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With large-scale non-equilibrium molecular dynamics simulations and in situ x-ray diffraction analysis, we conducted a systematic investigation into the effects of pre-existing shear strain (γ x y ) on the shock response of single crystal iron. Our findings reveal significant effects of γ x y on the deformation of the crystal structure during shock loading, leading to noticeable alterations in the propagation of shock waves. Specifically, during the elastic stage, the presence of γ x y results in a reduction of shock strength, consequently diminishing the magnitude of elastic lattice strain (ε e ). In the plastic stage, γ x y stimulates the α – ε phase transformation, and structure deformation undergoes a transition from the sequential activity of dislocation-to-transformation to the synchronous activity of dislocation and transformation. This transition inhibits the propagation of plastic waves and consequently broadens the elastic regime. Additionally, the introduction of γ x y activates different slip systems, as it alters the corresponding resolved shear stress. Concurrently, the presence of γ x y triggers the activation of different high-pressure phase variants. Our investigation sheds light on the fundamental physics of iron under shock compression and the influence of pre-existing shear strain on its behavior. [ABSTRACT FROM AUTHOR]

A 70-year-old man presented to the emergency department with pain and swelling in his right periorbital region after a fall. Physical examination revealed ecchymosis and tenderness in the area, but no apparent fractures were seen on a plain radiograph. However, a crescent-shaped radiolucency known as the black eyebrow sign was present, indicating a suspicion of occult orbital wall fracture. Computed tomography confirmed the diagnosis of nondisplaced fractures at the medial and inferior orbital wall. The patient was treated conservatively and followed up at the outpatient department. [Extracted from the article]