Fracture and friction: Stick-slip motion

Area of Science:

• Physics
• Materials Science
• Mechanical Engineering

Background:

• Stick-slip motion is a common phenomenon in systems involving friction between surfaces.
• Understanding the transition from static friction (stick) to kinetic friction (slip) is crucial for predicting system behavior.

Purpose of the Study:

• To analyze the nonequilibrium transition in elastic block sliding under shear stress.
• To investigate the relationship between critical stress, Griffith threshold, and crack propagation.
• To model inhomogeneous and homogeneous sliding modes and their transitions.

Main Methods:

• Solving the elastic problem for steady-state motion of periodic stick-slip patterns.
• Deriving equations of motion for slip pulse tips and resticking ends.
• Utilizing a linear friction law within slip regions.

Main Results:

• A discontinuous nonequilibrium transition from stick to sliding occurs at a critical stress, identified as the Griffith threshold.
• An inhomogeneous sliding mode transitions to homogeneous sliding at a critical velocity related to the critical stress.
• Steady-state analysis does not uniquely determine pattern parameters like primary wavelength, necessitating a "soft" selection mechanism.

Conclusions:

• The study provides a framework for estimating internal parameters of stick-slip patterns, including crack velocities and wavelength, as functions of driving velocity.
• The findings offer insights relevant to experimental observations of stick-slip phenomena.
• The analogy to first-order phase transitions aids in understanding pattern selection in these systems.