Design of an impact-induced energy release characteristics testing system for energetic structural materials based on SHPB

Energetic structural materials (ESMs) have provided a novel pathway for substantially enhancing the power of weapons. Their damage effects are significantly dependent on their dynamic mechanical properties and impact-induced energy release characteristics. However, current research has not yet established an integrated testing methodology that correlates these two aspects, leading to a lack of effective guidance for designing ESMs and optimizing warhead charge structures.

An impact-induced energy release characteristics testing system was established by integrating a split Hopkinson pressure bar (SHPB) apparatus. The system primarily comprised an SHPB impact loading system and an energy release characteristic testing system. The SHPB impact loading system was utilized to test the dynamic mechanical properties and to provide the impact load necessary to induce the energy release of ESMs. The energy release characteristic testing system, installed in conjunction with the SHPB impact loading system, mainly consisted of an energy release testing vessel, a pressure acquisition module, and a temperature acquisition module. A sample was clamped between the incident and transmitted bars of the SHPB, which were then placed inside the energy release testing vessel. Considering that the energy release reaction of ESMs in their actual service environment is primarily oxidation, the energy release calculation model was modified to account for oxygen consumption. The SHPB impact loading system and the energy release characteristic testing system were triggered by a stress pulse signal, thereby enabling the concurrent measurement of dynamic mechanical properties and energy release characteristics. The materials tested in this study were Ti–Zr–Hf–Ta-based energetic high-entropy alloys with solution treatment (ST) and aging treatment (AT), which represented typical ESMs.

The dynamic compressive yield strengths of the ST and AT alloys were 1657 and 1 816 MPa, respectively, with corresponding failure strains of 0.47 and 0.35. Upon instantaneous impact loading by the SHPB, the samples underwent deformation and fragmentation and released energy, leading to a rapid increase in the overpressure within the testing vessel. The measured peak overpressures for the ST and AT alloys were 9.19 and 268.63 kPa, respectively. According to the modified energy release calculation model, the energy releases per unit mass were 16.28 and 475.77 J/g, respectively. After recovering the samples from the testing vessel, the AT alloy exhibited more extensive fragmentation, consistent with its lower failure strain. Energy release images also showed that the sparks from the AT alloy rapidly filled the testing vessel, whereas the sparks from the ST alloy were concentrated near the sensors, further demonstrating that the energy release of the AT alloy was more intense than that of the ST alloy. This observation was consistent with the mechanical properties, degree of fragmentation, and energy release of the materials, thereby validating the effectiveness and reliability of the impact-induced energy release testing system and achieving the design goals.

The proposed system can acquire key energy release parameters, such as the energy release and the threshold for impact-induced energy release, as well as mechanical property parameters, including dynamic compressive strength and failure strain. This achievement allows for a quantitative correlation between the mechanical properties and energy release characteristics of ESMs, thereby providing experimental technical support for the development of novel ESMs. The system is characterized by its flexible assembly, ease of operation, precision, and efficiency, allowing for rapid assessment of the impact-induced energy release characteristics of ESMs under laboratory conditions.