| Abstrakt: |
The objective of this paper is to discus and to introduce an identification method of stick slip phenomenon when friction of two surfaces occures within multi directional contact friction. This interesting topic is discussed due the complexity of wear mechanism on multi directional contact friction and the attendance of stick slip wear. The identification is based on kinematics of particle on the contact surface. Assumption that stick slip happens more often when contact surfaces moving stop suddenly for awhile and start sliding again is very important principle. Pin on disk tribometer is modeled to be two surfaces contacting. However, pin is set to spin about its axis while the pin revolutes the disk relatively. Therefore, there are two variables of angular velocity, disk rotation and pin rotation. Ratio between pin rotational speed and disk rotational speed is used as the main parameter in this research. The research starts from analyzing particle's paths during contacts, discretizing and creating velocity field of points on the contact surfac of pine, recognizing ratio resulting zero speed points and finally identifying zero speed regions in particular ratios. The suspected stick slip regions, in turn, are verified by experimenting specimens of pin made of Ultra High Molecular Weight Poly Ethylene (UHMWPE). This pin spinning slides on the disk made of steel. The experimen variates four values of speed ratios which is 4.2, 5, 6.5, 10 and 20. Moreover, the surface worn is analized especially on the zero speed regions. Micrograph is taken at 20 times magnification in order to recognize wear mechanisms. The result shows that on all the ratios, the expected stick slip region and the micro graphic contact surface have similar pattern. Abraded and delaminated surfaces caused by adhesive wear occur on the zero speed region. In conclusion, this methodology of stick slip identification for directional contact friction is relatively accurate determination for stick slip path. [ABSTRACT FROM AUTHOR] |
