Panoramic deformation measurement of HMX compaction process via mirror assisted multi-view digital image correlation method

The sealed loading environment during the compaction process prevents the mechanical behavior of cyclotetramethylenetetranitramine (HMX) under compression from being fully understood. Elucidating the mechanical behavior of HMX during compaction is pivotal for refining pressing techniques and improving the accuracy of mechanical modeling. Herein, a transparent polymer cylindrical encapsulation compaction test apparatus was designed and used to observe the compaction process of HMX. Moreover, the mirror-assistedmirror-assisted multi-view digital image correlation (MV-DIC) method was used to measure the full-field deformation field of HMX during compaction. This proposed MV-DIC method involves two planar front-surface mirrors directly behind the sample, enabling a conventional binocular three-dimensional digital image correlation (3D-DIC) system to image the entire cylindrical surface. After calibrating the reflection transformation, a single-system full-field deformation measurement was achieved. An incremental calculation strategy was employed to mitigate the image decorrelation effect caused by large deformations of HMX during compaction. The axial displacement at the top end of HMX column was measured to be the maximum that gradually decreased along the axis. In the early stages of loading, significant eccentric loading occurred owing to HMX particles nonuniformity, which gradually diminished with increasing compaction depth. The strain field exhibited nonuniform wave-like compression characteristics. In the initial stage of eccentric loading, local tensile strains appeared in the region, which gradually transformed into compressive strains as compaction progressed, revealing the impact of HMX particles rearrangement and fragmentation on the macroscopic mechanical behavior. The experimental results confirmed the feasibility of mirror-assisted MV-DIC for measuring the full deformation field during the compaction process of HMX particles, providing an effective deformation field testing scheme for optimizing HMX particles pressing processes and mechanical modeling with the potential for engineering applications.