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High stress abrasive wear study on bamboo
Journal of Materials Processing Technology 183 (2007) 155–159
High stress abrasive wear study on bamboo Navin Chand ∗ , U.K. Dwivedi Regional Research Laboratory (CSIR), Hoshangabad Road, Habibganj Naka, Bhopal 462026, India Received 28 October 2004; received in revised form 20 September 2006; accepted 25 September 2006
Abstract High stress abrasive wear of bamboo in mainly two directions parallel and perpendicular to the fibre direction has been determined by using a Suga abrasion wear tester. Bamboo is a unidirectional natural composite. Unidirectional cellulosic fibres in bamboo provide unique directional wear properties. The anisotropic abrasive wear behaviour was observed due to difference in fibre vascular bundle orientation present in bamboo. Wear anisotropy of bamboo depended on load and abrasive grit size. Wear anisotropy dependence on load can be represented by the following relation: WTT = −aL2 + bL − c WLL Relation between wear anisotropy and grit size is found to be as follows: WTT = −eS 3 + fS 2 − gS + h WLL Weight loss dependence on grit size for bamboo follows the following equation W = xS 2 − yS + z Worn surfaces of bamboo and its debris were observed by using a SEM and discussed in this paper. © 2006 Elsevier B.V. All rights reserved. Keywords: Bamboo; High stress abrasive wear; SEM; Anisotropy
1. Introduction Bamboo is a well known constructional material throughout all the tropical countries. Bamboo is a natural lignocellulosic composite material, in which cellulosic fibres are embedded in a lignin matrix. Cells of bamboo have been categorized into two types: matrix tissue cells and sclerenchyma cells. Matrix tissue cells are leptodermous and act as the matrix. Sclerenchyma cells consist of vascular bundles are enveloped in the matrix tissue. Vascular bundles act as reinforcements in bamboo. A vascular bundle is made-up of several phloem fibres. A phloem fibre is made of several layers of pillar fibres. Micro-fibres in each layer of the pillar fibres are spirally arranged at a fixed spiral angle, which varies for different layers of pillar fibres. Vascular bundle is made-up of many right-handed spiral phloem fibres [1].
∗
Corresponding author. E-mail address: [email protected] (N. Chand).
0924-0136/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2006.09.036
Chemical constituents present in bamboo are cellulose, hemicellulose and lignin. Cellulose and hemicellulose are present in the form of holocellulose, which contribute to more than 50% of the total chemical constituents in bamboo. The second important chemical constituent present in bamboo is lignin. Lignin in bamboo acts as a binder or matrix for the cellulose fibres. Lignin is an energy storage system in bamboo and responds to mechanical stresses as a composite material [2]. Mechanical properties of bamboo have been reported earlier [3]. Bamboo has excellent mechanical properties with specific strength and modulus being comparable to that of unidirectional glass-reinforced plastic. Abrasive wear of bamboo (Phyllostachys pubescens) against a free abrasive consisting of quartz sand and bentonite was determined on a rotary-disk type abrasive wear tester by Tong et al. [1]. Fibres due to the molecular alignment show anisotropy in their physical, and electrical properties [4]. For unidirectional composites the model of Tandon and Weng, the self-consistent scheme [5] and the Halpin–Tsai [6] equations for modulus are used. The arbitrary fibre orientation modeling has been done
156
N. Chand, U.K. Dwivedi / Journal of Materials Processing Technology 183 (2007) 155–159
by Mlekusch [7]. By this method, it is possible to investigate the different fibre orientation behaviour. The behaviour of the composite is orientation-dependent (anisotropic). Anisotropy in a composite is caused by the orientation of the fibres, different composite properties are obtained for each fibre orientation distribution. A comprehensive overview of the methodology and the different possibilities for micro mechanical modeling of fibre-reinforced systems is given by Hashin [8]. For continuousfibre-reinforced systems a critical comparison of the results from different theories is reported in the literature [9]. Chand and Fahim in their previous paper reported abrasive wear for glass fibre reinforced composites [10]. In another paper Chand et al. [11] reported a new theory for abrasive wear mechanisms for FRP composites. Chand and Fahim [12] have also given a new macro mechanism theory for slurry abrasion for short glass fibre reinforced polyester composites. Lancaster [13] reported that carbon fibre polyester composites, show minimum wear, when fibres are perpendicular to the sliding surface. However, maximum wear was observed in the composite having longitudinal fibres. Tsukizoe and Ohmea [14] found that relative wear rate between longitudinal and transverse fibre cases was dependent on the type of carbon fibres. High strength carbon fibre epoxy composite shows high wear in transverse orientation than in longitudinal orientation, but in high modulus carbon fibre composite the reverse trend was found. Abrasive wear performance of bamboo is an important aspect to exploit its use in industrial applications. In fibre reinforced composite, dimension and orientation of fibres are important factors for their tribological properties. Wear data on natural composite structure of bamboo can provide clues and ideas for designs of composites for making anti-friction materials and wear-resistant materials. As per the basic knowledge, wear rate in lignocellulosic fibre is anisotropic but no body else has reported the high stress wear anisotropy behaviour of
composites and nobody has given the generalized equation for anisotropy dependence of bamboo with load and abrasive grit. The purpose of this paper is to study the wear behaviour of bamboo under varying load and abrasive grit size and to provide new equations for their abrasive wear results. It is expected that the wear behaviour of natural fibre composites in two directions namely parallel and perpendicular to the fibre alignment will be different. 2. Experimental 2.1. Materials Bamboo (Dentrocalamus strictus) was obtained from Sehore forest, India. Bamboo used in this study was solid bamboo, in which diameter of fibre is 0.3–0.5 mm and their complete characteristics are listed in Table 1. Unidirectional cellulose fibres reinforced in lignin (natural binder) makes it a natural composite. The density of the bamboo is 0.66 g/cc. Wear test specimens of bamboo were cut in a standard size of 45 mm × 35 mm × 5 mm. A section between two nodes was cut, which was in solid cylindrical form. From this solid cylindrical bamboo, strips were cut along the fibre and transverse direction. Two types of bamboo specimens were prepared and well polished. In the TT-type, the vascular bundle orientation was normal to the abrading surface (Fig. 1a). In the LL type the bundle orientation was parallel to the sliding direction (Fig. 1b) and the abrasion surface was from middle region of bamboo.
2.2. Tensile testing The tensile samples as per ASTM D 638 were prepared by cutting the bamboo strips. Samples were tested at 10 mm min−1 cross head speed of testing by using an electronic universal testing machine model UT-10 Scientific Testing (India). Average of three samples is reported here.
2.3. Wear testing Two-body abrasive wear tests were performed on bamboo samples by using a SUGA abrasion tester model-NUS1 (Japan), which is described elsewhere [15]. The rectangular specimen of 45 mm × 35 mm was slid against a rotating
Table 1 Some properties of bamboo in different directions S. no.
Direction
Density (g/cc)
Microfibril angle (◦ )
Cellulose (%)
Lignin content (%)
Elongation
Tensile strength (MPa)
1 2
Along the fibre direction Perpendicular to the fibre direction
0.66 0.66
2–10 –
60–62 –
38–40 –
11.3 0.14
167 19
Fig. 1. Schematic diagram of fibre orientation and sliding direction in bamboo sample.
N. Chand, U.K. Dwivedi / Journal of Materials Processing Technology 183 (2007) 155–159
157
wheel, on which abrasive papers of 120, 180, 320 and 400 grit sizes (John Oakey & Mohan Ltd., India) were mounted using a double sided adhesive tape. The embedded hard SiC particles abraded the test sample. The weight-loss was measured for each 400 cycles, which corresponds to 25.6 m sliding distance. A constant sliding speed of 2.56 m min−1 and four loads 1, 3, 5 and 7 N were applied for testing the samples.
2.4. SEM studies Worn surface and debris of bamboo were observed by using scanning electron microscope (model JEOL, Japan). The sample surfaces were gold before observing the surfaces.
3. Results and discussions The schematic look of the fibre arrangement in Bamboo in parallel and perpendicular fibre directions is shown in Fig. 1a LL, Fig. 1b TT, respectively. Wear ratio of bamboo in normal (WTT ) to parallel fibre direction (WLL ) or wear anisotropy for different loads and different grit size has been determined by using Suga Abrasion Tester. Fig. 2 shows the dependence of wear anisotropy at different applied loads 1, 3, 5 and 7 N for 25.6 m sliding distance. Wear anisotropy increased on increasing load. At 1 N load, TT sample shows minimum weight loss because this load is insufficient to cut cross section of fiber, only matrix is detached from bamboo. Increase of load from 1 to 5 N, value of WTT /WLL increased. Further increase of load from 5 to 7 N decreased anisotropy ratio. Minimum anisotropy occurred at 5 N load. Weight loss in TT direction increased as compared to LL direction at 5 N load. Following relationship between wear anisotropy WTT /WLL and load for bamboo is found WTT = −aL2 + bL − c WLL where WLL and WTT are the wear in parallel and perpendicular directions of fibres orientations and L is the applied load. Constants a, b and c for bamboo are 0.106, 0.692, and 0.508, respectively. Fig. 3 shows the dependence of wear anisotropy on different abrasive grit size. On increasing the grit size more removal
Fig. 2. Plot between abrasive wear anisotropy vs. applied load for bamboo.
Fig. 3. Plot between wear anisotropy vs. grit size for bamboo.
of material occurred due to the deep ploughing action. But anisotropy is minimum for 320 grit size. This may be because this particle size matches with the fibre diameter and hence it removed complete vascular bundles. Peak in the anisotropy has been observed for 180 grit size. Following relation between wear anisotropy and grit size for bamboo is proposed WTT = −eS 3 + fS 2 − gS + h WLL where S is the abrasive grit size and e, f, g and h are constants. The coefficient of correlation R2 value is 1. Above proposed equation is tested for the bamboo data, which fits well. Values of constant, e, f, g and h are 4E−08, 3E−05, 0.0073 and 1.0807, respectively, at 25.6 m sliding distance. Fig. 4 shows that variation in abrasive grit size from 400 to 120 grit increase the weight loss of the bamboo. It has been observed that weight loss is maximum in case of LL fibre direction, while minimum weight loss is found in TT direction. In perpendicular fibre alignment (TT) direction, weight loss reduced due to more resistance offered by the fibres. When fibres were perpendicular to wear directions (TT) they created more hindrance in the path of the abrading particles and resisted the movement of abrading particles, which reduced the wear. General weight-loss (W) behaviour with grit size in bamboo can
Fig. 4. Plot between weight loss vs. grit size for parallel (LL) and perpendicular (TT) direction for applied load = 5 N, sliding distance = 25.6 m.
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be represented by the following equation for both perpendicular and parallel direction wear. Only the coefficient will be different for two types of wear. This behaviour is equated in following relation W = xS 2 − yS + z where W is the weight loss in parallel and perpendicular direction of fibres orientations and S is the abrasive grit size. Above proposed equation is tested for the bamboo, which fits well. Constants x, y and z are 6E−07, 0.0004 and 0.0917 for LL and 4E−07, 0.0003 and 0.0529 for TT samples, respectively, for 25.6 m sliding distance. The R2 values were 0.9989 and 0.9857 for LL and TT samples, respectively. Fig. 5 shows the higher weight loss for the longitudinal direction than in perpendicular direction at different applied loads. In TT case, on applying 1 N load, bamboo fibre did not cut by hard abrasive, only binder (lignin) content pulverized and came out from bamboo. That is why at 1 N minimum weight loss is observed. In parallel orientation, (LL case) whole cell got abraded and removed during abrasion, which is visible in SEM
Fig. 5. Plot between weight loss vs. applied load for parallel (LL) and perpendicular (TT) direction at sliding distance = 25.6 m.
photos (Fig. 6a). Wear debris of matrix present between the fibres are easily swept away by the asperity interaction, resulting in high wear in the longitudinal case (LL). The real contact area of fibre with abrading particles in LL directions is more
Fig. 6. Scanning electron micrograph: (a) scanning electron micrograph of wear surfaces of LL case; (b) scanning electron micrograph of wear surfaces of TT case; (c) scanning electron micrograph of wear debris of TT case; (d) scanning electron micrograph of wear debris of LL case.
N. Chand, U.K. Dwivedi / Journal of Materials Processing Technology 183 (2007) 155–159
than that in TT orientation. In case of TT direction, cellulosic cells are oriented against the sliding direction, only cross section comes in contact and that did not remove easily (Fig. 6b). Wear debris of bamboo specimens are of two types. One part was very fine divided powder obtained in TT direction (Fig. 6c), which had adhered to the emery papers, used for abrasion during the wear process; the other part was micro fibrous type, which had got abraded from LL sample (Fig. 6d) on the emery papers. Debris obtained from TT-samples were due to the microcutting and micro-ploughing action. 4. Conclusions (1) The high stress wear anisotropy of bamboo depends on load and abrasive grit size. (2) A new equation between abrasive wear anisotropy and load for bamboo is proposed. (3) Another relation between abrasive wear anisotropy with abrasive grit is also suggested. (4) The high stress wear behaviour is affected by the vascular bundle fibre orientation with respect to the abrading surface and abrasive particle sizes. Acknowledgements Authors are highly thankful to IUC (DAEF-UGC) for their kind permission for carrying out the above morphological work.
159
One of the authors Mr. U.K. Dwivedi is highly thankful to CSIR for giving him senior research fellowship during this work. References [1] J. Tong, L. Ren, J. Li, B Chen, Abrasive wear behaviour of bamboo, Tribol. Int. 28 (5) (1995) 323–327. [2] S. Jain, R. Kumar, U.C. Jindal, Mechanical behaviour of bamboo and bamboo composite, J. Mater. Sci. 27 (1992) 4598–4604. [3] S.C. Lakkad, J.M. Patel, Mechanical properties of bamboo, a natural composite, Fibre Sci. Technol. 14 (1981) 319–322. [4] N. Chand, D. Jain, Composites Part A 36 (5) (2005) 594. [5] G.P. Tandon, G.J. Weng, The effect of aspect ratio of inclusions on the elastic properties of unidirectionally aligned composites, Polym. Compos. 5 (4) (1984). [6] J.C. Halpin, J.L. Kardos, The Halpin-Tsai equs: a review, Polym. Eng. Sci. 16 (5) (1976) 344–352. [7] B. Mlekusch, Thermoelastic properties of short-fibre-reinforced thermoplastics, Compos. Sci. Tech. 59 (6) (1999) 911–923. [8] Z. Hashin, Analysis of composite materials, J. Appl. Mech. 50 (1983) 481–505. [9] R.M. Christensen, A critical evaluation for a class of micromechanical models, J. Mech. Phys. Solids 38 (3) (1990). [10] N. Chand, M. Fahim, Tribol. Lett. 1 (1995) 301–307. [11] N. Chand, B. Majumdar, M. Fahim, Ind. J. Eng. Mater. Sci. 1 (1994) 273–278. [12] N. Chand, M. Fahim, Ind. J. Eng. Mater. Sci. 1 (1994) 165–168. [13] J.K. Lancaster, Br. J. Appl. Phys. 1 (1968) 549. [14] T. Tsukizoe, N. Ohmae, Tribol. Int. 8 (1975) 171. [15] N. Chand, M. Fahim, Tribology of FRP Materials, Allied Publishers Ltd., 2000, p. 47.
High stress abrasive wear study on bamboo Navin Chand ∗ , U.K. Dwivedi Regional Research Laboratory (CSIR), Hoshangabad Road, Habibganj Naka, Bhopal 462026, India Received 28 October 2004; received in revised form 20 September 2006; accepted 25 September 2006
Abstract High stress abrasive wear of bamboo in mainly two directions parallel and perpendicular to the fibre direction has been determined by using a Suga abrasion wear tester. Bamboo is a unidirectional natural composite. Unidirectional cellulosic fibres in bamboo provide unique directional wear properties. The anisotropic abrasive wear behaviour was observed due to difference in fibre vascular bundle orientation present in bamboo. Wear anisotropy of bamboo depended on load and abrasive grit size. Wear anisotropy dependence on load can be represented by the following relation: WTT = −aL2 + bL − c WLL Relation between wear anisotropy and grit size is found to be as follows: WTT = −eS 3 + fS 2 − gS + h WLL Weight loss dependence on grit size for bamboo follows the following equation W = xS 2 − yS + z Worn surfaces of bamboo and its debris were observed by using a SEM and discussed in this paper. © 2006 Elsevier B.V. All rights reserved. Keywords: Bamboo; High stress abrasive wear; SEM; Anisotropy
1. Introduction Bamboo is a well known constructional material throughout all the tropical countries. Bamboo is a natural lignocellulosic composite material, in which cellulosic fibres are embedded in a lignin matrix. Cells of bamboo have been categorized into two types: matrix tissue cells and sclerenchyma cells. Matrix tissue cells are leptodermous and act as the matrix. Sclerenchyma cells consist of vascular bundles are enveloped in the matrix tissue. Vascular bundles act as reinforcements in bamboo. A vascular bundle is made-up of several phloem fibres. A phloem fibre is made of several layers of pillar fibres. Micro-fibres in each layer of the pillar fibres are spirally arranged at a fixed spiral angle, which varies for different layers of pillar fibres. Vascular bundle is made-up of many right-handed spiral phloem fibres [1].
∗
Corresponding author. E-mail address: [email protected] (N. Chand).
0924-0136/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2006.09.036
Chemical constituents present in bamboo are cellulose, hemicellulose and lignin. Cellulose and hemicellulose are present in the form of holocellulose, which contribute to more than 50% of the total chemical constituents in bamboo. The second important chemical constituent present in bamboo is lignin. Lignin in bamboo acts as a binder or matrix for the cellulose fibres. Lignin is an energy storage system in bamboo and responds to mechanical stresses as a composite material [2]. Mechanical properties of bamboo have been reported earlier [3]. Bamboo has excellent mechanical properties with specific strength and modulus being comparable to that of unidirectional glass-reinforced plastic. Abrasive wear of bamboo (Phyllostachys pubescens) against a free abrasive consisting of quartz sand and bentonite was determined on a rotary-disk type abrasive wear tester by Tong et al. [1]. Fibres due to the molecular alignment show anisotropy in their physical, and electrical properties [4]. For unidirectional composites the model of Tandon and Weng, the self-consistent scheme [5] and the Halpin–Tsai [6] equations for modulus are used. The arbitrary fibre orientation modeling has been done
156
N. Chand, U.K. Dwivedi / Journal of Materials Processing Technology 183 (2007) 155–159
by Mlekusch [7]. By this method, it is possible to investigate the different fibre orientation behaviour. The behaviour of the composite is orientation-dependent (anisotropic). Anisotropy in a composite is caused by the orientation of the fibres, different composite properties are obtained for each fibre orientation distribution. A comprehensive overview of the methodology and the different possibilities for micro mechanical modeling of fibre-reinforced systems is given by Hashin [8]. For continuousfibre-reinforced systems a critical comparison of the results from different theories is reported in the literature [9]. Chand and Fahim in their previous paper reported abrasive wear for glass fibre reinforced composites [10]. In another paper Chand et al. [11] reported a new theory for abrasive wear mechanisms for FRP composites. Chand and Fahim [12] have also given a new macro mechanism theory for slurry abrasion for short glass fibre reinforced polyester composites. Lancaster [13] reported that carbon fibre polyester composites, show minimum wear, when fibres are perpendicular to the sliding surface. However, maximum wear was observed in the composite having longitudinal fibres. Tsukizoe and Ohmea [14] found that relative wear rate between longitudinal and transverse fibre cases was dependent on the type of carbon fibres. High strength carbon fibre epoxy composite shows high wear in transverse orientation than in longitudinal orientation, but in high modulus carbon fibre composite the reverse trend was found. Abrasive wear performance of bamboo is an important aspect to exploit its use in industrial applications. In fibre reinforced composite, dimension and orientation of fibres are important factors for their tribological properties. Wear data on natural composite structure of bamboo can provide clues and ideas for designs of composites for making anti-friction materials and wear-resistant materials. As per the basic knowledge, wear rate in lignocellulosic fibre is anisotropic but no body else has reported the high stress wear anisotropy behaviour of
composites and nobody has given the generalized equation for anisotropy dependence of bamboo with load and abrasive grit. The purpose of this paper is to study the wear behaviour of bamboo under varying load and abrasive grit size and to provide new equations for their abrasive wear results. It is expected that the wear behaviour of natural fibre composites in two directions namely parallel and perpendicular to the fibre alignment will be different. 2. Experimental 2.1. Materials Bamboo (Dentrocalamus strictus) was obtained from Sehore forest, India. Bamboo used in this study was solid bamboo, in which diameter of fibre is 0.3–0.5 mm and their complete characteristics are listed in Table 1. Unidirectional cellulose fibres reinforced in lignin (natural binder) makes it a natural composite. The density of the bamboo is 0.66 g/cc. Wear test specimens of bamboo were cut in a standard size of 45 mm × 35 mm × 5 mm. A section between two nodes was cut, which was in solid cylindrical form. From this solid cylindrical bamboo, strips were cut along the fibre and transverse direction. Two types of bamboo specimens were prepared and well polished. In the TT-type, the vascular bundle orientation was normal to the abrading surface (Fig. 1a). In the LL type the bundle orientation was parallel to the sliding direction (Fig. 1b) and the abrasion surface was from middle region of bamboo.
2.2. Tensile testing The tensile samples as per ASTM D 638 were prepared by cutting the bamboo strips. Samples were tested at 10 mm min−1 cross head speed of testing by using an electronic universal testing machine model UT-10 Scientific Testing (India). Average of three samples is reported here.
2.3. Wear testing Two-body abrasive wear tests were performed on bamboo samples by using a SUGA abrasion tester model-NUS1 (Japan), which is described elsewhere [15]. The rectangular specimen of 45 mm × 35 mm was slid against a rotating
Table 1 Some properties of bamboo in different directions S. no.
Direction
Density (g/cc)
Microfibril angle (◦ )
Cellulose (%)
Lignin content (%)
Elongation
Tensile strength (MPa)
1 2
Along the fibre direction Perpendicular to the fibre direction
0.66 0.66
2–10 –
60–62 –
38–40 –
11.3 0.14
167 19
Fig. 1. Schematic diagram of fibre orientation and sliding direction in bamboo sample.
N. Chand, U.K. Dwivedi / Journal of Materials Processing Technology 183 (2007) 155–159
157
wheel, on which abrasive papers of 120, 180, 320 and 400 grit sizes (John Oakey & Mohan Ltd., India) were mounted using a double sided adhesive tape. The embedded hard SiC particles abraded the test sample. The weight-loss was measured for each 400 cycles, which corresponds to 25.6 m sliding distance. A constant sliding speed of 2.56 m min−1 and four loads 1, 3, 5 and 7 N were applied for testing the samples.
2.4. SEM studies Worn surface and debris of bamboo were observed by using scanning electron microscope (model JEOL, Japan). The sample surfaces were gold before observing the surfaces.
3. Results and discussions The schematic look of the fibre arrangement in Bamboo in parallel and perpendicular fibre directions is shown in Fig. 1a LL, Fig. 1b TT, respectively. Wear ratio of bamboo in normal (WTT ) to parallel fibre direction (WLL ) or wear anisotropy for different loads and different grit size has been determined by using Suga Abrasion Tester. Fig. 2 shows the dependence of wear anisotropy at different applied loads 1, 3, 5 and 7 N for 25.6 m sliding distance. Wear anisotropy increased on increasing load. At 1 N load, TT sample shows minimum weight loss because this load is insufficient to cut cross section of fiber, only matrix is detached from bamboo. Increase of load from 1 to 5 N, value of WTT /WLL increased. Further increase of load from 5 to 7 N decreased anisotropy ratio. Minimum anisotropy occurred at 5 N load. Weight loss in TT direction increased as compared to LL direction at 5 N load. Following relationship between wear anisotropy WTT /WLL and load for bamboo is found WTT = −aL2 + bL − c WLL where WLL and WTT are the wear in parallel and perpendicular directions of fibres orientations and L is the applied load. Constants a, b and c for bamboo are 0.106, 0.692, and 0.508, respectively. Fig. 3 shows the dependence of wear anisotropy on different abrasive grit size. On increasing the grit size more removal
Fig. 2. Plot between abrasive wear anisotropy vs. applied load for bamboo.
Fig. 3. Plot between wear anisotropy vs. grit size for bamboo.
of material occurred due to the deep ploughing action. But anisotropy is minimum for 320 grit size. This may be because this particle size matches with the fibre diameter and hence it removed complete vascular bundles. Peak in the anisotropy has been observed for 180 grit size. Following relation between wear anisotropy and grit size for bamboo is proposed WTT = −eS 3 + fS 2 − gS + h WLL where S is the abrasive grit size and e, f, g and h are constants. The coefficient of correlation R2 value is 1. Above proposed equation is tested for the bamboo data, which fits well. Values of constant, e, f, g and h are 4E−08, 3E−05, 0.0073 and 1.0807, respectively, at 25.6 m sliding distance. Fig. 4 shows that variation in abrasive grit size from 400 to 120 grit increase the weight loss of the bamboo. It has been observed that weight loss is maximum in case of LL fibre direction, while minimum weight loss is found in TT direction. In perpendicular fibre alignment (TT) direction, weight loss reduced due to more resistance offered by the fibres. When fibres were perpendicular to wear directions (TT) they created more hindrance in the path of the abrading particles and resisted the movement of abrading particles, which reduced the wear. General weight-loss (W) behaviour with grit size in bamboo can
Fig. 4. Plot between weight loss vs. grit size for parallel (LL) and perpendicular (TT) direction for applied load = 5 N, sliding distance = 25.6 m.
158
N. Chand, U.K. Dwivedi / Journal of Materials Processing Technology 183 (2007) 155–159
be represented by the following equation for both perpendicular and parallel direction wear. Only the coefficient will be different for two types of wear. This behaviour is equated in following relation W = xS 2 − yS + z where W is the weight loss in parallel and perpendicular direction of fibres orientations and S is the abrasive grit size. Above proposed equation is tested for the bamboo, which fits well. Constants x, y and z are 6E−07, 0.0004 and 0.0917 for LL and 4E−07, 0.0003 and 0.0529 for TT samples, respectively, for 25.6 m sliding distance. The R2 values were 0.9989 and 0.9857 for LL and TT samples, respectively. Fig. 5 shows the higher weight loss for the longitudinal direction than in perpendicular direction at different applied loads. In TT case, on applying 1 N load, bamboo fibre did not cut by hard abrasive, only binder (lignin) content pulverized and came out from bamboo. That is why at 1 N minimum weight loss is observed. In parallel orientation, (LL case) whole cell got abraded and removed during abrasion, which is visible in SEM
Fig. 5. Plot between weight loss vs. applied load for parallel (LL) and perpendicular (TT) direction at sliding distance = 25.6 m.
photos (Fig. 6a). Wear debris of matrix present between the fibres are easily swept away by the asperity interaction, resulting in high wear in the longitudinal case (LL). The real contact area of fibre with abrading particles in LL directions is more
Fig. 6. Scanning electron micrograph: (a) scanning electron micrograph of wear surfaces of LL case; (b) scanning electron micrograph of wear surfaces of TT case; (c) scanning electron micrograph of wear debris of TT case; (d) scanning electron micrograph of wear debris of LL case.
N. Chand, U.K. Dwivedi / Journal of Materials Processing Technology 183 (2007) 155–159
than that in TT orientation. In case of TT direction, cellulosic cells are oriented against the sliding direction, only cross section comes in contact and that did not remove easily (Fig. 6b). Wear debris of bamboo specimens are of two types. One part was very fine divided powder obtained in TT direction (Fig. 6c), which had adhered to the emery papers, used for abrasion during the wear process; the other part was micro fibrous type, which had got abraded from LL sample (Fig. 6d) on the emery papers. Debris obtained from TT-samples were due to the microcutting and micro-ploughing action. 4. Conclusions (1) The high stress wear anisotropy of bamboo depends on load and abrasive grit size. (2) A new equation between abrasive wear anisotropy and load for bamboo is proposed. (3) Another relation between abrasive wear anisotropy with abrasive grit is also suggested. (4) The high stress wear behaviour is affected by the vascular bundle fibre orientation with respect to the abrading surface and abrasive particle sizes. Acknowledgements Authors are highly thankful to IUC (DAEF-UGC) for their kind permission for carrying out the above morphological work.
159
One of the authors Mr. U.K. Dwivedi is highly thankful to CSIR for giving him senior research fellowship during this work. References [1] J. Tong, L. Ren, J. Li, B Chen, Abrasive wear behaviour of bamboo, Tribol. Int. 28 (5) (1995) 323–327. [2] S. Jain, R. Kumar, U.C. Jindal, Mechanical behaviour of bamboo and bamboo composite, J. Mater. Sci. 27 (1992) 4598–4604. [3] S.C. Lakkad, J.M. Patel, Mechanical properties of bamboo, a natural composite, Fibre Sci. Technol. 14 (1981) 319–322. [4] N. Chand, D. Jain, Composites Part A 36 (5) (2005) 594. [5] G.P. Tandon, G.J. Weng, The effect of aspect ratio of inclusions on the elastic properties of unidirectionally aligned composites, Polym. Compos. 5 (4) (1984). [6] J.C. Halpin, J.L. Kardos, The Halpin-Tsai equs: a review, Polym. Eng. Sci. 16 (5) (1976) 344–352. [7] B. Mlekusch, Thermoelastic properties of short-fibre-reinforced thermoplastics, Compos. Sci. Tech. 59 (6) (1999) 911–923. [8] Z. Hashin, Analysis of composite materials, J. Appl. Mech. 50 (1983) 481–505. [9] R.M. Christensen, A critical evaluation for a class of micromechanical models, J. Mech. Phys. Solids 38 (3) (1990). [10] N. Chand, M. Fahim, Tribol. Lett. 1 (1995) 301–307. [11] N. Chand, B. Majumdar, M. Fahim, Ind. J. Eng. Mater. Sci. 1 (1994) 273–278. [12] N. Chand, M. Fahim, Ind. J. Eng. Mater. Sci. 1 (1994) 165–168. [13] J.K. Lancaster, Br. J. Appl. Phys. 1 (1968) 549. [14] T. Tsukizoe, N. Ohmae, Tribol. Int. 8 (1975) 171. [15] N. Chand, M. Fahim, Tribology of FRP Materials, Allied Publishers Ltd., 2000, p. 47.