eduzhai > Physical Sciences > Materials Sciences >

Mechanical and dry sliding wear properties of vinyl ester composites filled with granular fillers CaCO3 and CaSO4

  • sky
  • (0) Download
  • 20211030
  • Save
https://www.eduzhai.net International Journal of Composite M aterials 2012, 2(5): 101-114 DOI: 10.5923/j.cmaterials.20120205.06 Mechanical and Dry Sliding Wear Behavior of Particulate Fillers CaCO3 and CaSO4 Filled Vinyl ester Composites Sandee p Kumar1,*, Sant Ram Chauhan2 1Department of M echanical Engineering, Lovely Professional University, Phagwara, Punjab, 144402, India 2 Department of M echanical Engineering, National Institute of Technology, Hamirpur, 177005, India Abstract The imp roved performance of poly mers and their co mposites in industries and many other applications by the addition of part iculate fillers has shown great advantages and so has lately been the subject of considerable interest. In this paper, mechanical and tribological behavior of particu late fillers CaCO3 and CaSO4 filled v inyl ester co mposites have been presented. Wear tests were carried out in dry sliding conditions on a pin-on-disc friction and wear test rig. (DUCOM) at roo m temperature under slid ing velocity (1.57, 2.62 and 3.67 m/sec.), normal load (20, 40 and 60 N), filler content (0, 10 and 20 wt.%) and sliding d istance (1000, 3000 and 5000 m). The plans of experiments is based on the Taguchi technique, was performed to acquire data in a controlled way. An orthogonal array and analysis of variance (A NOVA ) were applied to investigate the influence of process parameters on the coefficient of friction and sliding wear behaviour of these composites. The coefficient of frict ion and specific wear rate were significantly influenced with increase in both the filler content. The results show that for pure vinyl ester the coefficient of frict ion and specific wear rate increases with the increase of normal load, sliding velocity and sliding d istance. The coefficient of friction and specific wear rate for CaCO3 filler decreases with the increase of filler content. But, for filler CaSO4 the coefficient of frict ion and specific wear rate decreases at 10 wt.% and then increases at 20 wt.%. It is believed that a thin film formed on stainless steel counterface was seems to be effective in improving the tribolog ical characteristics. The worn surfaces examined through SEM to elucidate the mechanis m of friction and wear behaviour. Keywords Sliding Wear, Poly mer-Matrix Co mposites, Fillers, Scanning Electron Microscopy 1. Introduction An informal nu mber of papers dealing with the tribological behaviors of polymer materials have been published. That is why the polymers are extending over a great area used in sliding co mponents like such as gears, cams, breaks, clutches, bearings, wheels and bushes. Adhesive wear includes galling, fretting, scuffing and surface fatigue. This refers to the damage produced when two mat ing surfaces move relative to each other under a normal load. Surface asperities interact and very high stresses, strain, and strain rates are generated in localized regions[1]. This type of wear occurs in bearings, piston rings, cylinders and in electrical contacts. In recent years attention has been focused on the sliding wear behavior o f poly mers and their co mposites due to their increasing use as bushings and seals in machinery. The research by various authors[2-4] reported that the friction between poly mers can be attributed by the two main mech an is ms i. e, d e fo r mat io n an d ad h es io n . Th e * Corresponding author: sandeep6437@gm ail.com (Sandeep Kumar) Published online at https://www.eduzhai.net Copyright © 2012 Scientific & Academic Publishing. All Rights Reserved deformation mechanism involves dissipation of energy in the contact area. The adhesion components of friction of polymer results from the breakage of bonds between the polymer and mating sliding surface[3]. Fran klin[5] studied the friction and wear behavior of POM poly mer and reported that the effect of slid ing speed on the wear of polymers does not always follow the generally accepted engineering rule of “h igher sliding speed, the higher wear rate”. Fro m the point of view of the coefficient of friction, Brentnall and Lancaster[6] reported that the friction coefficient of poly mers rubbing against metals decreases with the increase in load. So me researchers[7-9] reported that the coefficient off friction value increases with the increase in load. Finally, Byett and Allen[10] and Friedrich et al.[11] have reported that the coefficient off frict ion value increases with the increase in load. Many poly meric materials have an excellent strength-to-weight ratio, good corrosion resistance, wider choice of the materials, dimensional stability, high impact strength, light we ight and ease to manufacturing. So me poly mers also possess excellent tribolog ical p roperties[12]. The poly mers can be considered to be one of the competit ive materials for tribological applications because of their low friction values against steel counterparts, good damping properties, and self 102 Sandeep Kumar et al.: M echanical and Dry Sliding Wear Behavior of Particulate Fillers CaCO3 and CaSO4 Filled Vinyl ester Composites lubricating abilities. It has been observed that by assimilating filler part icles in the polymer based composites, synergistic effects may be achieved in the form of h igher modulus and reduction of the material cost[13-15]. The inclusion of such particles into polymers for co mmercial applications is focused at the cost reduction and stiffness improvement[16, 17]. Various kinds of polymers and polymer-matrix co mposites with different types of fillers such as Al2O3, SiC, TiO2, fly ash etc. have been the subject of extensive research in recent years as found from the literature[18-21]. But the potential of particulate fillers Ca CO3 and CaSO4 in vinyl ester matrix has not been reported so far. So, in this paper we are using these fillers (CaCO3 and CaSO4) with vinyl ester matrix and studying the effect of such fillers on mechanical and dry sliding wear behavior of the composites. Polymer composites containing different fillers and/or reinforcements that are frequently used for applicat ions like auto motive parts, gear assemblies, tub/ shower industries etc. in which friction and wear are critical issues. Calciu m carbonate (CaCO3) and calciu m sulfate (CaSO4) are the fillers, which are used in the automobile parts and tub/ shower industries respectively. Ho wever, study of the effect o f such filler addition is necessary to ensure that the mechanical properties of the co mposites are not affected adversely by the addition of such fillers. The importance of mechanical and tribolog ical properties has convinced many researchers to study the friction and wear behaviour and to improve the wear resistance of polymer based composites. Fro m the above mentioned literature it is understood that there is tremendous potentials of these fillers used for research on vinyl ester composites and studied under dry slid ing conditions. Since, the purpose of this paper is to study the mechanical and dry slid ing wear behaviour of fillers CaCO3 and CaSO4 filled v inyl ester composites. Taguchi method is used to optimize the process parameters of sliding wear in order to reduce the nu mber of experiments without sacrificing the informat ion. 2. Experimental Details 2.1. Speci men Preparati on The matrix used in this work is vinyl ester resin (density 1.28 g m/cc) was supplied by Northern Poly mer Pvt. Ltd. New Delhi. Methyl ethyl ketone pero xide (M EKP- 1.5%), Cobalt Naphthenate (1.5%) was used as catalyst and accelerator respectively. Three d ifferent types of composites are prepared for the study. The Calciu m Sulfate (CaSO4) and Calciu m Carbonate (CaCO3) having particle size 1.813 µm and 1.620 µm respectively were used as a filler material collected fro m the Pioneer Chemical Corporation, Delh i. The composites are made homogeneously. Firstly they are properly sterilized in a jar and then simply pour into the 10mm d iameter test tubes. There are three different types of composites are made for the current study with 0, 10 and 20 wt.% of the filler content. The accelerator Cobalt Naphthenate 1.5% is mixed thoroughly in vinyl ester resin and then catalyst 1.5% Methyl ethyl ketone peroxide (MEKP) was mixed in the resins prior to reinforcement. Befo re pouring the composite solution in the test tube, the test tube is sprayed with a release agent (Silicon spray) to ensure that the part will not adhere to the test tube after the curing of the composites samples. The cast of each composite is cured for 24 hour at roo m temperature before it is removed fro m the test tube. The other composite samples with fillers CaCO3 and CaSO4 of fixed weights (10 wt.% and 20 wt.%) percentage were fab ricated by the same technique. The fillers CaSO4 and CaCO3 were mixed thoroughly in the v inyl ester resin mechanically before pouring into the test tubes. The composites prepared for this study are designated as WCGV1, WCGV2, W CGV3, WCGV4, and WCGV5 respectively. The composition and designation of the co mposites prepared for this study are listed in Table 1. Table 1. Composition and designation of the composites Design at io n Detail composition WCGV1 Vinyl ester WCGV2 Vinyl ester +10 wt.% CaSO4 WCGV3 Vinyl ester +20 wt.% CaSO4 WCGV4 Vinyl ester +10 wt.% CaCO3 WCGV5 Vinyl ester +20 wt.% CaCO3 2.2. Fricti on and Wear Test Apparatus Dry sliding wear tests were conducted on a pin-on-disc friction and wear monitoring test rig (DUCOM ) as per ASTM G 99. The cylindrical pin specimens of 10mm diameter and 30mm length were tested against a disc made of hardened ground steel (EN-32, hardness 72HRC, surface roughness Ra= 0.07 µm). The specimen was held stationary and the disc was rotated while a normal force was applied through a lever mechanis m. The schematic diagram of the pin-on-disc apparatus is shown in the Figure 1. Du ring the test, frictional fo rce was measured by the transducer mounted on the loading arm. The frictional force readings were taken as the average of 100 readings of every 40 seconds for the required time period. For th is purpose a microprocessor controlled data acquis ition s ys tem was used. The average mass loss was used to calculate to the specific wear rate (Ks). The tests were conducted with sliding velocity (1.57, 2.62, 3.67 m/sec.), norma l load (20, 40, 60 N), filler content (0, 10, 20 %) for the sliding distance of 1000, 3000 and 5000 m. Sliding wear data reported here is the average of two runs. The initial weight before run and final weight after run is measured using a precision electronic balance with an accuracy of ± 0.01 mg. The specific wear rate (mm3/Nm) is then exp ressed on ‘volume loss’ basis. Ks = ∆m L ρ Fn International Journal of Composite M aterials 2012, 2(5): 101-114 103 Table 2. Parameters setting and levels for various control factors for wear test Control Fact ors Symbols Units Levels I II III Velo cit y A Normal Load B m/sec. 1.57 2.62 3.67 N 20 40 60 Filler Content C % 0 10 20 Sliding Dist an ce D m 1000 3000 5000 Where, Ks is the specific wear rate (mm3/ Nm), is the mass loss in the test duration in g m, is the density of the composite (gm/cm3), Fn is the applied normal load (N), L is the slid ing distance (m). The parameters setting and levels for various control factors for wear test are shown in the Table 2. Figure 1. Schematic diagram of pin-on disc apparatus 2.3. Scanning Electron Microscopy A FEI quanta FEG450 was used to analyze the worn surfaces of the polymer co mposites. The composite samples are mounted on stubs with gold plating. To enhance the conductivity of the samples, thin films of p latinu m are vacuum evaporated onto them before the photomicrographs were taken. with 13 colu mns at three levels. The operating conditions under which sliding wear tests carried out are given in the Table 2. In conventional full factorial experimental design, it would require 34 = 81 runs to study four factors each at three levels whereas, Taguchi’s factorial experiment approach reduces it to only 27 runs offering a great advantage in terms of experimental time and cost. The experimental observations are transformed into a signal-to-noise (S/N) ratio. There are three S/ N ratios available depending upon the type of characteristics (smaller-the-better, larger-the-better, nominal-the better). The S/N ratio for minimu m (friction and wear rate) coming under smaller is better characteristic, which can be calculated as logarithmic transformation of the loss function as shown below[26] S N = −10 log⁡� 1 n ( y12 + y22 + ⋯ yn2 � (1) Where ‘n’ is the repeated number trial conditions and y1, y2………yn are the response of the frict ion and slid ing wear characteristics. “Lower is better” (LB) characteristic, with the above S/N ratio transformation is suitable for minimizat ions of coefficient of friction and specific wear rate. The standard linear graph is used to assign the factors and interactions to various columns of the orthogonal array (OA). The plan of experiments is as follows: the first column is assigned to the velocity (A), the second column to normal load (B), the fifth column to filler content (C) and the ninth column to sliding distance (D) the third and fourth colu mn are assigned to (A×B)1 and (A×B)2 respectively to estimate interaction between the velocity (A) and the normal load (B), the sixth and seventh column are to (B × C)1 and (B×C)2 respectively to estimate the interaction between the normal load (B) and the filler content (C), the eight and eleventh column are assigned to (A × C)1 and (A × C)2 respectively to estimate the interaction between the velocity (A) and the filler content (C) and the remain ing colu mns are used to estimate the e xperimental e rror. The linear graph for L27 array is shown in the Figure 2. 2.4. Experi mental Design Taguchi design of experiment is a powerful analysis tool which is adopted for optimizing design parameters. Taguchi method provides the designer with a systematic and efficient approach for experimentation to determine near optimu m settings of design parameters for performance, quality and cost[22-25]. The most impo rtant stage in the design of experiment lies in the selection o f the control factors. In the present work, the impact of the four such factors are studied using L27 (313) orthogonal array wh ich has 27 rows corresponding to the number of tests (20 degree of freedo m) Fi gure 2. Linear graphs for L27 array 3. Results and Discussion The characterization of the co mposites reveals that inclusion of any particu late filler has very strong influence not only on the mechanical properties of co mposites but also 104 Sandeep Kumar et al.: M echanical and Dry Sliding Wear Behavior of Particulate Fillers CaCO3 and CaSO4 Filled Vinyl ester Composites on their sliding wear behavior. By incorporating these particulate fillers into the vinyl ester matrix, synergistic effects, as expected were achieved in the form of mod ified mechanical properties and improved slid ing wear resistance. A comparative study of modified behavior of the composites against the two different types of fillers is presented. 3.1. Density The composite under this investigation consists of three components such as matrix, fiber and part iculate filler. Hence, the density of the co mposite can be calcu lated using rule-of-mixture as shown in the fo llo wing expression Agarwal and Brout man[27]. ρcomposite = 1 �W m ρm �+� Wρ ff � + �W p ρp � (2) Where, W and ???????? represents the weight fraction and density respectively. The suffix m, f, and p stand for the matrix, fiber and particulate filler respectively. The actual or experimental density ???????????????????????????????? of the composite, however, can be determined by simple water immersion technique (Archimedes princip le). The vo lu me fraction of voids (Vv ) in the composites is calculated using the following equation: Vv = ρct − ρexp ρexp (3) Table 3. Composite designations and their experimental and theoretical den sit ies Comp o sit e Desig n at io n WCG V1 WCG V2 WCG V3 WCG V4 WCG V5 Composite Compositio ns Vinyl ester Vinyl ester + 10 wt.% CaSO4 Vinyl ester + 20 wt.% CaSO4 Vinyl ester + 10 wt.% CaCO3 Vinyl ester + 20 wt.% CaCO3 Exp eriment al Density (g/cm3) 1.2738 1.3307 1.3891 1.3400 1.4022 Th eoret ica l Density (g/cm3) 1.2800 1.3570 1.4439 1.3513 1.4311 Void Fract io n 0.4844 1.9381 3.7953 0.8362 2.0194 It can be noticed fro m Table 3 that composite density values calculated fro m weight fractions using Eq. (2) are not in agreement with the experimentally determined values. The difference between the co mposite or theoretical density and the actual or e xpe rimental density is a measure of voids and pores present in the composites. It is clear fro m the Table 3 that volume fraction of voids is small in WCGV1 due to absence of particulate fillers in it. As the filler content of CaSO4 and CaCO3 co mposites (WCGV2-WCGV5 ) increases from 10 wt.% to 20 wt.% the volume fract ions of voids increases as shown in the Table 3. The voids are more in the CaSO4 filler as co mparison to the CaCO3 filler. Th is may due to the particle size variat ions, because the particle size o f the CaSO4 (1.813 µm) and CaCO3 (1.620 µm) is higher respectively. The voids significantly affect some of the mechanical properties and even the performance of composites. Higher void contents usually mean lower fatigue strength, greater susceptibility to water penetration and weathering[27]. The knowledge of the void content is usually important for the estimation of the quality of the composites. 3.2. Mechanical Properties The experimental values of the properties of the particulate filled CaCO3 and CaSO4 co mposites under this investigation are presented in Table 4. Table 4. Mechanical properties of the composites Com posit es WC GV1 WC GV2 WC GV3 WC GV4 WC GV5 Tensil e st ren gt h (MP a) 39.04 21.65 18.58 24.81 20.77 Tensile Modulus (GP a) 0.583 0.797 0.808 0.698 0.744 Flexural st ren gth (MP a) 103.15 69.45 59.0 101.75 107.6 Compressi ve Strength (MP a) Hardnes s (HRB) 9.51 8.81 6.27 8.05 10.52 17.5 21.3 10.2 22.15 19.6 45 CaSO4 CaCO3 35 Tensile Strength (MPa) 25 15 0 10 20 Filler Content (wt. %) Figure 3. Variation of tensile strength of composites with filler type and cont ent The tensile test is performed on the universal testing mach ine (UTM) Hounsfield H25KS as per ASTM standard D 3039-76[28]. It is seen that in all the samples irrespective of the filler material the tensile strength of the composite decreases with increase in filler content. The pure vinyl ester has strength of 39.04 MPa in tension and it may be seen from Table 4 that this value drops to 21.65 MPa and 18.58 M Pa with addition of 10 wt.% and 20 wt.% o f CaSO4 filler International Journal of Composite M aterials 2012, 2(5): 101-114 105 respectively. The same phenomenon has been seen in CaCO3 filler, the values are drops to 24.81 M Pa to 20.77 MPa with the addition of the 10 wt.% and 20 wt .% of CaCO3 filler. Among the two fillers taken in th is study, the inclusion of CaSO4 filler causes maximu m reduction in the co mposite strength. It may occurs due to the interface bonding between the vinyl ester matrix and Ca SO4 filler is not good to transfer the tensile stress as that in CaCO3 filler content. The one more reason is that the corner points of the irregular shaped particulates result in stress concentration in the vinyl ester matrix. Now, it is interesting to note that the properties for tensile modulus is increasing with the addition of the both the filler CaSO4 and CaCO3 at 10 wt.% and 20 wt.% respectively as shown in Figure 4. 0.95 CaSO4 with the increase of the reinforcement of the filler in comparison to CaSO4 filler. The flexu ral properties are of great importance for any structural element. Co mposite materials used in structures are prone to fail in bending and therefore the development of new composites with imp roved flexu ral characteristics is essential. Fro m the results it may now be suggested that CaCO3 is potential candidate to be used as filler in making high flexural strength composites with the increase of the reinforcement of the filler in comparison to CaSO4 filler. CaSO4 holds good flexural strength at 10 wt.% filler content also more than WCGV1 and WCGV4 co mposites as shown in Figure 5. There may be one reason for this that the voids in WCGV2 (1.9381) is mo re in comparison to WCGV4 (0.8362). 12 CaSO4 CaCO3 CaCO3 10 0.8 8 0.65 Compression Strength (MPa) Tensile Modulus (GPa) 0.5 0 10 20 Filler Content (wt. %) 6 0 10 20 Filler Content (wt. %) Figure 4. Variation of tensile modulus of composites with filler type and cont ent Figure 6. Variation of compression strength of composites with filler type and content 115 CaSO4 24 CaCO3 100 20 CaSO4 CaCO3 Hardness (HRB) Flexural Strength (MPa) 85 16 70 12 55 0 10 20 Filler Content (wt. %) 8 0 10 20 Filler Content (wt. %) Figure 5. Variation of flexural strength of composites with filler type and cont ent The flexu ral test is conducted on the same UTM as per ASTM standard D 2344-84[29]. Figure 5 shows the comparison of flexu ral strengths of the co mposites obtained experimentally fro m the 3-point bend tests for composites (WCGV1-WCGV5 ). The flexural strength for the filler CaCO3 is increasing with the addition of the 10 wt.% to 20 wt.% filler content. But, for the filler CaSO4 it decreases with the addition of the filler content. Now, fro m the results it may now be suggested that CaCO3 is potential candidate to be used as filler in making high flexural strength composites Figure 7. Variation of Rockwell hardness of composites with filler type and cont ent Figure 6 shows the comp ressive strengths of the composites obtained experimentally for the composites (WCGV1-WCGV5 ). The co mpressive strength for filler CaSO4 decreases continuously with the addition of the 10 wt.% and 20 wt.% filler content and for filler CaCO3, it firstly decreases at the addition of 10 wt.% filler content and then increases with the addition of 20 wt.% filler content as shown in the Figure 6. Figure 7 shows the hardness of the composites (WCGV1-WCGV5 ) as obtained fro m the experiments. For 106 Sandeep Kumar et al.: M echanical and Dry Sliding Wear Behavior of Particulate Fillers CaCO3 and CaSO4 Filled Vinyl ester Composites composite WCGV1, the hardness is recorded as 17.5 HRB while for WCGV2 and WCGV3 the values are recorded as 21.3 HRB and 10.2 HRB respectively. On the other hand the values for co mposites WCGV4 and W CGV5 are recorded as 22.15 HRB and 19.6 HRB respectively. Fro m the analysis of the results we observed that the hardness of the CaCO3 filler is more as comparison to CaSO4. 3.3. Anal ysis of Experi mental Results The experimental data for coefficient o f friction and specific wear rate (Ks) for CaCO3 and CaSO4 fillers is reported in the Table 5 and 8 respectively. The data reported here is the average of two runs. From Table 5 the overall mean for the S/N ratio of the coefficient of friction and the specific wear rate for CaCO3 are found to be 4.1395 db and 92.5339 db respectively. On the other hand, from Table 8 the overall mean for the S/N ratio of the coefficient of friction and the specific wear rate for CaSO4 are found to be 3.3670 db and 89.8949 db respectively. Here, we saw that the overall mean fo r the S/N ratio of the coefficient of frict ion and specific wear rate is more in CaCO3 in co mparison to CaSO4 wh ich means that the coefficient of friction and specific wear rate is less in CaCO3. The analysis of the experimental data is carried using the software MINITA B 16 specially used for the design of experiment applications. Before analy zing the experimental data using this software for predict ing the measure of performance, the possible interaction between control factors are considered. Thus factorial design incorporates a simple means of testing for the presence of the interaction effects. Velo cit y (m/sec.) 1.57 1.57 Normal Load (N) 20 20 Filler Content (%) 0 10 Table 5. Experimental design for CaCO3 using L27 array Sliding COF Dist an ce (µ) (m) 1000 0.70 S/N Ratio (db) 3.09804 Wear (mm3/Nm) 0.0000771 3000 0.59 4.58296 0.0000462 S/N Ratio (db) 82.259 86.707 1.57 20 20 5000 0.54 5.35212 0.0000384 88.313 1.57 40 0 3000 0.75 1.57 40 10 5000 0.58 2.49877 4.73144 0.0000853 0.0000386 81.381 88.268 1.57 40 20 1000 0.45 1.57 60 0 5000 0.80 6.93575 1.93820 0.0000273 0.0000932 91.277 80.612 1.57 60 10 1000 0.47 1.57 60 20 3000 0.39 6.55804 8.17871 0.0000312 0.0000262 90.117 91.634 2.62 20 0 3000 0.78 2.62 20 10 5000 0.69 2.15811 3.22302 0.0000825 0.0000474 81.671 86.484 2.62 20 20 1000 0.64 2.62 40 0 5000 0.83 3.87640 1.61844 0.0000333 0.0000952 89.551 80.427 2.62 40 10 1000 0.59 2.62 40 20 3000 0.50 4.58296 6.02060 0.00000822 0.00000493 101.703 106.143 2.62 60 0 1000 0.75 2.62 60 10 3000 0.48 2.49877 6.37518 0.0000858 0.00000792 81.330 102.025 2.62 60 20 5000 0.46 6.74484 0.00000423 107.473 3.67 20 0 5000 0.85 3.67 20 10 1000 0.76 1.41162 2.38373 0.0000982 0.00000863 80.158 101.280 3.67 20 20 3000 0.61 3.67 40 0 1000 0.78 4.29340 2.15811 0.00000561 0.0000832 105.021 81.598 3.67 40 10 3000 0.66 3.67 40 20 5000 0.60 3.60912 4.43697 0.00000606 0.00000451 104.351 106.916 3.67 60 0 3000 0.80 3.67 60 10 5000 0.57 1.93820 4.88250 0.0000942 0.00000411 80.519 107.723 3.67 60 20 1000 0.52 5.67993 0.00000212 113.473 International Journal of Composite M aterials 2012, 2(5): 101-114 107 Figure 8 and 9 for CaCO3 shows graphically the effect of four control factors on coefficient of friction and specific wear rate of the composite specimens WCGV1 , WCGV4 and WCGV5. The analysis of the results gives the combination factors resulting in minimu m coefficient of frict ion and specific wear rate o f the co mposites. Analysis of these results leads to the conclusion that factors combination A1, B3, C3 and D2 gives min imu m coefficient of friction as shown in the Figure 8. It is observed that the interaction B× C shows significant effect on the coefficient of friction. Similarly the combination factors A3, B3, C3 and D2 gives minimu m specific wear rate as shown in the Figure 9. It is observed that interaction A×C has significant effect on the specific wear rate. Main Effects Plot for SN ratios Data Means Velocity 6 5 4 Mean of SN ratios 3 2 1.57 2.62 3.67 Filler Content 6 5 4 3 2 0 10 20 Signal-to-noise: Smaller is better Normal Load 20 40 60 Sliding Distance 1000 3000 5000 Figure 8. Effect of control factor on Coefficient of friction. (For CaCO3) Main Effects Plot for SN ratios Data Means Velocity 100 Normal Load 95 Mean of SN ratios 90 85 80 1.57 2.62 3.67 Filler Content 100 95 90 20 40 60 Sliding Distance 85 80 0 10 20 Signal-to-noise: Smaller is better 1000 3000 5000 Figure 9. Effect of control factor on Specific wear rate. (For CaCO3) For CaSO4 Figure 10 and 11 shows graphically the effect of four control factors on coefficient of friction and specific wear rate of the composite specimens WCGV1 , WCGV2 and WCGV3. Analysis of these results leads to the conclusion that factors combination A1, B3, C2 and D1 gives minimu m coefficient of friction as shown in the Figure 10. It is observed that the interaction B×C again shows significant effect on the coefficient of friction as in case of CaCO3 filler. The combination factors A3, B3, C2 and D1 gives minimu m specific wear rate as shown in the Figure 11. It is observed that interaction A×C has significant effect on the specific wear rate. Main Effects Plot for SN ratios Data Means Velocity 5 Normal Load 4 Mean of SN ratios 3 2 1.57 2.62 3.67 Filler Content 5 20 40 60 Sliding Distance 4 3 2 0 10 20 Signal-to-noise: Smaller is better 1000 3000 5000 Fi gure 10. Effect s of cont rol fact or for coefficient of frict ion. (For CaSO4) Main Effects Plot for SN ratios Data Means Velocity 96 92 88 Normal Load Mean of SN ratios 84 80 1.57 2.62 3.67 Filler Content 96 20 40 60 Sliding Distance 92 88 84 80 0 10 20 Signal-to-noise: Smaller is better 1000 3000 5000 Figure 11. Effect of control factor on Specific wear rate. (For CaSO4) 3.4. ANOVA and Effects of Factors In order to understand the impact of various control factors like velocity (A), normal load (B), filler content (C) and sliding distance (D) and interaction on the response of experimental data it is desirab le to develop the analysis of variance (A NOVA) to find the significant factors as well as interactions. ANOVA allows analyzing the influence of each variable on the total variance of the results. For CaCO3, Table 6a shows the results of ANOVA for the specific wear rate and Table 7a shows the results of ANOVA for coefficient of frict ion and for CaSO4, Table 9a shows the 108 Sandeep Kumar et al.: M echanical and Dry Sliding Wear Behavior of Particulate Fillers CaCO3 and CaSO4 Filled Vinyl ester Composites results of ANOVA for the specific wear rate and Table 10a shows the results of ANOVA for coefficient of frict ion. The analyses are performed with a level of significance 5% means at 95% level of confidence. In ANOVA table, the column shows the percentage contribution (P) of each variable in the total variation indicating the influence of specific wear rate and coefficient of frict ion. For filler CaCO3 it can be observed fro m the ANOVA Table 6a for specific wear rate that the filler content (P=57.981%), velocity (P=17.981%), normal load (P=5.523%) and the interactions A×C (P=10.218%), B×C (P=3.283) and A×B (P=3.097% ) has significant influence on the specific wear rate. However, the control factor sliding distance (P=0.303%) does not have a significant effect (both physically and statistically) on specific wear rate as their values are quit smaller than error (P=1.613%) so they are neglected. From the analys is of ANOVA and respons e Table 6b of the S/N ratio of specific wear rate, it is observed that the control factor filler content (C) has major impact on the specific wear rate fo llo wed by velocity (A), normal load (B) and sliding distance (D). It means that with increasing the filler content, velocity and norma l load the specific wear rate decreases i.e., increase the wear resistance as observed from the Figure 9. Table 6a. ANOVAtable for Specific wear rate. (For CaCO3) Source DF Seq SS Adj SS Adj MS F P (%) A 2 563.46 563.46 281.732 33.45 17.981 B 2 173.08 173.08 86.540 10.27 5.523 C 2 1816.92 1816.92 908.462 107.86 57.981 D 2 9.51 9.51 4.754 0.56 0.303 A*B 4 97.06 97.06 24.266 2.88 3.097 A*C 4 320.19 320.19 80.047 9.50 10.218 B*C 4 102.87 102.87 25.718 3.05 3.283 Residual Error 6 50.54 50.54 8.423 1.613 Tot al 26 3133.63 100.00 Level 1 2 3 Delt a Rank Table 6b. Response table for Specific wear rate. (For CaCO3) A B C 86.73 92.98 89.05 93.56 81.11 96.52 97.89 11.16 94.99 5.94 99.98 18.87 2 3 1 D 92.51 93.27 91.82 1.45 4 Source A B C D A*B A*C B*C Residual Error Tot al Table 7a. ANOVAtable for Coefficient of friction. (For CaCO3) DF Seq SS Adj SS Adj MS F 2 9.5096 9.5096 4.7548 33.39 2 11.6173 11.6173 5.8086 40.79 2 59.8532 59.8532 29.9266 210.15 2 1.6144 1.6144 0.8072 5.67 4 0.6990 0.6990 0.1748 1.23 4 1.7495 1.7495 0.4374 3.07 4 6.7443 6.7443 1.6861 11.84 6 0.8544 0.8544 0.1424 26 92.6416 P (%) 10.265 12.540 64.607 1.743 0.755 1.889 7.279 0.922 100.00 International Journal of Composite M aterials 2012, 2(5): 101-114 109 Table 7b. Response table for coefficient of friction. (For CaCO3) Table 9a for specific wear rate that filler content Level A B C D (P=44.375%), velocity (P=27.788%) and the interactions 1 2 3 Delt a Rank 4.875 4.122 3.422 1.453 3 3.375 4.066 4.977 1.602 2 2.146 4.548 5.724 3.578 1 4.197 4.406 3.815 0.591 4 In the same way fro m the ANOVA Tab le 7a for coefficient of friction the filler content (P=64.607%), normal load (P=12.540%), velocity (P=10.265%), sliding distance (P=1.743%) and the interactions B×C (P=7.279%), A × C (P=1.889%) has significant effect on the coefficient of friction. But, interaction A×B (P=0.755%) does not have a significant effect (both physically and statistically) on coefficient of friction as its value is quit smaller than error (P=0.922%) so it may neglected. So, fro m the analysis of ANOVA and response Table 7b of the S/N ratio of coefficient of frict ion, it is observed that the filler content (C) has majo r influence followed by normal load (B), velocity (A) and sliding distance (D) as for the coefficient of friction. For filler CaSO4, it can be observed from the ANOVA A×C (P=20.423%) and B× C (P=2.474%) has significant effect on specific wear rate. Ho wever, the control factors normal load (P=1.326%), slid ing distance (P=0.815%) and interaction A×B (P=0.859% ) do not have a significant effect (both physically and statistically) on specific wear rate as their values are quit smaller than residual error (P=1.941%) so they are neglected. Fro m the analysis of A NOVA and response Table 9b of the S/N rat io for specific wear rate, it is observed that the control factor filler content (C) has major impact on the specific wear rate fo llo wed by velocity (A), the normal load (B) and slid ing distance (D). It means that for filler CaSO4, with the increases of the filler content, velocity and normal load the specific wear rate decreases i.e., the wear resistance is good as observed fro m the Figure 11. But fro m the Figure 11 we also observed that for CaSO4 the filler content plays adverse effect when filler content is increases fro m 10 wt.% to 20 wt.%. At 10 wt.% for CaSO4 the specific wear rate is decreased and for 20 wt.%, it further increases. Table 8. Experimental design for CaSO4 using L27 array Velo cit y Normal Filler Content Sliding Distance COF (m/sec.) Load (N) (%) (m) (µ) 1.57 20 0 1000 0.70 S/N Ratio (db) 3.09804 Wear (mm3/Nm) 0.0000771 S/N Ratio (db) 82.259 1.57 20 10 3000 0.60 4.43697 0.0000432 87.290 1.57 20 20 5000 0.63 4.01319 0.0000483 86.321 1.57 40 0 3000 0.75 2.49877 0.0000853 81.381 1.57 40 10 5000 0.57 4.88250 0.0000373 88.566 1.57 40 20 1000 0.64 3.87640 0.0000498 86.055 1.57 60 0 5000 0.80 1.93820 0.0000932 80.612 1.57 60 10 1000 0.48 6.37518 0.0000325 89.762 1.57 60 20 3000 0.70 3.09804 0.0000535 85.433 2.62 20 0 3000 0.78 2.15811 0.0000825 81.671 2.62 20 10 5000 0.68 3.34982 0.0000458 86.783 2.62 20 20 1000 0.72 2.85335 0.0000588 84.612 2.62 40 0 5000 0.83 1.61844 0.0000952 80.427 2.62 40 10 1000 0.57 4.88250 0.00000812 101.809 2.62 40 20 3000 0.75 2.49877 0.0000685 83.286 2.62 60 0 1000 0.75 2.49877 0.0000858 81.330 2.62 60 10 3000 0.52 5.67993 0.00000783 102.125 2.62 60 20 5000 0.64 3.87640 0.0000786 82.092 3.67 20 0 5000 0.85 1.41162 0.0000982 80.158 3.67 20 10 1000 0.64 3.87640 0.00000652 103.715 3.67 20 20 3000 0.79 2.04746 0.00000785 102.103 3.67 40 0 1000 0.78 2.15811 0.0000832 81.598 3.67 40 10 3000 0.63 4.01319 0.00000558 105.067 3.67 40 20 5000 0.69 3.22302 0.00000582 104.702 3.67 60 0 3000 0.80 1.93820 0.0000942 80.519 3.67 60 10 5000 0.58 4.73144 0.00000333 109.551 3.67 60 20 1000 0.64 3.87640 0.00000401 107.937 110 Sandeep Kumar et al.: M echanical and Dry Sliding Wear Behavior of Particulate Fillers CaCO3 and CaSO4 Filled Vinyl ester Composites Source DF A 2 B 2 C 2 D 2 A*B 4 A*C 4 B*C 4 Residual Error 6 Tot al 26 Table 9a. ANOVATable for Specific wear rate. (For CaSO4) Seq SS 747.54 35.66 1193.77 21.93 23.11 549.40 66.55 52.22 2690.17 Adj SS 747.54 35.66 1193.77 21.93 23.11 549.40 66.55 52.22 Adj MS 373.769 17.831 596.883 10.967 5.777 137.351 16.636 8.703 F 42.95 2.05 68.58 1.26 0.66 15.78 1.91 P (%) 27.788 1.326 44.375 0.815 0.859 20.423 2.474 1.941 100.00 Table 9b. Response table for Specific wear rate. (For CaSO4) Level A B C D 1 85.30 88.32 81.11 91.01 2 87.13 90.32 97.19 89.88 3 97.26 91.04 91.39 88.80 Delt a 11.96 2.72 16.08 2.21 Rank 2 3 1 4 Table 10a. ANOVAtable for Coefficient of friction. (For CaSO4) Source DF Seq SS Adj SS Adj MS F P (%) A 2 2.8080 2.8080 1.4040 6.47 6.655 B 2 2.6152 2.6152 1.3076 6.02 6.199 C 2 29.3058 29.3058 14.6529 67.47 69.460 D 2 1.7235 1.7235 0.8618 3.97 4.085 A*B 4 1.7612 1.7612 0.4403 2.03 4.174 A*C 4 0.1993 0.1993 0.0498 0.23 0.472 B*C 4 2.4749 2.4749 0.6187 2.85 5.866 Residu al Error 6 1.3030 1.3030 0.2172 3.088 Total 26 42.1908 100 Table 10b. Response table for coefficient of friction. (For CaSO4) Level 1 2 3 Delt a Rank A 3.802 3.268 3.031 0.771 2 B 3.027 3.295 3.779 0.752 3 C 2.146 4.692 3.263 2.546 1 D 3.722 3.152 3.227 0.570 4 In the same way fro m the A NOVA Table 10a for coefficient of frict ion the filler content (P=69.460%), velocity (P=6.655%), normal load (P=6.199%), sliding distance (P=4.085%) and the interactions B×C (P=5.866%) and A × B (P=4.174%) has significant effect on the coefficient of friction. However, the interaction A × C (P=0.472%) do not have significant effect on the coefficient of friction as their values are quite smaller than the residual error (P=3.088%), so it may neglected. Fro m the analysis of the ANOVA and the response Table 10b for coefficient of friction it is observed that the filler content (C) has major influence follo wed by the velocity (A) normal load (B) and the sliding distance (D). Fro m the Fig. 10 for CaSO4, it is observed that the coefficient of frict ion is also increase with the increase of the filler content. It means that in 10 wt.% the coefficient of friction is less as comparison to 20 wt.% i.e., the reinforcement of the CaSO4 filler at 10 wt.% is mo re wear resistance. 3.5. Surface Morpholog y Figures 12a-c are the SEM p ictures of composites for minimu m, maximu m and nominal wear test conditions for CaCO3 filled vinyl ester co mposites. It has been found from the experimental analysis that the min imu m wear occurs at 3.67 m/sec., 60 N, 20 wt. %, 1000 m test parameter conditions, the maximu m wear occurs at 3.67 m/sec., 20 N, 0 wt. %, 5000 m test parameter conditions and the nominal wear occurs at 3.67 m/sec., 20 N, 10 wt. %, 1000 m test parameter conditions as shown in the Figures 12a-c. The micrograph in Figure 12a shows the resinous and matrix region. The filler CaCO3 covered the matrix region which results in less wear. Figure 12b shows the debris and wedge format ion regions due to long slid ing distance. Vinyl ester debris was adhered into the filler reg ion and micro cracks were identified which increases the wear rate. Figure 12c showing the thin layer fo rmation and debris which results the nomina l wea r. Similarly, Figures 13a-c are the SEM p ictures of composites for min imu m, maximu m and nominal wear test conditions for CaSO4 filled v inyl ester composites. It has been found from the experimental analysis that the minimu m wear occurs at 3.67 m/sec., 60 N, 10 wt. %, 5000 m test parameter conditions, the maximu m wear occurs at 3.67 m/sec., 20 N, 0 wt. %, 5000 m test parameter conditions and the nominal wear occurs at 3.67 m/sec., 20 N, 20 wt. %, 3000 m test parameter conditions as shown in the Figures 13a-c.

... pages left unread,continue reading

Document pages: 14 pages

Please select stars to rate!

         

0 comments Sign in to leave a comment.

    Data loading, please wait...
×