Squeaking at soft-rigid frictional interfaces

Area of Science:

• Tribology
• Materials Science
• Acoustics

Background:

• Squeaking is common in daily life, often attributed to stick-slip friction.
• Soft-rigid interfaces can detach via slip pulses, but mechanisms at squeaking velocities are unclear.

Purpose of the Study:

• Investigate the mechanisms behind squeaking at soft-rigid interfaces during high-velocity sliding.
• Determine the role of slip pulses and geometric confinement in generating squeaking sounds.

Main Methods:

• Experimental investigation of soft-rigid interfaces at squeaking-inducing velocities.
• High-speed imaging and acoustic analysis to observe pulse dynamics.
• Comparison of flat interfaces with those featuring surface ridges.

Main Results:

• Opening slip pulses propagate at the shear wave speed of the soft material, mediating slip.
• Irregular pulses in flat samples produce broadband noise.
• Surface ridges confine pulses, leading to regular frequencies matching the block's shear mode and consistent squeaking.

Conclusions:

• Squeaking at soft-rigid interfaces is driven by structure-stabilized slip pulse propagation.
• Geometric confinement transforms irregular dynamics into coherent pulse trains, explaining frequency generation.
• Findings offer insights into frictional rupture in engineered and natural systems.