The Effect of Surface Electroplating on Fragment Deformation Behavior When Subjected to Contact Blasts.

Preformed fragments can deform or even fracture when subjected to contact blasts, which might lead to a reduction of the terminal effect. Therefore, to solve this problem, the effect of surface electroplating on the fragment deformation behavior under contact blasts was analyzed. Firstly, blast recovery tests were carried out on uncoated and coated fragments. After the contact blast, the two samples produced different deformation behaviors: the uncoated fragments were fractured, while the coated fragments maintained integrity. The tests were simulated by finite element simulation, and the deformation behavior of the different samples matched well with the test results, which can explain the protective effect of the coating after quantification. In order to further reveal the dynamic behavior involved, detonation wave theory and shock wave transmission theory in solids were used to calculate the pressure amplitude variation at the far-exploding surface of the fragments. The theoretical results showed that the pressure amplitude of the uncoated samples instantly dropped to zero after the shock wave passed through the far-exploding surface, which resulted in the formation of a tensile zone. But the pressure amplitude of the coated samples increased, transforming the tensile zone into the compression zone, thereby preventing the fracture of the fragment near the far-exploding surface, which was consistent with the test and simulated results. The test results, finite element simulations, and theories show that the coating can change the deformation behavior of the fragment and prevent the fracture phenomenon of the fragment. It also prevents the material from missing and a molten state of the fragment in the radial direction by microscopic observation and weight statistics.

Study on Axial Dispersion Characteristics of Double-Layer Prefabricated Fragments.

The axial distribution of initial velocity and direction angle of double-layer prefabricated fragments after an explosion were investigated via an explosion detonation test. A three-stage detonation driving model of double-layer prefabricated fragments was proposed. In the three-stage driving model, the acceleration process of double-layer prefabricated fragments is divided into three stages: "detonation wave acceleration stage", "metal-medium interaction stage" and "detonation products acceleration stage". The initial parameters of each layer of prefabricated fragments calculated by the three-stage detonation driving model of double-layer prefabricated fragments fit well with the test results. It was shown that the energy utilization rate of detonation products acting on the inner-layer and outer-layer fragments were 69% and 56%, respectively. The deceleration effect of sparse waves on the outer layer of fragments was weaker than that on the inner layer. The maximum initial velocity of fragments was located near the center of the warhead where the sparse waves intersected, located at around 0.66 times of the full length of warhead. This model can provide theoretical support and a design scheme for the initial parameter design of double-layer prefabricated fragment warheads.

Editorial for the Special Issue "Materials under High Pressure".

The high-pressure-related problems of materials constitute a field at the confluence of several scientific disciplines [...].

Compressive Mechanical Properties and Shock-Induced Reaction Behavior of Zr/PTFE and Ti/PTFE Reactive Materials.

Existing research on PTFE-based reactive materials (RMs) mostly focuses on Al/PTFE RMs. To explore further possibilities of formulation, the reactive metal components in the RMs can be replaced. In this paper, Zr/PTFE and Ti/PTFE RMs were prepared by cold isostatic pressing and vacuum sintering. The static and dynamic compressive mechanical properties of Zr/PTFE and Ti/PTFE RMs were investigated at different strain rates. The results show that the introduction of zirconium powder and titanium powder can increase the strength of the material under dynamic loading. Meanwhile, a modified J-C model considering strain and strain rate coupling was proposed. The parameters of the modified J-C model of Zr/PTFE and Ti/PTFE RMs were determined, which can describe and predict plastic flow stress. To characterize the impact-induced reaction behavior of Zr/PTFE and Ti/PTFE RMs, a quasi-sealed test chamber was used to measure the over-pressure induced by the exothermic reaction. The energy release characteristics of both materials were more intense under the higher impact.