25.5 Conclusions The impulses and pull-off forces developed by metallic adhesion are characterized in the frame of the qualification of a mechanism for a space application, where a gold coated AuPt proof mass is released to free-fall by holding it with two opposed metallic tips which are quickly retracted. The results show evidence of adhesive bonds with pull-off force on the order of tens of mN and impulses on the order of tens of μN s, where the time duration of the adhesion failure is around 1 ms. The contact between the two metals shows evidence of gold transfer from the coating to the tip, which however does not expose the bulk material. This suggests that local ductile adhesive bonds are produced, according to similar results published on gold–gold contact. The maximum measured impulse exceeds the allowed momentum transfer, however a relevant margin is present in the in-flight release configuration thanks to a much larger quickness of retraction of the tip (at least a factor 10 in velocity). References 1. Eiden M, Seiler R (2004) Space mechanisms and tribology challenges of future space missions. Acta Astronaut 55:935–943 2. Roberts EW (2012) Space tribology: its role in spacecraft mechanisms. J Phys D Appl Phys 45:503001 (17pp) 3. Merstallinger A, Sales M, Semerad E, Dunn BD (2009) Assessment of cold welding between separable contact surfaces due to impact and fretting under vacuum. ESA STM-279. ISBN 978-92-9221-900-6 4. Gane N, Pfaelzer P, Tabor D (1974) Adhesion between clean surfaces at light loads. Proc R Soc Lond Ser A 340:495–517 5. Alcantar NA, Park C, Pan JM, Israelachvili JN (2003) Adhesion and coalescence of ductile metal surfaces and nanoparticles. Acta Mater 52:31–47 6. Antonucci F et al (2012) The LISA Pathfinder mission. Class Quantum Grav 29:124014 7. Bortoluzzi D, Benedetti M, Baglivo L, De Cecco D (2011) Measurement of momentum transfer due to adhesive forces: on-ground testing of inspace body injection in geodesic motion. Rev Sci Instrum 82:125107 8. Bortoluzzi D, De Cecco M, Vitale S, Benedetti M (2008) Dynamic measurements of impulses generated by the separation of adhered bodies under near-zero gravity conditions. Exp Mech 48:777–787 9. Bortoluzzi D, Benedetti M, Baglivo L, Vitale S (2010) A new perspective in adhesion science and technology: testing dynamic failure of adhesive junctions for space applications. Exp Mech 50:1213–1223 10. Bortoluzzi D, Benedetti M, Conklin JW (2013) Indirect measurement of metallic adhesion force as a function of elongation under dynamic conditions”. Mech Syst Signal Process 38:384–398 11. Bortoluzzi D, Benedetti M, Conklin JW, Zanoni C (2012) Measurement of metallic adhesion force-to-elongation profile under high separationrate conditions. In: SEM international conference & exposition on experimental and applied mechanics, Bethel, 11–12 June 2012 12. Rabenorosoa K, Cle´vy C, Lutz P, Gauthier M, Rougeot P (2009) Measurement setup of pull-off force for planar contact at the microscale. Micro Nano Lett 4(3):148–154 Fig. 25.5 Microscope view of the contact areas between the release tip and the TM. Left a native contact. Right the area of contact after two measurement campaigns. The radius of the damaged surface is on the order of that expected from the Hertzian contact (~35 μm) 166 D. Bortoluzzi et al.
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