טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentLevinson Ofer
SubjectExperimental Investigation of Static Friction
DepartmentDepartment of Mechanical Engineering
Supervisors Professor Emeritus Izhak Etsion
Dr. Gregory Halperin


Abstract

According to the classic friction forces laws postulated by Leonardo da Vinci and Amonton, friction force does not depend on the contact area created between the planes coming into contact. An additional prevalent claim assumes that the magnitude of the friction coefficient between two elements is constant and does not depend on the contact geometry or on the normal load. However, later experimental and theoretical research works, from the first half of last century, show that new discoveries contradict old rules of classical friction theory. The experimental and theoretical works dealing with research of static friction coefficients showed significant contradictions between experimental results and the known laws of classic friction theory. This research intends to focus on comparison between the models lately developed and the experimental results that were published on the subject of prediction of friction force and static friction coefficient. For this purpose we chose to check through a series of experiments the elastically perfectly plastic contact model developed by L. Kogut and I. Etsion of the Technion Mechanical Engineering Faculty.  The model provides a prediction of the real contact area between spherical surface and rigid flat. The model also predicts the static friction force and friction coefficient that will be developed. An experimental measurement system was constructed in order to make it possible to measure friction forces under normal load in several geometrical conditions. The results obtained indicate the creation of a real contact area, similar to the prediction by the model analyzed, as well as a reduction of 66% in the static friction coefficient with the increasing of the normal load