Friction Reduction through Ultrasonic Vibration Part 1: Modelling Intermittent Contact

Area of Science:

• Tribology
• Haptics
• Biophysics

Background:

• Ultrasonic vibration can alter finger pad friction, inducing haptic sensations.
• Intermittent contact and squeeze film levitation are proposed mechanisms for this friction modulation.

Purpose of the Study:

• To understand the principles governing friction modulation by intermittent contact using numerical models.
• To identify key parameters influencing friction reduction during ultrasonic vibration.

Main Methods:

• Developed finite element (FE) analysis and spring-Coulombic slider models.
• Optimized FE model parameters using measured contact phase shifts.
• Interpreted FE results with the spring-slider model to identify a dimensionless group.

Main Results:

• Identified a dimensionless group correlating friction reduction with an exponential function.
• Friction reduction depends on vibration amplitude, frequency, intrinsic friction, and exploration velocity.
• Friction reduction is independent of normal force and skin elastic moduli when intermittent contact is well-developed.

Conclusions:

• The developed models provide a framework for understanding ultrasonic friction modulation.
• A dimensionless group effectively rationalizes friction reduction under specific conditions.
• Further experimental validation is planned to support the modeling findings.