DYNAMIC FRICTION MODEL OF OSCILLATORY JOURNAL BEARING
Dynamic Friction Model of Oscillatory Journal Bearing
Principal Investigator: Professor Michael Khonsari
Graduate Student: Xiaobin(Mel) Lu
Contact Information: Professor Michael Khonsari
robots to construction machinery, oscillation is quite common of bearing
assembly motion. Complexity is introduced by the time-dependent sliding
velocity. During one single oscillation cycle, the friction may vary
from boundary, to mixed and then hydrodynamic lubrication regime, with
the changing velocity. Hysteresis has been observed in experiments and
simulated by calculations. It is a phenomenon that the friction coefficient
that when the velocity increases to a specific value is different from
that when the velocity decreases to that value. Nevertheless, there
is not a widely acceptable dynamic friction model which covers all those
three lubrication regimes so far. Also the characteristics of friction
induced temperature need to be keenly investigated.
Part I: Thermal analysis
CeRom is equipped with a specially designed Tribometer made by Lewis
Research Inc to measure the friction coefficient and the temperature
field in oscillation of journal bearing. Figure 1 is the assembly of
the oscillatory journal bearing. Figure 2 is one measurement of the
friction coefficient and Figure 3 is the corresponding temperature history
of four thermocouples.
trying to use the experimental friction coefficient as input to
simulate the temperature field of the assembly. The simulation
should make good match for the four thermocouples' measurement.
The temperature field in one simulation is shown in figure 4.
Part II: Dynamic Friction modeling
As you can see in the friction coefficient graph, its value has
dynamic characteristic in the oscillation process. Figure 5 displays
this phenomenon. Please note that in this experiment, the lubricant
is grease. When using oil as lubricant, this phenomenon will be
expected to be more extinctive.
examination based on established model by pioneers tells us its
possible mathematic description, as show in figure 6. A deeper
exploration of this dynamic model is being carried on.