Hydrodynamic Kelvin-Helmholtz instability on metallic surface.

Area of Science:

• Physics
• Materials Science
• Mechanical Engineering

Background:

• Kelvin-Helmholtz instability on metallic surfaces is critical in high-velocity impacts like explosive welding and planetary events.
• Instability evolution forms wavy morphologies, enabling material bonding and mixing.
• The dynamic behavior and elastoplastic control mechanisms of this instability remain poorly understood.

Purpose of the Study:

• To introduce a theoretical framework for understanding Kelvin-Helmholtz instability evolution driven by tangential velocity in metals.
• To elucidate the dynamic characteristics and underlying mechanisms of instability in metallic materials.

Main Methods:

• Development of a new analytical theory to describe instability evolution.
• Numerical simulations to observe amplitude growth, tangential motion, and wavy morphology formation.
• Identification of an instability boundary based on loading velocities, surface properties, and material characteristics.

Main Results:

• Unstable metallic surfaces demonstrate amplitude growth and tangential motion, overcoming yield strength depression to form waves.
• An instability boundary was identified, differentiating stable and unstable evolutions across various conditions.
• Analytical methods using scale-independent variables successfully reproduced numerical findings, revealing key instability characteristics.

Conclusions:

• The developed theory accurately describes Kelvin-Helmholtz instability evolution in metals under tangential velocity.
• Material properties, particularly corrugated surface characteristics, are crucial for predicting instability in laboratory-scale oblique impact experiments.
• This work provides a foundational understanding for controlling material behavior in high-impact scenarios.