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Characterization of abrasive grain’s behavior and wear mechanisms
Wear 254 (2003) 1294–1298
Characterization of abrasive grain’s behavior and wear mechanisms H. Hamdi∗ , M. Dursapt, H. Zahouani Laboratoire de Tribologie et Dynamique des Systèmes, UMR 5513 CNRS/ECL/ENISE, 58 rue Jean Parot, 42023 Saint-Etienne Cedex 2, France Received 7 September 2002; received in revised form 16 January 2003; accepted 13 February 2003
Abstract Grinding is a finishing process largely used in motor industry, aeronautics, space industry and precision cutting tool manufacturers. The grinding process can be summarized by the action of a grinding wheel on a workpiece. The wheel is constituted by abrasive grains. Thus grinding is in fact the action of grains on the workpiece. The grain behavior changes according to numerous parameters (geometry, mechanical characteristics, wear mechanisms). In some cases abrasive wear is observed while micro-cutting is obtained in some other cases. In this paper two useful and complementary experimental approaches for the interface physics understanding is presented. The study of the cutting power is carried out using a high-speed scratch test device in order to understand the grain behavior and the wear mechanisms for several wheel surface speeds. In this paper an approach for the specific abrasion energy computation is also presented. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Abrasion; Wear mechanisms; Scratch test; Cutting physics; Surface morphology
1. Introduction The grinding process is widely used in motor industry, aeronautics, space industry and precision cutting tool manufacturers. This process is largely studied during the last 20 years [1–4] but the understanding of the physical phenomena in the interface wheel–workpiece is not completed. In this paper two useful and complementary experimental approaches for the interface physics understanding is presented. One is realized on a testing grinder fitted out with forces sensors and using a grinding wheel with only one grain. The grain behavior is studied by analyzing the specific abrasion energy. Moreover, the study of the scratches obtained on the workpiece gives some qualitative information about the abrasive wear or the metal cutting. The results obtained are compared with those given by the sclerometer for low scratch speed. For both experimentation the specific abrasion energy is computed from the dynamic tangential force measurement and the analysis of the scratch topography. 2. High-speed scratch test 2.1. Principle The principle of the high-speed scratch test is illustrated in Fig. 1. The specific grinding wheel used is equipped with ∗ Corresponding author. Tel.: +33-4-77438434; fax: +33-4-77438499. E-mail address: [email protected] (H. Hamdi).
only one blue corundum grain (Figs. 1 and 2). The shape of the corundum grain could be seen in Fig. 2 and the size could be determined using the same figure. The testing characteristics are the following: the scratch velocity Vs is about 37.3 m s−1 for a grinding wheel diameter equal to 250 mm and a rotation speed about 2850 rpm, the feed speed Vw is about 30 m min−1 and finally the depth of cut is imposed and equal to 20 m. The grain have a rotation and a translation movement. So, the expected result is a succession of scratches on the workpiece (Fig. 3). During the test, the normal and tangential forces are recorded by the way of a piezoelectric dynamometer KisTler 5257A (Fig. 1). The sample is a quench bearing steel (AISI 52100, 62 HRC). 2.2. Scratch analysis The scratch morphology given in Fig. 4 is obtained by means of a tactile profilemeter and analyzed with the TopoSurf image processing software. From the scratch morphology lots of qualitative information or explanation could be extracted. First, the scratch morphology shows that one grain induces several manufacturing scratches, three in our case (Fig. 4). So, the first conclusion is that one grain is not only constituted by one cutting edge like it was found in the past [5]. In our case, there are three or more active cutting edges as the manufacturing scratches MS1 , MS2 and MS3 could have illustrated it (Fig. 4).
0043-1648/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0043-1648(03)00158-3
H. Hamdi et al. / Wear 254 (2003) 1294–1298
1295
Fig. 1. High-speed scratch test.
Fig. 4. Scratch morphology.
Fig. 2. Grain topography.
The frontal roll present at the end of the scratch (Fig. 4) is in fact a chip which is not ejected from the workpiece. Moreover, lateral rolls are observed in some area of the scratch. So, during the scratch test there is a lateral flow of the material as it could be expected. This lateral flow of the material is more important in some area of the scratch and in some other it is unobserved as it is illustrated on the extracted transversal profile (Fig. 5). If the manufacturing scratch MS1 is particularly studied (Figs. 4 and 5), it
Fig. 3. Succession of scratches on the workpiece.
is clear that the lateral rolls are virtually non-existent for the whole length of the scratch. Moreover MS1 is manufactured by the highest cutting edge of the grain (Fig. 2). This shows that for this cutting edge it seems that metal cutting occurs while for the other one abrasive wear and plowing seems to have happened. In fact, the study of the physical phenomena of the metal cutting must take into account the grain topography (Fig. 2) and an abrasive grain has several cutting edges and not only one as it was suggested in the literature [5]. From the scratch analysis (Fig. 4) and the phenomena interpretations, the concept of minimum chip as it is widely explained for other machining process like turning or milling could be introduced in the abrasive grain scale. The study of the shape of the scratch gives some other interesting information. In fact, if the theoretical trajectory of the grain [6] and the experimental measurement of the scratch shape are compared, the way the material move in the vertical direction could be qualitatively understood (Fig. 6). The theoretical depth of the scratch is greater than the experimental one like it could be observed in Fig. 6. So, during the scratch test there is probably an elastic strain of the ma-
Fig. 5. Transversal profile extracted from the scratch (Fig. 4).
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H. Hamdi et al. / Wear 254 (2003) 1294–1298
Fig. 9. The principle of the sclerometer.
Fig. 6. Superposition of the theoretical and experimental trajectory.
a numerical integration must be performed to compute the specific abrasive energy. Let W denote the mechanical energy given by the following equation: 1 W= Ft (x) dx (2) 0
The scratch length l is equal to 5 mm in our case (Fig. 4). So 5 Ft (x) dx = 85.34 × 10−3 J (3) W= 0
Fig. 7. Background of the chip.
terial in front of the cutting edge. Then when the mechanical stresses are higher, a part of the material gets round the grain in the lateral (lateral roll, Fig. 4) and/or vertical way, the rest results in a chip (Fig. 7) [6].
And finally the specific abrasive energy is equal to W Es = = 15.86 J mm−3 Ve
(4)
The present result must be confronted to the result obtained with the sclerometer exposed in the sequel.
3. Standard scratch test: sclerometer
2.3. Specific abrasive energy
3.1. Principle
The specific abrasive energy Es is the energy needed to removed a volume of material. This quantity is widely used by abrasive manufacture to qualify the grain behavior. It is computed using Eq. (1) [6,7]: l Ft (x) dx Es = 0 (1) Ve
The sclerometer principle [6,7] is illustrated in Fig. 9. The aim is to score a surface with an indenter. A normal force Fn = 20 N and a displacement are imposed to the indenter. The tangential force Ft is measured by a piezoelectric sensor during the test. The scratch velocity in this case is equal to 0.3 mm s−1 while for the high-speed scratch test it is equal to 37.3 m s−1 . So, the influence of the scratch velocity could be studied. Like for the high-speed scratch test the indenter is a blue corundum grain and the workpiece is a quench bearing steel (AISI 52100).
where Ft is the tangential force (N), Ve the material volume removed (m3 ), and l the length of the scratch (m). In the case of this present study the material volume removed Ve , in the above experimental condition, is established using the TopoSurf image processing software and is equal to Ve = 5.38 × 10−3 mm3 (Fig. 4). The acquired tangential force (Fig. 8) is not constant. So,
Fig. 8. Tangential force for the high-speed scratch test.
3.2. Scratch analysis Figs. 10 and 11 show that in the case of the standard scratch test the lateral rolls are less marked as compared to those obtained in a high-speed scratch test. The differences between the two experiments is first the velocity and second the trajectory. Do those differences influence the metal cutting physic? Any response could be given with the present scratch analysis. Like it is previously noticed, the scratch in the sclerometer test is constituted by several manufacturing scratches too. So, the grain have several cutting edges.
H. Hamdi et al. / Wear 254 (2003) 1294–1298
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Fig. 12. Tangential force in the sclerometer test.
The volume of the material removed is equal to Ve = 1.34× 10−4 mm3 , so the specific abrasive energy is equal to Es = 52.23 J mm−3 .
4. Discussion Fig. 10. Sclerometer scratch morphology.
Fig. 11. Transversal profile extracted from the scratch (Fig. 10).
3.3. Specific abrasive energy The specific abrasive energy is computed using Eq. (1). The analysis of the scratch represented in Fig. 10 by means of TopoSurf gives the volume Ve = 1.34 × 10−4 mm3 of the material removed. The acquired tangential force represented in Fig. 12 could be considered as constant. In the steady state, the mean of the tangential force Ft is equal to 10 N for a scratch length equal to 0.7 mm (Fig. 12). So the specific abrasive energy is computed as follows: l l Ft (x) 0.3 dx Ft (x)(l − 0.3) 0.3 Ft (x) dx Es = = = (5) Ve Ve Ve
In Table 1, it is observed that the specific abrasion energy decreases when the scratch speed increases. Such analysis could involve some mistakes and could lead to some conclusions like the scratch velocity influence the physical phenomena as the metal cutting, the wear mechanisms, the plowing, etc. The greatest care must be taken, and an analysis of the two above experiments must be done. First, the experimental conditions are different. In the standard scratch test case a normal force Fn is imposed and in the high-speed scratch test the cutting depth is imposed. Such differences give a first incidence on the maximum normal force measured and cutting depth. Secondly, a physic analysis of the two experiences shows that the trajectories of the two grains are different from one process to another. In one case, the trajectory is linear and in the other one it is circular. This observation has an important consequence on the forces distribution (Figs. 8 and 12) and may have an incidence on the way the material is removed. In fact, during the high-speed scratch test the depth of scratch varies theoretically from 0 up to 20 m. This is why the tangential force distribution is not constant (Fig. 8). Moreover, the cutting angle varies too during the high-speed scratch test which may affect the specific abrasive energy. The sclerometer experiment gives some advantages. It is easy to make use of this way of investigation for several reasons. First, the low velocity of the grain during the scratch test make the acquirement of the forces more easier. Secondly, the grain could be easily replaced on the indenter (Fig. 9), which is a great advantage when the life time and the wear mechanisms of a grain population are studied. Finally, the sclerometer is useful when an abrasive manufacture
Table 1 Recapitulative table
Sclerometer High-speed scratch test
Ft,max (N)
Fn,max (N)
Depth of the scratch (m)
Vs
Ve (mm3 )
Es (J mm−3 )
10 7
20 67
5 20
0.3 mm s−1 37 m s−1
1.34 × 10−4 5.38 × 10−3
52.23 15.86
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H. Hamdi et al. / Wear 254 (2003) 1294–1298
will study the influence of the shape and the cutting angles of the grain on the specific abrasion energy. This could be a fast way to classify a population of grain and extract those presenting the best abrasive behavior. The high-speed scratch test gives some advantages too. It allows to study the grain abrasive behavior in the case of grinding conditions which impose the trajectories, the velocity and the depth of cut. The main drawback is to hold the grain in position on the disk (Fig. 1) which make the experiment heavy when several grains must be compared. The comparison of the two experiments is critical in term of the effect of the velocity on the grain behavior and the abrasive phenomena. The experiment conditions are different and induce two types of trajectories which may have an influence on the expected results. At last, the two experiments are complementary because one (the sclerometer) allows an easy classification of an abrasive grain population in terms of life time, wear resistance and specific abrasive energy, and the other permits a second selection when good mechanical behavior is expected in the grinding process condition. 5. Conclusion In this paper two experiments which give some interesting information on the grain behavior are presented. The high-speed scratch test for the study of the grain behavior is the nearest of the real process and give more qualitatively physics information of the grinding process. In further investigations, it seems that it is interesting to study the in-
fluence of the velocity on the grain behavior in the case of high-speed scratch test. Moreover, the experimental results of the grain behavior presented in this paper must be confronted to some numerical simulation of the scratch test. At last, if the behavior of the grain on the metal cutting characteristics and physics will be understood, the grinding process and its effects on the workpiece will be better understood too. References [1] E. Minke, E. Brinksmeier, The use of conventional grinding wheels in high-performance grinding processes, in: Proceedings of the First International Machining and Grinding Conference (SME), SME Identification, Product ID MR95-199, Paper No. MR95-199, Dearborn, USA, 1995, 12 pp. [2] J.W. Kim, H. Gupta, High speed grinding: evaluation of wheel performance and surface integrity, J. Mater. Process. Manuf. Sci. 5 (2) (1996) 115–126. [3] F. Klock, E. Brinksmeier, C. Evans, T. Howes, I. Inasaki, E. Minke, H.K. Toenshoff, J.A. Webster, D. Stuff, High-speed grinding: fundamentals and state of the art in Europe, Japan, and the USA, CIRP Ann. Manuf. Technol. 46 (2) (1997) 715–724. [4] B.N. Colding, A wear relationship for turning, milling and grinding— machining economics, Ph.D. Thesis, Stockholm, 1959. [5] J. Verkerk, Final report concerning CIRP cooperative work in the characterisation of grinding wheel topography, Ann. CIRP 26 (2) (1977) 385–395. [6] H. Hamdi, Contribution to the study of the physical phenomena in the wheel–workpiece interface in the case of traditional and high speed grinding, Ph.D. Thesis, Ecole Central de Lyon, 2000, 170 pp. [7] V. Jardret, H. Zahouani, T.G. Mathia, Technique for analysis of scratch genesis: morphological and rheological point of view, in: T.S. Sudarshan, M. Jeandin (Eds.), Surface Modification Technologies VIII, The Institute of Materials, 1995, pp. 222–228.
Characterization of abrasive grain’s behavior and wear mechanisms H. Hamdi∗ , M. Dursapt, H. Zahouani Laboratoire de Tribologie et Dynamique des Systèmes, UMR 5513 CNRS/ECL/ENISE, 58 rue Jean Parot, 42023 Saint-Etienne Cedex 2, France Received 7 September 2002; received in revised form 16 January 2003; accepted 13 February 2003
Abstract Grinding is a finishing process largely used in motor industry, aeronautics, space industry and precision cutting tool manufacturers. The grinding process can be summarized by the action of a grinding wheel on a workpiece. The wheel is constituted by abrasive grains. Thus grinding is in fact the action of grains on the workpiece. The grain behavior changes according to numerous parameters (geometry, mechanical characteristics, wear mechanisms). In some cases abrasive wear is observed while micro-cutting is obtained in some other cases. In this paper two useful and complementary experimental approaches for the interface physics understanding is presented. The study of the cutting power is carried out using a high-speed scratch test device in order to understand the grain behavior and the wear mechanisms for several wheel surface speeds. In this paper an approach for the specific abrasion energy computation is also presented. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Abrasion; Wear mechanisms; Scratch test; Cutting physics; Surface morphology
1. Introduction The grinding process is widely used in motor industry, aeronautics, space industry and precision cutting tool manufacturers. This process is largely studied during the last 20 years [1–4] but the understanding of the physical phenomena in the interface wheel–workpiece is not completed. In this paper two useful and complementary experimental approaches for the interface physics understanding is presented. One is realized on a testing grinder fitted out with forces sensors and using a grinding wheel with only one grain. The grain behavior is studied by analyzing the specific abrasion energy. Moreover, the study of the scratches obtained on the workpiece gives some qualitative information about the abrasive wear or the metal cutting. The results obtained are compared with those given by the sclerometer for low scratch speed. For both experimentation the specific abrasion energy is computed from the dynamic tangential force measurement and the analysis of the scratch topography. 2. High-speed scratch test 2.1. Principle The principle of the high-speed scratch test is illustrated in Fig. 1. The specific grinding wheel used is equipped with ∗ Corresponding author. Tel.: +33-4-77438434; fax: +33-4-77438499. E-mail address: [email protected] (H. Hamdi).
only one blue corundum grain (Figs. 1 and 2). The shape of the corundum grain could be seen in Fig. 2 and the size could be determined using the same figure. The testing characteristics are the following: the scratch velocity Vs is about 37.3 m s−1 for a grinding wheel diameter equal to 250 mm and a rotation speed about 2850 rpm, the feed speed Vw is about 30 m min−1 and finally the depth of cut is imposed and equal to 20 m. The grain have a rotation and a translation movement. So, the expected result is a succession of scratches on the workpiece (Fig. 3). During the test, the normal and tangential forces are recorded by the way of a piezoelectric dynamometer KisTler 5257A (Fig. 1). The sample is a quench bearing steel (AISI 52100, 62 HRC). 2.2. Scratch analysis The scratch morphology given in Fig. 4 is obtained by means of a tactile profilemeter and analyzed with the TopoSurf image processing software. From the scratch morphology lots of qualitative information or explanation could be extracted. First, the scratch morphology shows that one grain induces several manufacturing scratches, three in our case (Fig. 4). So, the first conclusion is that one grain is not only constituted by one cutting edge like it was found in the past [5]. In our case, there are three or more active cutting edges as the manufacturing scratches MS1 , MS2 and MS3 could have illustrated it (Fig. 4).
0043-1648/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0043-1648(03)00158-3
H. Hamdi et al. / Wear 254 (2003) 1294–1298
1295
Fig. 1. High-speed scratch test.
Fig. 4. Scratch morphology.
Fig. 2. Grain topography.
The frontal roll present at the end of the scratch (Fig. 4) is in fact a chip which is not ejected from the workpiece. Moreover, lateral rolls are observed in some area of the scratch. So, during the scratch test there is a lateral flow of the material as it could be expected. This lateral flow of the material is more important in some area of the scratch and in some other it is unobserved as it is illustrated on the extracted transversal profile (Fig. 5). If the manufacturing scratch MS1 is particularly studied (Figs. 4 and 5), it
Fig. 3. Succession of scratches on the workpiece.
is clear that the lateral rolls are virtually non-existent for the whole length of the scratch. Moreover MS1 is manufactured by the highest cutting edge of the grain (Fig. 2). This shows that for this cutting edge it seems that metal cutting occurs while for the other one abrasive wear and plowing seems to have happened. In fact, the study of the physical phenomena of the metal cutting must take into account the grain topography (Fig. 2) and an abrasive grain has several cutting edges and not only one as it was suggested in the literature [5]. From the scratch analysis (Fig. 4) and the phenomena interpretations, the concept of minimum chip as it is widely explained for other machining process like turning or milling could be introduced in the abrasive grain scale. The study of the shape of the scratch gives some other interesting information. In fact, if the theoretical trajectory of the grain [6] and the experimental measurement of the scratch shape are compared, the way the material move in the vertical direction could be qualitatively understood (Fig. 6). The theoretical depth of the scratch is greater than the experimental one like it could be observed in Fig. 6. So, during the scratch test there is probably an elastic strain of the ma-
Fig. 5. Transversal profile extracted from the scratch (Fig. 4).
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H. Hamdi et al. / Wear 254 (2003) 1294–1298
Fig. 9. The principle of the sclerometer.
Fig. 6. Superposition of the theoretical and experimental trajectory.
a numerical integration must be performed to compute the specific abrasive energy. Let W denote the mechanical energy given by the following equation: 1 W= Ft (x) dx (2) 0
The scratch length l is equal to 5 mm in our case (Fig. 4). So 5 Ft (x) dx = 85.34 × 10−3 J (3) W= 0
Fig. 7. Background of the chip.
terial in front of the cutting edge. Then when the mechanical stresses are higher, a part of the material gets round the grain in the lateral (lateral roll, Fig. 4) and/or vertical way, the rest results in a chip (Fig. 7) [6].
And finally the specific abrasive energy is equal to W Es = = 15.86 J mm−3 Ve
(4)
The present result must be confronted to the result obtained with the sclerometer exposed in the sequel.
3. Standard scratch test: sclerometer
2.3. Specific abrasive energy
3.1. Principle
The specific abrasive energy Es is the energy needed to removed a volume of material. This quantity is widely used by abrasive manufacture to qualify the grain behavior. It is computed using Eq. (1) [6,7]: l Ft (x) dx Es = 0 (1) Ve
The sclerometer principle [6,7] is illustrated in Fig. 9. The aim is to score a surface with an indenter. A normal force Fn = 20 N and a displacement are imposed to the indenter. The tangential force Ft is measured by a piezoelectric sensor during the test. The scratch velocity in this case is equal to 0.3 mm s−1 while for the high-speed scratch test it is equal to 37.3 m s−1 . So, the influence of the scratch velocity could be studied. Like for the high-speed scratch test the indenter is a blue corundum grain and the workpiece is a quench bearing steel (AISI 52100).
where Ft is the tangential force (N), Ve the material volume removed (m3 ), and l the length of the scratch (m). In the case of this present study the material volume removed Ve , in the above experimental condition, is established using the TopoSurf image processing software and is equal to Ve = 5.38 × 10−3 mm3 (Fig. 4). The acquired tangential force (Fig. 8) is not constant. So,
Fig. 8. Tangential force for the high-speed scratch test.
3.2. Scratch analysis Figs. 10 and 11 show that in the case of the standard scratch test the lateral rolls are less marked as compared to those obtained in a high-speed scratch test. The differences between the two experiments is first the velocity and second the trajectory. Do those differences influence the metal cutting physic? Any response could be given with the present scratch analysis. Like it is previously noticed, the scratch in the sclerometer test is constituted by several manufacturing scratches too. So, the grain have several cutting edges.
H. Hamdi et al. / Wear 254 (2003) 1294–1298
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Fig. 12. Tangential force in the sclerometer test.
The volume of the material removed is equal to Ve = 1.34× 10−4 mm3 , so the specific abrasive energy is equal to Es = 52.23 J mm−3 .
4. Discussion Fig. 10. Sclerometer scratch morphology.
Fig. 11. Transversal profile extracted from the scratch (Fig. 10).
3.3. Specific abrasive energy The specific abrasive energy is computed using Eq. (1). The analysis of the scratch represented in Fig. 10 by means of TopoSurf gives the volume Ve = 1.34 × 10−4 mm3 of the material removed. The acquired tangential force represented in Fig. 12 could be considered as constant. In the steady state, the mean of the tangential force Ft is equal to 10 N for a scratch length equal to 0.7 mm (Fig. 12). So the specific abrasive energy is computed as follows: l l Ft (x) 0.3 dx Ft (x)(l − 0.3) 0.3 Ft (x) dx Es = = = (5) Ve Ve Ve
In Table 1, it is observed that the specific abrasion energy decreases when the scratch speed increases. Such analysis could involve some mistakes and could lead to some conclusions like the scratch velocity influence the physical phenomena as the metal cutting, the wear mechanisms, the plowing, etc. The greatest care must be taken, and an analysis of the two above experiments must be done. First, the experimental conditions are different. In the standard scratch test case a normal force Fn is imposed and in the high-speed scratch test the cutting depth is imposed. Such differences give a first incidence on the maximum normal force measured and cutting depth. Secondly, a physic analysis of the two experiences shows that the trajectories of the two grains are different from one process to another. In one case, the trajectory is linear and in the other one it is circular. This observation has an important consequence on the forces distribution (Figs. 8 and 12) and may have an incidence on the way the material is removed. In fact, during the high-speed scratch test the depth of scratch varies theoretically from 0 up to 20 m. This is why the tangential force distribution is not constant (Fig. 8). Moreover, the cutting angle varies too during the high-speed scratch test which may affect the specific abrasive energy. The sclerometer experiment gives some advantages. It is easy to make use of this way of investigation for several reasons. First, the low velocity of the grain during the scratch test make the acquirement of the forces more easier. Secondly, the grain could be easily replaced on the indenter (Fig. 9), which is a great advantage when the life time and the wear mechanisms of a grain population are studied. Finally, the sclerometer is useful when an abrasive manufacture
Table 1 Recapitulative table
Sclerometer High-speed scratch test
Ft,max (N)
Fn,max (N)
Depth of the scratch (m)
Vs
Ve (mm3 )
Es (J mm−3 )
10 7
20 67
5 20
0.3 mm s−1 37 m s−1
1.34 × 10−4 5.38 × 10−3
52.23 15.86
1298
H. Hamdi et al. / Wear 254 (2003) 1294–1298
will study the influence of the shape and the cutting angles of the grain on the specific abrasion energy. This could be a fast way to classify a population of grain and extract those presenting the best abrasive behavior. The high-speed scratch test gives some advantages too. It allows to study the grain abrasive behavior in the case of grinding conditions which impose the trajectories, the velocity and the depth of cut. The main drawback is to hold the grain in position on the disk (Fig. 1) which make the experiment heavy when several grains must be compared. The comparison of the two experiments is critical in term of the effect of the velocity on the grain behavior and the abrasive phenomena. The experiment conditions are different and induce two types of trajectories which may have an influence on the expected results. At last, the two experiments are complementary because one (the sclerometer) allows an easy classification of an abrasive grain population in terms of life time, wear resistance and specific abrasive energy, and the other permits a second selection when good mechanical behavior is expected in the grinding process condition. 5. Conclusion In this paper two experiments which give some interesting information on the grain behavior are presented. The high-speed scratch test for the study of the grain behavior is the nearest of the real process and give more qualitatively physics information of the grinding process. In further investigations, it seems that it is interesting to study the in-
fluence of the velocity on the grain behavior in the case of high-speed scratch test. Moreover, the experimental results of the grain behavior presented in this paper must be confronted to some numerical simulation of the scratch test. At last, if the behavior of the grain on the metal cutting characteristics and physics will be understood, the grinding process and its effects on the workpiece will be better understood too. References [1] E. Minke, E. Brinksmeier, The use of conventional grinding wheels in high-performance grinding processes, in: Proceedings of the First International Machining and Grinding Conference (SME), SME Identification, Product ID MR95-199, Paper No. MR95-199, Dearborn, USA, 1995, 12 pp. [2] J.W. Kim, H. Gupta, High speed grinding: evaluation of wheel performance and surface integrity, J. Mater. Process. Manuf. Sci. 5 (2) (1996) 115–126. [3] F. Klock, E. Brinksmeier, C. Evans, T. Howes, I. Inasaki, E. Minke, H.K. Toenshoff, J.A. Webster, D. Stuff, High-speed grinding: fundamentals and state of the art in Europe, Japan, and the USA, CIRP Ann. Manuf. Technol. 46 (2) (1997) 715–724. [4] B.N. Colding, A wear relationship for turning, milling and grinding— machining economics, Ph.D. Thesis, Stockholm, 1959. [5] J. Verkerk, Final report concerning CIRP cooperative work in the characterisation of grinding wheel topography, Ann. CIRP 26 (2) (1977) 385–395. [6] H. Hamdi, Contribution to the study of the physical phenomena in the wheel–workpiece interface in the case of traditional and high speed grinding, Ph.D. Thesis, Ecole Central de Lyon, 2000, 170 pp. [7] V. Jardret, H. Zahouani, T.G. Mathia, Technique for analysis of scratch genesis: morphological and rheological point of view, in: T.S. Sudarshan, M. Jeandin (Eds.), Surface Modification Technologies VIII, The Institute of Materials, 1995, pp. 222–228.