Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer

Area of Science:

• Tribology
• Solid-state physics
• Materials science

Background:

• Friction and wear negatively impact engineered systems.
• Ultrasonic lubrication utilizes high-frequency vibrations (above 20 kHz) for solid-state lubrication.
• This method is applicable where conventional lubricants fail and allows for electrical modulation of friction.

Purpose of the Study:

• To investigate how linear sliding velocity affects friction force and wear reduction under ultrasonic lubrication.
• To quantify the effectiveness of ultrasonic lubrication across different speeds.

Main Methods:

• A custom pin-on-disc tribometer with a piezoelectric stack vibrating at 22 kHz was used.
• Friction force, volume loss, and surface roughness were measured with and without ultrasonic vibrations.
• Measurements were conducted at 1-4 MPa pressure and sliding velocities of 20.3, 40.6, and 87 mm/sec.

Main Results:

• Effective friction force reduction was 62% at 20.3 mm/sec, decreasing to 29% at 87 mm/sec.
• Wear reduction remained consistently at 49% across all tested speeds.
• Optical profilometry characterized wear surfaces.

Conclusions:

• Ultrasonic lubrication effectively reduces both friction and wear.
• Friction reduction is speed-dependent, diminishing as sliding velocity increases.
• Wear reduction is largely independent of sliding velocity within the tested range, showing consistent benefits.