Abstract:To enhance the understanding of safety of multi-chamber mixing processes， a multiphase flow CFD numerical model based on the Eulerian method was established for the continuous mixing of multi-component materials in a multi-chamber kneader， taking a cast polymer bonded explosive （PBX） as the object. Experimental verification was conducted to confirm the reliability of the model. Based on the model， the influence laws of key process and structural parameters including blade rotation speed， kneading clearance and blade profile on the mixing safety stimulus were studied. The results show that the pressure level gradually decreased from the feeding chamber to the discharging chamber. Increasing the blade rotation speed was beneficial for reducing the pressure in the chambers， but the shear stimulus significantly increased. As the blade rotation speed increased from 15 r·min^-1 to 75 r·min^-1， the peak pressure in the kneader decreased from 402966 Pa to 258107 Pa， and the peak shear stress increased from 6268.5 Pa to 16607.9 Pa. Increasing the kneading clearance significantly reduced the pressure and shear stress in the chambers. As the kneading clearance increased from 1 mm to 5 mm， the peak pressure in the kneader decreased from 391094 Pa to 284478 Pa， and the peak shear stress decreases from 8320.5 Pa to 3982.6 Pa. Compared with the two-wing-two-wing blades， four-wing-two-wing blades produced stronger shear stimuli due to more kneading sites， but the blade profile had a smaller impact on the kneading pressure. When the four-wing-two-wing blades and two-wing-two-wing blades were used in chambers 1-7， the peak shear stresses in the kneader were 7481.3 Pa and 4518.1 Pa， respectively.

Abstract:To enhance the mechanical properties of HTPB four-composite solid propellants， 3-［2-（2-aminoethylamino）ethylamino］propyl-trimethoxysilane （A1130） and ureidopropyltriethoxysilane （A1160） were employed to modify the surface of HMX and qy-HMX， followed by their application in solid propellant formulation. Scanning electron microscope （SEM）， X-ray diffraction （XRD）， X-ray photoelectron spectroscopy （XPS）， atomic force microscope （AFM） and thermal analysis （DSC-TG） were used to test the morphology， structure and performance of samples. The interfacial enhancement effects were systematically investigated using an electronic universal testing machine and dynamic thermomechanical analyzer （DMA） to assess mechanical properties and adhesion characteristics. Results demonstrate that the silane treatment forms continuous coating layers without changing the crystalline structure. Silane coating inhibits effectively the transformation of HMX， increasing the phase transition temperature of HMX@A1130 and HMX@A1160 to 193.9 ℃ and 201.4 ℃， which are 2.3 ℃ and 9.8 ℃ higher than that of raw HMX. The mechanical tests reveal significant improvements in propellant tensile strength across both high temperature （70 ℃） and low temperature （-50 ℃） conditions. Notably， A1130-modified propellant exhibits an enhanced tensile strength with the adhesion index reduced from 1.52 to 1.24 at -50 ℃/500 mm·min^-1. The tensile strength of propellants modified with HMX@A1130 and HMX@A1160 increases by 29.9% and 31.6%， and the maximum elongation increase by 29.9% and 31.6%， respectively. DMA results show that the peak value of loss factor for the A1130-modified propellant decreases from 0.51 to 0.47， indicating a mitigation of the interfacial ‘dewetting’ phenomenon at low temperatures. The fracture surface morphology analysis results are in good agreement with the tensile test and DMA test. The addition of two silane coupling agents has a significant interfacial modification effect， and A11330 can inhibit the interfacial ‘dewetting’ on hydroxyl-terminated polybutadiene system.

Abstract:As an emerging data-driven technology， machine learning provide a promising pathway for the intelligent research and development of energetic materials. However， data scarcity and heterogeneity have become the core bottleneck that restricts modeling accuracy and practical application. Focusing on the acquisition path and the existing of energetic material data， this review evaluates the mainstream data optimization strategies from two perspectives： quantity expansion and quality improvement. For data quantity expansion， recent advances in SMILES enumeration， generative adversarial networks， and transfer learning are introduced for enhancing model generalization ability. For data quality improvement， the roles of outlier detection， standardized preprocessing， and feature engineering in improving model robustness and interpretability are discussed. It is shown that effective data optimization can not only alleviate data limitations but also significantly enhance prediction stability and structural extrapolation capabilities under small-sample and structurally complex conditions. Finally， future directions are proposed， including the development of high-throughput experimental platforms， unification of data standards， and establishment of intelligent closed-loop systems. It is expected to provide a feasible roadmap and methodological reference for advancing the data ecosystem and intelligent design of energetic materials.

Abstract:

Abstract:In recent years， the frequent occurrence of terrorist attacks and industrial accidental explosions has triggered in-depth research and extensive application of blast wall structures in the field of protective engineering. According to the development sequence， structural characteristics， and explosion-resistant mechanisms of blast walls， this paper classifies and reviews blast walls into traditional blast walls and new-type blast walls. Traditional blast walls mainly use conventional building materials to resist explosive shockwaves through the inherent properties of the walls themselves. In contrast， new-type blast walls further enhance their explosion resistance through material and structural innovations. Material innovations mainly involve the use of high-strength materials， fiber-reinforced composites， etc.， which are used to construct the walls， incorporated into the raw materials （such as concrete） of the walls， or attached to the wall surfaces to improve the overall strength and stability of the walls. Structural innovations involve designs such as multi-layer wall structures and sandwich fillings， aiming to enhance the overall explosion-resistant effect by leveraging the performance advantages of different materials. This paper summarizes and generalizes the explosion-resistant performance evaluation， application scenarios， experimental and numerical simulation methods， as well as related research results， covering key factors such as material selection， dimension design， shape optimization， and reinforcement methods of blast walls， providing a reference basis for future blast wall designs.

Abstract:In order to meet the dual constraint requirements of safety current and anti-electromagnetic radiation power of semiconductor bridge initiating explosive devices， based on GJB 344A-2020" General specification for insensitive electric initiators"： Non-fire test standard， the electro-magnetic-thermal multi-physical field coupling model was constructed on COMSOL Multiphysics platform by numerical simulation method. By integrating the parallel shunt mechanism of negative temperature coefficient （NTC） thermistor， the loop resistance was monitored in real time and the current input was dynamically compensated. The effects of thermal safety under three working conditions of constant current 1A， constant power 1 W and double constraints 1A1W were compared and analyzed. The results show that the power of 1 A constant current condition is only 0.78 W， which deviates from the standard by 22% because the loop resistance is reduced to 0.78 Ω. The initial current of 1W constant power condition is 0.91 A， which is lower than the safety threshold. The dynamic adjustment strategy realizes the coordinated stability of current and power through closed-loop control. The heat balance temperature of the bridge area is controlled at 449.06 K， and the shunt rate is increased from 29% to 41.26% compared with the 1A constant current condition， and the shunt rate is increased by 0.6% compared with the 1W constant power condition.

Abstract:The combustion process of energetic materials （EMs） is a complex multi-stage process. By studying their thermal decomposition and combustion reactions， establishing precise combustion reaction kinetics models enables effective prediction of the thermal behavior of EMs， which is of significant importance for their synthesis， production， transportation， storage， and practical application in modern weaponry and equipment. Compared to traditional EMs， third-generation EMs exhibit higher energy density， which imposes more stringent requirements on their thermal stability. This review summarizes recent advances in thermal properties and combustion research of third-generation EMs， including both ionic and covalent types. The current research status on thermal properties and combustion reactions of typical third-generation EMs is expounded from three perspectives： thermal decomposition profiles， decomposition pathways/mechanism， and combustion performance. It identifies the shortcomings of the current research and proposes the research direction of the thermal behavior of the third-generation energetic materials. It is proposed to construct a multi-scale coupled research system： high-precision measurement of combustion parameters via novel experimental apparatus， accurate diagnosis of combustion intermediates， and cross-scale modeling combining quantum chemistry-machine learning-fluid mechanics to achieve full-chain analysis from free-radical mechanisms to macroscopic flame propagation.

Abstract:To address the issue of highly localized blast loads caused by limited distribution layers in shallow-buried layered fortifications， an equivalent single-degree-of-freedom （SDOF） dynamic analysis method considering the characteristics of localized loads was proposed. This method was used for evaluating the response of the roof slab of supporting structural layers. Based on the selected mode shape functions and the energy equivalence principle， dynamic coefficient calculation methods for both elastic and plastic response stages of the structure were established. The validity of the method was verified through finite element simulations. Results indicate that the static deflection curve under uniformly distributed loads can still serve as the mode shape function under localized loads， with acceptable deviations. If localized loads are simplified to uniformly distributed loads for design purposes based on equal impulse principle， the maximum displacement of the structure may be significantly underestimated， with errors potentially reaching up to 9.7 times. In the plastic response stage of the structure， the dynamic coefficient of structural resistance is negatively correlated with the degree of plastic deformation. The product of the total load duration and the structure’s natural frequency significantly influences the structural response： when this value is less than or equal to 1， the response is impulse-dominated； when it approaches 10， moderately extending the pressurization time favours structural resistance to blast loads； when the product exceeds 50， the beneficial effect of extending the pressurization tends to saturate. This method effectively characterizes the dynamic response characteristics of supporting structure layers in shallow-buried fortifications under localized blast loads， providing a theoretical support for the blast-resistant design of related protective structures.

Abstract:To investigate the stress wave effect in semi-infinite concrete targets under penetration-implosion loadings induced by reactive jet （RJ）， two sets of RJ peneration-implosion experiments were conducted to obtain stress wave data and characteristic damage patterns of concrete targets. LS-DYNA software combined with a restart algorithm was used for staged numerical simulations of the penetration-implosion process， and to analyze the stress wave propagation characteristics in concrete under the combined action of RJ penetration and explosion. The findings demonstrate that numerical and experimental results showed good agreement in stress waves and target damage features. During the penetration stage of RJ， concrete failure occurs after successive loadings of dynamic stress wave zone and static high-pressure zone， with the latter having a faster loading rate but a shorter action duration. The concrete damage caused by RJ penetration accelerates energy dissipation， reduces peak stress during the explosion stage， but accelerates stress wave propagation. Compared with the undamaged target， the peak stress of the explosion in the target after RJ penetration decreased by up to 47%， and the growth rate of the stress wave propagation speed could reache up to 7%. However， when the depth of measuring point exceeds 335 mm， the influence of RJ penetration on the explosion stage can be ignored.

Abstract:Reinforced concrete structures are frequently subjected to impact loads during their service life， leading to complex dynamic responses that are often difficult to predict. To systematically investigate the influence of concrete heterogeneity on the impact response and scaling effect of geometrically similar RC beams. Using a comparative analytical approach， three numerical models were established： a homogeneous RC beam （Homogeneity） and two heterogeneous RC beams （Heterogeneity-I and Heterogeneity-II）. The displacement， impact force， and reaction force were compared. Furthermore， damage modes， deflection curves， and energy absorption characteristics were analyzed to explore the intrinsic mechanisms of scaling effect. The results indicate that the concrete heterogeneity is one of the factors contributing to the scaling effect in the displacement of geometrically similar RC beams， while its influence on impact force and reaction force is relatively minor. The intrinsic mechanism of the above-mentioned phenomenon may be the difference in damage modes due to heterogeneity， which enhances the local response of the RC beams with analysis of deflection curves and energy absorption. Additionally， within the scope of this study， higher impact velocities lead to more pronounced scaling effect in the displacement. These findings provide theoretical insights for impact-resistant design of concrete structures and for similitude analysis in scaled experimental studies.