Impact cratering on a granular bed by hydrogel spheres having intermediate property between solid and liquid

Area of Science:

• Geophysics
• Materials Science
• Fluid Dynamics

Background:

• Solid sphere impacts on granular beds produce craters whose size depends solely on impact kinetic energy.
• Hydrogel spheres, unlike solid spheres, possess elastic properties that influence impact dynamics.
• Understanding impact cratering is crucial for planetary science and material deformation studies.

Purpose of the Study:

• To investigate the low-speed impact of a hydrogel sphere on a granular bed.
• To determine the factors controlling the crater diameter resulting from hydrogel sphere impacts.
• To differentiate the cratering dynamics between small and large indentations of the hydrogel sphere.

Main Methods:

• Experimental investigation of hydrogel sphere impacts on granular materials.
• Analysis of crater diameter as a function of impact kinetic energy and sphere elasticity.
• Derivation of force balance equations relating impact energy, Young's modulus, and crater dimensions.

Main Results:

• Hydrogel sphere impact crater diameter depends on both kinetic and elastic energies.
• Two distinct impact dynamics were observed: small and large indentation.
• For small indentations, crater diameter scales with the 1/4 power of ejecta energy, incorporating elastic energy.
• A relationship between impact kinetic energy, Young's modulus, and crater diameter was derived.

Conclusions:

• The elastic properties of hydrogel spheres significantly alter impact cratering compared to solid spheres.
• The derived relationship reconciles with the 1/4 power law for solid spheres at high Young's modulus limits.
• Young's modulus has a greater influence on crater diameter in large indentation scenarios than in small ones.