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PRELIMINARY THEORETICAL RESULTS UPON CONTACT PRESSURE ASSESSMENT BY AID OF REFLECTIVITY


Cornel SUCIU
suciu@fim.usv.ro

Emanuel DIACONESCU
emdi@fim.usv.ro

Department of Mechanical Engineering, University of Suceava, ROMANIA


 

Abstract.  Several different experimental methods for investigating contact features can be found in literature. The idea to optically investigate the surfaces of contacting bodies [1-8], led to the development of a new technique to measure the pressure distributions in a real contact [9-11].
One of the contacting surfaces is covered, prior to contact establishment, by a special gel. The contact closing removes the excess gel and, during a certain time interval, the contact pressure transforms the entrapped substance in an amorphous solid. In each point, the refractive index of this solid depends on the pressure acting during transformation. After contact opening, the reflectivity of this coating depends on the former contact pressure and it is mapped by aid of a laser profilometer, thus becoming an indicator of contact pressure.
This paper studies the effect of pressure on the refractive index of the solidified gel layer, as well as the different parameters that influence its reflectivity. Using molecular physics and optics, a theoretical model of reflectivity is studied and it is found to be strongly influenced by both pressure and gel layer thickness. From this model, pressure distribution laws are found for different ranges of reflectivity and gel layer thickness.
 

 

Keywords:  contact pressure, refractive index, reflectivity, solidified gel layer

 

 

References

  1. Diaconescu, E.N., and Glovnea, M.L., “Evaluation of Contact Area by Reflectivity,” Proc., 3rd AIMETA International Tribology Conference, Italy, on CD, 2002

  2. Glovnea, M.L., and Diaconescu, E.N., “A New Method for Experimental Investigation of Elastic Contacts,” (in Romanian), Symp. on Tradition and Continuity in Railway Research, Vol.II, Bucharest, 1994, pp. 77-82.

  3. Diaconescu, E.N., “A New Tool for Experimental Investigation of Mechanical Contacts, Part I: Principles of Investigation Method,” VAREHD 9, Suceava, 1998, pp. 255-260.

  4. Diaconescu, E.N. and Glovnea, M.L., “A New Tool for Experimental Investigation of Mechanical Contacts, Part II: Experimental Set-Up and Preliminary Results,” VAREHD 9, Suceava, 1998, pp. 261-266.

  5. Diaconescu, E.N., and Glovnea, M.L., “Validation of Reflectivity as an Experimental Tool in Contact Mechanics,” VAREHD 10, Suceava, 2000, pp. 471 – 476

  6. Diaconescu, E.N., and Glovnea, M.L., “Visualization and Measurement of Contact Area by Reflectivity,” Trans. of the ASME, J. of Trib., Vol. 128, october 2006, 915 – 917

  7. Yamaguchi, K., Uchida, M., and Abraha, P., “Measurement of Pressure on Contact Surface by Reflection of Light (Effect of Surface Etching),” Proceedings of the Japan International Tribology Conference, Nagoya, 1990, pp. 1271-1276.

  8. Yamaguchi, K., Uchida, M., and Abraha, P., “Measurement of the Pressure Distribution on Contact Surfaces by the Detection of a Transferred Oil Film,” Surface Science 377–379 (1997), 1015–1018

  9. Diaconescu, E. N., Glovnea, M. L., Petroşel, O., “A New Experimental Technique to Measure Contact Pressure,” Proc. of 2003 STLE/ASME Joint International Tribology Conference, Ponte Vedra Beach, Florida USA, 2003.

  10. Suciu, C., Diaconescu, E., Spinu, S., “Experimental Set-Up And Preliminary Results Upon A New Technique To Measure Contact Pressure,” Proceedings of VarEHD14, Suceava, 9-11 October, 2008, ISSN 1844-8917, Acta Tribologica, vol. 16, 2008 ISSN 1220 - 8434.

  11. Suciu, C., Diaconescu E., “Contact Pressure Assessement by Reflectivity of a Solidified Gel Layer,” Proceedings of the 2nd European Conference on Tribology, ECOTRIB 2009, Faculty of Engineering, Pisa, Italy, June 7 - 10, 2009

  12. Ditchburn, R. W., Light, Vol. II, Blackie & Son, Second Edition, 1963.

  13. Diaconescu, E. N., 2004, „Solid-Like Properties of Molecular Liquids Subjected to EHD Conditions - Theoretical Investigations”, Proceedings of 2004 ASME/STLE International Joint Tribology Conference, Long Beach, California USA, October 24-27,

  14. Born, M., and Wolf, E., 1980, Principles of Optics, Sixth Edition, Pergamon Press.