76743855 material science effect of different lubrication types on coefficient of frictiion

7/28/2019 76743855 Material Science Effect of Different Lubrication Types on Coefficient of Frictiion

1/12

Running head: Effect of Different Lubrication Types on Coefficient of Friction 1

EFFECT OF DIFFERENT LUBRICATION TYPES ON COEFFICIENT OF FRICTION

[Your Name]

[Name of Your Institution]


2/12

Effect of Different Lubrication Types on Coefficient of Friction 2

Materials

The experiment was done on ferrite steel and copper, and various effects on lubrication on

coefficient friction were determined. Ferrite steel also known as mild steel contains 0.2% of

carbon and consists mostly of iron. Ferrite has a body centered cubic (B.C.C) kind of structures

that holds a little carbon, and are usually as alpha or delta ferrite. Carbons stabilize austenite

which is more soluble in it than in ferrite, so as temperature are increased for austenite alloy of

iron it converts to ferrite and thus have a ferrite-iron alloy with carbon thus forming the ferrite-

steel. By varying the treatment with amounts of carbon, results to a wide variety of steel.

Figure1: shows variation of carbon for different variety of steel.

Wear resistance for ferrite steel can be controlled by heat treatment, nitriding and carburizing. A

hard coating can also be added. [5, 6]

Copper is the second material was subjected to the experiment. In tribological experiment is used

as additives into oil lubricants. Copper nanoparticles have good friction reduction and wear

resistance; they increase sliding speed between the contacts. Copper tribological properties are

better at higher temperature than at a lower temperature. Copper forms a kind of protective

coating with a lower elastic modulus and hardness on the wearing surface. Generally copper has

a high machinability property, by adding about 0.5% tellurium and sulphur raises the


3/12


machinability from about 20 to 90%.copper does not rust, thus is resistant to corrosion. In other

cases where copper is not used as additives to lubricants, its tribology properties would be

determined in areas of electrical contacts. Electrical contacts are subject to tear and wear and

thus a durability test is critical before installation of electrical connections. [2]

Other materials used in the experiment were the lubricants; lubricants of varying viscosity were

used. They included aqua (water), Olea europaea (olive cooking oil), silicone lubricants and

highly viscous lubricant.

Procedure

The Pin-on-disk method on high temperature tribiometer was used. The material or rather the

specimen is fabricated into round bars known as pin. The pins were developed using orthodox

methods such as turning or grindings as to get the best shape of the pin. Usually the pins are

about 10mm radius and rounded tips.

Before the pins are machined and taken to the precipitating hardening treatment, the pins are put

into a heated solution. For steel pins after treatment the following mechanical properties would

be obtained:

Tensile properties Set1 Set2 Set3

0.2% yield strength(MPa) 1237 1096 921

Rupture strength (MPa) 1332 1140 1017

Elongation (%) 14.2 15 18

Hardness (HRC) 43.2 37 33

Figure3: A table showing the mechanical properties of the after treatment


4/12


After specimen preparation, the specimens were placed on a tribiometer with the upper

specimen, the pin attached to the strain-gauge and the lower specimen usually in disc shape

attached to the bottom. The radiuses of the sliding track, the velocity of the disc and revolution

counters were set to 0.5m/s. At another instance, the normal load of 5N was set. These settings

were done for each case of the four lubricants. The counters were set to stop at every 200 meters

of the sliding intervals for a maximum of 2400meters . [1, 2]

To obtain the results, the specimens were cleaned by rubbing using dry cloths and then using a

flux of compressed air. These specimens were then dried for 10 minutes in a furnace of

temperatures 80celcius. A campanula was used to cover the specimens, and its temperature was

maintained at 25 Celsius and the humidity at 55 to 60%.

Results and discussion

In this study tribology test was aimed at prediction of friction between copper and ferrite steel.

The wear rate and the wear coefficient were predicted by getting the different results from the

Pin-on-disk device were recorded. Graphs were plotted with excel charts, the mean value of the

Pin-on-disk device against load and speed of the sliding material were used to plot the graphs.

The standard error was used to plot points that the mean value deviated from the true value. The

standard error is got by dividing the standard deviation by the square root of the total number of

measurement that was made. As the standard deviation is divided by the number of

measurement, the standard error becomes smaller as the measurements number increases. This

shows a higher confidence level to the mean used. The error bars would show this confidence

level physically.


5/12


The coefficient of friction from the Pin-on-disk device was used to draw graphs against load and

speed. The different results varied with the different lubricants used. At first a constant load of

5N was used on the pin-on-disk device to provide a constant force on the two rubbing surfaces.

The second procedure involved varying the speed of the rotating pin. The results were as shown

in the graphs below:

Cooking oil

Figure1: Constant Load of 5N at different speeds on steel and copper


6/12


Figur2: Constant speed of 0.5m/s with different loading on steel and Copper

Water



7/12


Figure4: Constant speed of 0.5m/s with different loading on steel and copper

High Viscous lubricants



8/12



Less viscous lubricants

Figure7: Constant Load of 5N at different speeds on steel and steel and copper


9/12



Discussion and Conclusions

A test approach for wear and tear between the two materials was established by varying the

speed and loads on the tribiometer used. The uses of different lubricants show the effect of

lubricants on the wear coefficient. It is found that the coefficient of friction is consistent with

parameters of speed and force. The coefficients of friction increases with an increase of speed up

to a given level, this is when using less viscous lubricants but decreases with an increase of

speed. In case of highly viscous lubricants the coefficient of friction increases at lower speed but

it later decreases at higher speed. The rate of change of wear dependent on the type of material,


10/12


in this case the rate of change of wear in steel was faster in all cases since the graph were steeper

as compared with copper. [2, 4]

In conclusion a lubricant influences the coefficient of friction and the rate of wear of such

material in contact. The coefficient of friction is determined by the hydrodynamic theory and it is

observed that a rise in friction is due to high eccentric limit of the lubricant. From our experiment

evident that Reynolds steady state equation for lubrication that is given by F Vh/D, this is the

drag Force (F) is directly proportional to the velocity of the sliding materials (V) and the

lubricants viscosity and inversely proportional to the thickness of the lubricants (D). From the

experiment is evident the non-linearity of the lubricated friction, unlike the dry friction that has

its force directly proportional to the load applied. This experiment also shows the hydro-dynamic

nature of the lubricants that goes against the laws of friction. For dry friction, the force of friction

is usually independent of the area apparently in contact and the velocity of the sliding motion.

From our result varying the load or velocity caused a change in the coefficient of friction. By

using different lubricants in different sliding speeds it evident of the viscosity dependency on

temperature. At high speeds the temperature are higher and so the viscosity of the lubricants

seem to decrease thus leading to an increase of Coefficient of frication. From figure 6, as the

speed increases the coefficient of friction of steel decreases since it is a good conductor of heat

i.e. the lubricants effect is not much decreased as that on copper. Another effect associated with

speed and lubrication is the stribeck phenomenon: at low speed or rather velocities the

hydrodynamic pressures that do occur at the material is negligible thus explain the decrease of

coefficient of friction as the velocity increases. The stricbeck phenomenon also explains the

decrease of friction between the two sliding materials: as the tangential load is increased, the

amount of slippage between the contacts decreases. [1, 5, 6, 8]


11/12


References

[1]. Lenard, J., b, J. U., & c, B. W. (2006). The effect of lubricant additives

on the coefficient of friction in the flat-die test. Canada: Department of

Mechanical Engineering University of Waterloo.

[2]. Beardmore, R. (2012, january 28). Factors affecting the friction

between surfaces . Retrieved May 5, 2012, from ROYMECH:

http://www.roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htm

[3]. Gwidon W. Stachowiak, A. W. (2005). Engineering Tribology. New York:

Butterworth-Heinemann.

[4]. MAHDAVIAN, S. M., & MA1, Y. W. (1983). FURTHER STUDY IN FRICTION,

METALLIC TRANSFER AND WEAR. Australia: Department of Mechanical

Engineering, University of Sydney.

[5]. Maranian, P. (2010). Reducing Brittle and Fatigue Failures in Steel

Structures. Mississipi: ASCE Publications.

[6]. Ossia, C. V. (2010). Industrial Lubrication and Tribology. Korea:

Emerald Group Publishing Limited.

[7]. Workel, M. F., & Dowson1, D. (2007). Engineering Tribology.

Measurements of the coefficients of friction of different lubricants during

impact under high pressure and shear, 6.

[8].Sderberg, A. (2009). Interface modeling: friction and wear. Lindstedtsvgen:

Stockholm.


12/12


76743855 material science effect of different lubrication types on coefficient of frictiion

Documents