Active control of friction between sliding surfaces is of significant interest in automotive applications. It has been
shown that the friction force between sliding surfaces can be reduced by superimposing ultrasonic vibrations on
the sliding velocity. This principle can be applied to systems in which solid state lubrication is advantageous.
This paper investigates ultrasonic lubrication for creating adaptive seat belts with controllable force at the interface
between the D-ring and webbing. By precisely controlling the seat belt force during a crash event, superior
restraint can be achieved relative to existing systems which are designed as a compromise for various occupants
and loading conditions. Proof-of-concept experiments are conducted in order to experimentally determine the
performance limits and mechanics of a seat belt webbing subjected to macroscopic sliding motion and superimposed
out-of-plane ultrasonic vibrations. The experimental setup consists of a high-capacity ultrasonic plastic
welder and an apparatus for creating controlled relative motion between the welder tip and seat belt webbing.
Analytical modeling using LuGre friction is presented which characterizes the parametric dependence of friction
reduction on system settings in the presence of ultrasonic vibrations.
The ability to control the effective friction coefficient between sliding surfaces is of
particular fundamental and technological interest for automotive applications. It has been shown that the friction force
between sliding surfaces can be reduced by superimposing ultrasonic vibrations on the macroscopic sliding velocity. We
developed a systematic approach based on experiments and models to describe and characterize the friction force
between sliding surfaces in the presence of ultrasonic vibrations generated by a piezoelectric transducer. The controlling
parameters in this study are static contact pressure, relative velocity, voltage, and frequency. Using a low power PMN-PT
driver, we experimentally demonstrate a decrease of up to 68 % in effective friction coefficient and analytically show
the underlying principle behind the friction reduction. The trends show a decrease in the effect with increasing sliding
velocity and normal load. The results underscore the role of ultrasonic power in harnessing the friction control concept