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

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