Microscopic and Macroscopic Fragmentation Characteristics under Hypervelocity Impact Based on MD and SPH Method.

Area of Science:

• Materials Science
• Physics
• Computational Mechanics

Background:

• Hypervelocity impacts exhibit distinct fragmentation behaviors at different scales.
• Understanding these scale-dependent phenomena is crucial for material design and impact analysis.

Purpose of the Study:

• To investigate and compare the fragmentation characteristics of microscopic and macroscopic scales under hypervelocity impact.
• To elucidate the underlying physical mechanisms governing these scale differences.

Main Methods:

• Simulations using Molecular Dynamics (MD) for microscopic scale and Smoothed Particle Hydrodynamics (SPH) for macroscopic scale.
• Analysis of penetration resistance, debris cloud formation, residual velocity, crater diameter, and expansion angles.

Main Results:

• Microscopic scale shows higher penetration resistance under low shock intensity due to material strength and surface tension.
• Under high shock intensity, microscopic impacts result in narrower debris clouds and smaller ejecta compared to macroscopic impacts.
• Kinetic energy conversion to internal energy is significantly higher at the microscopic scale, evidenced by increased melting and disordered atoms.

Conclusions:

• Significant scale-dependent differences exist in hypervelocity impact fragmentation.
• MD simulations provide detailed insights into micro-scale physical changes, including melting and atomic disorder.
• Incident kinetic energy strongly correlates with atomic disorder at the micro-scale.