Experimental testing and numerical simulation of partially cohesive jet formation in high-energy high-entropy alloy liners

The shaped charge warhead is a critical means of neutralizing armored and fortified targets. It primarily destroys the target through explosive detonation, which results in the liner being crushed to form a high-speed jet. Traditional copper liners form condensed jets, resulting in deep penetration but producing extremely limited post-target damage. Conversely, reactive materials such as Al/PTFE produce divergent particle jets with strong after-effects but suffer from insufficient penetration capability. Energetic high-entropy alloys(EHEAs) can form a “partially cohesive jet”, which is cohesive at the core to ensure penetration and divergent at the periphery to enhance behind-target damage, thereby offering a novel solution to the trade-off between penetration depth and post-effect damage. However, the jet coherence of EHEAs remains challenging to quantify, and no suitable simulation model currently exists.

An integrated test system for jet morphology and post-effect damage was designed. This system uses pulsed X-ray technology to capture the jet morphology and simultaneously assesses penetration and post-effect damage capabilities through the main and post-effect targets. The study proposes a “jet cohesion factor”, defined as the ratio of the area of the central condensed region in the jet X-ray image to the total area. This factor enables a quantitative description of the jet's cohesive state. Additionally, the post-effect damage is calculated by analyzing the scattering angles formed by the perforation distribution on the target surface. To overcome the limitation that the current SPH method cannot quantitatively control the jet cohesion factor, this study develops a secondary correction algorithm for jet morphology based on the SPH algorithm. By introducing an improved Sigmoid function to regulate jet particles, the algorithm achieves a concentrated jet core and controllable edge divergence, thereby accurately reproducing the partially cohesive jet morphology observed in EHEAs.

The present study focused on two Ti–Zr–V–Nb–Al EHEAs with different mechanical properties (Alloy A and Alloy B). The experimental findings demonstrated that Alloy A, characterized by its reduced plasticity(4.8%), exhibited a lower jet cohesion degree (67.5%) and a larger post-effect scattering angle (31.2°). The post-effect target displayed a damage pattern consisting of a main hole accompanied by numerous small holes. In contrast, Alloy B, which demonstrated higher plasticity (8.4%), exhibited a higher jet cohesion degree (78.6%) and a smaller scattering angle (29.6°). The post-effect damage consisted mainly of a main hole accompanied by several larger holes. By adjusting the algorithm parameters, the simulated jet cohesion factors for Alloys A and B were determined to be 67.9% and 77.8%, respectively. Additionally, the deviations of the simulation scattering angles from the experimental values were found to be less than 10%, the simulation results were highly consistent with the experimental data.

The present study successfully developed an integrated testing methodology and a numerical simulation method for the partially cohesive jets formed by EHEA liners. By incorporating the jet cohesion factor, a quantitative approach is provided for elucidating the jet's cohesive state. Furthermore, the jet's morphology control algorithm effectively addresses the lack of adequate simulation models. The high consistency (over 90% agreement) between experimental and simulation outcomes for critical parameters (cohesion factor, scattering angle) substantiates the efficacy of the proposed methodologies. These findings not only provide critical technical support for the rapid performance evaluation and compositional microstructure optimization of EHEA liners but also offer a novel scientific approach for assessing the multifunctional damage efficiency of shaped charge warheads.