Rolling, Sliding and Torsion friction of single silica microspheres: Comparison of nanoindentation based experimental data with DEM simulation Part A

Transcription

1 Faculty of Science and Technology Chair of Surface and Materials Technology Institute of Materials Engineering Rolling, Sliding and Torsion friction of single silica microspheres: Comparison of nanoindentation based experimental data with DEM simulation Part A Regina Fuchs, Jan Meyer, Thorsten Staedler and Xin Jiang (University of Siegen, Germany) Thomas Weinhart, Vanessa Magnanimo, Stefan Luding (University of Twente, Netherlands) Aditya Kumar - University of Siegen Workshop Dialogue: Experiment-Model, Universität Siegen, 1 st and 2 nd of October 2012

2 Particle/surface interaction Starting Point Is it possible to measure rolling of single silica microspheres on surfaces with a commercial nanoindenter setup?

3 Particle/surface interaction Proof of principle Proof of principle: Pure sliding experiments Borsilica spheres with diameter of 20µm Indenter: Diamond flat end (diameter 20µm), Colloid probe (diameter 20µm) Contact pair: glass and diamond

4 friction coefficient Particle/surface interaction Proof of principle 0,9 0,8 A B 0,7 0,6 0,5 0,4 0,3 0,2 0, F(N) / µn

5 Particle/surface interaction Proof of principle What happens in case of a free sphere? Contact: diamond glass diamond

6 friction coefficient Particle/surface interaction Proof of principle 1 0,9 0,8 A B C 0,7 0,6 0,5 0,4 0,3 0,2 0, F(N)/ µn

7 friction coefficient Particle/surface interaction Proof of principle 0,6 0,5 Combination of different motion 0,4 0,3 0,2 Rolling 0, F(N)/ µn

8 Particle/surface interaction Proof of principle Conclusion: Sliding experiment: Same friction coefficient for case A (colloid over diamond) and B (diamond over fixed sphere) Rolling experiment: Clear difference compared to sliding experiments Friction coefficient (after critical load) one order of magnitude smaller than sliding friction coefficient Lateral forces much smaller than in sliding experiment Critical torsional moment necessary for rolling critical Load exist Well known in Literature 1;2 Our assumption: Rolling friction for F(N) > 100µN 1. Shigeki Saito, Hideki T. Miyazaki, Tomomasa Sato, and Kunio Takahashi, J Appl Phys 92 (9), 5140 (2002) 2. M. D. M. Peri and C. Cetinkaya, Philosophical Magazine 85 (13), 1347 (2005)

9 Particle/surface interaction Friction loop F(L)/µN Rolling friction coefficient ~ Need for best possible measurement strategies Friction Loop Δ = M b + M f 2 Friction loops are utilized 40%RH, RT 2 µm lateral displacement 1 µm/s scan speed Various normal loads M b 0 M f Δ W W = half-width of the loop Δ = offset of the loop M b = Lateral force backward M f = lateral force forward Lateral displacement /µm Advantages: - Compensation of Instrument Artifact - Compensation of System Artifact - Reduce Error - Comparable to AFM measurements

10 F(L) / µn Particle/surface interaction Result (1) 5 Quartz 4 Silicon Quartz and Silicon similar lateral forces Linear relationship F(L) vs. F(N) F(N) /µn

11 F(L) /µn Particle/surface interaction Result (2) µm sphere 5µm sphere Small F(N): F(L) for 5µm and 20µm spheres similar F(N) higher: plastic deformation in case of 5µm sphere has to be proven by experiments F(N) /µn

12 Particle/surface interaction Rail system Movement of Sphere (15µm scratch) sometimes differs from scratch axis! correlation between rolling and torsion? Is distinction between rolling and torsion friction coefficient possible? 25 Reducing degrees of freedom 45 Rolling Torsion 65 Angle between rail-slopes will determine composition of friction

13 Particle/surface interaction Rail system Rail System: Reducing degree of freedom Produced by FIB Rail material: Silicon Different angle of the rail θ = 0, 25, 45 (later up to 85 ) Focal point of sphere shifted to 60% (inside rail) Comparison of nanoindentation based experimental data with the Discrete Element Method (DEM) simulation

14 F(L) /µn Particle/surface interaction Results Rail system Increasing lateral force with angle of rail system! More PART B F(N)/ µn

15 Particle/surface interaction Conclusion Proof of principle: Clear difference between friction coefficient of pure sliding and rolling Commercial nanoindenter setup useful to measure rolling and sliding friction Friction loop: Best possible resolution reduced Error Compensation of Artifact Substrate: Similar surfaces show similar F(L) vs. F(N) behavior F(L) vs. F(N) linear relationship Radius of Spheres: 5µm spheres show at higher load a non-linear F(L) vs. F(N) behavior Understanding of plastic deformation possible Rail system: Correlation between rolling and torsion

16 Particle/surface interaction Outlook Comparison with DEM Simulation!!! More Rolling, Sliding and Torsion friction of single silica microspheres: Comparison of nanoindentation based experimental data with DEM simulation Part B

17 Thank you for your attention!