Da Yu’s research while affiliated with Nanjing University of Science and Technology and other places

The complex mechanical transfers in multibody dynamical systems lead to large deviations of the measured signals of accelerometers and other sensors from their real state quantities, which results in difficulties in state identification and decision-making for mechatronic equipment. A novel state reconstruction method of extended Kalman filter-aided time neural network is proposed for multibody dynamical systems in this paper. First, we designed a least-squares dual extend Kalman filter (DLEKF) method for multibody dynamic systems with parameter uncertainties, which includes a system state filter and structural parameter estimator. Then, we design a multidimensional short time-series lightweight Gate Recurrent Unit (GRU) neural network with DLEKF, which realize state reconstruction of unmeasurable subsystems by relying on less input data and computational resources. Finally, the effectiveness of the proposed method is verified via simulations and experiments. Compared with the extend Kalman filter and long time-series neural network methods, the MSE of the proposed method in this paper is reduced by 79.9% and 67.7%. Further we take an interpretable analysis to argue the superiority of the proposed method and prove that the proposed method has good application prospects.

Tantalum electrolytic capacitors have performance advantages of long life, high temperature stability, and high energy storage capacity and are essential micro-energy storage devices in many pieces of military mechatronic equipment, including penetration weapons. The latter are high-value ammunition used to strike strategic targets, and precision in their blast point is ensured through the use of penetration fuzes as control systems. However, the extreme dynamic impact that occurs during penetration causes a surge in the leakage current of tantalum capacitors, resulting in a loss of ignition energy, which can lead to ammunition half-burst or even sometimes misfire. To address the urgent need for a reliable design of tantalum capacitor for penetration fuzes, in this study, the maximum acceptable leakage current of a tantalum capacitor during impact is calculated, and two different types of tantalum capacitors are tested using a machete hammer. It is found that the leakage current of tantalum capacitors increases sharply under extreme impact, causing functional failure. Considering the piezoresistive effect of the tantalum capacitor dielectric and the changes in the contact area between the dielectric and the negative electrode under pressure, a force–electric simulation model at the microscale is established in COMSOL software. The simulation results align favorably with the experimental results, and it is anticipated that the leakage current of a tantalum capacitor will experience exponential growth with increasing pressure, ultimately culminating in complete failure according to this model. Finally, the morphological changes in tantalum capacitor sintered cells both without pressure and under pressure are characterized by electron microscopy. Broken particles of Ta–Ta2O5 sintered molecular clusters are observed under pressure, together with cracks in the MnO2 negative base, proving that large stresses and strains are generated at the micrometer scale.

In modern warfare, fortifications are being placed deeper underground and with increased mechanical strength, placing higher demands on the target speed of the penetrating munitions that attack them. In such practical scenarios, penetrating fuze inevitably experience extreme mechanical loads with long pulse durations and high shock strengths. Experimental results indicate that their shock accelerations can even exceed those of the projectile by several times. However, due to the unclear understanding of the dynamic transfer mechanism of the penetrating fuze system under such extreme mechanical conditions, there is still a lack of effective methods to accurately estimate and design protection against the impact loads on the penetrating fuze. This paper focuses on the dynamic response of penetrating munitions and fuzes under high impact, establishing a nonlinear dynamic transfer model for penetrating fuze systems, which can calculate the sensor overload signal of the fuze location. The results show that the relative error between the peak acceleration obtained by the proposed multibody dynamic transfer model and that obtained by experimental tests is only 15.7%, which is much lower than the 26.4% error between finite element simulations and experimental tests. The computational burden of the proposed method mainly lies in the parameter calibration process, which needs to be performed only once for a specific projectile‐fuze system. Once calibrated, the model can rapidly conduct parameter scanning simulations for the projectile mass, target plate strength, and impact velocity with an extremely low computational cost to obtain the response characteristics of the projectile‐fuze system under various operating conditions. This greatly facilitates the practical engineering design of penetrating ammunition fuze.

The development of electromagnetic interference (EMI) shielding materials with excellent EMI shielding effectiveness (SE), and superior mechanical performance is of great importance in daily life and in the military, where they are used for intelligent transportation systems and ammunition. Generally, shielding performances can be realized via reflection loss and absorption loss. However, it is still a challenge to enhance these two kinds of electromagnetic wave loss in the same material at the same time to achieve ideal shielding performance. Herein, a flexible Ag NDs/CNT@PC/Ni‐9 film composed of five conductive layers and four porous layers is prepared by alternating Ag NDs/CNT layers and PC/Ni layers through self‐assembly. The obtained film with a thickness of 890 μm exhibits a remarkable SE performance of 138 dB in the X‐band. Additionally, with a series of continuous volcanic mechanical impacts (>10 000 g), the maximum instantaneous acceleration is decreased by 30.02% due to the buffering of the film, which constitutes a much‐improved energy absorption cushion relative to that of traditional buffering materials, such as foam metal and rubber. A material integrated with strong EMI shielding and high mechanical shock resistance is designed, which provides an effective strategy for the development of functional materials for extreme environments.

With the advantage of high energy density, lithium batteries are widely used in industrial and military applications. However, under the complex conditions of vehicle collision and high-speed flight ammunition, lithium-ion batteries have functional failure, which seriously affects the safety and stability of systems using batteries. In this paper, research on the electric parameter drift of lithium-ion batteries under high impact is carried out through a machete test system, and the experimental phenomena are analyzed theoretically. Based on this, an equivalent circuit model is established to analyze the failure phenomenon and mechanism of lithium-ion batteries under more extreme impact scenarios, which are difficult to test in the laboratory. Finally, the mechanical impact dynamic (MID) model of lithium-ion batteries at the moment of high impact is established, and the influence of separator thickness, elastic modulus and other parameters on the impact resistance of lithium-ion batteries is revealed, which provides a reference for the optimization design of lithium-ion batteries under a high-impact environment.

Electromagnetic launch technology has important applications in many fields. However, the extremely harsh multi-physics environment during the launch is quite different from that of conventional guns. Little experimental research studied the dynamic distribution of the extreme impact environment and magnetic fields in the projectile. To this end, this paper designs a projectile-borne storage testing system for the dynamic measurement of harsh multi-physics environments. The detailed assessment of the measured dynamic multi-physics field shows that the velocity skin effect (VSE) is an important factor affecting the dynamic results. It causes a higher current density in the armature, and the magnetic induction and acceleration in the dynamic experiment are lower than those in the static-based experiment and simulation. Moreover, it causes the concentrated heat on the trailing edge of the armature, which lead to the melt-wave erosion, even affects the movement of integrated projectile during launch. Furthermore, the physical mechanism behind these phenomenon is revealed, and the causes of muzzle velocity error are analyzed. In conclusion, a feasible, dynamic measurement method for multi-physics coupled environments is presented, which can provide references for follow-up modeling and simulation researches and promote the development of railguns.