Impact Of Dimple Density On Tribological Performance Of PTFE Composite

Impact Of Dimple Density On Tribological Performance Of PTFE Composite

Wakchaure P.B.1

P.G. Scholar

Amrutvahini College of Engg. Sangamner.

Prof. Aher V.S.2

Asso.Prof.

Amrutvahini College of Engg. Sangamner.

Prof. Mishra A.K.3

H.O.D, Mechanical Dept

Amrutvahini College of Engg. Sangamner.

Prof. Wakchaure V.D.4

Asso.Prof.

Amrutvahini College of Engg. Sangamner.

Abstract

Surface texturing has emerged in the last decade as a viable option of surface engineering resulting in significant improvement in tribological properties like wear resistance, friction coefficient, load capacity etc. of mechanical components. In the present investigation the effect of surface texturing on tribological properties of PTFE (PTFE+40% Bronze) composite material considering various texture patterns so as to observe the comparative friction and wear behavior of PTFE composite with & without surface texturing on mating surface at dry & wet lubrication by using a pin-on-disc Tribometer. The results shows that the coefficient of friction varies considerably with surface texture patterns, some texture patterns shows a higher load carrying capacity & due to that negative coefficient of friction was observed. Wear of the some textured surface is higher compared with non textured surface. Scanning Electron Micrographs shows that wear of some textured surfaces was reduced compared with the non textured surface at both the lubricating conditions.

Keywords: Surface Texturing, Dimples, Tribometer.

1. INTRODUCTION

   Surface Engineering is a novel expression that named the sub-discipline of material science dealing with the optimization of solid surface phase in order to functionalize the items during their interaction with the environment and the surrounding systems. From the technological point of view, Surface Engineering is meant to be considered an attractive instrument for tribological challenges: several solutions involving chemical, structural and morphological modification by means of adding material or reshaping surface topography, can be adopted with the aim of improving performances, reducing friction and wear, and/or increasing hardness and toughness.

   Surface texturing involves modifications of surface topography, creating a uniform micro relief with regularly shaped asperities or depressions. Nowadays, surface texturing delineates a scientific and technological open-frontier where the area of micro-fabrication converge to surface science committed to study and demonstrate the various mechanisms of integrated micro-effects resulting in a macro-benefit that optimizes performances.

2. EXPERIMENTAL METHODOLOGY

   Experimental set up of a pin-on-disc Tribometer (TR- 20LE) was used for the readings of wear and frictional force.

   Fig. No. 1. Experimental setup of Pin on Disc Tribometer The TR-20LE Pin on disc wear testing is advanced

   regarding the simplicity and convenience of operation, ease of specimen clamping and accuracy of measurements, both of wear and frictional force along with lubrication and environmental facility.

   The machine is designed to apply loads up to 20 kg and is intended both for dry and lubricated test conditions. It facilitates study of friction and wear characteristics in sliding contacts under desired test conditions within machine specifications. Sliding occurs between the stationary pin and a rotating disc. Normal load, rotational speed and wear track diameter can be varied to suit the test conditions. Tangential frictional force and wear are monitored with electronic sensors and recorded on PC. These parameters are available as a function of load and speed.

3. PREPARATION OF SPECIMEN

   PTFE composite material is in the form of cylindrical rod with dimentions 6 mm diameter and 105 mm length. The test specimens (pins) of 6 mm diameter and 30 mm length are cut. The disc of materal AISI SS 304 stainless steel plate of the surface roughness Ra for counter surface i.e. for disc is The surface texture patterns were made on the SS 304 plate by the Lasers. The size of the dimple is taken 300 Micron &

   densities of the dimples are varied as 10%, 20%, 30%. The no. of dimples for the 3 tracks is as follows:

   Track No.1: Non Textured Surface

   Track No.2: 300(µm) Diameter & Density (10%) Track No.3: 300(µm) Diameter & Density (20%) Track No.4: 300(µm) Diameter & Density (30%)

   Table.1: Typical properties of 40 % Bronze filled PTFE composites

   Sr. No.	Property	Unit	40 % Bronze filled PTFE
   1.	Density	gm / cc	3.1-3.2
   2.	Tensile Strength	kgf / cm2	125-150
   3.	Elongation	%	100-175
   4.	Compressive Strength	kgf / cm2	85-100
   5.	Flexural Strength	kgf / cm2	85
   6.	Flexural Modulus	kgf / cm2	14000
   7.	Hardness	Shore	70-75
   8.	Dielectric Strength	kv / mm	Conductive

   Experimental Parameters: Sliding velocity- 0.12 m/sec, Time- 60 min,

   Load- 12 Kg,

   Lubricant- Watmans Watol S. R. Bearing oil 3 during the wet test conditions.

4. OBSERVATION TABLE

   11

   S.N	Time (min)	Wear (µ)		F.F (N)		C.O.F
   		Dry	Wet	Dry	Wet	Dry	Wet
   1	0	0	0	36.7	1.4	0.3076	0.0117
   2	5	0	0	36.8	1.8	0.3084	0.0151
   3	10	0	0	37.4	1.7	0.3134	0.0142
   4	15	0	0	37.9	1.6	0.3176	0.0134
   5	20	0	0	38.2	1.6	0.3201	0.0134
   6	25	0	0	38.3	1.6	0.3210	0.0134
   7	30	1	0	38.6	1.6	0.3235	0.0134
   8	35	1	0	38.8	1.6	0.3251	0.0134
   9	40	1	1	39.1	1.6	0.3277	0.0134
   10	45	1	1	39.2	1.5	0.3285	0.0126
   50	1	1	39.3	1.4	0.3293	0.0117
   12	55	1	1	39.4	1.4	0.3302	0.0117
   13	60	1	1	39.4	1.5	0.3302	0.0126

   S.N	Time (min)	Wear (µ)		F.F (N)		C.O.F
   		Dry	Wet	Dry	Wet	Dry	Wet
   1	0	0	0	36.7	1.4	0.3076	0.0117
   2	5	0	0	36.8	1.8	0.3084	0.0151
   3	10	0	0	37.4	1.7	0.3134	0.0142
   4	15	0	0	37.9	1.6	0.3176	0.0134
   5	20	0	0	38.2	1.6	0.3201	0.0134
   6	25	0	0	38.3	1.6	0.3210	0.0134
   7	30	1	0	38.6	1.6	0.3235	0.0134
   8	35	1	0	38.8	1.6	0.3251	0.0134
   9	40	1	1	39.1	1.6	0.3277	0.0134
   10	45	1	1	39.2	1.5	0.3285	0.0126
   11	50	1	1	39.3	1.4	0.3293	0.0117
   12	55	1	1	39.4	1.4	0.3302	0.0117
   13	60	1	1	39.4	1.5	0.3302	0.0126

   Table No. 2- Experimental data of Track No. 1

   Table No.3 – Experimental data of Track No.2

   S.N	Time Min	Wear (µ)		F. F (N)		C.O.F
   		Dry	Wet	Dry	Wet	Dry	Wet
   1	0	0	0	36.2	18.6	0.3034	0.1559
   2	5	0	0	37.3	19.6	0.3126	0.1643
   3	10	0	0	37.6	20.6	0.3151	0.1726
   4	15	0	0	38	20.1	0.3184	0.1684
   5	20	1	0	38.2	19.6	0.3201	0.1643
   6	25	1	0	38.4	19	0.3218	0.1592
   7	30	1	0	38.8	18.5	0.3251	0.1550
   8	35	2	0	38.8	18.9	0.3251	0.1584
   9	40	2	0	38.9	18.5	0.3260	0.1550
   10	45	2	2	39.3	18.9	0.3293	0.1584
   11	50	2	3	39.4	16.5	0.3302	0.1383
   12	55	2	3	39.6	9.6	0.3319	0.0804
   13	60	2	3	39.7	9.6	0.3327	0.0804

   Table No. 4 – Experimental data of Track No.3

   Sr No	Time Min	Wear (µ)		F.F (N)		C.O.F
   		Dry	Wet	Dry	Wet	Dry	Wet
   1	0	0	0	47.2	20.4	0.3955	0.1710
   2	5	0	0	48.3	18.4	0.4048	0.1542
   3	10	0	0	49.1	21.6	0.4115	0.1810
   4	15	0	0	51.5	22.3	0.4316	0.1869
   5	20	0	0	52.7	21.2	0.4416	0.1777
   6	25	0	0	53.5	20.7	0.4483	0.1735
   7	30	-1	0	53.9	18.8	0.4517	0.1575
   8	35	-1	0	54	15.2	0.4525	0.1274
   9	40	-1	3	54.2	0.5	0.4542	0.0042
   10	45	-1	3	54.4	0.4	0.4559	0.0034
   11	50	-1	3	54.4	0.3	0.4559	0.0025
   12	55	-1	3	54.5	0.3	0.4567	0.0025
   13	60	-1	3	54.8	0.3	0.4592	0.0025

   Table No. 5 – Experimental data of Track No. 4

   S.N	Time Min	Wear (µ)		F.F (N)		C.O.F
   		Dry	Wet	Dry	Wet	Dry	Wet
   1	0	0	0	38.1	22.3	0.3193	0.1869
   2	5	0	0	39.5	22.2	0.3310	0.1860
   3	10	0	0	40.8	21.8	0.3419	0.1827
   4	15	0	0	41.6	21	0.3486	0.1760
   5	20	0	0	42.4	20	0.3553	0.1676
   6	25	0	0	42.8	18.8	0.3587	0.1575
   7	30	0	0	43.6	18	0.3654	0.1508
   8	35	1	1	44.8	16.9	0.3754	0.1416
   9	40	1	3	45.7	4.7	0.3830	0.0394
   10	45	1	3	46.2	-0.3	0.3872	-0.002
   11	50	1	3	47.3	-0.3	0.3964	-0.002
   12	55	1	3	48.2	-0.3	0.4039	-0.002
   13	60	1	3	48.3	-0.3	0.4048	-0.002

5. RESULTS

   1. Wear of the 300 micron size dimple at dry lubrication

      Graph No. 1: Wear v/s Time plot when density of the dimples increases at dry lubrication

   2. Wear of the 300 micron size dimple at wet lubrication

      Graph No. 2: Wear v/s Time plot when density of the dimples increases at wet lubrication

   3. C.O.F of the 300 micron size dimple at dry lubrication

      Graph No. 3: C.O.F v/s Time plot when density of the dimples increases at dry lubrication

   4. C.O.F of the 300 micron size dimple at wet lubrication

      Graph No. 4: C.O.F v/s Time plot when density of the dimples increases at Wet lubrication

   5. C.O.F at dry lubrication changes w.r.t change in density of dimples

      Graph No. 5: C.O.F v/s Tracks at dry lubrication

   6. C.O.F at wet lubrication changes w.r.t change in density of dimples

      Graph No. 6: C.O.F v/s Tracks at wet lubrication

   7. C.O.F at wet lubrication changes w.r.t change in density of dimples

      Graph No. 7: Wear v/s Tracks at dry lubrication

   8. C.O.F at wet lubrication changes w.r.t change in density of dimples

      Graph No.8: Wear v/s Tracks at wet lubrication

6. DISCUSSION

   From the above oservations & calculations it can be shown that at dry lubrication condition the coefficient of friction increases as the texturing density increases & wear remains constant for all the texturing densities. The Frictional force goes on increasing when the density of the dimples are increased beyond the 10% & wear during the experimentation varies at very smaller values comparison with each other texturing patterns.

7. SEM ANALYSIS

   Fig No. 2: SEM image of Pin Before Testing

   Dry Wet

   Fig No. 3: SEM image of Pin After Testing on Track No.1

   Dry Wet

   Fig No. 4: SEM image of Pin After Testing on Track no.2

   Dry Wet

   Fig No. 5: SEM image of Pin After Testing on Track No.3

   Dry Wet

   Fig No. 6: SEM image of Pin After Testing on Track No.4

8. CONCLUSIONS

• C.O.F increases with the density of the dimples.

• SEM images shows that the wear of textured surface is low compared with non textured surface in both dry & wet lubrication conditions.

• Load carrying capacity of textured surface is increased in higher dimple density track due to that it shows negative C.O.F in wet lubrication.

• It improves the mechanical efficiency & bearing life.

REFERENCES

1. M.H.Chon, Sangil Park Micro CNC surface texturing on polyoxymethylene (POM) and its tribological performance in lubricated sliding Tribology International 44 (2011) 859867

2. Wan Yi, Xiong Dang-Sheng The effect of laser surface texturing on frictional performance of face seal journal of materials processing technology 1 9 7 ( 2 0 0 8 ) 96100

3. Andriy Kovalchenko et al. Friction and wear behavior of laser textured surface under lubricated initial point contact Wear 271 (2011) 1719 1725

4. Kristian Tønder Micro- and macro-modifications of pivoted slider bearings: Performance comparisonand texturing versus width reduction Tribology International 44 (2011) 463467

5. Piotr Ste et al. Deterministic and stochastic components of regular surface texture generated by a special grinding process Wear 271 (2011) 514518

6. G. Ryk et al. Testing piston rings with partial laser surface texturing for friction reduction Wear 261 (2006) 792796.

7. Kristian Tønder Dimpled pivoted plane bearings: Modified coefficients Tribology International 43 (2010) 23032307

8. Fatu Aurelian n et al. Wall slip effects in (elasto) hydrodynamic journal bearings Tribology International 44 (2011) 868877

9. Surya P.Mishra et al. Tribological studies of unpolished laser surface textures under starved lubrication conditions for use in air-conditioning and refrigeration compressors Tribology International 44 (2011) 18901901

10. R. Rahmani a et al. An analytical approach for analysis and optimization of slider bearings with infinite width parallel textures Tribology International 43 (2010) 15511565

11. Cem Sinano et al. Effects of shaft surface texture on journal bearing pressure distribution Journal of Materials Processing Technology 168 (2005) 344 353

12. R.K. Sharma et al. Experimental studies of pressure distributions infinite slider bearing with single continuous surface profiles on the pads Tribology International 42 (2009) 10401045

13. Waldemar Koszela et al. Experimental investigation of oil pockets effect on abrasive wear resistance Tribology International 46 (2012) 145153

14. Tianchang Hua et al. Tribological investigation of MoS2 coatings deposited on the laser textured surface Wear 278 279 (2012) 77 82

15. Jianliang Li et al. Effect of surface laser texture on friction properties of nickel-based composite Tribology International 43 (2010) 11931199

16. Lidia Galda et al. Dimples shape and distribution effect on characteristics of Stribeck curve Tribology International 42 (2009) 15051512

17. Sihuan Yuan et al. Orientation effects of micro- grooves on sliding surfaces Tribology International 44 (2011) 10471054

18. Nikhil Bhata et al. Performance of inherently compensated flat pad aerostatic bearings subject to dynamic perturbation forces Precision Engineering (2012)

19. Pradeep L. Menezes et al. Effect of surface roughness parameters and surface texture on friction and transfer layer formation in tinsteel tribo-system journal of materials processig technology 2 0 8 ( 2 0 0 8 ) 372382.

20. No¨ el Bruneti _ere n et al. Numerical analysis of a surface-textured mechanical seal operating in mixed lubrication regime Tribology International 49 (2012) 8089

21. Ivan Krupka et al. Effect of surface texturing on elasto hydro dynamically lubricated contact under transient speed conditions Tribology International 44 (2011) 11441150

22. Izhak Etsion State of the Art in Laser Surface Texturing http://tx.technion.ac.il/~merei02/public/15_State%20 of%20the%20Art%20in%20Laser%20Surface.pdf

23. Izhak Etsion , G.Halparen A Laser Surface Textured Hydrostatic Mechanical Seal Journal of Tribology Transactions Vol. 45 (2002), 3 430-434.

24. Izhak Etsion, Y. Kligerman Improving Tribological Performance of Piston Rings by Partial Surface Texturing Journal Transactions of the ASME Vol. 127, July 2005

25. Andriy Kovalchenko Oyelayo Ajayi, Ali Erdemir, George Fenske, Izhak Etsion, The effect of laser surface texturing on transitions in lubrication regimes during unidirectional sliding contact Journal Tribology International 38 (2005) 219225.