Micro-jetting and micro-spallation at metal interfaces under intense shock loading play pivotal roles in applications such as inertial confinement fusion (ICF). These phenomena exhibit inherent complexity due to their multi-scale dynamics, strong nonlinearity, and coupled multi-field interactions. Under extreme irradiation conditions, the formation of high-pressure nanoscale helium bubbles significantly alters interface failure mechanisms. Using molecular dynamics methods, we investigate micro-jet growth and damage evolution in helium-containing copper subjected to double supported shock loadings. Helium bubbles demonstrate lower critical activation stress thresholds for expansion compared to void nucleation, with these thresholds being dependent on bubble distribution and number density. Under low-pressure primary shocks, helium-containing metals produce more pronounced micro-jets than pure metals. During secondary shocks, helium bubbles promote jet fragmentation, resulting in higher maximum velocities at micro-jet tips while maintaining comparable velocity distributions in micro-jet bodies. Secondary shocks show negligible effects on bulk helium bubbles that were previously compressed by initial shocks and partially rebounded due to rarefaction waves without complete recovery. Near-surface ruptured bubble walls may reattach to bubble bases after secondary shocks, temporarily re-trapping helium atoms that are subsequently released during unloading-induced re-expansion and rupture. The collapse mechanism of helium bubbles under secondary shock is closely related to the helium bubbles size and the strength of secondary shock. This study establishes fundamental physical understanding and provides a theoretical foundation for future cross-scale investigations of coupled micro-jetting and micro-spallation evolution in irradiated helium-containing metals.

To investigate the dynamic mechanical properties of early-age concrete-mudstone composites under impact loading, split Hopkinson pressure bar (SHPB) tests integrated with a high-speed camera were conducted on composite specimens with curing ages of 1, 3, and 7 d. Digital image correlation (DIC) technology was employed to analyze the evolution of displacement and strain fields, systematically revealing the dynamic damage and failure characteristics of the composites. The test results indicate that as the strain rate increases, the composite specimens exhibit significant strain rate dependence across all curing ages, and their dynamic strength growth follows a logarithmic function model. The energy dissipation density increases linearly with incident energy. DIC measurements show that the maximum surface displacements of the 1, 3, and 7 d specimens are 1.56, 1.34, and 1.19 mm, respectively, with corresponding maximum strains of 1.8%, 1.6%, and 1.3%. This study elucidates the dynamic mechanical behavior and damage-failure mechanisms of early-age concrete-mudstone composites under impact loading, providing a theoretical foundation for damage prevention and control in surrounding rock-initial support structures during tunnel blasting construction.

By combining first-principles calculations under the framework of density functional theory (DFT) and the CALYPSO crystal structure prediction method, the structural stability of the inert element helium (He) and alkaline-earth metals under high-pressure conditions has been systematically investigated. The calculations reveal that among the alkaline-earth metals, strontium (Sr) forms compounds with He exhibiting relatively low energy values. Consequently, the crystal structure of Sr₂He at 400 GPa was predicted. Electron localization function (ELF) and density of states (DOS) analyses show no tendency for covalent bond formation between Sr and He atoms. Furthermore, Bader charge analysis reveals ionic bonding between Sr and He atoms, with charge transfer occurring from He to Sr. These results provide key insights into the bonding mechanism of Sr₂He. This study elucidates the crystal structure, bonding nature, and electronic properties of Sr₂He, offering theoretical support for understanding the stability and physical properties of such metastable materials and providing important guidance for their experimental synthesis.