Localized microjetting in the collapse of surface macrocavities

Area of Science:

• Materials Science
• Mechanics of Materials
• Solid Mechanics

Background:

• Surface macrocavities can collapse under dynamic loading conditions.
• Understanding microjetting phenomena is crucial for predicting material failure.
• Previous studies on cavity collapse did not fully capture multiscale mechanisms.

Purpose of the Study:

• To investigate the multiscale mechanism of hemicylindrical annular surface macrocavity collapse in steel.
• To elucidate the role of high-strain, high-strain rate plastic flow of copper in cavity collapse.
• To characterize the microjetting phenomena associated with this collapse process.

Main Methods:

• Experimental investigation of cavity collapse.
• Computational simulations to model plastic flow and microjet formation.
• Analysis of microjet characteristics, including length and scaling with cavity radius.

Main Results:

• A two-stage microjetting process was identified during cavity collapse.
• Lateral microjets form from localized shear flow in copper during cavity filling.
• Subsequent collision of these microjets at the cavity apex generates additional horizontal microjets.
• Microjet lengths scale linearly with cavity radius and are significantly smaller than the cavity size.
• The microjet development is sensitive to the specific geometry of the cavity.

Conclusions:

• The collapse mechanism is distinct from previously observed jetting phenomena in other scenarios.
• The findings provide new insights into the complex interplay between material flow and cavity dynamics.
• This research contributes to a better understanding of material behavior under extreme conditions.