Effect of surface texturing on friction under starved lubrication conditions

Effect of surface texturing on friction under starved lubrication conditions FADI ALI SUPERVISOR: prof. Ing. Martin Hartl, Ph.D. Institute of Machine and Industrial Design Department of Machine Design Faculty of Mechanical Engineering Brno University of Technology

CONTENTS INTRODUCTION LITERATURE REVIEW TITLE AND AIM OF THESIS METHODS PRELIMINARY RESULTS PUBLICATIONS 1/21

INTRODUCTION Material science Friction and wear Tribology Lubrication and Lubricants Coating (DLC, Ceramic, ) Surface engineering Surface treatment Advanced materials Composite materials Surface texturing Oil properties (Chemistry) Boundary lubrication Mixed lubrication HD and EHD lubrication Film thickness and friction Dents, dimples, grooves, Trapping wear debris (BL) Acting as oil reservoir (HL) Enhancing film thickness and pressure (EHL) 2/21

LITERATURE REVIEW Andersson et al. 2007 Effect of micro-textures on the coefficient of friction and wear RESULTS Reducing friction and wear under lubricated sliding conditions, in comparison with smooth surfaces. Friction graphs obtained with the SRV tribometer, for a smooth steel disc and for laser-textured discs 3/21

LITERATURE REVIEW Nélias et al. 2000 Effect of micro-textures size on the pressure distribution and film thickness profile in EHL contacts. RESULTS No effect for small size of micro-dents. Positive effect for intermediate size(no cavitations) Negative effect for large size due to the cavitations. Effect of micro-dimples size on the pressure distribution and film thickness profile 4/21

LITERATURE REVIEW Mourier et al. 2008 Effect of micro-dents depth RESULTS Deep micro-cavities Deep micro-cavities cause a reduction in film thickness. Shallow micro-cavities enhance film thickness. Shallow micro-cavities 5/21

LITERATURE REVIEW Ai et al. 1994 Effect of slide-to-roll ratio (SRR) RESULTS Limited effect under pure rolling conditions. Positive effect when the sliding is introduced. SRR=0 SRR=2 6/21

LITERATURE REVIEW Effect of micro-dents on rolling contact fatigue (RCF) Coulon et al. 2004 Nélias et al. 2000 RESULTS Low stress concentration was found under pure rolling. Slide-to-roll ratio increases the stress level. Location of concentrated pressure depends on the direction of sliding. Pressure profiles for smooth and dented contact stress field in the vicinity of micro-dent 7/21

LITERATURE REVIEW Dumont et al. 2002 Effect of micro-dents under starved conditions RESULTS The beneficial increase of film thickness is lost if the contact becomes fully flooded. a) Fully flooded contact b) Starved contact Damiens et al. 2004 Film thickness under starved lubrication 8/21

ANALYSIS OF LITERATURE Problem Status Effect of micro-textures on friction and load carrying capacity for conformal contacts Etsion, I., State of the Art in Laser Surface Texturing, ASME thickness in non-conformal contacts (EHL) thickness Contact, ASME in Journal starved of Tribology EHL Pettersson, U. and Jacobson, S., "Influence of Surface Texture on Boundary Lubricated Sliding Contacts", Tribology International Effect of micro-textures on friction in starved EHL Partially solved (Numerically) Zhao, J., Sadeghi, F. and Nixon, H., A Finite Element Analysis of Surface Pocket Effects in Hertzian Line Kovalchenko, A., Ajayi, O., Erdemir, A., Fenske, G., Etsion, I., The Effect of Laser Surface Texturing on Transitions in Lubrication Regimes During Unidirectional Sliding Contact, Tribology International Not solved 10/21

ANALYSIS OF LITERATURE Problem Status Effect of micro-textures on friction and load carrying capacity for conformal contacts thickness in non-conformal contacts (EHL) thickness in starved EHL Coulon S, Jubault I, Lubrech AA, Ville F, Vergne P (2004) Pressure profiles measured within lubricated contacts in presence of dented surfaces. Comparison with numericalmodels. Tribol Int Mourier L, Mazuyer D, Lubrecht AA, Donnet C (2006) Transient increase of film thickness in micro- Effect textured EHL of micro-textures contacts. Tribol Int on friction in starved EHL Partially solved (Numerically) Nelias D, Ville F (2000) Detrimental effects of debris dents on rolling contact fatigue. Trans ASME J Tribol Ai XL, Cheng HS (1994) The influence of moving dent on point EHL contacts. Tribol Trans Not solved Krupka I, Hartl M (2007) The effect of surface texturing on thin EHD lubrication films. Tribol Int 12/21

ANALYSIS OF LITERATURE Problem Status Effect of micro-textures on friction and load carrying capacity for conformal contacts thickness in non-conformal contacts (EHL) thickness in starved EHL Partially solved (Numerically) Effect of micro-textures on friction in starved EHL Not solved Dumont M, Lugt PM, Tripp JH (2002) Surface feature effects in starved circular EHL contacts. Trans ASME J Tribol 14/21

AIM OF THESIS TITLE Effect of surface texturing on friction under starved lubrication conditions. AIM OF THESIS Studying experimentally the effect of artificial micro-dents on reducing the coefficient of friction in sliding motion between non-conformal surfaces under starved lubrication Experimental investigation of micro-textures on pressure and film thickness in starved EHL Micro-textures in reciprocating motion with starved EHL Optimizing the distribution of micro-dents by means of experimental approach 16/21

METHODS Torque sensor with amplifier circuit EHL contact D/A Card 17/21

METHODS Advantage of setup: Possibility of measuring friction and film thickness simultaneously Disadvantage of setup: Calibration for friction measurements Low sensitivity for low loads (W<10 N) Load=40 N, ue= 6.2 mm/s, SRR= -1.58 0.075 0.074 Smooth Micro-grooved (h=0.4µm, w= 42µm, l=160µm) COF 0.072 0.07 0.068 0.066 0 2 4 6 8 Time (min) 18/21 10

METHODS Disadvantage of MTM: No film thickness measurements Mini Traction Machine (MTM) 19/21

PRELIMINARY RESULTS Micro-dents in starved EHL Reducing friction under starved condition Negligible benefits under fully flooded 0.09 Smooth Textured 0.12 0.08 Smooth Textured Load=32N, SRR=-1,starved 14µL 0.11 Coefficient of friction Coefficient of friction Load=32N, SRR=-1,fully flooded 0.07 0.06 0.1 0.09 0.08 0.07 0.05 0.06 0.04 0 1 2 3 4 5 6 7 8 0.05 0 1 2 4 5 Time [min] Time [min] 3 20/21 6 7 8

PRELIMINARY RESULTS 0.3 0.2 Profile of micro-groove Distribution of micro-grooves and dimensions in µm Transverse micro-grooves in starved EHL Reducing friction under starved condition Enhancing film thickness µm 0.1 0-0.1-0.2-0.3-0.4 Shoulder 65 nm 42µm COF Load=40 N, u e = 2.9 mm/s, SRR= -5.6 (Reverse motion) 0.084 0.082 0.08 0.078 0.076 Smooth Micro-grooved (h=0.4µm, w= 42µm, l=160µm) Film thickness nm 600 500 400 300 200 100-0.5 0 40 80 120 160 200 240 µm Micro-grooved (h=0.4µm, w=42µm, l=160µm) Smooth X X 0 0 0.074 0 2 4 6 8 10 Time (min) 0-300 -200-100 0 100 200 300 Position on X axis µm 21/21

Effect of surface texturing on friction under starved lubrication conditions Publications ALI, F.; KRUPKA, I.; HARTL, M.: Enhancing the parameters of starved EHL point conjunctions by artificially induced replenishment, Tribology International, Vol.66, (2013), No.1, pp.134-142,issn 0301-679X, Elsevier journal article ALI, F.; KŘUPKA, I.; HARTL, M.: An Approximate Approach to Predict the Degree of Starvation in Ball Disk Machine Based on the Relative Friction, TRIBOLOGY TRANSACTIONS, Vol.56, (2013), No.4, pp.681-686,issn 1040-2004, Taylor & Francis journal article ALI, F.; KŘUPKA, I.; HARTL, M.: Friction of smooth and textured non-conformal surfaces under starved conditions, Tribology and Design II, pp.29-40, ISBN 978-1-84564-610-3, (2013), WIT Transactions on Engineering Sciences conference paper ALI, F.; KŘUPKA, I.; HARTL, M.: Analytical and experimental investigation on friction of non-conformal point contacts under starved lubrication, MECCANICA, Vol.45, (2012), No.1, pp.1-9, ISSN 0025-6455, Springer journal article ALI, F.; HARTL, M.: FRICTION OF NON-CONFORMAL CONTACTS UNDER STARVED EHD LUBRICATION, MM Science Journal, Vol.2012, (2012), No.12, pp.374-377,issn 1803-1269, (MM) Science Journal journal article 22/21

THANK YOU FOR LISTENING FADI ALI Institute of Machine and Industrial Design Department of Machine Design Faculty of Mechanical Engineering Brno University of Technology

Effect of surface texturing on friction under starved lubrication conditions Questions: 1- what is the role of materials and oil chemistry on starvation? Materials Elastic modulus Poisson's ratio Roughness Contact dimensions Wetability Contact angle Surface energy Surface tension forces Capillary effect Van der Waals force Replenishment Oil spread Oil chemistry Viscosity Additives Size of molecule Starvation 24/15

Effect of surface texturing on friction under starved lubrication conditions Questions: 1- what is the role of material and oil chemistry on starvation? Priority of parameters after introducing sliding from starvation point of view 1. Viscosity 2. Oil amount 3. Operating conditions (speed) 4. Temperature 5. Surface tension forces 6. Capillary effect 7. Contact geometry 8. Van der Waals force 9. Surface energy 10. Contact angle 11. 12. Considered In my thesis 25/15

Effect of surface texturing on friction under starved lubrication conditions Questions: 2- Is there any algorithm to optimize the distribution of micro-textures? What is the optimum distribution? In EHL contacts (even in the starved regime) wear is minimum since separation is larger than the scale of roughness (adhesive wear is minimum) The optimum distribution of micro-textures results in the lowest friction (not wear) for given operating conditions. Distribution of micro-textures can be optimized by modifying the density of textured area and dimensions (a, b ) between dents. This approach is experimental but it could be also mathematical. 26/15