Investigation on Surface Quality in Machining of Hybrid Metal Matrix Composite (Al-SiC B4C)

Transcription

1 International Conference on Thermal, Material and Mechanical Engineering (ICTMME'0) July 5-6, 0 Singapore Investigation on Surface Quality in Machining of Hybrid Metal Matrix Composite (Al-SiC B4C) Vignesh. S, Sanjeev. C Abstract In this paper, turning experiments on machining of particle reinforced Hybrid Metal Matrix composite (MMC) have been carried out. The reinforcement particles selected are Silicon-Carbide of 0% by weight and Boron-Carbide of 5% by weight respectively. Stir casting method is followed to prepare cylindrical rods of specific length and diameter. Poly Crystalline Diamond (PCD) insert of grade 600 is used for turning operations. Taguchi s method of design of experiment is followed by using orthogonal array L 9. Three level machining parameters selected are cutting speed, feed rate and depth of cut. The influence of these parameters on machined surface quality is determined by measuring the surface roughness of the workpiece by surface roughness tester. Using S-N ratio method ranking of the cutting parameters are done and it is observed that for surface quality feed rate is the most influencing parameter followed by cutting speed and by the depth of cut. The optimal cutting conditions are arrived as feed rate 0. mm/rev, cutting speed as 70 m/min and depth of cut as 0.5mm. The S-N plot is drawn to show the characteristics of each parameter with respect to surface roughness. The results are validated by analysis of variance method (ANOVA) and the percentage of contribution of feed, speed and depth of cut are determined. Tool wear study also performed for a duration of 0 minutes. Keywords PCD, Taguchi s method, Orthogonal array, S/N ratio, ANOVA. A I. INTRODUCTION T the advent of modern processing technique the research activities in developing Metal matrix composites are developed and much more technological advancement are achieved. Metal matrix composites are materials fabricated by reinforcement of ceramic particles in a tough metal matrix. In general the incorporation of carbide particles enhances the mechanical properties like specific strength, stiffness, hardness, adhesive, abrasive, diffusion wear resistance, and thermal properties. By choosing the particle shape, size and distribution, the mechanical properties can be fine tuned to the requirement [4][] Hybrid metal matrix composites are unique material fabricated by reinforcements of at least two types of ceramic particles in to a tough metal matrix. The matrix forming the Vignesh. S is with the Mechanical Engineering Department, Sri Venkateswara College of Engineering, Sriperumbudur, CO 6005 INDIA (phone: ; vignesh_shiv@yahoo.co.in). Sanjeev. C is with the Mechanical Engineering Department, Sri Venkateswara College of Engineering, Sriperumbudur, CO 6005 INDIA (phone: ; sanjeev_icy@yahoo.com). base alloy for the composite material. For the past decade the usage of Al-Carbide composites have been increased in the industries of automotive, aircraft, locomotive companies and advanced arm systems such as satellite bearing, inertia navigation system, and laser reflector [0]. Hybrid metal matrix composites are economically cheaper in both raw materials and method of fabrication. Due to the reinforcement of ceramic materials, the machining of these metal matrix composites become significantly more difficult than those of conventional materials [][][]. The non-homogeneous and anisotropic nature combined with the abrasive reinforcements render their machining difficult. The tool wear rate is very high and the work piece may get damaged due to the plucking effect of the tool on the ceramic particles. These factors lead to uneconomical machining resulting poor surface quality. The Machinability of a material may be evaluated by assessing any one the machining parameter like surface roughness, tool life, cutting force, cutting temperature, electrical power consumption. From the open literature survey it is well known factor that PCD inserts are most suitable for machining operations and has significant effect on cutting performance [6][8]. II. MATERIAL AND EXPERIMENTAL METHODS A. Material The material used for turning test samples was Al56-SiCp- B 4 Cp. This Hybrid metal matrix composite is fabricated by using stir-casting method. The compositions are 0% SiC particles and 5% B4C particles []. The test samples were fabricated in the form of cylindrical rods of specific length and diameter. The microstructure of the specimen is observed and is shown in Fig.. 50X Silicon Carbide Boron Fig. Microstructure of Al(56) Metal Matrix Composite with particles of 0% SiC and 5% B4C B. Experimental Methods All tables and figures you insert in your document are only 6

2 International Conference on Thermal, Material and Mechanical Engineering (ICTMME'0) July 5-6, 0 Singapore to help you gauge the size of your paper, for the convenience of the referees, and to make it easy for you to distribute preprints. selecting cutting speed, feed rate and depth of cut as machining parameters each of three levels (Table. III).The surface quality of the machined specimen is observed using Surftest (Fig.) instrument which determines the Average surface roughness (Ra) of the specimen and the results are tabulated as shown in Table. IV. [5][7] Workpiece Fig. Experimental Setup In this paper the experiment is designed by Taguchi method having orthogonal array L 9. The experiment is conducted by TABLE I SPECIFICATION OF PCD INSERT Characteristic Grade 600 Volumetric % of diamond 90 Transverse rupture strength (GPa).7 Elastic modulus (GPa) 850 Average particle size (μm) 4 Compressive strength (GPa) 7.5 Knoop hardness - (kg/mm) 4000 TABLE II CHEMICAL COMPOSITION OF THE ALUMINUM ALLOY (AL 56) MATRIX Element % Weight Element % Weight Si 7.95 Ti 0.0 Cu 0.87 Ni 0.0 Mg 0.60 Zn 0.0 Mn 0.06 Pb 0.04 Fe 0. Sn 0.0 Cr 0.00 V 0.00 Zr 0.00 Al ** ** The remaining % is aluminum Surf tester Fig. Mitutoyo Surftest Instrument 7

3 International Conference on Thermal, Material and Mechanical Engineering (ICTMME'0) July 5-6, 0 Singapore TABLE III MACHINING PARAMETERS AND THEIR LEVELS Machining Parameters Unit Symbol Levels Cutting Speed m /min v Feed mm/rev F Depth of Cut Mm D TABLE IV EXPERIMENTAL DATA Sl No. Cutting Speed (m/min) Feed (mm/rev) Depth Of Cut (mm) SURFACE ROUGHNESS Microns R R R Ravg Values of S/N Ratios TABLE V RESPONSE TABLE FOR MEAN S-N RATIOS Levels Cutting Speed Feed rate Depth of Cut Rank II I III Optimal Parameters 70 m/min 0. mm/rev 0.5 mm TABLE VI RESPONSE TABLE FOR MEANS RA Levels Cutting Speed Feed rate Depth of Cut Rank II I III Optimal Parameters 70 m/min 0. mm/rev 0.5 mm TABLE VII ANALYSIS OF VARIANCE FOR MEAN RA Source DoF Seq SS Mean square F Contribution % v f d Error Total

4 International Conference on Thermal, Material and Mechanical Engineering (ICTMME'0) July 5-6, 0 Singapore SURFACE PLOT V Ravg 4 5 F Fig. 4 Surface plot of Surface roughness vs feed and cutting speed Main Effects Plot for SN ratios Data Means A B Mean of SN ratios 0 8 C 0 8 Signal-to-noise: Larger is better III. RESULT AND DISCUSSION The investigation on the surface quality of Aluminium metal matrix composites require more analysis due to the presence of abrasive phase in the reinforcing SiC and B4C particles. Due to these hard phase particulates on machining, discontinuous chips are produced, resulting different machining characteristics. In Taguchi deign, the term signal represents the desirable value and "noise" represents the undesirable value. The objective of using S/N ratio is measure of performance to develop products and processes insensitive to noise factors[]. The S/N ratio is calculated for the nine experiments using the formula () S/N = -0 log 0 {/ x (R + R + R Where indicates the number of trials and R, R, R are the observed values. The mean S-N ratio values are calculated level wise (Table. V) from which feed is determined as most Fig. 5 S-N Ratio )} influencing factor followed by cutting speed and then by the depth of cut. The optimal cutting conditions are obtained as: v = 70 m/min, f = 0.mm/rev, d = 0.5mm. The response table for mean surface roughness (Table. VI) also arrived giving the same results as S/N ratio results. The results of S-N ratio & mean Ra are validated by analysis of variance (ANOVA) which is one of the most popularly used statistical method. This analysis (Table. VI) reveals that the percentage of contribution of all parameters for better machining characteristics. It is observed that feed rate has % followed by cutting speed 6.9% and for the depth of cut 5.9%. As the percentage of error is.% which is lesser than 5% (permissible limit of error) it may be stated that the design, conduction, observation and analysis are in the correct direction. The surface plot is drawn that represents the effect of Ra with respect to v and f (Fig. 4). The mean S-N plot (FIG-E) is also shown. The results proved that the roughness of the machined surface is highly influenced by the feed. Based on the above discussions and also evident from Fig. 4, Fig. 5 Table. V and Table. VI the optimum conditions for the surface roughness could be established. 9

5 International Conference on Thermal, Material and Mechanical Engineering (ICTMME'0) July 5-6, 0 Singapore A. Toolwear From the above observations best machining parameter was determined as cutting speed 70 m/min, feed rate 0. mm/rev and depth of cut 0.5 mm. Now setting this cutting condition as a constant parameter and machined the samples for a time duration of 0minutes and the tool flank wear study was carried out. Fig. 6 shows the Scanning Electron Microscope (SEM) image of fresh insert. Fig. 7 shows SEM image of PCD 600 grade insert after machining the work piece for 0 minute duration. It is proved that hard silicon and boron carbide particles which have higher hardness than diamond abrading the cutting tool It is observed that the tool life of PCD 600 grade is performing well in the chosen cutting condition. 50X BUE Nose region Substrate Material Fig. 6 SEM image of fresh PCD 600 grade Built up edge ( ). It is determined that the feed rate is the dominant parameter for surface roughness followed by the cutting speed. Compared to other parameters the depth of cut shows minimal effect on surface roughness.. The results of ANOVA revealed that minimal surface roughness could be obtained significantly for hybrid composite turning operations through the specified machining conditions. 4. The surface plot and Graphs for Mean S-N ratio and Mean Ra are also represented. 5. Main cause of tool wear is believed to be abrasion. REFERENCES [] Tomac N and Tonnessen K, Machinability of particulate Aluminum Metal Matrix Composites, Annals of the CIRP, vol. 4, in 99, pp [] P.K. Rohatgi, Future Directions in Solidification of Metal Matrix Composites, Key Engineering Materials, G.M. Newaz et al., Ed., Trans. Tech., Switzerland, vol 04-07, 995, pp 9- [] K. Palanikumar, Application of Taguchi and response surface methodologies for surface roughness in machining glass fiber reinforced plastics by PCD tooling, Trans. AFS, vol 0, 99, pp Volume 8(5) October 999 [4] J.E. Allison and G.S. Cole, Metal Matrix Composites in the Automotive Industries, J. Met., vol 45 (No. 4), 99, pp 0-5 [5] L.M. Orsborn and G.R. Shook, Machining Experience with Discontinuously Reinforced, Proc. Sym. on Machining of Composite Materials (Chicago, IL), -5 Nov 99, pp 57-6 [6] B.H. Yan and C.C. Wang, Machinability of SiC Particle Reinforced Aluminium Alloy Composite Material, J. Jpn. Inst. Light Met., vol 4 (No. 4), 99, pp 87-9 [7] A. Jawaid, S. Barnes, and S.R. Ghadimzadeh, Drilling of Particulate Aluminium Silicon Carbide Metal Matrix Composites, Proc.Sym. on Machining of Composite Materials (Chicago, IL), - 5 Nov 99, p 5-47 [8] C. Lane, Machinability of Aluminium Composites as a Function of Matrix Alloy and Heat Treatment, Proc. Sym. on Machining of Composite Materials (Chicago, IL), -5 Nov 99, pp -5 [9] C. Lane, The Effect of Different Reinforcements on PCD ToolLife of Aluminium Composites, Proc. Sym. on Machining of Composite Materials (Chicago, IL), -5 Nov 99, pp 7-7 [0] P. Chen, High Performance Machining of SiC Whisker Reinforced Aluminium Composite by Self Propelled Rotary Tools, CIRP Ann. vol 4, 99, pp 59-6 [] Metals Hand Book, Vol 6, Machining, 9th ed., ASM International, pp 9-48, 75, 07, [] C.T. Lane, Requirements for Machining MMC Castings, Trans. AFS, vol 0, 99, pp Volume 8(5) October 999. Fig. 7 SEM image of worn out insert after 0 minute duration IV. CONCLUSIONS The surface quality obtained in turning aluminium (Al 56) metal matrix composites with reinforcements of ceramic particles with 0% by weight of SiC and 5% by weight of B4C under different cutting conditions with a PCD tool of 600 grade, have been investigated using Taguchi s orthogonal array (L 9 ). The following conclusions are drawn based on the experimental and analytical results:. By using Taguchi method, the effect of machining parameters on the surface quality (Ra) has been evaluated and optimal machining conditions would be arrived to minimize the surface roughness. 0