Acta Armamentarii

Electronic edition of this issue

2022, 43(9): 0.

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Research and Comparison of Protection Rating in Domestic and Foreign Bulletproof Standards

ZHANG Yangyang, ZHAO Hongshan, PENG Wei, HU Chundong, YANG Zhigang, DONG Han

2022, 43(9): 2017-2036. doi:10.12382/bgxb.2022.0626

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Well-developed bulletproof standards can not only correctly classify the protection grade of the bulletproof materials, but also offer efficient and practical guidance for commanders to choose different protective equipment when facing danger. Each country or an international organization establish their bulletproof standards according to their own particular circumstances, and therefore the protection levels vary from country to country. Several common bulletproof standards are summarized from four aspects: body armors, bulletproof helmets, armored vehicles and ballistic transparent materials. A side-by-side comparison of the projectile penetration energy for each protection level in different ballistic protection standards was conducted, and the bullet core and morphological structure of several of the commonly tested projectiles were compared and analyzed. Through the comparison and analysis of the commonly used bulletproof standards, the similarities and differences between domestic and foreign standards in terms of protection levels and the power of the tested projectiles were summarized. The results are expected to inspire and help researchers engaged in related industries to choose or improve their ballistic resistance standards.

Design and Features of Exoskeleton Assisting Individual-Soldier Rescue

SONG Jiyuan, ZHU Aibin, TU Yao, ZHANG Jialin, ZHANG Yulin

2022, 43(9): 2037-2047. doi:10.12382/bgxb.2021.0729

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To address the lack of physical strength of individual rescuers during rescuing the wounded in armored vehicles, a study of assistance methods is carried out. Based on the research on the biological motion mechanism of the bending and lifting of the human body, an analysis of the mechanism design, kinematics and dynamics of the supporting exoskeleton are carried out. A parallel booster mechanism for lifting heavy objects is developed based on the concept of distributed load, integrating the exoskeleton scheme and external limb schemes. The feasibility of the prototype is verified by experiments. The results show that the rescue exoskeleton robot can effectively support the rescuer in lifting heavy objects, dispersing load, and enhancing rescue efficiency.

Simulation and Experimental Study of the Traction and Deployment of an Interceptive Space Net wih Anti-UAV

LIU Yiming, XIONG Ziming, CHEN Xi, ZHONG Sidong, WANG Derong

2022, 43(9): 2048-2057. doi:10.12382/bgxb.2022.0258

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For the interception of combat Unmanned Aerial Vehicles (UAVs), a space net method is proposed, different from the existing method based on space web topology. The dynamics model of the space net is established with a focus on key issues such as traction and deployment performance and flight attitude of the space net. Changes in the attitude, internal force, and configuration of the net at different time points are studied through a numerical simulation of the isometric model. A ground launch test is conducted under the same working conditions for verification. Results show that the net deployment process is consistent between the simulation and experiment, verifying the feasibility and effectiveness of the interception method and providing a reference for the simulation and experimental research of large-deformation flexible systems.

Performance of Explosive-proof Equipment in Protecting Against High-level TNT Explosion Sound

LIU Han, ZHAO Yao, GUO Zhiwei, FENG Shunshan, HUANG Guangyan

2022, 43(9): 2058-2074. doi:10.12382/bgxb.2022.0064

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High-level explosive noise (HLEN) is a non-lethal damage accompanying explosions, which can directly damage one's auditory system. Using the mechanism analysis of the HLEN's awareness and propagation, explosive noise tests with different TNT mass are conducted to study the sound pressure (p_sp), sound pressure level (p_spl), propagation laws of free air burst (FAB), flexible explosive proof (FEP), and steel explosive proof (SEP). The HLEN protection performances of FEP and SEP are compared with that of FAB. The results show that the HLEN has typical characteristics of low frequency and high p_sp & p_spl. At 20 m to 40 m from the explosion center, the peak p_sp attenuations are about 50%, 52%, 48%, and the peak p_spl attenuations are about 5.7%, 4.7%, and 4.9% for FAB, FEP and SEP, respectively. The peak p_sp/p_spl travel time is equal, i.e., Δt_FAB=Δt_SEP=Δt_FEP=0.057 s. FEP can weaken the peak p_sp by 52% to 93.5% and reduce the peak p_spl by 4.8% to 9.1%. SEP can decrease the peak p_sp by 24.6% to 93% and reduce the peak p_spl by 1.4% to 6.9%. Human ear injuries are graded on a scale of Ⅰ to Ⅳ. With FAB, the injury is mainly grade Ⅳ and Ⅲ. With FEP, the injury is mainly grade Ⅲ and grade Ⅲ-Ⅱ. With SEP, the injury is mostly grade Ⅳ-Ⅲ and grade Ⅲ.

Numerical Simulation of Bludgeoning Effect of Fragments Penetrating Head Target Wearing Bulletproof Helmet

NIE Weixiao, WEN Yaoke, DONG Fangdong, QIN Bin, LUO Xiaohao, TONG Liangcheng

2022, 43(9): 2075-2085. doi:10.12382/bgxb.2022.0428

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In order to study the killing effect of low-velocity fragments on the human head target wearing a bulletproof helmet, this paper firstly verified the accuracy of the simulation model of the composite helmet and the finite element head model based on the 3D-DIC test of the bullet penetrating the bulletproof helmet and the head impact test. Then, the numerical model of the 6 mm steel ball fragment penetrating the human head target wearing a bulletproof helmet was constructed, and the numerical simulation of the penetration effect of the fragment from the front, side and top directions were carried out. The research results show that when the fragment penetrates at a target speed of 600 m/s, the transient bulge heights at the impact points of the frontal, side and top penetration bullets are 10.2 mm, 11.3 mm and 11.5 mm, respectively, indicating that there is head support. In the case of a helmet, the height of the back bulge caused by fragment penetration is similar; the skull stress at the bottom of the impact point during frontal penetration is the largest, and the stress at the bottom of the impact point of side penetration is the smallest. The skull stress caused by fragment penetration will not exceed the damage threshold, which indicates that low speed Fragment penetration did not cause skull damage; peak intracranial pressures were 495 kPa, 110 kPa, and 327 kPa due to frontal, lateral, and top penetration, respectively, indicating the best protection in the mid-lateral, frontal and top penetrations Peak intracranial pressure can cause brain damage.

Assessment Method for Probability of Occurance of Different Injury Severities in Personnel Based on Fragment Penetration Depth

WANG Jianmin, CHEN Kuijun, LI Tonghua, LI Guanhua, FAN Zhuangqing, ZHANG Jieyuan, CHEN Bin, YANG Guangming, KANG Jianyi, CHEN Jing, DUAN Zhaoxia, CAO Lingyu, WANG Han

2022, 43(9): 2086-2100. doi:10.12382/bgxb.2022.0513

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Fragments are the primary killing factor of explosive weapons, and the assessment of the severity of fragment-induced personnel damage is the main part of the killing power assessment of explosive weapons. This study focuses on the operational capability requirements of battlefield personnel, screens the important tissues and organs related to injury severity determination; establishes the injury severity criteria for different tissues and organs at different penetration depths based on AIS and MCIS-based injury severity assessment; proposes a calculation model for the penetration depth of fragments in soft tissues, and calculates the probability of occurrence of different injury seventies induced by fragments at different penetration depths. The results show that the probability of occurrence of different injury severities can be effectively predicted based on the fragment penetration depth, which provides technical support for the assessment of the target killing power of fragments.

Behind-Helmet Blunt Trauma of a Pistol Bullet Striking Ballistic Helmet-Covered Human Head and Neck Target

SHEN Zhouyu, WEN Yaoke, YAN Wenmin, DONG Fangdong, ZHANG Junbin, LI Ying

2022, 43(9): 2101-2112. doi:10.12382/bgxb.2021.0858

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Although bulletproof helmets can effectively prevent pistol bullets from penetration, the transient deformation may still cause serious damage to human head. To study behind-helmet blunt trauma, a progressive damage constitutive model is developed to simulate the mechanical properties of composite bulletproof helmets by using the Abaqus user material subroutine VUMAT. Then, the accuracy of the simulation model is verified using the Three-Dimensional Digital Image Correlation test results of the bulletproof helmet. Then, numerical simulation of the 9 mm lead pistol bullet impacting human head and neck target wearing a bulletproof helmet at 343 m/s is carried out. Blunt impact effect characteristics such as helmet bulge height, skull stress, intracranial pressure, and cervical stress are obtained. The results show that without the helmet, the transient maximum bulge height at the top impact point reaches 27.70 mm; with the helmet, the transient maximum deformation of the helmet shell at the impact point is reduced to 10.73 mm, due to the support of the helmet. During blunt impact, the maximum stress on the skull reaches 46.97 MPa and some units fail, indicating a concave fracture in the skull. The maximum intracranial pressure reaches 208.70 kPa, which can cause moderate damage to the brain and other important organs. The cervical vertebra is under a great deal of stress, so is the central nucleus pulposus of each intervertebral disc. The maximum stress on C₂-C₃ intervertebral disc is 2.65 MPa. Our research results provide scientific guidance to the treatment of blunt head and neck injury and the design of bulletproof helmets.

Experimental Study and Constitutive Model for the Dynamic Mechanical Properties of Ballistic Gelatine

JIANG Mingfei, XU Hui, HUANG Chenlei, LIU Kun, WU Zhilin

2022, 43(9): 2113-2120. doi:10.12382/bgxb.2022.0449

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Ballistic gelatine is widely employed as a soft tissue simulant in biomedical applications and terminal ballistics. The accurate measurement of the dynamic mechanical properties of ballistic gelatine has been a topic of great interest in wound ballistics. To solve the problems of weak transmission signal and non-uniform deformation of gelatine materials during dynamic testing, the Hopkinson pressure bar device is equipped with aluminum alloy pressure bars and semiconductor strain gauges, and the pulse shaping technology and slice specimens are adopted. Dynamic mechanical properties tests for 10% and 20% ballistic gelatine at 4℃ are conducted. The results show that the mechanical response of gelatine is nonlinear, and the stress-strain curve consists of an elastic stage and three plastic strengthening stages. The stress dynamic increase factor is linearly related to the logarithm of the normalized strain rate. A polynomial constitutive model that takes into account the strain rate effect can well describe the mechanical behaviours of gelatine at a high strain rate. The research results can provide support for the numerical simulation of small-arms projectiles penetrating gelatine targets.

Protective Performance of Helmet Based on Blast Shock Wave

WU Yang, QIN Bin, WANG Shu, XIONG Manman, AN Shuo, LU Haitao, ZHANG Xianfeng

2022, 43(9): 2121-2128. doi:10.12382/bgxb.2022.0553

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To deal with the problem of blast shock wave causing traumatic brain injury, the protective performance of helmets based on blast shock waves was investigated. Combined with the pressure sensor and the head surrogate as the simulation target, the test method of protection against blast shock waves for different helmet structures and different positions in the helmet was developed. The pressure-time curves of the forehead, calvaria and back of head were obtained and the propagation principle of the blast shock wave on the surface of head with or without protection in the experiment were analyzed. The results showed that the helmets can effectively attenuated the peak overpressure of shock waves. The peak overpressure on the forehead could be attenuated from 352.57 kPa without helmet to 151.31 kPa with QGF-03 helmet and to 11.36 kPa with the full-face helmet. At the same time, the shock waves were prone to diffraction and superposition/convergence during the propagation in the head surrogate with helmet. The peak overpressure of the back of head with QGF-03 helmet and FAST helmet respectively increased by 50%-100% and 9% compared to the situation without helmet, and the duration of overpressure on head with helmet was significantly increased. The mask could significantly reduce the effect of the blast shock wave on the head and the peak overpressure of the shock wave on the forehead and face could be attenuated by 75%. The full-face helmet had the best protection effects and the peak overpressure on forehead, calvaria and back of head were respectively reduced by 90%, 87% and 80%. Moreover, the airtightness has a positive effect on protection against shock waves.

QIN Bin, ZANG Liwei, GAO Tong, AN Shuo, LUO Xiangna

2022, 43(9): 2129-2135. doi:10.12382/bgxb.2022.0551

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The non-living simulation target applicable to the evaluation of conducted electrical weapons (CEWs) is conducive to eliminating the differences bewteen experimental animals, which is of great significance for the accurate evaluation of the performance of CEWs and ensuring their safe use. Firstly, the output characteristics of a police CEW applied to a swine are tested, and the capacitive impedance for living targets is identified. Secondly, based on the similar component and volume as well as salt content adjustment, we prepared the gelatin simulation targest containing 0.1%,0.2% and 0.4% salt. The CEWs output test result shows similarities of equivalent impedance curves for gelatin and animal targets, and the relationship between impedance curve subsection and the shock loading frequency is identified; the gelatin target containing 0.1% salt shows the best similarity to the living animal with the error less than 7.72% in terms of output current and less than 26.63% in terms of output voltage and equivalent impedance.

Research on the Ballistic Performance of Hybrid Structural Composites

LI Weiping, LONG Zhizhou, CHEN Junxian, ZHANG Hua, MA Tian

2022, 43(9): 2136-2142. doi:10.12382/bgxb.2022.0456

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In order to explore the influence of different hybrid structures on ballistic performance, according to the mechanical properties of aramid Ⅱ and aramid Ⅲ fibers, 7 kinds of composite materials with different hybrid ratios were designed and prepared, and each hybrid ratio had two layering sequences, i.e. aramid Ⅲ as a bullet-facing surface or a back surface. 1.1 g standard stimulating fragments and 51-type 7.62 mm lead-cored bullets were used to test the performance of composite materials with different hybrid structures, the effects of layup sequence and hybrid ratio, etc. on such as the impact resistance and the ballistic performance were studied. The results show that: under low-speed impact, with the increase of the content of aramid Ⅲ composite material, the maximum load time of the composite material of the hybrid structure decreases gradually, indicating that the aramid Ⅲ can absorb more energy during the same period of time; the aramid Ⅲ composite material is a bullet-facing surface or a back surface, and the ballistic limit v₅₀ thereof increases with the increase of the aramid Ⅲ content, the trend is that the v₅₀ at the beginning increase faster, and when the content of aramid Ⅲ exceeds 30wt%, the v₅₀ increases significantly slower. When the content of aramid Ⅲ exceeds 70wt%, the v₅₀ does not increase significantly. When the aramid Ⅲ composite material is located on the bullet-facing surface, the v₅₀ of the composite material of the hybrid structure is higher, and this phenomenon is most obvious when the content of the aramid Ⅲ composite material is 30wt% to 70wt%. Meanwhile, the increase in the content of the aramid Ⅲ composite material is beneficial to reduce the deformation of the bulletproof helmet after being shot.

Stabbing Resistance Mechanism of High-performance Composite Fabrics

LIU Yuhang, HUANG Guangyan, ZHANG Hong, ZHOU Hongyuan

2022, 43(9): 2143-2151. doi:10.12382/bgxb.2021.0513

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Recently，there are frequent incidents of police officers and doctors being stabbed. Stabbing-resistant clothing plays a significant role as the last line of defense of human lives. It is typically made of high-strength composite fibers. Despite extensive stabbing resistance testing，the mechanism of such products' stabbing resistance performance remains unclear. Three typical stab-resistant materials，namely plain woven aramid fabric with epoxy resin，unidirectional high-performance polyethylene fiber cloth，and pure plain woven aramid fabric，are herein examined through bending stiffness，hardness，quasi-static stabbing，and dynamic stabbing tests. The stabbing resistance mechanism of the three materials under specific areal densities are studied. The results show that high-bending stiffness and hardness significantly enhance the quasi-static and dynamic stabbing performance of the product，showing a higher reaction force and smaller deformation. In addition，as most of the weapon's kinetic energy is transformed into the kinetic energy and deformation energy of the stab-resistant clothing and the backing material，less energy is absorbed for material damage. Therefore，it is more important to enhance the hardness and bending stiffness of the stab-resistant clothing rather than boosting its energy absorption capacity. A new generation of lightweight，flexible stab-resistant products can be developed based on our theoretical findings.

Ballistic Performance of Two-Dimensional UHMWPE Fabric

XIE Yachen, HUANG Guangyan, ZHANG Hong, ZHOU Ying

2022, 43(9): 2152-2163. doi:10.12382/bgxb.2021.0648

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Due to its high modulus, high strength, and low density, ultra-high molecular weight polyethylene fiber (UHMWPE) fabric is widely applied in explosive fragment protection. Based on the results of ballistic tests performed on UHMWPE two-dimensional (2D) woven fabric, a numerical mesoscale model is initially developed using the Abaqus finite element analysis method. The fabric size and boundary fixing methods are considered in the mesoscale model. At the same time, ballistic tests are carried out as a foundation for numerical simulation. Since the smaller fabric size influences the ballistic performance of 2D woven fabric and the increase in fabric size leads to higher calculation costs, a meso-macro hybrid scale model is established. This modified model has a higher calculation efficiency and its numerical results are in good agreement with the experimental results. The ballistic performance of the fabric under the impact of projectiles with different head shapes of heads (flat, sharp, or hemispherical) is studied and compared with the experimental results by using the meso-macro hybrid scale model. The ballistic limit and the fabric failure are characterization parameters used to measure the ballistic performance. It is concluded that the 2D woven fabric has the best impact resistance against flat-nose projectile. Under low-velocity impacts below 100 m/s, the impact resistance against sharp-nose projectiles is better than that against hemisphere-nose ones. Under high-speed impacts above 100 m/s, the impact resistance against hemisphere-nose projectiles is better than that against sharp-nose projectiles.

Mechanical Testing of Biological Soft Tissue and Related Theoretical Research

KANG Wei, XU Peng, BU Weiping, YUE Yanxian, WANG Lizhen, FAN Yubo

2022, 43(9): 2164-2171. doi:10.12382/bgxb.2022.0444

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Reasonable constitutive models and correct material parameters are the prerequisites for effective numerical calculation and target preparation to characterize the mechanical response of biological soft tissues under high-speed impact. The typical mechanical testing methods for biological soft tissues and materials are elaborated from single loading mode to shear loading and even mixed loading, and detailed theoretical derivation is carried out. The results show that: principal elongations under each loading mode are obtained, based on which the principal stress plane, maximum deformation value, and direction can be obtained to evaluate the maximum stress plane and damage degree of the biological soft tissue and its corresponding bionic target, which is convenient for in-depth exploration of the correlation between the microstructure of the biological soft tissue as well as simulated material design and their macro mechanical properties, with the aim of establishing a more scientific and reasonable bionic human target.

Experimental Investigation of Underwater Blast Injuries to Beagles

SHEN Wenni, HOU Lijun, TANG Jiawei, MU Chunyuan, ZHANG Haoyu, XU Tao

2022, 43(9): 2172-2181. doi:10.12382/bgxb.2022.0461

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To study the underwater blast injury modes and thresholds for human, beagle dogs are adopted for gram-and kilogram-level underwater blast tests. The response of beagles to shock wave and bubble pulsation loadings is observed. Air containing organs such as lung and auditory apparatus suffer the most from the shock wave, bubble pulsation, negative pressure and other loads. Whether the head is above the water or not, the brain will be injured to some extent. Under the same underwater blast loading, the damage radius for a beagle in diving position is approximately 2.5 times that of one in swimming position. From experiments, the injury modes and thresholds for beagles under underwater blast are concluded, which can be used to predict and treat underwater shock injuries.

Dynamic Physical Response Law of Protected/Unprotected Head Surrogate Under Shock Wave

XIONG Manman, QIN Bin, XU Cheng, AN Shuo, WU Yang

2022, 43(9): 2182-2189. doi:10.12382/bgxb.2022.0483

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To explore the dynamic physical response of cranial brain under shock wave in warfare conditions, a physical model of protected/unprotected head surrogate impacted by shock wave from a soldier's rocket muzzle and intracranial pressure is developed. The pressure and evolution of different intracranial parts are analyzed. The intracranial pressure evolution for protected/unprotected head surrogates are compared. Under muzzle shock wave, the time-overpressure curve of unprotected intracranial pressure exhibits atypical shock wave characteristics. Unlike typical shock waves, the overpressure rises more slowly and lasts longer. The overpressure curve exhibits alternating oscillations of positive and negative pressure. The oscillation period is about 1 ms. The peak overpressure varies significantly in different intracranial parts. The counter shock side of the intracranial exhibits a significant negative pressure. The peak positive pressure on the counter shock side is nearly twice of that on the shock side, but the pressure impulses at different intracranial points are close to one another. Overpressure attenuation rates of different protected intracranial parts vary significantly. Compared with other intracranial parts, the overpressure attenuation rate of the counter shock side is highest. Moreover, the negative pressure effect on the counter shock side is weakened when covered with armor. The attenuation rate of the overpressure on the shock side is not obvious. The peak overpressure even increases in some parts with amor covered.

Assessment of Behind-Armor Trauma Based on Human Anatomical Structure

LI Zixuan, WEN Yaoke, DONG Fangdong, XIA Hailong, PENG Lei, ZHENG Hao

2022, 43(9): 2190-2199. doi:10.12382/bgxb.2022.0383

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To evaluate the severity of damage to the human body caused by the blunt bullet or its penetrating through the body armor when the human target wears body armor, a digital model of human body wearing an armor is developed based on real human anatomy data. Then, the process of the bullet penetrating the protected gelatin target is captured by high-speed photography. The evolution data of the instantaneous space cavity inside the gelatin target is obtained. A simplified model of the instantaneous space cavity is established. The Abbreviated Injury Scale (AIS) method is used to evaluate tissue and organ damage. Damage scores of the corresponding parts of the human body under blunt hit and penetrating hit are obtained based on MAIS and NISS damage assessment algorithms, respectively. Besides, mortality rate is predicted. Human susceptibility assessment software is developed to obtain a severity score of damage caused to the human body when a small-caliber bullet bluntly hits and penetrates the body wearing an body armor at different speeds. When a small-caliber bullet hits the human chest with a body armor at 638 m/s, it causes blunt damage; the human injury score is MAIS=3, NISS=27, and the mortality prediction result is 12.88%. When a small-caliber bullet hits at 714 m/s, it penetrates the body armor and directly invades human tissue; the human injury score is MAIS=5, NISS=75, and the mortality prediction result is 97%.

Dynamic Head-Neck Response to Bullet Impact and Effects of Passive Muscles on the Neck

FAN Xin, HUANG Xingyuan, CHANG Lijun, WANG Tianhao, ZHAO Yongfei, CAI Zhihua

2022, 43(9): 2200-2209. doi:10.12382/bgxb.2022.0457

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To address the threat of projectiles and fragments in a battlefield, head-neck dynamic response to bullet impact and the effects of passive neck muscles are studied. By establishing an effective helmet-head-neck finite element model, the impact of 9 mm handgun bullets is simulated to examine the human head-neck mechanical response with or without passive muscles. The results show that in the case of front impact, stress is concentrated on the frontal head bone and the lower cervical vertebrae when the neck is extended. When the front side of the intervertebral disc fails to stretch, the passive muscles on the neck relieve the extension of the head and neck, reducing the cervical spine injury. Under the effect of passive muscles, the displacement of the head's centroid is reduced by 31.38%, and the stress exerted on the junction between cervical vertebrae and intervertebral disc as well as the maximum intervertebral disc stress are relieved by 28.76%. Thus, passive muscles play an important role in protecting the body, and thus must be considered when assessing neck injuries. The results provide reference for the assessment of neck injuries and the design of neck protective equipment.

Application of Boron Carbide Ballistic Ceramics in Human Protective Equipment

WEI Rubin, DONG Bin, WANG Xiaowei, ZHANG Wenting, LIU Xin, DU Yamei, ZHAI Wen

2022, 43(9): 2210-2218. doi:10.12382/bgxb.2022.0478

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Boron carbide ceramics are characterized by high strength, high wear resistance, high hardness, and low density, thus being the most ideal material for ceramic armor. This study reviews the application progress of ballistic-resistant boron carbide ceramics that meet the need for high-performance and lightweight human protective equipment. Factors affecting the ballistic performance of boron carbide ballistic ceramics are analyzed, the advantages and disadvantages of different sintering processes compared, and the sintering aid system and ceramic toughening technology approaches summarized. Lastly, the challenges and development needs facing the application of boron carbide ballistic ceramics are analyzed.

Effects of Chamber Offset on Dynamic Response of Small-caliber Cased Telescoped Ammunition During Engraving

XU Hui, ZHANG Ruijie, JIANG Mingfei, LIU Kun, WU Zhilin

2022, 43(9): 2219-2230. doi:10.12382/bgxb.2022.0380

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To study the effects of chamber offset on the dynamic response of small-caliber cased telescoped ammunition during engraving, we use explicit dynamic methods and couple classical internal ballistic equations while considering the combined effects of the polymer projectile cap and the barrel on the projectile. A numerical simulation model of bullet-barrel interactions during the dynamic engraving process is established. The effects of the chamber offset on the centroid offset, the in-bore declination angle, and the engraving resistance of the projectile are analyzed. The design of the projectile cap structure is optimized. Using multi-parameter synchronous measurement, the attitude measurement and accuracy experiments of the projectile are carried out, and the effectiveness of the optimization is verified. The results show that, with the increase of the chamber offset, the centroid offset, the in-bore declination angle, and the engraving resistance of the projectile all increase. Yet, the accuracy of the bullet/gun system will be reduced, and the system life and safety adversely affected. By optimizing the structure of the projectile cap, the in-bore centroid offset of the projectile can be significantly reduced, and the deviation angle and maximum engraving resistance reduced. The results can provide technical support for the design and optimization of the cased telescoped ammunition and gun system.

Ablation Behavior and Microscopic Mechanism of Large-caliber Machine Gun Barrel

DOU Caihong, JIN Pengfei, CHEN Junyu, WANG Congzhen, LI Jianjun, ZHANG Cheng, ZHANG Cheng, HUANG Jinfeng

2022, 43(9): 2231-2240. doi:10.12382/bgxb.2022.0561

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In order to further explore the ablation mechanism of gun barrels, the ablation morphology and microstructure characteristics of the typical gun made of steel 30SiMn2MoV and the new developed long-life gun made of steel MPS700V were comparatively studied using scanning electron microscopy, transmission electron microscopy and other methods. Based on this, the evolution mechanism of the two ablated steel gun barrels was revealed by comparing the different ablation performances through ignition tests. The microstructure of the two ablated gun barrels showed that three different zones appeared at the crack tip, namely sulfide zone, oxide zone and matrix zone, and that molten amorphous oxides were found in the oxide zone. The thickness of the oxide zone and sulfide zone in MPS700V barrel was less than those in 30SiMn2MoV barrel. The ablation simulation experiments showed that the critical ablation pressure of MPS700V barrel with a diameter of 1-10 mm was more than 30% higher than that of 30SiMn2MoV barrel with the same size. The critical ablation pressure of the chrome-plated MPS700V sample with a diameter of 3.2 mm was more than 39% higher than that of the chrome-plated 30SiMn2MoV sample with the same size. So the anti-ablation performance of MPS700V steel is better than 30SiMn2MoV steel. It was also found that oxides and dendrites were observed both in 30SiMn2MoV steel and MPS700V steel after the ablation simulation tests, which were similar as the structure of the failed gun barrels. By comparing the microstructure, thermodynamics and kinetics characteristics of failed gun barrels and the samples under promoted ignition, it is proposed that the ablation of the gun barrels is caused by the combustion of gun steels in the micro zones on the barrel surface under high-temperature and high-pressure conditions, and the corresponding microstructure evolution model based on micro combustion is proposed.

Influence of the Material of Small-caliber Bullet Jacket on Its Motion in Hot Barrel

HUANG Chenlei, JIANG Mingfei, CHEN Li, LI Zhongxin, WU Zhilin

2022, 43(9): 2241-2251. doi:10.12382/bgxb.2021.0812

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The barrel temperature of the 95-1 automatic rifle is too high and firing dispersion is high after multiple shots are fired. Using 5.8 mm bullet as the research object, an in-bore motion model under the coupling of multiple physical fields is established and verified by firing tests. Based on the basic principle of heat transfer, the influence of different bullet jacket materials on the motion in hot barrel is studied by the finite element method. The results show that, under room temperature, the in-bore swing angle of copper jacket bullets is smaller than that of copper clad steel ones. With the increase of barrel temperature, the in-bore swing angle of copper jacket bullet increases significantly. Under the same pressure, the muzzle velocity of copper jacket bullets is lower than that of copper clad steel ones. After firing 30 and 60 rounds, copper bullet muzzle velocity decreases by 2.2 m/s and 1.8 m/s, respectively. The in-bore motion time is increased by 2.6 μs and 4.7 μs with the increase of barrel temperature. After firing 30 and 60 rounds, the muzzle velocity of copper clad steel bullets decreases by 0.7 m/s and increases by 1.4 m/s, and the in-bore motion time decreases by 1.7 μs and 0.8 μs, respectively. The research results can provide theoretical reference for the design of small-caliber ammunition.

Failure Mechanism of the Fixed Rigid Ejection Mechanism in Firearms

FANG Yichuan, WANG Yongjuan, SHA Jinlong, NI Xiaoyang, LU Xingyu

2022, 43(9): 2252-2262. doi:10.12382/bgxb.2022.0090

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Thisstudy employs the failure mode and effect analysis (FMEA) method to study the failure mechanism and mathematical modelling of fixed rigid ejection mechanism, and to obtain failure modes and influencing factors. The two main controlling factors are the ejecting speed and the relative position of the ejector and ejection opening. Adynamics model is developed and the performance parameters are obtained. The failure criteria are acquired based on failure modes. The failure boundary analysis and experimental verification of the main factors are carried out using the structural parameters of a small-caliber automatic rifle as an example. Both theoretical calculations and experimental results indicate that higher ejecting speed leads to higher reliability. Besides, a significant bidirectional boundary effect is found in ejection opening displacement,demonstrated as the under-constrained(over-constrained) effect of the ejection opening on the cartridge case and changing position of the impact point. The direct causes of case jamming failure are the inward rebound of the cartridge case and secondary impacts.

Theoretical and Experimental Study of Projectile Dynamic Engraving Resistance

XU Hui, HUANG Chenlei, WANG Xikuo, LIU Kun, LI Zhongxin, WU Zhilin

2022, 43(9): 2263-2273. doi:10.12382/bgxb.2021.0875

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The projectile's engraving process is nonlinear and transient, which affects barrel life and shooting accuracy. To reveal the mechanism of projectile/gun interaction, a dynamic engraving resistance model is developed by combining theoretical analysis, experimental study, and numerical simulation. Using explicit dynamic finite element method and Abaqus software, the dynamic engraving process of the projectile is simulated. Using the multi-parameter synchronous measurement technique, dynamic engraving experiments are carried out to verify the validity of numerical simulation. Based on the completely inelastic collision assumption, the dynamic engraving resistance model is established. The model includes the effects of material static strength, dynamic deformation resistance, and high-speed sliding friction, and is connected with projectile movement and structural parameters of the projectile/gun. Besides, results of the established model are compared with numerical simulation results, and the key factors affecting engraving resistance are analyzed. The results show that the dynamic engraving resistance first increases and then decreases. It reaches its maximum at the moment when the projectile's cylindrical part is completely engraved in the chamber throat. In addition, projectile velocity and volume change rate are two key factors that affect engraving resistance. The proposed theoretical calculation results are in good agreement with the simulation results, which verifies the accuracy of the theoretical model and provides theoretical foundation for the optimization of light weapon systems and design of barrel structures.

Gun Aiming Equivalence and Shooting Efficiency Autocorrection before Delivery

LI Ruidong, LIU Keyan, CAO Yanfeng, WANG Yongjuan

2022, 43(9): 2274-2282. doi:10.12382/bgxb.2021.0607

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A method of gun aiming equivalence and shooting efficiency autocorrection of firearms is proposed to replace the traditional pre-delivery shooting correction process mainly based on live-shot tests. Based on optical principles and an image recognition method, an equivalent space model for launching line and aiming baseline is established with factors such as matching errors considered. Based on the external ballistic characteristics and relative position errors, a mathematical model for mechanical aiming adjustment is established. Input photoelectric detection and signal exclusion processing are used to calculate the equivalent beam signal set and then obtain the calibration parameters. A set of autocorrection device and software system for shooting efficiency has been developed. Test results show that the autocorrection method is effective and feasible to meet the shooting accuracy requirements before delivery.

Human Biomechanics in Prone Position Shooting without Support

CHENG Yong, WANG Yaping, CAO Jie, WANG Xinrui

2022, 43(9): 2283-2290. doi:10.12382/bgxb.2021.0467

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Tofurther understand human biomechanicsinprone positionshooting without support, investigation is made on the interaction between human and the gun by using QBZ95. The human-gun model in prone position without supportis established by AnyBody. Muscle responsesduring shooting,time sequence at the point of muscle activation,and force characterization of joints are obtained, andthe effect of different joint angles of the armon muscle activation is analyzed.The results show thatat the action time of gunpower gas and impact time of recoil,the rhomboidmuscleon the right side is most activated.At the impact time of counter-recoil, the biceps on the right side is most activated.The agonist thatkeeps the scapula and shoulder joint stable is activatedfirst, followed by the accessory agonist.The impact on the joints is mostly exerted on the acromioclavicular joint, followed by the glenohumeral joint and the elbowjoint.When shooting with QBZ95 in the prone position, both arms should be abducted less than 30 degrees.

Principle and Method of Enhancing Grenade Power by Changing the Steel Material

WANG Shushan, ZHAO Chuan, SUN Yuhui, LIU Dongqi, ZHANG Xuejun, WANG Guangzhi

2022, 43(9): 2291-2299. doi:10.12382/bgxb.2022.0131

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This study investigates the principle and method of enhancing the power of natural fragmentation projectiles (warheads) such as grenades through changing the steel material, providing theoretical and technical support for the innovation, development, and application of shell materials. Through theoretical deduction and experimental study, the principle and method are developed-to improve power by adjusting the grain size d and the scale parameter μ of the steel. Based on this, two new steel materials for projectiles, 40SiMn2X and 50SiMnX, are produced, and a 122 mm grenade projectile structure is selected for tests. Static explosive power tests are conducted using standard shell material 50SiMnVB and two new materials for comparison. The results show that the principle and method of enhancing grenade power by changing steel material are scientific, reasonable, and practical. The new shell steel 40SiMn2X and 50SiMnX exhibit excellent mechanical properties, and have increased the radius of power for light armored vehicles and personnel targets by 31.6% and 12.3%, respectively. Both two materials have achieved progress in applications against both targets, showing important application value.

Gradient Design of Segmented Rod Projectile

YU Zheng, WANG Shu, DONG Fangdong, ZHENG Zhijun, CUI Shitang, ZHANG Yongliang

2022, 43(9): 2300-2306. doi:10.12382/bgxb.2022.0460

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In order to give full play to the penetration efficiency of segmented rod projectile, the LS-DYNA software Lagrangian algorithm was used to simulate the penetration of tungsten alloy long rod projectile into armored steel. The typical physical images of long rod penetration and the time history curves of important physical quantities were obtained, which verifies the effectiveness of the finite element model. Two kinds of segmented rods with length gradient distribution and diameter gradient distribution are constructed, and their penetration efficiency was compared. The results show that when the total effective length of the segmented rod projectile is fixed, the length of each segment is uniform and equal, and the penetration ability of the segmentation rod is the greatest; The penetration depth of segmented rod with diameter gradient distribution in each segment is greater than that of the segmented rod with length gradient distribution in each segment.

Fragmentation Characteristics of 12.7mm Armor-piercing Incendiary Projectile and Ceramic/Metal Composite Target DuringPenetration

YU Yilei, WANG Xiaodong, REN Wenke, MA Minghui, JIANG Zhaoxiu, GAO Guangfa

2022, 43(9): 2307-2317. doi:10.12382/bgxb.2021.0497

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Ballistic impact tests are conducted using 12.7 mm AP and ceramic/metal composite armor with different ceramic materials. The relationship between different ceramic materials and the main failure characteristics of the recovered projectile core and ceramics is analyzed by observing the macro failure characteristics. A multistage screening and weighing of fragments of the projectile core and target with different ceramic materials is carried out to analyze the size distribution of the fragments. The results show that fracture toughness has obvious effects on the fracture morphology and particle size distribution of both the ceramics and the projectile. As the fracture toughness of ceramics increases, the mass of small fragments decreases, the mass of large fragments increases, and the degree of breakage decreases. In addition, radial cracks decrease with the increase in the fracture cone angle of the ceramic, leading to an increase in the overall volume of the ceramic cone as well as in the percentage of the fragmented area. The ceramic fragments are mostly large particle sizes. The overall broken scale of the ceramic cone increases, and the broken degree decreases. The size distribution of fragments in the projectile and ceramic cone meets the Rosin-Rammler distribution model. As for the fragmentation of the projectile, larger fragments are mainly caused by the compression shear fracture and tensile fracture due to stress unloading, while smaller fragmentation only occurs at the nose of the projectile, mostly due to the interaction between the microcracks generated by stress waves and the intergranular cracks induced by the impact. The main failure characteristics of the ceramic panel are radial cracks and ceramic cones.

Ballistic Performance of Ceramic/Metal Composite Armor Systems with Different Thickness Ratios

SI Peng, BAI Fan, LIU Yan, YAN Junbo, HUANG Fenglei

2022, 43(9): 2318-2329. doi:10.12382/bgxb.2021.0844

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The ballistic performance of ceramic armor systems with different structures is studied to optimize the structural design of the armor. The FEM-SPH coupling calculation model is verified through ballistic experiments and numerical simulations. The process of a long-rod projectile impacting a ceramic-metal composite armor is then simulated, and the influence of different thickness ratios of ceramic to the metal back plate on interface breakdown analyzed. The results show two main protective mechanisms of the ceramic composite armor. When the projectile velocity's is less than 1 000 m/s and the ceramic thickness is increased from 15 mm to 25 mm for a bi-layer ceramic composite armor with a total thickness of 30 mm, the dwell time of the composite armor would be more than doubled, and the maximum energy consumption of the projectile body can reach 50%. When the velocity of the projectile exceeds 1 000 m/s, the energy consumption is dominant in the penetration phase, and the maximum energy absorption during penetration is 85%. When the composite armor has a metal to ceramic thickness ratio of 2∶1, the missile body stays longer on the interface and achieves a relatively high ballistic protection efficiency. Our results can be used as a reference for the design of armor structures.

High-density Alloy Selection Criteria for Liners of Explosively Formed Projectiles

FU Heng, JIANG Jianwei, WANG Shuyou, MEN Jianbing, LI Mei

2022, 43(9): 2330-2338. doi:10.12382/bgxb.2021.0826

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To solve the problem of fragmentation failure of high-density alloys in explosively formed projectiles (EFPs), explosive loading tests are conducted on flyer plates of tungsten-nickel alloy with different tungsten contents. Based on the analysis of forming performance and failure mechanism of the tested materials, as well as common characteristics of traditional liner materials, the selection criteria for high-density alloy material for EFP liner are proposed. The criteria are verified by explosive loading forming and penetration tests. According to the results, the reason why tungsten-nickel alloy can hardly form a complete projectile is that, in the matrix, tungsten particles in the second phase can lead to dislocation accumulation at the phase boundary under large deformation state. This will cause inevitable stress concentration and result in material fracture through nucleation and microcrack growth. Thus, high-density alloy selected for manufacturing EFP liners should possess a single-phase structure of complete solid solution. And the solvent metal must have a ductile-brittle transition temperature lower than the temperature of the service environment if it has a non-face-centered cubic structure. Both the flyer plate and the liner made of the single-phase solid solution alloy selected in accordance with the above criterion can form complete penetrators. The experimental results are consistent with the expected results. Our research results can be used as the reference for the design, selection, and application of high-density alloys for EFP liners.

Numerical Simulation of the Penetration of M855A1 EPR into Steel Targets

WANG Jirui, LIU Conghe, FAN Junling, JIAO Ting, GONG Jianpo, HAN Xiao

2022, 43(9): 2339-2349. doi:10.12382/bgxb.2022.0448

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M855A1 is a small-calibre high-velocity rifle bullet with the structure of the new type of small-and medium-calibre armour-piercing projectile. Compare to its predecessor, M855/SS109, M855A1 has enhanced penetration performance against hard targets and lethality against soft targets. To study the penetration performance of the new 5.56 mm M855A1, numerical simulations of the process of M855A1 penetrating structural steel target and armoured steel target at different ranges were carried out using the finite element software ANSYS/LS-DYNA. The deformation and damage evolution of the round and steel target during penetration were analysed, and the relationship between range and maximum penetration thickness was fitted as a function, with a fitting accuracy higher than 99%. The results showed that the M855A1 round can meet the demand for penetration performance against hard targets of modern high velocity small-calibre rifle bullets, and its structure is more efficient in utilising the kinetic energy of the round under low-velocity and thin-target conditions.

Kinematic Model of Penetration of Rigid Fragments into UHMWPE Laminates

DONG Fangdong, YANG Geng, WANG Shu, WANG Zhijun, FENG Zhiwei

2022, 43(9): 2350-2359. doi:10.12382/bgxb.2022.0552

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To reveal the interaction mechanism between the killing element and UHMWPE laminates, the ballistic test of cemented carbide fragments penetrating UHMWPE laminates was carried out. The residual velocity of the fragments after penetrating the laminates at different incident velocities and the fracture failure morphology of the laminates were obtained. Then based on the wave theory and energy conservation, the energy dissipation model of rigid fragments penetrating into the laminates was established, and the transfer laws of energy in different forms during fragment penetration were analyzed. It is found that the energy transfer caused by shear failure, and tensile and compression deformation of the laminates in the penetration process is dominant in various forms of dissipated energy. The comparison with the experimental results shows that the proposed model can effectively describe the penetration process of the fragment into the laminates, which can provide some insights into the killing mechanism of the protected target and trajectory design.

Numerical Simulation of Penetration Resistance of Kevlar and Ceramic Composite Structures

WANG Xiaodong, XU Yongjie, DONG Fangdong, WANG Hao, ZHENG Nana

2022, 43(9): 2360-2366. doi:10.12382/bgxb.2022.0447

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To evaluate the effects of Kevlar-129 and alumina (Al₂O₃) ceramic composite armor on the anti-penetration performance, a flat-head projectile model penetrating the composite armored unit is established. During the numerical simulation of penetration, by changing the speed of the penetrator and structure of the composite armor, the speed change curve of the penetrator at different speeds is obtained. The speed of the penetrator after penetrating the composite armor at different speeds and the capacity of absorbing kinetic energy are analyzed. The results show that the composite structure combining Kevlar and Al₂O₃ ceramics can better resist penetration, and the position of the Kevlar interlayer has a great influence on the penetration resistance performance, which provides technical reference for the design of lightweight composite armor plates in the future.

Characteristics of Underwater Explosion of the Shock Wave Loads Transfer in the Gas Turbine Structure

YAO Xiongliang, XIONG Banghu, WANG Zhikai, YANG Nana, ZHANG Wenqi, WAN Zechen

2022, 43(9): 2367-2378. doi:10.12382/bgxb.2022.0466

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In order to study the characteristics of the shock wave loads induced damage to the gas turbine structure in an underwater explosion, the transfer law of the shock wave loads of the underwater explosion in the main structure of the gas turbine was investigated, and the load transfer prediction was made for the gas turbine through the equivalent mechanical model. For the finite element simulation acceleration signals measured on the transfer path in the gas turbine, the empirical mode decomposition method and the corresponding Hilbert Huang transform were used to analyze the time-frequency domain and energy distribution of the signals. The results showed that: for the underwater explosion induced shock wave loads, the frequency information and load intensity can be obtained by the Hilbert-Huang transform and empirical mode decomposition method; the shock wave energy along the transfer path in the gas turbine varies with the load; as the transfer distance increases, the proportion of high-frequency energy decreases, which corresponds to the stress response of the gas turbine; at the same time, the mechanical model of the gas turbine can predict the load transfer of the gas turbine. The findings of this study could provide insights into the protection of the gas turbine against impact.

PSO-LSSVM-Based Ammunition Assembly Quality Prediction Method

QIU Jiarong, ZENG Pengfei, SHAO Weiping, ZHAO Lijun, HAO Yongping

2022, 43(9): 2379-2387. doi:10.12382/bgxb.2021.0867

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Based on particle swarm optimization (PSO)-least squares support vector machines (LSSVM), an ammunition assembly quality prediction method is proposed to address the problems of complex ammunition assembly process, existence of various influencing factors for the assembly process quality, and low assembly efficiency. Through gray entropy correlation analysis, key quality characteristics affecting the ammunition assembly quality are extracted and used as the input vectors of the prediction model to reduce the complexity and calculation workload. Using PSO-LSSVM as the modeling tool, the parameters of LSSVM are optimized by the PSO algorithm, and a prediction model is developed for ammunition assembly quality. Taking the prediction of runout during the docking assembly of a certain type of ammunition as an example, the model is compared with LSSVM model and Back-Propagation (BP) neural network prediction model. The experimental results demonstrate that the proposed PSO-LSSVM-based prediction method for ammunition assembly quality is feasible and effective, which can accurately predict the quality of ammunition assembly.

Study on Interior Ballistic Characteristics of Cased Telescoped Ammunition with Dynamic Impact Engraving Considered

CHANG Renjiu, XUE Xiaochun, YU Yonggang

2022, 43(9): 2388-2398. doi:10.12382/bgxb.2021.0519

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To accurately predict the interior ballistic characteristics of telescoped ammunitions，the deformation，failure mode，and groove formation mechanism of the nylon cartridge belt during the dynamic impact engraving process of the telescoped ammunition are studied. A three-dimensional finite element model considering the complex structure of the engraving system and the dynamic impact characteristics of the telescoped projectile is established by using LS-DYNA software，and simulation is performed.On this basis，considering the new principle of two-stage ignition and programmed combustion of the ammunition，an integrated model for the initial interior ballistics of the ammunition during and after engraving is also established. The numerical results are compared with the experimental results.The results show that the fracture failure mode of the belt material under the action of rifling is mainly shear failure，and the engraving process can be divided into two stages. The belt material is deformed significantly due to the extrusion of rifling during both stages，so the corresponding extrusion resistance is also evident. Eventually，the dynamic impact extrusion resistance of the projectile is expressed by fitting. The results of the model are in good agreement with the test results，verifying the accuracy of the model and providing a useful reference for the design of the charge structures of such novel ammunition.

Study of Traumatic Ballistic Characteristics of Ultra-high Speed Steel Balls Striking Soap and Biological Targets

LI Guanghua, ZHANG Liangchao, WENG Changmei, ZHANG Dongdong, ZHANG Jieyuan, CHEN Kuijun, DUAN Chaoxia, KANG Jianyi, WANG Jianmin

2022, 43(9): 2399-2407. doi:10.12382/bgxb.2022.0536

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By comparing the traumatic ballistic performance of different velocities steel balls striking soap targets and biological targets, the similarities and differences of dynamic responses between the two under hypervelocity fragmentation strikes were explored. A 0.72 g steel ball with different velocities (1 000 m/s, 2 000 m/s, 3 000 m/s, 4 000 m/s) was used to strike the soap target and the hind limb muscle fullness of experimental animals, respectively. The ballistic manifestations of the targets were observed after the strikes, including the size of the entrance and exit, the shape and size of the wound cavity, the extent of injury and the degree of injury in the experimental animals. From 1 000 m/s to 4 000 m/s, the ballistic entrance became larger as the velocity of the steel ball increased. And the ballistic exit gradually increased from 1 000 m/s to 3 000 m/s. At 4 000 m/s velocity, the projectile failed to penetrate the soft tissue, forming a hemispherical wound cavity. The steel ball striking the soap at 1 000 m/s formed a 5 cm diameter entrance and 0.6 cm size exit cone; the steel ball striking the soap at 2 000 m/s formed a 16 cm diameter entrance and 3 cm size exit cone. 4 000 m/s speed striking the soap formed a 25 cm×25 cm×17 cm spherical crater, which did not penetrate the soap. The diameters of the profile projections on different wound depths of the animal transient cavity, animal wound cavity and soap cavity were measured from the ballistic entrance as the starting point at a spacing of 1 cm, respectively. Comparison of the profile diameter change curves under steel ball strikes at the same speed revealed that the profile diameters of the soap cavity and the animal transient cavity were similar at different wound depths of 5 cm to 10 cm at different speeds. Under the ultra-high speed steel ball strike, the cavity formed by the soap target and the transient cavity formed by the biological target at the front end of the wound channel were similar in size. The soap target can reflect the biocidal effect of the hypervelocity steel ball to some extent.

Global Sensitivity Analysis of Bullet's Angular Velocity Based on Sobol and EFAST Method

WEI Wei, ZHANG Jingwen, CHANG Sijiang, WANG Haosheng, WANG Jianzhong

2022, 43(9): 2408-2416. doi:10.12382/bgxb.2022.0546

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For the needs of conducting exterior ballistic tests or studying flight dynamics, various devices for flight state measurement are often installed outside the bullets. Due to the interference of various random factors in the shooting and flight of bullets, the output of bullet borne measurement device is directly affected. In order to better design the experiment and process related data, this paper adopts the scheme of measuring the angular velocity of the bullet with the attitude measurement device. Using the five-degree-of-freedom rigid body trajectory equations, Sobol's method based on Monte Carlo method for target practice and Extended Fourier amplitude sensitivity test method (EFAST) is used to analyze the influence of the output of attitude measurement on the sensitivity of initial velocity fluctuation, initial disturbance and other factors. The results of quantitative analysis show that: (1) The initial velocity and initial angle of attack have a great influence on the radial output of the attitude measurement device along the bullet body, and the initial velocity can significantly influence the axial output of the attitude measurement device; (2) Both Sobol's method and the EFAST method can quantitatively analyze the contribution rate of parameters to output variables. However, EFAST is more robust and efficient.

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