Coefficient of restitution as a fluctuating quantity.

Area of Science:

• Physics
• Materials Science
• Tribology

Background:

• The coefficient of restitution (COR) is crucial for understanding impact dynamics.
• Previous studies often assume Gaussian distributions for COR, neglecting surface effects.
• Particle surface properties can significantly influence energy dissipation during collisions.

Purpose of the Study:

• To investigate the coefficient of restitution (COR) of spherical particles impacting a flat plate.
• To analyze the probability density function (PDF) of the COR at various impact velocities.
• To explain observed non-Gaussian fluctuations in COR measurements.

Main Methods:

• Experimental measurement of the COR for spherical particles impacting a flat plate.
• Analysis of the probability density function (PDF) of the COR.
• Modeling the influence of particle surface roughness on impact dynamics.

Main Results:

• Observed non-Gaussian fluctuations in the COR, deviating from typical Gaussian distributions.
• The PDF of the COR, p(ɛ), was characterized by two exponential functions at fixed impact velocities.
• Demonstrated that particle roughness leads to energy transfer between linear and rotational degrees of freedom, explaining the observed PDF.

Conclusions:

• Particle surface roughness is a critical factor affecting the coefficient of restitution.
• The observed non-Gaussian COR distributions arise from energy transfer between translational and rotational motion.
• This finding necessitates a re-evaluation of impact models that do not account for surface topography and rotational dynamics.