Machinability Studies of Turning Al/SiC/B 4 C Hybrid Metal Matrix Composites using ANOVA Analysis

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1 International Conference on Thermal, Material and Mechanical Engineering (ICTMME'0) July 5-6, 0 Singapore Machinability Studies of Turning Al/SiC/B 4 C Hybrid Metal Matrix Composites using ANOVA Analysis Vibu Nanthan.M, Vidhusan.C, and Vignesh.S Abstract - This paper presents the detailed discussions on machining of Aluminium - silicon carbide (0% by weight of particles) and boron carbide (5% by weight of particles) Hybrid Metal Matrix Composites (Al/SiC/B 4 C MMC).SiC and a B 4 C particle range from 40µm to 80 µm. The cylindrical rods of diameter 65 mm and length 00 mm are fabricated and subsequently machined using medium duty lathe of kw spindle power to study the machinability issues of Hybrid MMC using Poly Crystalline Diamond (PCD) insert of 600 grade. The optimum machining s have been identified by Analysis Of Variance (ANOVA). Confirmation test is also conducted to validate the test result. Experimental results have shown that machining performance can be improved effectively through this approach. Results show at higher cutting speeds, good surface finish is obtained with faster tool wear. It is concluded that, tool wear and cutting force are directly proportional to the cutting speed, where as surface roughness is inversely proportional to the cutting speed. Keywords - Turning, cutting force, tool wear, PCD, surface roughness, Taguchi method. Vibu Nanthan.M is with Sri Venkateswara college of Engineering, Pennalur, Sriperumbudur 60 05, Tamil Nadu, India (corresponding author to provide phone: ; vibunanthan@rocketmail.com). Vidhusan.C, is Sri Venkateswara college of Engineering, Pennalur, Sriperumbudur 60 05, Tamil Nadu, India. He is pursuing his Bachelor of engineering in Mechanical engineering. Vighnesh.S is with the Sri Venkateswara college of Engineering, Pennalur, Sriperumbudur 60 05, Tamil Nadu, India. He is pursuing his Bachelor of engineering in Mechanical engineering. C I. INTRODUCTION ONSIDERABLE research work in the field of material science has been progressed towards the development of new light weight, high performance engineering materials like composites. Metallic matrix hybrid composites are one among them. Metal matrix composites have become the necessary materials in various engineering applications like aerospace, marine and automobile engineering applications, because of their light-weight, high strength, stiffness and resistance to high temperature []. However, the final conversion of these composites in to engineering products is always associated with machining, either by turning or by milling. A continuing problem with hybrid MMCs is that they are difficult to machine, due to the hardness and abrasive nature of the reinforcing particles [, ]. The presence of hard ceramic particles in the composites makes them extremely difficult to machine as they lead to rapid tool wear [4, 5]. The hard SiC particles in Al/SiC MMCs which intermittently come in contact with the tool surface and acts as small cutting edges like those of the grinding wheel. These particles act as abrasive between cutting tool and work piece and resulting in formation of high tool wear, poor surface finish [5-7, 6, 7]. Most of the researchers focused on drilling investigation on the Hybrid composites of various reinforcements and different combinations. Little research has been done on turning of Al56/SiC p /B 4 C. In the view of above machining problems, the main objective of the present work is to investigate the influence of different cutting s on surface finish and cutting force criterion. The taguchi L 7 orthogonal array is utilized for experimental planning for turning of Al-SiC-B 4 C Hybrid MMC. The results are analyzed to achieve optimal surface roughness and cutting force. Desirability function analysis (DFA) was performed to combine the multiple performance characteristics in to one numerical score called composite desirability value to determine the optimal machine settings. Analysis of variance (ANOVA) is also performed to investigate the most influencing s on the surface finish and force. II. TAGUCHI TECHNIQUE Taguchi technique is a powerful tool for the design of high quality systems [8-0]. It provides a simple, efficient and systematic approach to optimize design for performance, quality and cost. The methodology is valuable when design

2 International Conference on Thermal, Material and Mechanical Engineering (ICTMME'0) July 5-6, 0 Singapore TABLE-I CHEMICAL COMPOSITION OF Al-SiC(0p) B 4 C (5 P )- HybridMMC Type of Hybrid MMC Particula temmc Reinforcemen t SiC and B 4 C µm 0.00 %Sic B 4 C% %Si %Mg %Fe %Cu %Mn %Zn %Ti %Al Balance Symbol A TABLE- II MACHINING PARAMETER AND THEIR LEVELS Speed Unit m/min B Feed mm/rev C Depth of mm cut s are qualitative and discrete. Taguchi design can optimize the performance characteristics through the setting of design s and reduce the sensitivity of the system performance to the source of variation [0, ]. This technique is multi step process, which follow a certain sequence for the experiments to yield an improved understanding of product or process performance. This design of experiments process made up of three main phases: the planning phase, the conducting phase and analysis interpretation phase. The planning phase is the most important phase; one must give a maximum importance to this phase. The data collected from all the experiments in the set are analyzed to determine the effect of various design s. This approach is to use a fractional factorial approach and this may be accomplished with the aid of orthogonal arrays. Analysis of variance is a mathematical technique, which is based on least square approach. The treatment of the experimental results is based on the analysis of average and analysis of variance composites was Poly Crystalline Diamond (PCD) insert of fine grade (600 grade). The PCD inserts used were of ISO coding CNMA 0408 and tool holder of ISO coding PCLNR 00M. The specifications for PCD insert are as follows: substrate for PCD is tungsten carbide, nose radius 0.8 mm, shank height- 5 mm, shank width 5 mm, average particle size - 4µm, volume fraction of diamond- 90%, compressive strength- 7.5 GPa, elastic modulus 850 GPa. Boron Carbide III. EXPERIMENTAL PROCEDURE Commercially Fabricated cylindrical bars having 0% of SiC particles and 5% of B 4 C on matrix of Al 56, using stir casting method of diameter 65 mm and 00 mm long are turned on self centered three jaw chuck, medium duty lathe of spindle power kw. Parameters such as surface roughness of machined component were measured by Mitutoyo surftest (Make-Japan Model SJ-0) measuring instrument with the cutoff length.5 mm. force was measured by using Unitech lathe tool dynamometer with digital indicator. The cutting tool selected for machining Al-SiC metal matrix Silicon Carbide Fig..Microstructure of Al 56 reinforced with 0% SiC and 5 % B 4 C 4

3 International Conference on Thermal, Material and Mechanical Engineering (ICTMME'0) July 5-6, 0 Singapore TABLE - III. EXPERIMENTAL LAYOUT USING AN L7 ORTHOGONAL ARRAY AND CORRESPONDING RESPONSE VALUES Group Parameter No. A Speed B Feed C Depth of cut Surface Roughne ss (Ra) in Microns force (F) in N IV. ANALYSIS OF VARIANCE Analysis of Variance (ANOVA) is a method of apportioning variability of an output to various inputs. Table 6 shows the results of ANOVA analysis. The purpose of the analysis of variance is to investigate which machining s significantly affect the performance characteristics. This is accomplished by separating the total variability of thevalue, which is measured by the sum of the squared deviations from the total mean of the composite desirability value, into contributions by each machining and the error. First, the total sum of the squared deviations SST from the total mean of the value γ m can be calculated as: p SS T ( j m ) j () Where, p is the number of experiments in the orthogonal array and γj is the mean value for the j th experiment. The total sum of the squared deviations SST is decomposed in to two sources: the sum of the squared deviations SSd due to each machining and its interaction effects and the sum of the squared error SSe. The percentage contribution by each of the machining in the total sum of the squared deviations SST can be used to evaluate the importance of the machining change on the performance characteristic. In addition, the Fisher s F- test can also be used to determine which machining s have a significant effect on the performance characteristic. Usually, the change of the machining s has a significant effect on performance characteristic when F is large. The ANOVA was performed at 95% confidence level. From the table- IV it is clearly understood that, feed has high contribution on surface roughness (87.5%), followed by depth of cut (.98%) and interaction effect of cutting speed and feed(.89%). It is also observed that cutting speed has sizeable contribution on surface roughness(.69%). TABLE IV. ANOVA TABLE FOR SURFACE ROUGHNESS Source Degrees SS MS F CAL P% of Freedom A B C A*B A*C B*C Error Total

4 International Conference on Thermal, Material and Mechanical Engineering (ICTMME'0) July 5-6, 0 Singapore TABLE V RESPONSE TABLE FOR SURFACE ROUGHNESS Surface roughness - - Max- Min Speed (A) Feed rate (B) Depth of Cut (C) Total mean of composite desirability = TABLE VII RESPONSE TABLE FOR THE CUTTING FORCE Source Degrees SS MS F CAL P% of Freedom A B C A*B A*C B*C Error Total Main Effects Plot (data means) for Ra 6 cutting speed feed 5 Main Effects Plot (data means) for force 4 cutting speed feed Mean of Ra depth of cut Mean of force depth of cut Fig. Main effect plots for surface roughness 80 It is clearly understood that, cutting speed has high contribution on power consumed (57.4%), followed by feed (5.888%) and depth of cut(8.99%). It is also observed that interaction effect of cutting speed and feed has sizeable contribution on power consumed (.9%). TABLE VI. ANOVA TABLE FOR CUTTING FORCE force - - Max- Min Speed (A) Feed rate (B) Depth of Cut (C) Total mean of composite desirability = From the table- VI it is clearly understood that, cutting speed has high contribution on cutting force (4.58%), followed by feed (6.66%) and interaction effect of cutting speed and feed(.74%). It is also observed that depth of cut has sizeable contribution on surface roughness(.69%) From fig, it is clearly under stood that optimum s are A B C. Fig Main effect plots for force VI. TOOLWEAR From the above observations best machining was determined as cutting speed 00 m/min, feed rate 0. mm/rev and depth of cut 0.5 mm (experimental reading number ). Now setting this cutting condition as a constant and machined the samples for a time duration of 0minutes and the tool flank wear study was carried out. Tool was monitored for normal types of wear namely flank wear, crater wear and nose wear using a tool maker s microscope. Tool flank wear was caused by abrasive nature of the hard particles present in the work piece. At low cutting speed worn flank encourages the adhesion of work piece material on the tool insert and formed Built-Up-Edge [, 5, 7]. Fig-4 shows the Scanning Electron Microscope (SEM) image of fresh insert. Fig- 5 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 [4] It is observed that the tool life of PCD 600 grade is performing well in the chosen cutting condition 6

5 International Conference on Thermal, Material and Mechanical Engineering (ICTMME'0) July 5-6, 0 Singapore 50x Fig. 4 Nose Substrate SEM image of fresh PCD 6000 grade [] D. Rouby and P. Reynaud, Fatigue behaviour related to interface modification during load cycling in ceramic matrix fibre composites, Compos Sci Technol Vol.48, 99, PP [4] I.Cifti, Turker and U. Sekar, Evaluation of tool wear when machining SiC reinforced Al-04 alloy matrix composites, Mater. Des. Vol. 5, 004, PP [5] J.Monaghan and P. O Reilly, The drilling of an Al/SiC metal matrix composites, J. Mater. Process. Technol. Vol., 99, PP [6] B. Mubaraki, S.Bandyopadhyay, R. F. Fowle, P. Mathew and P. J.Health, Drilling studies of an Al0 Al metal matrix composite. Part I Drill wear Characteristics, J. Mater. Sci. Vol.0, 995, PP [7] M. Ramulu, P. N. Raoo and H. Kao, Drilling of Al0 p /606 metal matrix composites, J. Mater. Process. Technol. Vol. 4, 00, PP [8] G.Taguchi, Taguchi on Robust Technology Development Methods.ASME Press,, New York, 99, PP [9] G. Taguchi and S. Konishi, Taguchi methods, orthogonal arrays and linear graphs. In: Tools for Quality Engineering. American Supplier Institute, 987, PP [0] P. J. Ross, Taguchi i techniques for quality Engineeringg Mc Graw-Hill, New York.998. [] K. R. Roy, A primer on Taguchi Method. Van Nostrad Reinhold, New York.990. Fig. 5 SEM image of worn out insert after 0 minute duration VII. CON NCLUSION The use of orthogonal array with ANOVA analysis to optimize the Al-SiC(0p)-B 4 C(5p) Hybrid Composites machining process has been reported in this paper. As a result, optimization of the complicated multiple performance characteristics can be greatly simplified through this approach. It is shown that the performance characteristics of the turning process of Al-SiC(0p)-B 4 C(5p) Hybrid Composites such as surface roughness, and cutting force are improved together by using the proposed method in this study. Confirmatory experiment proves that predicted and experimental values are very close to each other. Tool flank wear was caused by abrasive nature of the hard particles present in the work piece. REFERENCES [] [] N. Tomac and K. Tonnessen, (99), Machinability of particulate Aluminum Metal Matrix Composites,. Annals of the CIRP, Vol.4, 99, PP K. Weinert, (99), A consideration of tool wear mechanism when machining metall matrix composites (MMC), CIRP Ann, Vol. 4, 99, PP