The scattering of fragments is a notable characteristic of the explosive detonation of a shelled charge. This study examines the fracture and fragmentation of the shell and the process by which natural fragments form under the strains of implosion. The analysis takes into account both the explosive's energy output and the casing's dynamic response. For this purpose, utilizing a thermochemical code as an alternative to the conventionally employed cylinder test, the Jones-Wilkins-Lee equation of state (JWL EOS) was calibrated within a range of relative specific volume up to 13. The detonation of the shelled charge was subsequently analyzed using the continuum-discontinuum element method (CDEM). Following this, the formation mechanisms and scattering characteristics of natural fragments were scrutinized. The analysis found that the shell predominantly experiences shear failure with uniform evolution, displaying a "hysteresis effect" and two mutation stages in the evolution of tensile failure. Within the JWL EOS's calibrated range, the representation of fragment displacement and velocity improved by 47.97% and 5.30%, respectively. This study provides valuable guidance for designing the power field of warheads and assessing their destructive power.

为研究TNT装药空中爆炸温度场的热效应,开展了1、5 和10 kg三种质量的TNT药柱在空气中的爆炸实验.采用WRe5/26 热电偶获取了不同爆心距处的温度—时间曲线,分析了TNT装药温度峰值随距离和装药质量变化的规律.实验结果表明:TNT在自由场中爆炸时,热电偶响应温度—时间曲线呈单峰状.随着爆心距的增加,升温速率和降温速率逐渐下降,曲线的下降部分因未反应产物的二次燃烧会产生波动,延长温度持续时间;爆心距变化会对温度持续时间造成较大影响,但是质量的改变对温度持续时间影响较小,在自由场爆心近距离内时间变化率最大不超过10%;温度峰值与装药质量成正比,与爆心距成反比,在相同传播距离下,峰值下降的幅度随装药质量增大而减小.

为分析周边固支效应靶的变形稳健性,结合薄板冲击响应模型,建立薄板变形稳健性的表征方法和极限状态函数,提出了一种基于Monte-Carlo法的薄板变形稳健性分析方法,并探讨抽样次数、载荷参量、几何参量和材料参量对变形稳健性及灵敏度的影响.结果表明:当抽样次数大于30万次时,薄板变形稳健性结果趋于稳定,说明其非线性较强;薄板变形稳健性随半径厚度比、厚度的增大而降低;薄板半径标准差的灵敏度最大,是薄板变形稳健性的主控参量.研究结果为周边固支效应靶的设计与压力测量应用提供了参考.

To study the influence of buried depth of explosives on the propagation characteristics of air blast waves on the surface of soils, contact explosion tests and 5kg TNT explosion tests with buried depths of 0.108, 0.228 and 0.85m were carried out. The peak pressure, impulse and positive pressure time at multiple scaled distances were obtained, and the effects of buried depth on the propagation characteristics of shock waves were analyzed. The results show that the peak pressure and impulse of shock wave decrease with increasing the buried depth and the scaled distance. For contact explosion, the peak pressure at a scaled distance of 4 is 3.24% of that at a scaled distance of 1, while for the explosion test with buried depths of 0.108m the peak pressure at a scaled distance of 4 is 25.02% of that at a scaled distance of 1. When the buried depth is 0.108m, the peak pressure and impulse at the scaled distance of 1 are 8.7% and 20.4% of the corresponding values for the contact explosion, respectively. In addition, the positive pressure time under two conditions is analyzed. The positive pressure time increases exponentially with increasing the distance from the detonation center, and the positive pressure time increases logarithmically in the explosion test with the depth of 0.85m. Based on the further analysis of the experimental data, engineering calculation models for peak pressure and impulse as the function of buried depth and scaled distance are established, which can be used as a reference for the evaluation of performance and damage effect for ammunition under shallow-buried explosions.

In this paper, a modified single-degree-of-freedom (SDOF) model of reinforced concrete (RC) beams under close-in explosion is proposed by developing the specific impulse equivalent method and flexural resistance calculation method. The equivalent uniform specific impulse was obtained based on the local conservation of momentum and global conservation of kinetic energy. Additionally, the influence of load uniformity, boundary condition and complex material behaviors (e.g. strain rate effect, hardening/softening and hoop-confined effect) was considered in the resistance calculation process by establishing a novel relationship between external force, bending moment, curvature and deflection successively. The accuracy of the proposed model was verified by carrying out field explosion tests on four RC beams with the scaled distances of 0.5 m/kg1/3 and 0.75 m/kg1/3. The test data in other literatures were also used for validation. As a result, the equivalent load implies that the blast load near the mid-span of beams would contribute more to the maximum displacement, which was also observed in the tests. Moreover, both the resistance model and test results declare that when the blast load becomes more concentrated, the ultimate resistance would become lower, and the compressive concrete would be more prone to softening and crushing. Finally, based on the modified SDOF model, the calculated maximum displacements agreed well with the test data in this paper and other literatures. This work fully proves the rationality of the modified SDOF method, which will contribute to a more accurate damage assessment of RC structures under close-in explosion.

为了研究浅埋条件下装药爆炸产生的爆坑和冲击波,通过国内外文献调研,从爆坑形成过程、爆炸冲击波传播特性、多参量(土体性质、装药埋深及装药自身属性)对爆坑和爆炸冲击波特性的影响进行分析总结.概述了可预估爆坑参数的经验公式以及可表征爆炸冲击波传播特性的经验模型,根据爆坑和爆炸冲击波的研究不足提出了相应的研究建议,并在此基础上展望了该领域发展趋势,为深入研究浅埋条件下装药爆炸威力、摸清弹药浅埋爆炸的威力底数提供借鉴,研究结果可为其他研究者提供参考.

为研究装药速度对三波点高度的影响,对不同速度下装药的近地动爆过程开展了数值模拟,获取了动爆冲击波场演化历程图像,定量研究了近地面动爆冲击波流场演化情况.仿真结果表明:装药速度对三波点的高度有较大影响,在速度正方向上,装药速度越大,同时刻三波点高度越高,且变化幅度随装药速度的增加而增大,马赫波形成位置到爆心投影点的距离较静爆时更远,在距爆心投影点相同水平距离处三波点高度越低,在速度负方向上则反之;在速度正方向距爆心投影点相同水平距离处,B炸药和C4 炸药形成的马赫波高度相当,二者的三波点迹线更贴近于地面,TNT装药的三波点高度较高.

Shallow-buried explosion is a typical working condition of ammunition. Studying the overpressure propagation law of air shock wave in shallow-buried explosion is helpful to completely characterize the ammunition power in actual combat. In this paper, a numerical model of shallow-buried explosion of cylindrical charge based on Euler method is established in the framework of simulation software AUTODYN, which simulates the formation process of crater when cylindrical charge is initiated under the conditions of different charge amount and different buried depth, and analyzes the propagation law of explosion shock wave in the air. The following conclusions are drawn: compared with the mass of charge, the depth of burial has more influence on the surface air shock wave. According to the simulation data, the empirical formulas related to the peak overpressure of shock wave and the charge, buried depth and horizontal detonation center distance are fitted.

In order to study the influence of proportional burial depth and proportional distance of charges on the peak pressure of shallow buried explosion air shock wave,the peak pressure of shallow buried explosion air shock wave at 7proportional distances under 3 proportional burial depth conditions was tested.The test data were fitted combined with dimensional analysis,and the empirical formula of the peak pressure of shallow buried explosion air shock wave was obtained.The results show that the peak pressure of air shock wave decreases with the increase of proportional burial depth and proportional distance;With the increase of proportional distance,the influence of proportional burial depth on the peak pressure of air shock wave decreases;Peak pressure of air shock waveΔP D is related to charge quantity Q,explosion center distance R and burial depth L,its empirical formula is:■.

Aiming at the damage effect of reinforced concrete beams subjected to close-in explosion, numerical simulation and dimensional analysis are carried out to study the damage of beams under close-in explosion with spherical charge. The damage characteristics of beams were obtained by the methods of AUTODYN and DYNA. Using dimensional analysis, the relationship between the damage characteristics of reinforced concrete beams and the stand-off distance is deduced. The empirical equation of the beam punching shear failure characteristics is fitted on the basis of numerical simulation. The results show that the simulation method is more efficient than the fluid-solid coupling calculation; the proposed empirical equation is in good agreement with the experimental results. The relationship between failure width and the stand-off distance obtained by the fitting and the modelling method have reference value for the research on the damage effect of reinforced concrete beams.

改进了在动爆条件下基于弹药炸点的破片区截测速方法,分析了破片贯穿靶板后的速度偏转现象,提出了一种采用归一化方法结合最小距离原则进行破口点集配准,以此识别破片飞散方向的方法.模拟试验结果表明,63.3％的破片角度测量误差绝对值在4°以内,86.7％的破片测量误差绝对值在8°以内.该方法易于实施,数据处理简单,为实战条件下弹药威力场的测试及毁伤效应研究提供了技术手段.

针对近场爆炸作用下钢筋混凝土梁的毁伤效应,对比了数值模拟和试验结果,采用数值模拟方法得到了梁结构参数、钢筋、混凝土及装药形状对梁局部破坏的影响规律.结果表明:纵筋强度和配筋率的减少改变了梁的破坏模式,梁的迎爆面及背爆面破坏区域基本无变化;加密箍筋使背爆面破坏尺寸减小;装药形状改变了梁表面冲击波形状,导致梁局部破坏尺寸随炸药长径比增加而增加;梁高度增加导致梁破坏模式由冲剪破坏变为层裂破坏,背爆面混凝土损失区域扩大,宽度增加减少了梁的局部破坏尺寸.

In the present study, various test methods in the free field and confined explosions of cast HMX-based thermobaric explosives (TBX) and TNT are applied to quantify the explosion performance of TBX. The results show that the Mach reflection overpressure $$\Delta p$$  and impulse  $$I$$  of TBX in the free field are much larger than those of TNT at the same relative distance from the explosion center. Based on the measured experimental data, semi-empirical formulas for calculating the overpressure at different distances from the TNT and TBX charges are derived. The fireball temperature and the duration of temperature higher than 1500°C of TBX are seen to be significantly greater. The measured peak pressure of the two explosives blast in an explosion tank are compared with the values predicted by modified calculation models, and the results are in good agreement. In addition, the quasi-static pressure generated by TBX in the explosion tank is 30.9% higher than that of TNT, which obviously reveals thermobaric effects of TBX. Based on the overpressure and quasi-static pressure calculation model, the TNT equivalents of TBX are calculated to correctly evaluate the TBX performance. The related contents in this paper will guide the formulation and performance assessment of TBX.

为明确弹体平动和转动速度对破片场初速分布作用,基于矢量叠加法和SPH数值计算研究了平动与转动速度单独作用下的破片场初速分布变化,开展了平转动作用的耦合影响研究.研究表明:单独作用时,相比转速,平动速度作用效果更强,作用能力对破片静爆飞散方向更敏感;平转动速度作用相互影响,对于静爆飞散方向不同的破片,平动速度对其加速能力存在差异,转速增加使差异降低;平动速度增加会使差异提升.平动速度增加导致破片弹道交叉,施加转速可以缓解该现象.

This paper develops the pressure-impulse (P-I) diagram to conduct damage assessment of simply supported reinforced concrete (RC) beams under close-in explosion based on the equivalent single-degree-of-freedom (SDOF) model. Firstly, eleven close-in explosion tests are carried out with different charge weight, scaled distances and offset distances of explosives relative to the mid-span of RC beams. Test results show that the maximum rotation angle can characterize the comprehensive spalling/bending damage under asymmetric load, therefore it is selected as the damage criteria. Then, the equivalent SDOF model is improved by considering the influence of asymmetric load on flexural resistance, and is verified through the test results. Both test results and SDOF model show that increasing the offset distance results in asymmetric bending failure and reduces peak deflection. Through comparative analysis, the equivalent uniform load is chosen to be the axis of P-I diagram. The asymptotes and shape parameters of P-I curves are related to the offset distance and load uniformity. The relationship is derived through curve fitting and validated with the test results and the calculated results of SDOF model. This work expands the application scope of P-I diagram, which contributes to a more comprehensive damage assessment of RC structures under close-in explosion.

爆炸作用下钢筋混凝土梁会呈现多种破坏模式,针对近场爆炸载荷作用下钢筋混凝土梁的冲剪破坏,联合等效单自由度模型和临界剪切裂纹理论,提出一种预测钢筋混凝土梁冲剪破坏的方法,并通过开展两发球形梯恩梯装药近场爆炸试验,观察了钢筋混凝土梁的破坏形态,验证了冲剪破坏的预测方法.结果表明:提出的预测方法可用来评估钢筋混凝土梁在近场爆炸作用下是否发生冲剪破坏,对掌握钢筋混凝土梁的爆炸效应特征具有参考意义.

为了研究炸药爆轰产物的演化规律,建立了产物自由膨胀模型和等体积放热模型,基于自编热化学程序(DLCHEQ)和多种经验方法,计算了标准爆热弹实验中PETN、RDX、HMX和TNT 4种炸药产物从CJ点到常温点的组分和热力学状态演化过程.结果表明,基于DLCHEQ计算的3个重要物理量(CJ状态、准静压和爆热值)都与实验值吻合很好,远小于其他方法的计算误差,验证了 DLCHEQ的可靠性.CJ点后产物组分间发生了显著的化学反应.计算揭示了外界条件对产物组分间反应的影响规律:敞开空间爆炸时产物发生吸热且大量生成气体的反应;封闭空间爆炸时产物发生放热且大量消耗气体的反应.计算还预言了 4种炸药可能存在独特的组分对称现象:CJ点爆轰产物主要组分和低温点(300～400 K)基本一致.

Polyurea is an elastomeric material that can be applied to enhance the protection ability of structures under blast and impact loading. In order to study the compressive mechanical properties of SiC/polyurea nanocomposites under quasi-static and dynamic loading, a universal testing machine and split Hopkinson pressure bar (SHPB) apparatus were used respectively. The stress-strain curves were obtained on polyurea and its composites at strain rates of 0.001–8000 s−1. The results of the experiment suggested that increase in the strain rates led to the rise of the flow stress, compressive strength, strain rate sensitivity and strain energy. This indicates that all of the presented materials were dependent on strain rate. Moreover, these mechanical characters were enhanced by incorporating a small amount of SiC into polyurea matrix. The relation between yield stress and strain rates were established using the power law functions. Finally, in order to investigate the fracture surfaces and inside information of failed specimens, scanning electron microscopy (SEM) and micro X-ray computed tomography (micro-CT) were used respectively. Multiple voids, crazes, micro-cracks and cracking were observed in fracture surfaces. On the other hand, the cracking propagation was found in the micro-CT slice images. It is essential to understand the deformation and failure mechanisms in all the polyurea materials.

As composite structures develop, polyurea coating has been applied to improve the protective performance of multi-layered composite structures subjected to blast or impact loading. In order to investigate the ballistic resistance of polyurea coated Carbon Fiber Reinforced Plastics (CFRP) composites, impact experiments were conducted using a 14.5 mm ballistic gun with cylindrical projectile. The effect of polyurea coating position and coating thickness were analyzed and discussed. The impact velocity of projectile was selected from 600 m/s to 1406 m/s for polyurea coated CFRP composite plates. The energy absorption ratios were calculated to assess the ballistic behavior. Damage zone of CFRP plates were determined by ultrasonic C-scan images. The failure mechanism of CFRP laminates and polyurea were analyzed by an optical microscope and scanning electron microscopy (SEM). The results showed that the deformation of projectiles increased with the increase of initial impact velocity. Energy absorption ratio and damage level of RPU2 configuration was better than pure CFRP plates. The optical microscope and SEM images showed that failure modes were compression-shear failure on the front side of polyurea, tension-shear failure, petaling failure, spallation and punching perforation failure on the rear side of polyurea. Overall, polyurea coating can significantly boost the composite plates’ ballistic performance when spraying polyurea on the CFRP composites’ rear side.

为研究基于单面刻蚀的微机电系统制造工艺对模态局部化加速度计的影响,通过分析释放和刻蚀工艺对模态局部化加速度计结构的影响以及对加速度计幅频特性和初始工作点的影响研究了粘附和根切对模态局部化加速度计的影响.结果表明:释放氧化层时由于液体张力的存在极易使得器件层与基底层发生粘附,导致器件失效;根切会导致谐振器之间的质量差异,从而导致加速度计初始幅值比较大的漂移,增加了信号检测的难度.可见基于单面刻蚀的微机电系统制造工艺会增加模态局部化加速度计传感器的不确定性.