EFFECT OF SURFACE ROUGHNESS PARAMETERS AND SURFACE TEXTURE FOR REDUCED FRICTION. S.Syahrullail 1,N.Nuraliza 1*,

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1 EFFECT OF SURFACE ROUGHNESS PARAMETERS AND SURFACE TEXTURE FOR REDUCED FRICTION S.Syahrullail 1,N.Nuraliza 1*, 1 Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, UTM Skudai, Johor, Malaysia * nuralizanoorawzi@gmail.com Keywords: surface roughness, coefficient of friction, double fractionated palm olein, Pin on disk tester ABSTRACT The aim of the present research was to investigate the possibility of contact surfaces with reduced friction using surface roughness analysis. For this purpose, various aluminum pin samples with different lubricant using different sliding speed values were prepared. To evaluate influence of roughness parameters on friction and wear, lubricated pin-on-disk tests were carried out under different speed contact conditions. Test results show that surfaces with high values surface roughness results in reduced friction. To investigate the effect of surface topography on surface roughness parameters and consequently on friction, real roughness profiles were virtually altered to achieve virtually textured surfaces. INTRODUCTION Lubricated friction is a case of fluid friction where a fluid separates two solid surfaces and a technique employed to reduce wear of one or both surfaces in close proximity moving relative to each other by interposing a substance called a lubricant between the surfaces. The conventional lubricant known as lubricating oil in industry can cause serious pollutant to our environment and giving awareness on the greenhouse effect. Therefore, to overcome these problem vegetable oils has been introduced and it s not new ideas. When two metal surfaces in contact, the amount of the asperities and interaction within the contact area will be increased thereby causing frictions which insist motion wear of the metal parts and a generation of excessive heat. Commonly, the wear and friction changes with the load, speed [1], temperature [2], surface roughness [3, 4, and 5], type of material or mating components [6] and environment. Lubrication is an excellent, alternative way to reduce friction, and is suitable for engines and machinery, and the presence of lubricants [7, 8] in machines and engines can overcome the economic implications of wear for the manufacturing industry. This research work considered one alternative of producing a lubricant from vegetable oils with specific emphasis on palm olein. Palm oil from the oil palm (Elaeis guianensis) has in recent

2 years become the world s most important vegetable oil. Palm oil is one of the most widely used plant oils in the world, which is grown in a mass plantation in tropical countries [9]. Today, vegetable oils were aimed by the researcher all over the world as an alternative source of lubricant. Vegetable oils can yield easily biodegradable ester type lubricants from renewal resources. In addition, the presence of long chain fatty acid in vegetable oil has the ability to show a better lubricating property attributed to the lower coefficient of friction obtained [10,11]. Vegetable oils contain very low volatility which is due to the high molecular weight of the triglyceride molecules in the composition and it's also good in viscosity properties. In this paper, the coefficient of friction and wear performance of double fractionated palm olein was investigated using a pin on disk tribo-tester machine. The experiments were conducted under various different sliding speeds and other parameter according to ASTM G The results from the investigation, the surface roughness obtained lubricated with double fractionated palm olein is higher than hydraulic oil and engine oil as sliding speed were increased. MATERIAL AND LUBRICANTS: Spherical pin samples were prepared with 6mm diameter, 30 mm in height and disk with a diameter of 165mm and height of 10mm. Double Fractionated palm olein (DFPO) was used as a test lubricant in this experiment. In this study, hydraulic oil was used to compare with the double fractionated palm olein. After completion of each test, plain disk should be polished using abrasive paper, 1000 micron to grind the surface because each test must be repeated three times to get an accurate result. To measure the surface roughness of the pin and disk, the surface roughness profile was used to determine the pattern both specimen surface which consisted of a stylus protector. EXPERIMENTAL PROCEDURE: Before starting the experiment, the pin and disk need to be clean using acetone to confirm there is no additional particle on the surfaces. The surfaces of the pin and disk were polished using abrasive paper, 1000µm to a surface roughness value, Ra, of about 0.4±0.1µm using surface roughness profiler consists a stylus detector to determine the pattern of the disk and pin surfaces. Then, the machine of each experiment was set up according to the parameter set up by a researcher. Spherical pin firmly attaches to hardened jaws specimen holder parallel to the plain disk because it to ensure that pin and disc touch to maximum contact surface. Then, all parameters such as speed (RPM) and time were inserted. All the tests were carried out at room temperature, 34± 2 C. In this experiment, the constant load 10N and different sliding speeds which are predictable to affect the friction and wear characteristics were considered. The surface finished of wear sample and disk was measured before and after the experiment. During the wear and friction coefficient test, different speeds were applied which were 1m/s for low speed until 5.0m/s for high speed. Three tests were carried out for each parameter and condition.

3 RESULT AND DISCUSSION Surface roughness (µm) Double fractionated palm olein Hydraulic Engine Oil-SAE Speed (m/s) surface roughness (µm) Double Fractionated palm olein Hydraulic oil Engine oil-sae Speed (m/s) Figure 6: surface roughness of DFPO, Engine oil and hydraulic oil for (a) A5083 and (b) AL1100 Surface roughness, or Ra, is another parameter that can have an effect on wear resistance and the coefficient of friction on the mating surface. Theoretically, on surfaces with low roughness, Ra has shallow grooves or asperities, while on surfaces with high roughness; Ra has deep asperities or is rough. Surfaces with deep asperities can cause the lubricant to be trapped into the small crevices and work as an oil reservoir on the mating surface. The condition of the surface depends on what type of lubricant is applied to it, and it will ultimately affect wear rates as well as the coefficient of friction. Therefore, it will give a rough or slightly rough effect to the worn scar surface. Figure 6 shows the distribution of the arithmetic mean value for surface roughness, Ra, for all the experimental conditions. At a lower speed, surface roughness for palm oil was high compared to mineral-based oil, but it increased progressively after the sliding speed was increased. The surface roughness for the pin lubricated with palm olein became greater as the palmitic acid from the palm olein reacted with the surface. This phenomenon was also accelerated by the existence of the double bond oxygen molecule inside the double fractionated palm olein (DFPO). This reaction lead to the oxidation of the metal surface and forced the pin material to become brittle and easy to break off. At the same time, the higher the sliding speed, the higher the local temperature at the contact point between the pin and disk. The lubricant that was used to coat the pin broke down because of the increase in temperature caused by the rubbing. Furthermore, the high surface roughness value affected the mechanical properties of the components and the low viscosity palm oil reduced the wear while the coefficient of friction increased in the long run.

4 The mineral-based oil had a low surface roughness because large wear scars were created which generated excessive heat at the start of the experiment. The most interesting observation was that vegetable oil proved to have a good film thickness and force relationship due to the long fatty acid chains (palmatic acid) in the oil. This made its film lubricant bond strongly with the oxide layer on the metal surface, therefore, making it good for surface protection.this is due to the contact between the pin and the disk all the time during the experimental period, the pin is continuously rubbing the rotating disk. According to the adhesive theory, toughing asperities adhere together at first and the plastic shearing of the junction so formed will remove or pluck of the softer asperities leaving them sticking to the hard surface. Due to this reason, the wear will be increased as long as rubbing action between the saucer and the pin still occurring. Another important finding was that shows soft material (al 1100) produce higher value of surface roughness compare to the hard material (a 5083) shows low value of surface roughness. CONCLUSION Under ASTM experimental conditions, the double fractionated palm olein showed better antifrictional and anti-wear performance when compared to hydraulic oil and engine oil-sae 40. The surface roughness for both lubricating oils were increased as the sliding speed increased, and the free unsaturated fatty acids played in the palm olein an important role in reducing the coefficient of friction and wear. ACKNOWLEDGEMENT The authors wish to thank the Faculty of Mechanical Engineering at the Universiti Teknologi Malaysia for their support and cooperation during this study. The authors also wish to thank Research Management Centre (RMC) for the Research University Grant (GUP-03H58) from the Universiti Teknologi Malaysia, Fundamental Research Grant Scheme (FRGS) from the Ministry of Higher Education (MOHE) and E-Science Grant and ERGS from the Ministry of Science, Technology and Innovation (MOSTI) of Malaysia for their financial support. REFERENCES [1] Wan Nik, W.B., Ani, F.B., Masjuki, H.H., Eng Giap, S.G., Rheology of Bio-edible Oils According to Several Rheology Models and its Potential as Hydraulic Fluid, Industrial Crops and Products, 22, 3, pp [2] Jianbo Hu, Zexue Du, Changxiu Li, Enze Min, Study On The Lubrication Properties Of Biodiesel As Fuel Lubricity Enhancers, Fuel,84, pp

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