טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentPearl Ari
SubjectInfluence of Simultaneous Shot-Peening Parameters
on Friction Under lubricated Condition
DepartmentDepartment of Mechanical Engineering
Supervisors Dr. Haytam Kasem
Professor Emeritus Izhak Etsion
Full Thesis textFull thesis text - English Version


Abstract

One way to reduce energy consumption is to increase the efficiency of energy use. A large percentage of energy is spent to overcome friction between mechanical parts which are in contact and are experiencing relative motion. Friction is governed by mechanical, chemical and topographical properties of the topmost layers of the surfaces in contact. Modifying the proprieties of the topmost layers of the surfaces is an obvious choice when trying to reduce friction.

The chosen method in this study for modifying materials’ surfaces is the use of Simultaneous Shot-Peening “SSP” with mixed hard and soft particles. This mechano-chemical treatment has been shown to reduce friction in previous research. The mechanism of the mechano-chemical surface treatment, as explained by Varenberg et al. consists of chemically activating  the surface by mechanical means using hard and chemically stable particles while simultaneously adding a tribologically beneficial particles to bond chemically to the activated surface. This can be done using shot-peening, where both types of particles are simultaneously shot at the surface. Shot-peening is a cold-working method in which particles are shot at high speeds at a surface and cause extensive plastic deformations on the topmost layers of the surface  thus increasing its chemical reactivity and diffusivity.

The aims of the current study are experimentally investigating the influence of certain operational parameters employed during the treatment process on the frictional behavior of the treated surface. Alumina particles were used as hard particles to cause deformations and sulfides were used as soft particles to bone to the surface and hence improve the tribological proprieties. The investigated parameters are: the size of alumina particles, the type of sulfide, the cleaning method of the surfaces and the time waited between the treatment and the friction experiment.

Friction experiments in this study were performed using a roller-block tribometer. The control of the test conditions (normal load, sliding speed and rate of lubrication) allow the simulation of boundary and mixed lubrication regimes.

The results showed that the optimal treatment would be using the larger alumina coupled with a sulfide, cleaning the surface using pressurized air and then waiting at least a week, between the time of the treatment and use.