rate of surface roughness improvement slightly decreased at the beginning of the finishing experiment. The over-supply of lubricant could either cause fluid lubrication between the abrasive and the target surface or wash the abrasive away from the finishing area. This reduces the number of the abrasive cutting edges acting on the surface, disturbing the finishing action. The 0.3 ml amount, which was determined to be the optimized amount in this study, was, therefore, applied to the following finishing experiments. 5.2. Effects of ferrous particle size on finishing characteristics

5.1. Effects of lubricant volume on finishing characteristics The lubricant volume was varied from 0.1 to 0.35 ml, i.e. 53–185 vol.% of the mixture of the iron particles with diamond abrasive. Fig. 3 shows the changes of material removal and surface roughness with finishing time in the condition of 330 ␮m iron particles with 4–8 ␮m diamond abrasive, respectively. The less lubricant supplied, the smaller was the material removal. The increase of the lubricant must sustain the required condition for the smooth relative motion of the abrasive against the inner surface of the tube. This increase of lubricant enhanced the material removal, generating the smoothly finished surface in a shorter finishing time. This effect is seen in Table 3, which shows the changes in surTable 3 Changes in surface roughness and material removal with finishing time after 5 min Lubricant (ml) 0.1

0.2

0.25

0.3

0.35

Roughness Ra (␮m) (before finishing) 2.84 2.86 2.65 2.96 2.98 0.66 0.81 0.32 0.38 0.57 Roughness Ra (␮m) (after finishing) Roughness Ra improvement (%) 76.80 71.70 87.90 87.20 80.90 Material removal (mg) 6.14 6.92 8.78 10.0 8.73

4

40

M: 510 µm Ra: 510 µm Ra: 150 µm

3

30

Ra: 330 µm

2

20

M: 330 µm M: 150 µm

1

10

0

Material removal M mg .

5. Finishing characteristics

Surface roughness Ra µm

Fig. 3. Changes in material removal (a) and surface roughness (b) with finishing time.

Fig. 4 shows changes in surface roughness Ra and material removal with finishing time in the condition of 4–8 ␮m diamond abrasive. Of the three kinds of iron particles, the case of the 150 ␮m iron particles generated the least magnetic force. This effected insufficient material removal to remove the deep scratches originally presented on the initial surface under the condition. The surface roughness was in turn hardly changed. The highest material removal was obtained with the case of the 510 ␮m iron particles. This is a result of the greatest depth of cut of the diamond abrasive pushed against the surface by the greatest magnetic force acting on the largest particles. This, however, must have over-cut the material from the surface and disturbed the surface roughness improvement. The finished surface roughness resulting from the 510 ␮m iron particles showed 0.09 ␮m Ra , which is a larger value than that in the case of 330 ␮m iron particles: 0.07 ␮m Ra . Accordingly, these experiments demonstrated that the finished surface is controlled by the ferrous particle size, which influences the magnetic force acting on the ferrous particles that generates the finishing force of the abrasive. The experiments using 330 ␮m iron particles showed the most effective

0 0

5

10 Finishing time

15 min

20

Fig. 4. Changes in surface roughness and material removal with finishing time.

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30

Ra M 25

0-1 µm 2-4 µm 4-8 µm 8-12 µm

3

20

2

15 10

1 5 0

Material removal M mg .

Surface roughness Ra µm

4

139

0 0

5

10 15 Finishing time min

20

Fig. 5. Changes in surface roughness and material removal with finishing time.

finishing performance of any of the sizes of ferrous particles employed in this study. 5.3. Effects of size of diamond abrasive on finishing characteristics The experiments made use of diamond abrasive with four different grain distributions mixed with 330 ␮m iron particles. The other experimental conditions were the same as those listed in Table 1. Fig. 5 shows the changes in surface roughness Ra and material removal with finishing time. The cases of 2–4, 4–8, and 8–12 ␮m diamond abrasive show nearly linear rates of material removal over finishing time, and the case of the 2–4 ␮m diamond abrasive shows slightly less material removal compared to the 4–8 or 8–12 ␮m diamond abrasive. The three sizes of abrasive produced finished surface roughness Ra of 0.05, 0.07, and 0.13 ␮m for 2–4, 4–8, and 8–12 ␮m diamond abrasive, respectively. The 0–1 ␮m diamond abrasive shows a significantly smaller rate of material removal, and the rate of material removal decreased over time. Even so, the 0–1 ␮m diamond abrasive improved the surface roughness the most, and the finished surface roughness after 20 min was 0.02 ␮m Ra . Downsizing the diamond abrasive grains increases the number of the abrasive grains sandwiched between the iron particles and the inner surface of the tube at each contact point. The magnetic force acting on the iron particle is distributed among the abrasive grains sandwiched between the iron particles and the inner surface of the tube. The higher the number of the abrasive grains, the smaller is the force that acts on each abrasive pressed against the surface. This results in the smaller depth of cut by smaller finishing force of the abrasive in the case of smaller abrasive, which eventually produces smoother finished surfaces. Fig. 6 shows photo of inner surfaces of tubes before and after finishing for 20 min with 0–1 ␮m diamond abrasive. While nothing shows on the rough surface before finishing, the reflection appears on the smoothly finished surface. This illustrates the changes in the surface texture obtained by the

Fig. 6. Photograph of inner surface of tubes before and after finishing for 20 min.

finishing process. To obtain the smoothest surface with the smallest material removal, the surface must be cut gradually from the peaks of the uneven surface. The finishing mechanism will next be considered using the changes in the surface roughness profiles and bearing area curves. 5.4. Generating mechanism of finished surface Fig. 7 shows changes in surface roughness profiles (a) and bearing area curves (b) with finishing time in the case of 0–1 ␮m diamond abrasive. Fig. 7a(i) shows the unevenness of the initial surface. The periodically observed peaks and valleys were generated by the previous manufacturing process. After 5 min, the peaks of the surface roughness profile were flattened, but the valleys remained untouched. If the diamond abrasive is smaller than the width of the valleys of the surface, it can reach into the valleys. While the width of the valley

Fig. 7. Changes in surface roughness profile (a) and bearing area curve (b) with finishing time.

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was approximately 200 ␮m in Fig. 7a(i), the grain distribution of the diamond abrasive was 0–1 ␮m, and, therefore, the diamond abrasive could reach into the valleys during the process. The diamond abrasive, however, applied only minimal force, that is, the gravitational force, to the surface unless it was pressed against the surface by the iron particles. Because of the lack of the finishing force, the diamond abrasive inside the valleys of the surface could not remove enough material needed for finishing. The mean diameter of the iron particles used for the experiment was 330 ␮m, which hardly went into deep valleys. Only the abrasive sandwiched between the peaks of the surface and the ferrous particles, thus, took part in finishing performance and gradually removed the material from the peaks of the surface, resulting in the efficient finishing performance with minimum material removal. Consequently, the surface roughness profile became flat except for a couple of small valleys after 10 min, as shown in Fig. 7a(iii). In accordance with the changes in the surface roughness profile with finishing time, the slope of the bearing area curves becomes gentler, as shown in Fig. 7b. The gentler the slope of the bearing area curve, the less is the unevenness of the surface. The slight slope of the curve at 10 min is a resulted from a few slight valleys remaining on the surface. According to previous research on an internal finishing of SUS304 stainless steel workpiece using composite magnetic abrasive, consisting of Al2 O3 abrasive grains and iron, the Al2 O3 abrasive grains remove the material from not only the peaks of the uneven surface but also the valleys as far as the abrasive cutting edges penetrate into the valleys [13]. The mean diameter of the commonly used composite magnetic abrasive, irregularly-shaped due to the manufacturing process, is 80 ␮m, and that of the Al2 O3 abrasive grains is under 10 ␮m. As a result, the relatively longer wavelength components of the roughness profiles remain on the surface after finishing process. This is the major difference in the finishing mechanism between the cases using the composite magnetic abrasive and the mixture consisting of conventional abrasive and ferrous particles. As shown in Fig. 5, the improvement of the surface roughness was unchanged after 10 min of finishing with the 0–1 ␮m diamond abrasive despite continued removal of material. To further study this mechanism, the surface was microscopically examined using scanning electron microscope (SEM). Fig. 8 shows the SEM micrographs of inner surface of a tube

Fig. 8. SEM micrographs of inner surface of tube before (a) and after (b) finishing for 20 min.

before and after finishing for 20 min. Alumina ceramic tube is made by a powder sintered molding process, and the initial surface texture is shown in Fig. 8a. Several pores are observed in Fig. 8b; this must disturb the further improvement of the surface smoothness and are confirmed as valleys of the surface on the surface roughness profiles shown in Fig. 7. According to the results shown in Figs. 6–8, some diamond abrasive might have possibly removed an entire Al2 O3 grain instead of cutting a part of the grain projecting out of the surface. This must create new pores on the surface, disturbing the improvement in surface smoothness. In the case of 0–1 ␮m diamond abrasive, the turning point at which grains are removed appeared after finishing around 10 min. As long as the process removes the material from the peaks of the surface gradually, the process may possibly improve the form accuracy of the tube in addition to simultaneously improving the surface roughness. The effects of the process on the roundness were, therefore, investigated. 5.5. Roundness of inside alumina ceramic tube As shown in Fig. 9, the finishing experiments were performed on a section that was 15 mm away from the edge of the tube. The length of the finished portion was 23 mm, which is the sum of the magnet width (18 mm) and the amplitude of the vibration of the magnet in the direction of the tube axis (5 mm). A point 29 mm from the edge of the tube was taken to the represent the finished part, and a point 43 mm from the edge of the tube was chosen to represent the unfinished part for the roundness measurements. The form profile was measured using the cutoff value of 50 undulations per revolution (upr), and the form-error of the profile, i.e. roundness, was calculated according to the minimum zone circle (MZC) method. Fig. 9 shows form profiles of the unfinished and finished parts in case of 0–1 ␮m diamond abrasive with 330 ␮m iron particles. It is apparent that the form profile of the finished part is more fully-rounded out in comparison to the unfinished part. While the unfinished part has a roundness of 29.1 ␮m, the finished part measures 16.6 ␮m in roundness. As mentioned above, the mass of iron particles exhibits flexibility in their configuration in the presence of magnetic field and follows the overall form of the surface as long as the particles penetrate into the valleys of the surface. Since the mass of the iron particles was considerably greater than the undulation of the profile curve, shown in Fig. 9a, it could exactly trace neither the relatively shorter wavelength components of profile curve, that is roughness profile, nor the longer wavelength components of profile curve. In terms of the relatively longer wavelength components of the profile curve, the material was removed even more from the projections of the undulations of the profile curve. The accumulation of this cutting action must reduce the form-error of the profile of the finished part. Conversely, the internal finishing of SUS304 stainless steel tube using the composite magnetic abrasive demonstrated that the changes in the roundness with the finishing process

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141

Fig. 9. Roundness profiles of unfinished (a) and finished (b) surface.

was hardly significant on the form profiles [14]. This is also a result of the difference in the material removing mechanism between the composite magnetic abrasive and the simple mixture of the conventional abrasive with ferrous particles, described in Clause 5.4. Consequently, the finished surface is highly dependent on the lubricant volume, which affects the abrasive contact against the surface; on the ferrous particle size, which changes the finishing force acting on the abrasive; and on the abrasive grain size, which controls the depth of cut. Further, the experiments demonstrated the feasibility of the process to correct the form-error.

7. Conclusions

6. Residual stress Tubes cut at an angle of 45◦ were used for measurements of residual stress of the inner surface with an X-ray stress measuring apparatus. The penetration depth of the X-ray into the surface layer was calculated to be 186 ␮m. Fig. 10 shows the results of residual stress measurements of the unfinished 100

Residual stress MPa

75 50

Direction of circumference Direction of tube axis

Tube

25 0 -25

Unfinished surface Finished surface

-50 -75

-100

and finished surfaces of the same tube used for the roundness tests. In the case of the crystalline material, i.e. alumina ceramic tubes, the entrance angle of X-ray into the surface is extremely critical to the measured value of residual stress, so a wide variation of measurements may be obtained from a sample depending on the entrance angle. The values of the residual stress shown in Fig. 10 are both within the typical range and are commonly not considered to be significantly different. The results demonstrated that the proposed process enables control of surface finishes with minimal effect on the residual stress of the finished surface.

Direction of tube axis

Direction of circumference

Fig. 10. Residual stress of unfinished and finished surface.

The results of this study can be summarized as follows: (1) This study showed the feasibility of using a magnetic field assisted finishing process with a mixture of conventional abrasive and ferrous particles for the internal finishing of alumina ceramic tubes and gained an understanding of the mechanism involved. (2) The finished surface is determined by the amount of lubricant, which affects the abrasive contact against the surface; by the ferrous particle size, which changes the finishing force acting on the abrasive; and by the abrasive grain size, which controls the depth of cut. (3) The process removes material from the peaks of the uneven surface to generate a smooth surface. Further, the material is removed even more from the projections of the undulations of the profile curve. As a result, the process enables simultaneous control of the surface roughness and form accuracy. (4) The experiments also found that the process enables fine surface finishes with minimal effect on the residual stress in the target surface.

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Acknowledgments The authors would like to express their gratitude to Mr. Zenpei Tachibana of Kyocera Corporation Ltd. for his offer of workpieces and to Mr. Takuya Shimizu of Rigaku International Corporation for his support in the measurements of residual stress in the workpieces. The authors also thank Mr. Mohd Khairul Annuar B. Otman for his interest in this work.

References [1] Kingery WD, Bowen HK, Uhlmann DR. Introduction to ceramics, 2nd ed. New York: Wiley; 1976. [2] Jahanmir S. Friction and wear of ceramics. New York: Marcel Dekker, Inc.; 1994. [3] Bando S, Tsukada A, Kondo T. A study on precision internal finishing for alumina ceramics tube—trial manufacture of the abrasive tool and its performance. J Jpn Soc Abrasive Technol 2001;45(1):46–9 [in Japanese]. [4] Baron YM. Technology of abrasive machining in a magnetic field. Leningrad: Masino-Strojenije; 1975 [in Russian]. [5] Ruben HJ. In: Niku-Lari A, editor. Advances in surface treatment, vol. 5. New York: Pergamon Press; 1987. p. 239–56.

[6] Kyoei Denko Co., Ltd. Ultra-precision internal finishing process for flexible pipes. Mech Eng 2002;30(9)79. The Nikkan Kogyo Sinbun, Ltd. [in Japanese]. [7] Yamaguchi H, Shinmura T, Kobayashi A. Development of an internal magnetic abrasive finishing process for nonmagnetic complex shaped tubes. JSME Int J Ser C 2001;44(1):275–81. [8] Shimbo Y. In: Takagi T, Uesaka M, editors. Development of a new process for deburring and edge finishing of complexly shapes industrial precision parts by the application of magnetic field-assisted machining. Appl Electromagnet Mech 2001;131–2. [9] Anzai M, Nakagawa T, Yoshioka N, Banno S. Development of magnetic abrasive finishing system for electric razor blades. Proc Jpn Soc Prec Eng Fall Annu Meet 1999;221–2. [10] Yamaguchi H, Shinmura T. Development of an environmentally conscious magnetic field assisted finishing process—internal finishing of SUS304 stainless steel clean pipes. J Jpn Soc Prec Eng 2002;68(1):119– 24 [in Japanese]. [11] Wang D, Yamaguchi H, Shinmura T. Magnetic field assisted mechanochemical polishing process for inner surface of silicon nitride ceramic components. Trans Jpn Soc Mech Eng 2002;68:673(C):2770–6 [in Japanese]. [12] Engineering Ceramics Catalogue. Kyocera Corporation Ltd. [13] Yamaguchi H, Shinmura T. Study of the surface modification resulting from an internal magnetic abrasive finishing process. Wear 1999;225– 229(I):246–55. [14] Yamaguchi H, Shinmura T. Study on a new internal finishing process by the application of magnetic abrasive machining—discussion of the roundness. J Jpn Soc Prec Eng 1996;62(11):1617–21 [in Japanese].