Available online at www.sciencedirect.com ScienceDirect Procedia Engineering 97 (2014) 941 – 950 s12th GLOBAL CONGRESS ON MANUFACTURING AND MANAGEMENT, GCMM 2014 Evaluation of Properties for Al-SiC Reinforced Metal Matrix Composite for Brake Pads Rathod Abhik a*, Umasankar Va, M. Anthony Xaviora a SMBS, VIT University,Vellore 632014,Tamilnadu,India Abstract MMC has been used in engineering application in broad way because of their mechanical and physical properties. They are broadly used in the field of automobile and aerospace because of their high strength to weight ratio, lighter weight, lower cost, and good behaviour. In present study the mechanical and wear behaviour of aluminium metal matrix composite and SiC has been discussed. Brake Pad is manufactured by route of powder metallurgy which is widely preferred because of its low cost, high volume production, ease of operation, sustainability and attractive manufacturing process. Brake pads are developed with light alloy Aluminium 2014 reinforced with SiC to augment the strength and wear resistance and explore the advantage of low density of the matrix. © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2014 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selectionand and peer-review responsibility of the Organizing of GCMM 2014. Selection peer-review underunder responsibility of the Organizing Committee Committee of GCMM 2014 Keywords: MMC; Brake pad; Powder Metallurgy. 1. Introduction Brake pad is one of the most important parts of braking system which is mounted on a brake disc rotor on each wheel. Braking system also contains many other parts like cylinders (master cylinders, wheel cylinders, tandem cylinders) and control system which may be operated by hydraulic system or pneumatic system. In different types of breaking system varieties of materials are used for brake pads. Binders, fillers, friction modifiers and reinforcement are four important classes of ingredients into which they are often categorized. Asbestos is most frequently used brake pad material in which asbestos fibres are embedded in matrix of polymer along with other several ingredients. Many research works have been carried out for the Asbestos free brake pad materials over few years. Current trend has come out for the * Corresponding author. Tel.: +91-942-955-5777 E-mail address: abhik.mech@gmail.com 1877-7058 © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the Organizing Committee of GCMM 2014 doi:10.1016/j.proeng.2014.12.370 942 Rathod Abhik et al. / Procedia Engineering 97 (2014) 941 – 950 utilization of composite brake pad materials which provide more economical benefits and also preservation of environment. To develop brake pad materials for the fulfilment of requirement many factors have to be considered like stable coefficient of friction and lower wear rate at different operating speed, pressure, temperature, environmental condition etc. For the fulfilment of above requirement it is important of having appropriate combination of materials and selection of materials is not an easy task rather it is a complex process which require lot of experience. Due to carcinogenic nature of asbestos fibres use of asbestos fibres have been reduced day by day. [1] Now days MMC has been used in engineering application in broad way because of their mechanical and physical properties. They are broadly used in the field of automobile and aerospace because of their high strength to weight ratio, lighter weight, lower cost, and good behaviour. AMCs are also used because of their superior strength with appropriate toughness ductile matrix, well bonding particle matrix interface, homogenously distribution of particles etc. [2] Recent research has been focused on the compaction method to manufacture cost effective and highly dense material through powder metallurgy method. The possibility of obtaining uniform parts and reducing tedious and expensive machining processes is the prime reason for using powder metallurgy method. [1] Nomenclature d h V M m ρ BHN p di D Diameter of compaction die Height of compaction die Total volume of compaction die Total mass of compaction Mass of samples Sintered Density Brinell Hardness Number Applied force Diameter of Indentation Diameter of Indenter 2. Experimental Procedure 2.1. Raw Material And Formulation Aluminium 2014 was used as a main raw material which is called matrix material and it is reinforced with SiC. The break pad material was developed with process starting with selection of material, weighing, mixing, compacting and sintering. Material was grouped based on different percentage of reinforcement used. In this metal matrix composite Aluminium 2014 was metal matrix and sic was reinforcement. Table 1 and 2 shows the grouping of new material. Table 1. Formulation of SiC reinforced Aluminium brake pad materials for Sample 1 Raw materials Percentage (%) Aluminium 2014 80 SiC 20 Total 100 Table 2. Formulation of SiC reinforced Aluminium brake pad materials for Sample 2 Raw materials Percentage (%) 90 Aluminium 2014 10 SiC Total 100 Rathod Abhik et al. / Procedia Engineering 97 (2014) 941 – 950 943 The calculation of weight measuring is shown below here, d = diameter of compaction die = 2.5cm h = height of compaction die = 1.4cm V = Total volume of compaction die V= πr2h = π x (1.25)2 x 1.4 = 6.8722cm3 Therefore, m= xV = 2.7gm/cm3 x 6.8722cm3 = 18.55gm = Total mass of compaction Hence according to % of reinforcement For Sample 1(20% reinforcement) m for reinforcement = 3.71gm m for matrix material = 14.84gm For Sample 2 (10% reinforcement) m for reinforcement = 1.86gm m for matrix material = 16.70gm 2.2. Preparation of Material Experimental Data Material mixing speed = 50 rpm Material mixing time = 30 minutes Compacting Load = 150 KN Sintering Temperature = 550 0C Rate of Heating = 150/min Dwell Time = 10 min Sintering Time = 30 minutes Two different combinations were prepared according to different volume percentage of SiC like 10% and 20% through route of powder metallurgy for the development of SiC reinforced aluminium break pad materials. Ball mill mixer was used for getting evenly distributed ingredients. The mixing process was done for getting uniform and homogeneous powder. All materials used were in powder form and powder metallurgy was used for developing brake pad materials. The powder of Aluminium 2014 (80%) and SiC (10% & 20%) was compacted in die under load of 150 kN using UTM (Universal Testing Machine) for 20 minutes. Sintering was done in Micro Wave furnace at 5500C for 30 minutes. 944 Rathod Abhik et al. / Procedia Engineering 97 (2014) 941 – 950 2.3. Characterization of Brake Pad Materials Density was measured using specific gravity which depends on the ingredients of brake pad materials. The true density of the specimen was determined by weighing the specimen on a digital weighing machine and measuring their volume by liquid displacement method.[1] 3. Result And Discussion 3.1. Density and porosity of Brake pad material Density after sintering was carried out at the laboratory level and it is depends on ingredients of brake pad materials. Figure a shows the density difference of two different reinforced samples. The calculation of sintered density is shown below. The sintered density is measured according to Archimedes principle as shown in below  Hence, according to above equation, For Sample 1(20% reinforced) ρTh. = 2.7 x 0.8 + 3.21 x 0.2 = 2.802gm/cm3 For Sample 2(10% reinforced) ρTh. = 2.7 x 0.9 + 3.21 x 0.1 = 2.751gm/cm3 For Sample 1(20% reinforced) Weight in air Density of fluid Weight in fluid = 17.2gm = 0.9gm/cm3 = 10.80gm Hence, according to above equation, = 2.42gm/cm3 Rathod Abhik et al. / Procedia Engineering 97 (2014) 941 – 950 945 For Sample 2(10% reinforced) Weight in air = 18.4gm Density of fluid = 0.9gm/cm3 Weight in fluid = 10.80gm Hence, according to above equation, = 2.18gm/cm3 Fig. 1 shows the density difference between two samples Fig. 1 Density Difference From the above figure we can say that sample 1 has higher density than sample 2 hence, sample 1 contains better properties than sample 2 For the automotive brake pad materials porosity is playing an important role and absorbing energy and heat is a main function of porosity which is important for the effectiveness of the braking system. As far as theory is concerned higher friction coefficient and wear rate because of higher contact areas between the mating surfaces due to lower porosity. Brake pad should have a certain amount of porosity to minimize the effect of water and oil on the friction coefficient.[1] Porosity can be calculated using following equation For sample 1(20% reinforced) = 14% 946 Rathod Abhik et al. / Procedia Engineering 97 (2014) 941 – 950 For Sample 2(10% reinforced) = 21% Fig. 2 Porosity From the figure 2 we can say that with reduction in % reinforcement porosity increases 3.2. Hardness of the Brake pad Materials The Brinell hardness number can be given by following equation From the above equation the calculation of brinell hardness values is shown below For Sample 1(20% Reinforced) p = Applied Force = 500kgf d = Diameter of Indentation = 3.33mm D = Diameter of indenter = 5mm Therefore, BHN = 50 For Sample 2(10% Reinforced) p = Applied Force = 500kgf d = Diameter of Indentation = 3.86mm D = Diameter of indenter = 5mm Therefore, BHN = 35 Rathod Abhik et al. / Procedia Engineering 97 (2014) 941 – 950 Figure 3 shows the Brinell hardness values for two different reinforced brake pad materials Fig. 3 Brinell Hardness Number From figure 3 we can say that sample 1(20% reinforced) has high hardness value than sample 2(10% reinforced). Sample 1 contains high hardness because of using high percentage of reinforcement i.e. SiC. Sample 1 is brittle in nature because of high hardness value while sample 2 is ductile in nature because of low hardness value which shows higher wear, porosity and low density. Different percentage of reinforced material shows different value of hardness. 3.3. Wear Testing Wear is a most common phenomenon of brake pad materials. Wear testing was done with the help of abrasive sheet of grid size 80 of 25cm length. Wear was measured for different length of abrasive sheet like 100cm to 500cm. Both samples were abraded for a distance of 100cm to 500cm with each pass of 25 cm made on a fresh abrasive surface. Then abrasion was measured using digital weighing machine where difference in weight between two consecutive distances shows a wear rate. [3]. Table 3 show the wear rate of two different reinforced samples Table 3. Wear Rate of Sample 1(20% reinforced) and Sample 2(10% reinforced) Length(cm) Wear Rate(gm./cm) Sample 1 Wear Rate(gm./cm) Sample 2 100 150 200 250 300 350 400 450 500 0.0137 0.0298 0.0658 0.0938 0.1158 0.1358 0.1458 0.1588 0.2158 0.0067 0.0207 0.0285 0.0376 0.0576 0.0700 0.0766 0.1001 0.1119 947 948 Rathod Abhik et al. / Procedia Engineering 97 (2014) 941 – 950 Figure 4 and 5 shows the cumulative wear rate for sample 1 and sample 2 Fig. 4 Cumulative wear rate for sample 1 Fig. 5 Cumulative Wear rate for sample 2 Fig 4 and 5 shows the graph of Brinell hardness number v/s over all wear rate Fig. 6 BHN v/s overall wear rate From the figure 6 we can say that with increase in BHN overall wear rate is also increases Rathod Abhik et al. / Procedia Engineering 97 (2014) 941 – 950 3.4. Surface Morphology The microscope which has 400X magnification was used to analyze the surface morphology of both samples i.e. sample 1(20% reinforced) and sample 2 (10% reinforced). Sample 1(as in figure e) and sample 2 (as in figure f) shows that Aluminium 2014 properly clumps with the SiC reinforcement. Figure e and f shows surface morphology of sample 1 and 2 Fig. 7 Surface Morphology for Sample 1 Fig. 8 Surface Morphology for Sample 2 949 950 Rathod Abhik et al. / Procedia Engineering 97 (2014) 941 – 950 4. Conclusion From the result and discussion part we can conclude that: 1. 2. 3. 4. 5. Because of lower density of Sample 1(20% Reinforced) has higher wear rate i.e. 48% than Sample 2(10% Reinforced) Sample 1(20% Reinforced) has higher hardness i.e. 30% than Sample 2(10% Reinforced) because of high density. With decreasing with reinforcement porosity is increases by 7% With increase in BHN overall wear rate is also increases by 48% The hardness value obtain is too lower than the pure aluminium specimen because of less sintering time and compaction pressure. Acknowledgement The authors would like to express gratitude to Brakes India Limited and especially to Mr. R.VASU (Vice President & Corporate Management Representative Corporate QHSE System) and Mr. S. SRINIVASA RAGHAVAN (Divisional manager, Engineering Research & Development) for their expert advice, all the persons who gave their kind assistance during the preparation of samples and also to all other non-teaching staff who have contributed in the completion of the project. Reference [1]. M.A. Maleque1, A. Atiqah1, R.J. Talib and H. Zahurin “New Natural Fibre Reinforced Aluminium Composite For Automotive Brake Pad”. [2]. Y.Q. Liu, S.H. Wei, J.Z. Fan, Z.L. Ma, T. Zuo “Mechanical Properties of a Low-thermal-expansion Aluminium/Silicon Composite Produced by Powder Metallurgy”. [3]. H.M.Rootare, J.M.Powers and R.G.Craig “Wear of Composites by Abrasives of Varying Hardness”. [4]. Y. Wang, W.M. Rainforth, H. Jones, M. 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