The densification and mechanical behaviors of large-diameter polymer-bonded explosives processed by ultrasonic-assisted powder compaction.

[Display omitted] • Ultrasonic vibration was applied on the compaction process of PBX powder. • By application of ultrasonic increase in the compressive modulus and the tensile fracture and strength was measured. • Enhanced homogeneity and microstructure evolution were reported by applying ultrasonic vibration. • The ultrasound assistance can effectively improve the densification level of samples and lower internal total particle surface area. Improving the density of parts, structural homogeneity, and mechanical properties are the most challenging issues in the PBX compaction process. In this study, the ultrasonic-assisted PBX compaction technique and equipment were introduced and designed. With this equipment, it is found that the density of compacted PBX parts increases, and the diameter expansion and density differences decrease by applying ultrasonic vibration. The influences of compaction pressure, hold time and particle size on the compaction were also analyzed. The results indicate that increasing the pressure and time, while decreasing the particle size, results in a higher density and strength of PBX parts. Then, the microstructures were analyzed to show the mechanism of density distributions. It is found that the density increase is due to the particle's rearrangement leading to a "dense" structure and smaller particle sizes with ultrasonic vibration. Finally, the compressive modulus and strength, and the tensile fracture and strength were found to increase by applying ultrasonic vibration. These mechanical properties decrease along the radial and axial direction, indicating the surface effect of the ultrasonic vibration. [ABSTRACT FROM AUTHOR]