Defence Technology(防务技术)最新文献_第2页

A tensile wearable SHF antenna with efficient communication in defense beacon technology 在国防信标技术中实现高效通信的拉伸可穿戴式 SHF 天线

IF 5 Q1 ENGINEERING, MULTIDISCIPLINARY

Defence Technology(防务技术)

Pub Date : 2024-11-01 DOI: 10.1016/j.dt.2024.05.005

Pooja Naresh Bhatt , Rashmi Pandhare

The study projects a flexible and compact wearable pear-shaped Super High Frequency (SHF) antenna that can provide detailed location recognition and tracking applicable to defense beacon technology. This mini aperture with electrical dimensions of 0.12λ₀ × 0.22λ₀ × 0.01λ₀ attains a vast bandwidth over 3.1–34.5 GHz Super High Frequency (SHF) frequency band at S₁₁ ≤ −10 dB, peak gain of 7.14 dBi and proportionately homogeneous radiation pattern. The fractional bandwidth (% BW) acquired is 168% that envelopes diversified frequency spectrum inclusive of X band specifically targeted to all kinds of defense and military operations. The proposed antenna can be worn on a soldier's uniform and hence the Specific Absorption Rate simulation is accomplished. The Peak SAR Value over 1 g of tissue is 1.48 W/kg and for 10 g of tissue is 0.27 W/kg well under the safety standards. The flexibility is proven by analyzing the full electromagnetic simulations for various bending conditions. Time response analysis is attained with its Fidelity Factor and Group Delay. Communication excellence is determined using Link Budget Analysis and it is seen that margin at 100 Mbps is 62 m and at 200 Mbps is 59 m. Prototype is fabricated along with experimental validation. All the results show harmony in shaping the antenna to provide critical situational awareness and data sharing capabilities required in defense beacon technology for location identification.

该研究预测了一种灵活紧凑的可穿戴梨形超高频（SHF）天线，可提供适用于国防信标技术的详细位置识别和跟踪。这种微型孔径的电气尺寸为 0.12λ0 × 0.22λ0 × 0.01λ0，可在 3.1-34.5 GHz 超高频（SHF）频段上获得巨大的带宽，S11 ≤ -10 dB，峰值增益为 7.14 dBi，辐射模式比例均匀。获得的分数带宽（% BW）为 168%，可覆盖包括 X 波段在内的多样化频谱，专门针对各种国防和军事行动。拟议的天线可以佩戴在士兵的制服上，因此可以完成比吸收率模拟。1 克组织的峰值 SAR 值为 1.48 W/kg，10 克组织的峰值 SAR 值为 0.27 W/kg，远低于安全标准。通过分析各种弯曲条件下的全电磁模拟，证明了其灵活性。通过保真系数和群延迟进行时间响应分析。利用链路预算分析确定了通信性能的优劣，100 Mbps 的裕度为 62 米，200 Mbps 的裕度为 59 米。所有结果表明，该天线的形状与国防信标识别技术所需的关键态势感知和数据共享功能相吻合。

{"title":"A tensile wearable SHF antenna with efficient communication in defense beacon technology","authors":"Pooja Naresh Bhatt , Rashmi Pandhare","doi":"10.1016/j.dt.2024.05.005","DOIUrl":"10.1016/j.dt.2024.05.005","url":null,"abstract":"<div><div>The study projects a flexible and compact wearable pear-shaped Super High Frequency (SHF) antenna that can provide detailed location recognition and tracking applicable to defense beacon technology. This mini aperture with electrical dimensions of 0.12<em>λ</em><sub>0</sub> × 0.22<em>λ</em><sub>0</sub> × 0.01<em>λ</em><sub>0</sub> attains a vast bandwidth over 3.1–34.5 GHz Super High Frequency (SHF) frequency band at S<sub>11</sub> ≤ −10 dB, peak gain of 7.14 dBi and proportionately homogeneous radiation pattern. The fractional bandwidth (% BW) acquired is 168% that envelopes diversified frequency spectrum inclusive of X band specifically targeted to all kinds of defense and military operations. The proposed antenna can be worn on a soldier's uniform and hence the Specific Absorption Rate simulation is accomplished. The Peak SAR Value over 1 g of tissue is 1.48 W/kg and for 10 g of tissue is 0.27 W/kg well under the safety standards. The flexibility is proven by analyzing the full electromagnetic simulations for various bending conditions. Time response analysis is attained with its Fidelity Factor and Group Delay. Communication excellence is determined using Link Budget Analysis and it is seen that margin at 100 Mbps is 62 m and at 200 Mbps is 59 m. Prototype is fabricated along with experimental validation. All the results show harmony in shaping the antenna to provide critical situational awareness and data sharing capabilities required in defense beacon technology for location identification.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"41 ","pages":"Pages 198-210"},"PeriodicalIF":5.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141032947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of silica fume and glass powder for enhanced impact resistance in GGBFS-based ultra high-performance geopolymer fibrous concrete: An experimental and statistical analysis 硅灰和玻璃粉对增强基于 GGBFS 的超高性能土工聚合物纤维混凝土抗冲击性的影响：实验和统计分析

IF 5 Q1 ENGINEERING, MULTIDISCIPLINARY

Defence Technology(防务技术)

Pub Date : 2024-11-01 DOI: 10.1016/j.dt.2024.05.015

G. Murali , Anoop Kallamalayil Nassar , Madhumitha Swaminathan , Parthiban Kathirvel , Leong Sing Wong

Solid waste recycling is an economically sound strategy for preserving the environment, safeguarding natural resources, and diminishing the reliance on raw material consumption. Geopolymer technology offers a significant advantage by enabling the reuse and recycling of diverse materials. This research assesses how including silica fume and glass powder enhances the impact resistance of ultra-high-performance geopolymer concrete (UHPGC). In total, 18 distinct mixtures were formulated by substituting ground granulated blast furnace slag with varying proportions of silica fume and glass powder, ranging from 10% to 40%. Similarly, for each of the mixtures above, steel fibre was added at a dosage of 1.5% to address the inherent brittleness of UHPGC. The mixtures were activated by combining sodium hydroxide and sodium silicate solution to generate geopolymer binders. The specimens were subjected to drop-weight impact testing, wherein an examination was carried out to evaluate various parameters, including flowability, density at fresh and hardened state, compressive strength, impact numbers indicative of cracking and failure occurrences, ductility index, and analysis of failure modes. Additionally, the variations in the impact test outcomes were analyzed using the Weibull distribution, and the findings corresponding to survival probability were offered. Furthermore, the microstructure of UHPGC was scrutinized through scanning electron microscopy. Findings reveal that the specimens incorporating glass powder exhibited lower cracking impact number values than those utilizing silica fume, with reductions ranging from 18.63% to 34.31%. Similarly, failure impact number values decreased from 8.26% to 28.46% across glass powder contents. The maximum compressive and impact strength was recorded in UHPGC, comprising 10% silica fume with fibres.

固体废物回收利用是一项经济合理的战略，有利于保护环境、保护自然资源和减少对原材料消耗的依赖。土工聚合物技术可实现多种材料的再利用和再循环，具有显著优势。本研究评估了硅灰和玻璃粉如何增强超高性能土工聚合物混凝土（UHPGC）的抗冲击性。通过用不同比例的硅灰和玻璃粉（10% 至 40%）替代磨细高炉矿渣，共配制出 18 种不同的混合物。同样，针对 UHPGC 固有的脆性，上述每种混合物都添加了 1.5% 的钢纤维。混合物通过氢氧化钠和硅酸钠溶液进行活化，生成土工聚合物粘结剂。对试样进行落重冲击试验，以评估各种参数，包括流动性、新鲜和硬化状态下的密度、抗压强度、表明开裂和失效发生的冲击次数、延展性指数和失效模式分析。此外，还利用威布尔分布分析了冲击试验结果的变化，并提供了与存活概率相对应的结论。此外，还通过扫描电子显微镜仔细观察了 UHPGC 的微观结构。研究结果表明，与使用硅灰的试样相比，使用玻璃粉的试样显示出较低的开裂冲击数值，降低幅度为 18.63% 至 34.31%。同样，不同玻璃粉含量的破坏冲击数值也从 8.26% 降至 28.46%。含有 10%硅灰和纤维的 UHPGC 的抗压强度和冲击强度最大。

{"title":"Effect of silica fume and glass powder for enhanced impact resistance in GGBFS-based ultra high-performance geopolymer fibrous concrete: An experimental and statistical analysis","authors":"G. Murali , Anoop Kallamalayil Nassar , Madhumitha Swaminathan , Parthiban Kathirvel , Leong Sing Wong","doi":"10.1016/j.dt.2024.05.015","DOIUrl":"10.1016/j.dt.2024.05.015","url":null,"abstract":"<div><div>Solid waste recycling is an economically sound strategy for preserving the environment, safeguarding natural resources, and diminishing the reliance on raw material consumption. Geopolymer technology offers a significant advantage by enabling the reuse and recycling of diverse materials. This research assesses how including silica fume and glass powder enhances the impact resistance of ultra-high-performance geopolymer concrete (UHPGC). In total, 18 distinct mixtures were formulated by substituting ground granulated blast furnace slag with varying proportions of silica fume and glass powder, ranging from 10% to 40%. Similarly, for each of the mixtures above, steel fibre was added at a dosage of 1.5% to address the inherent brittleness of UHPGC. The mixtures were activated by combining sodium hydroxide and sodium silicate solution to generate geopolymer binders. The specimens were subjected to drop-weight impact testing, wherein an examination was carried out to evaluate various parameters, including flowability, density at fresh and hardened state, compressive strength, impact numbers indicative of cracking and failure occurrences, ductility index, and analysis of failure modes. Additionally, the variations in the impact test outcomes were analyzed using the Weibull distribution, and the findings corresponding to survival probability were offered. Furthermore, the microstructure of UHPGC was scrutinized through scanning electron microscopy. Findings reveal that the specimens incorporating glass powder exhibited lower cracking impact number values than those utilizing silica fume, with reductions ranging from 18.63% to 34.31%. Similarly, failure impact number values decreased from 8.26% to 28.46% across glass powder contents. The maximum compressive and impact strength was recorded in UHPGC, comprising 10% silica fume with fibres.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"41 ","pages":"Pages 59-81"},"PeriodicalIF":5.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141508136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Properties of high cis-1,4 content hydroxyl-terminated polybutadiene and its application in composite solid propellants 高顺式-1,4 含量羟基封端聚丁二烯的性能及其在复合固体推进剂中的应用

IF 5 Q1 ENGINEERING, MULTIDISCIPLINARY

Defence Technology(防务技术)

Pub Date : 2024-10-01 DOI: 10.1016/j.dt.2024.04.014

In this paper, high cis-1,4 content hydroxyl-terminated polybutadiene (cis-HTPB) with different molecular weights was prepared through the oxidative cracking process using cis-butadiene rubber as raw material. Firstly, this article comprehensively compared the differences between cis-HTPB and conventional I-HTPB in terms of molecular weight distribution, functionality, viscosity, molecular polarity, and other physicochemical properties, which provided effective data support for its subsequent application. In addition, the reaction kinetics study showed that cis-HTPB with isocyanate curing agent has high reactivity, allowing it to be rapidly cured at low temperatures, and the cured elastomers had excellent mechanical properties, with tensile strength and elongation up to 1.89 MPa and 1100%, respectively. It was also found that cis-HTPB has extremely excellent low-temperature resistance, and the glass transition temperature (T_g) of its cured elastomer is as low as −101 °C. Based on the above studies, cis-HTPB is applied as a binder in composite solid propellants for the first time to investigate its practical performance, and the results indicated that cis-HTPB-based propellants have excellent process and mechanical properties.

本文以顺丁橡胶为原料，通过氧化裂解工艺制备了不同分子量的高顺式-1,4 含羟基封端聚丁二烯（顺式-HTPB）。首先，本文全面比较了顺式-HTPB 与传统 I-HTPB 在分子量分布、官能度、粘度、分子极性等理化性质方面的差异，为其后续应用提供了有效的数据支持。此外，反应动力学研究表明，顺式-HTPB 与异氰酸酯固化剂的反应活性高，可在低温下快速固化，固化后的弹性体具有优异的机械性能，拉伸强度和伸长率分别高达 1.89 兆帕和 1100%。研究还发现，顺式-HTPB 具有极其优异的耐低温性能，其固化弹性体的玻璃化转变温度（Tg）低至 -101 ℃。在上述研究的基础上，首次将顺式-HTPB 用作复合固体推进剂的粘合剂，研究其实用性能，结果表明顺式-HTPB 基推进剂具有优异的工艺性能和机械性能。

{"title":"Properties of high cis-1,4 content hydroxyl-terminated polybutadiene and its application in composite solid propellants","authors":"","doi":"10.1016/j.dt.2024.04.014","DOIUrl":"10.1016/j.dt.2024.04.014","url":null,"abstract":"<div><div>In this paper, high <em>cis</em>-1,4 content hydroxyl-terminated polybutadiene (<em>cis</em>-HTPB) with different molecular weights was prepared through the oxidative cracking process using <em>cis</em>-butadiene rubber as raw material. Firstly, this article comprehensively compared the differences between <em>cis</em>-HTPB and conventional I-HTPB in terms of molecular weight distribution, functionality, viscosity, molecular polarity, and other physicochemical properties, which provided effective data support for its subsequent application. In addition, the reaction kinetics study showed that <em>cis</em>-HTPB with isocyanate curing agent has high reactivity, allowing it to be rapidly cured at low temperatures, and the cured elastomers had excellent mechanical properties, with tensile strength and elongation up to 1.89 MPa and 1100%, respectively. It was also found that <em>cis</em>-HTPB has extremely excellent low-temperature resistance, and the glass transition temperature (<em>T</em><sub>g</sub>) of its cured elastomer is as low as −101 °C. Based on the above studies, <em>cis</em>-HTPB is applied as a binder in composite solid propellants for the first time to investigate its practical performance, and the results indicated that <em>cis</em>-HTPB-based propellants have excellent process and mechanical properties.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"40 ","pages":"Pages 199-209"},"PeriodicalIF":5.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140765286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A novel framework to intercept GPS-denied, bomb-carrying, non-military, kamikaze drones: Towards protecting critical infrastructures 拦截不使用 GPS、携带炸弹的非军事神风特攻队无人机的新型框架：保护关键基础设施

IF 5 Q1 ENGINEERING, MULTIDISCIPLINARY

Defence Technology(防务技术)

Pub Date : 2024-10-01 DOI: 10.1016/j.dt.2024.05.001

Protection of urban critical infrastructures (CIs) from GPS-denied, bomb-carrying kamikaze drones (G-B-KDs) is very challenging. Previous approaches based on drone jamming, spoofing, communication interruption and hijacking cannot be applied in the case under examination, since G-B-KDs are uncontrolled. On the other hand, drone capturing schemes and electromagnetic pulse (EMP) weapons seem to be effective. However, again, existing approaches present various limitations, while most of them do not examine the case of G-B-KDs. This paper, focuses on the aforementioned under-researched field, where the G-B-KD is confronted by two defensive drones. The first neutralizes and captures the kamikaze drone, while the second captures the bomb. Both defensive drones are equipped with a net-gun and an innovative algorithm, which, among others, estimates the locations of interception, using a real-world trajectory model. Additionally, one of the defensive drones is also equipped with an EMP weapon to damage the electronics equipment of the kamikaze drone and reduce the capturing time and the overall risk. Extensive simulated experiments and comparisons to state-of-art methods, reveal the advantages and limitations of the proposed approach. More specifically, compared to state-of-art, the proposed approach improves: (a) time to neutralize the target by at least 6.89%, (b) maximum number of missions by at least 1.27% and (c) total cost by at least 5.15%.

保护城市关键基础设施（CIs）免受全球定位系统失效、携带炸弹的神风特攻队无人机（G-B-KDs）的攻击非常具有挑战性。以往基于无人机干扰、欺骗、通信中断和劫持的方法无法应用于本案例，因为 G-B-KD 不受控制。另一方面，无人机捕获方案和电磁脉冲（EMP）武器似乎是有效的。然而，现有方法同样存在各种局限性，而且大多数方法都没有研究 G-B-KDs 的情况。本文重点关注上述研究不足的领域，即 G-B-KD 与两架防御型无人机的对抗。第一架无人机将神风特攻队无人机化解并捕获，而第二架无人机则捕获炸弹。两架防御型无人机都配备了网炮和创新算法，其中包括利用真实世界的轨迹模型估算拦截位置。此外，其中一架防御型无人机还配备了电磁脉冲武器，以破坏神风特攻队无人机的电子设备，减少捕获时间和总体风险。广泛的模拟实验以及与最先进方法的比较揭示了所提方法的优势和局限性。更具体地说，与最先进的方法相比，建议的方法在以下方面有所改进：（a）使目标失效的时间至少缩短了 6.89%；（b）最大任务次数至少减少了 1.27%；（c）总成本至少减少了 5.15%。

{"title":"A novel framework to intercept GPS-denied, bomb-carrying, non-military, kamikaze drones: Towards protecting critical infrastructures","authors":"","doi":"10.1016/j.dt.2024.05.001","DOIUrl":"10.1016/j.dt.2024.05.001","url":null,"abstract":"<div><div>Protection of urban critical infrastructures (CIs) from GPS-denied, bomb-carrying kamikaze drones (G-B-KDs) is very challenging. Previous approaches based on drone jamming, spoofing, communication interruption and hijacking cannot be applied in the case under examination, since G-B-KDs are uncontrolled. On the other hand, drone capturing schemes and electromagnetic pulse (EMP) weapons seem to be effective. However, again, existing approaches present various limitations, while most of them do not examine the case of G-B-KDs. This paper, focuses on the aforementioned under-researched field, where the G-B-KD is confronted by two defensive drones. The first neutralizes and captures the kamikaze drone, while the second captures the bomb. Both defensive drones are equipped with a net-gun and an innovative algorithm, which, among others, estimates the locations of interception, using a real-world trajectory model. Additionally, one of the defensive drones is also equipped with an EMP weapon to damage the electronics equipment of the kamikaze drone and reduce the capturing time and the overall risk. Extensive simulated experiments and comparisons to state-of-art methods, reveal the advantages and limitations of the proposed approach. More specifically, compared to state-of-art, the proposed approach improves: (a) time to neutralize the target by at least 6.89%, (b) maximum number of missions by at least 1.27% and (c) total cost by at least 5.15%.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"40 ","pages":"Pages 225-241"},"PeriodicalIF":5.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141038220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Research status and challenges in the manufacturing of IR conformal optics 红外保偏光学器件制造的研究现状与挑战

IF 5 Q1 ENGINEERING, MULTIDISCIPLINARY

Defence Technology(防务技术)

Pub Date : 2024-10-01 DOI: 10.1016/j.dt.2024.04.015

The infrared conformal window is one of the most critical components in aircraft. Conformal windows with high performance bring low aberrations, high aerodynamic performance, reliability in extreme working environments, and added value for aircraft. Through the past decades, remarkable advances have been achieved in manufacturing technologies for conformal windows, where the machining accuracy approaches the nanometer level, and the surface form becomes more complex. These advances are critical to aircraft development, and these manufacturing technologies also have significant reference values for other directions of the ultra-precision machining field. In this review, the infrared materials suitable for manufacturing conformal windows are introduced and compared with insights into their performances. The remarkable advances and concrete work accomplished by researchers are reviewed. The challenges in manufacturing conformal windows that should be faced in the future are discussed.

红外保形窗是飞机上最关键的部件之一。高性能的保形窗具有低像差、高气动性能、在极端工作环境下的可靠性，并能为飞机带来附加值。过去几十年来，保形窗制造技术取得了显著进步，加工精度接近纳米级，表面形状也变得更加复杂。这些进步对飞机的发展至关重要，同时这些制造技术也对超精密加工领域的其他方向具有重要的参考价值。本综述介绍了适用于制造保形窗的红外材料，并比较了这些材料的性能。此外，还回顾了研究人员取得的重大进展和完成的具体工作。还讨论了未来在制造保形窗方面应面临的挑战。

引用次数: 0

Comparative impact behaviours of ultra high performance concrete columns reinforced with polypropylene vs steel fibres 用聚丙烯纤维和钢纤维加固的超高性能混凝土柱的冲击行为比较

IF 5 Q1 ENGINEERING, MULTIDISCIPLINARY

Defence Technology(防务技术)

Pub Date : 2024-10-01 DOI: 10.1016/j.dt.2024.04.016

Polypropylene (PP) fibres have primarily used to control shrinkage cracks or mitigate explosive spalling in concrete structures exposed to fire or subjected to impact/blast loads, with limited investigations on capacity improvement. This study unveils the possibility of using PP micro-fibres to improve the impact behaviour of fibre-reinforced ultra-high-performance concrete (FRUHPC) columns. Results show that the addition of fibres significantly improves the impact behaviour of FRUHPC columns by shifting the failure mechanism from brittle shear to favourable flexural failure. The addition of steel or PP fibres affected the impact responses differently. Steel fibres considerably increased the peak impact force (up to 18%) while PP micro-fibres slightly increased the peak (3%–4%). FRUHPC significantly reduced the maximum mid-height displacement by up to 30% (under 20° impact) and substantially improved the displacement recovery by up to 100% (under 20° impact). FRUHPC with steel fibres significantly improved the energy absorption while those with PP micro-fibres reduced the energy absorption, which is different from the effect of PP-macro fibre reported in the literature. The optimal fibre content for micro-PP fibres is 1% due to its minimal fibre usage and low peak and residual displacement. This study highlights the potential of FRUHPC as a promising material for impact-resistant structures by creating a more favourable flexural failure mechanism, enhancing ductility and toughness under impact loading, and advancing the understanding of the role of fibres in structural performance.

聚丙烯（PP）纤维主要用于控制受火或受冲击/爆破载荷的混凝土结构中的收缩裂缝或减轻爆炸剥落，但对提高承载能力的研究有限。本研究揭示了使用聚丙烯微纤维改善纤维增强超高性能混凝土（FRUHPC）柱冲击性能的可能性。研究结果表明，添加纤维可将破坏机制从脆性剪切破坏转变为有利的弯曲破坏，从而显著改善 FRUHPC 柱的抗冲击性能。添加钢纤维或聚丙烯纤维对冲击响应的影响各不相同。钢纤维显著提高了冲击力峰值（高达 18%），而聚丙烯微纤维则略微提高了峰值（3%-4%）。FRUHPC 可将最大中高位移大幅降低 30%（在 20° 冲击下），并将位移恢复大幅提高 100%（在 20° 冲击下）。含有钢纤维的 FRUHPC 显著提高了能量吸收能力，而含有聚丙烯微纤维的 FRUHPC 则降低了能量吸收能力，这与文献中报道的聚丙烯超细纤维的效果不同。由于纤维用量极少，峰值和残余位移较低，因此 PP 微纤维的最佳纤维含量为 1%。这项研究强调了 FRUHPC 作为抗冲击结构材料的潜力，它能创造更有利的弯曲破坏机制，提高冲击荷载下的延展性和韧性，并加深人们对纤维在结构性能中作用的理解。

{"title":"Comparative impact behaviours of ultra high performance concrete columns reinforced with polypropylene vs steel fibres","authors":"","doi":"10.1016/j.dt.2024.04.016","DOIUrl":"10.1016/j.dt.2024.04.016","url":null,"abstract":"<div><div>Polypropylene (PP) fibres have primarily used to control shrinkage cracks or mitigate explosive spalling in concrete structures exposed to fire or subjected to impact/blast loads, with limited investigations on capacity improvement. This study unveils the possibility of using PP micro-fibres to improve the impact behaviour of fibre-reinforced ultra-high-performance concrete (FRUHPC) columns. Results show that the addition of fibres significantly improves the impact behaviour of FRUHPC columns by shifting the failure mechanism from brittle shear to favourable flexural failure. The addition of steel or PP fibres affected the impact responses differently. Steel fibres considerably increased the peak impact force (up to 18%) while PP micro-fibres slightly increased the peak (3%–4%). FRUHPC significantly reduced the maximum mid-height displacement by up to 30% (under 20° impact) and substantially improved the displacement recovery by up to 100% (under 20° impact). FRUHPC with steel fibres significantly improved the energy absorption while those with PP micro-fibres reduced the energy absorption, which is different from the effect of PP-macro fibre reported in the literature. The optimal fibre content for micro-PP fibres is 1% due to its minimal fibre usage and low peak and residual displacement. This study highlights the potential of FRUHPC as a promising material for impact-resistant structures by creating a more favourable flexural failure mechanism, enhancing ductility and toughness under impact loading, and advancing the understanding of the role of fibres in structural performance.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"40 ","pages":"Pages 138-153"},"PeriodicalIF":5.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141023485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Spontaneous ignition of corrugated cardboard under dynamic high radiant flux 动态高辐射通量下瓦楞纸板的自燃

IF 5 Q1 ENGINEERING, MULTIDISCIPLINARY

Defence Technology(防务技术)

Pub Date : 2024-10-01 DOI: 10.1016/j.dt.2024.05.010

Understanding the response of solid combustibles under high radiant fluxes is critical in predicting the thermal damage from extreme scenarios. Unlike the more moderate radiant fluxes in conventional hydrocarbon fires, extreme events such as strong explosion, concentrated sunlight and directed energy can generate dynamic radiant fluxes at the MW/m² level, creating a unique threat to materials. This study investigates the pyrolysis and spontaneous ignition behaviors of corrugated cardboard by using both experimental and numerical methods, under 10-cm dynamic high radiant fluxes ranging from 0.2 to 1.25 MW/m² for 10 s. The spontaneous ignition process at dynamic high radiant fluxes was recorded and quantified. Two ignition modes were found at the critical radiant flux of 0.4 MW/m², namely hot-gas spontaneous ignition and hot-residue piloted ignition. The latter is not the focus of this paper due to its extremely small probability of occurrence. The research reveals that the increase in flux intensity induces shorter delay times for both pyrolysis and ignition, lower ignition energy density, along with a corresponding rise in the critical mass flux and surface temperature at ignition moment. The simulation results are generally aligned with the experimental findings, despite some divergences may be attributed to model simplifications and parameter assumptions. The work contributes to a deeper insight into material behavior under extreme radiation, with valuable implications for fire safety and hazard assessment.

了解固体可燃物在高辐射通量下的反应对于预测极端情况下的热损害至关重要。与传统碳氢化合物火灾中较为温和的辐射通量不同，强烈爆炸、集中阳光和定向能等极端事件可产生兆瓦/平方米级别的动态辐射通量，从而对材料造成独特的威胁。本研究采用实验和数值方法研究了瓦楞纸板在 10 厘米动态高辐射通量（0.2 至 1.25 兆瓦/平方米）条件下 10 秒钟的热解和自燃行为。在 0.4 兆瓦/平方米的临界辐射通量下发现了两种点火模式，即热气体自发点火和热残留物先导点火。由于后者发生的概率极小，因此不是本文的重点。研究表明，通量强度的增加会缩短热解和点火的延迟时间，降低点火能量密度，同时相应提高临界质量通量和点火时刻的表面温度。模拟结果与实验结果基本一致，尽管有些差异可能是由于模型简化和参数假设造成的。这项工作有助于深入了解极端辐射下的材料行为，对消防安全和危险评估具有重要意义。

{"title":"Spontaneous ignition of corrugated cardboard under dynamic high radiant flux","authors":"","doi":"10.1016/j.dt.2024.05.010","DOIUrl":"10.1016/j.dt.2024.05.010","url":null,"abstract":"<div><div>Understanding the response of solid combustibles under high radiant fluxes is critical in predicting the thermal damage from extreme scenarios. Unlike the more moderate radiant fluxes in conventional hydrocarbon fires, extreme events such as strong explosion, concentrated sunlight and directed energy can generate dynamic radiant fluxes at the MW/m<sup>2</sup> level, creating a unique threat to materials. This study investigates the pyrolysis and spontaneous ignition behaviors of corrugated cardboard by using both experimental and numerical methods, under 10-cm dynamic high radiant fluxes ranging from 0.2 to 1.25 MW/m<sup>2</sup> for 10 s. The spontaneous ignition process at dynamic high radiant fluxes was recorded and quantified. Two ignition modes were found at the critical radiant flux of 0.4 MW/m<sup>2</sup>, namely hot-gas spontaneous ignition and hot-residue piloted ignition. The latter is not the focus of this paper due to its extremely small probability of occurrence. The research reveals that the increase in flux intensity induces shorter delay times for both pyrolysis and ignition, lower ignition energy density, along with a corresponding rise in the critical mass flux and surface temperature at ignition moment. The simulation results are generally aligned with the experimental findings, despite some divergences may be attributed to model simplifications and parameter assumptions. The work contributes to a deeper insight into material behavior under extreme radiation, with valuable implications for fire safety and hazard assessment.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"40 ","pages":"Pages 65-77"},"PeriodicalIF":5.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141050054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Blast injury risks to humans within a military trench 军事战壕内的爆炸对人体造成伤害的风险

IF 5 Q1 ENGINEERING, MULTIDISCIPLINARY

Defence Technology(防务技术)

Pub Date : 2024-10-01 DOI: 10.1016/j.dt.2024.03.006

In land warfare, trenches serve as vital defensive fortifications, offering protection to soldiers while engaging in combat. However, despite their protective function, soldiers often sustain injuries within these trenches. The lack of corresponding blast data alongside empirical injury reports presents a significant knowledge gap, particularly concerning the blast pressures propagating within trench spaces following nearby explosions. This absence hinders the correlation between blast parameters, trench geometry, and reported injury cases, limiting our understanding of blast-related risks within trenches.

This paper addresses the critical aspect of blast propagation within trench systems, essential for evaluating potential blast injury risks to individuals within these structures. Through advanced computational fluid dynamics (CFD) simulations, the study comprehensively investigates blast injury risks resulting from explosions near military trenches. Employing a sophisticated computational model, the research analyzes the dynamic blast effects within trenches, considering both geometrical parameters and blast characteristics influenced by explosive weight and scaled distance.

The numerical simulations yield valuable insights into the impact of these parameters on blast injury risks, particularly focusing on eardrum rupture, lung injury, and traumatic brain injury levels within the trench. The findings elucidate distinct patterns of high-risk zones, highlighting unique characteristics of internal explosions due to confinement and venting dynamics along the trench. This study underscores the significance of detailed numerical modeling in assessing blast injury risks and provides a novel knowledge base for understanding risks associated with explosives detonating near military trenches. The insights gained contribute to enhancing safety measures in both military and civilian contexts exposed to blast events near trench structures.

在陆战中，战壕是重要的防御工事，为士兵作战提供保护。然而，尽管战壕具有保护功能，士兵们还是经常在战壕内受伤。缺乏相应的爆炸数据以及经验性伤害报告是一个重大的知识空白，特别是关于附近爆炸后战壕空间内传播的爆炸压力。这种缺失阻碍了爆炸参数、战壕几何形状和所报告的受伤案例之间的相关性，限制了我们对战壕内爆炸相关风险的了解。本文探讨了战壕系统内爆炸传播的关键问题，这对于评估这些结构内人员的潜在爆炸伤害风险至关重要。通过先进的计算流体动力学（CFD）模拟，该研究全面调查了军事战壕附近爆炸造成的爆炸伤害风险。研究采用了一个复杂的计算模型，分析了战壕内的动态爆炸效应，同时考虑了几何参数以及受爆炸物重量和缩放距离影响的爆炸特征。数值模拟就这些参数对爆炸伤害风险的影响提出了宝贵的见解，尤其侧重于战壕内的耳膜破裂、肺部伤害和脑外伤水平。研究结果阐明了高风险区域的独特模式，突出了由于海沟沿线的封闭和排气动力学而产生的内部爆炸的独特特征。这项研究强调了详细数值建模在评估爆炸伤害风险方面的重要意义，并为了解与军事战壕附近爆炸物爆炸相关的风险提供了新的知识基础。所获得的见解有助于加强在战壕结构附近暴露于爆炸事件的军事和民用环境中的安全措施。

{"title":"Blast injury risks to humans within a military trench","authors":"","doi":"10.1016/j.dt.2024.03.006","DOIUrl":"10.1016/j.dt.2024.03.006","url":null,"abstract":"<div><div>In land warfare, trenches serve as vital defensive fortifications, offering protection to soldiers while engaging in combat. However, despite their protective function, soldiers often sustain injuries within these trenches. The lack of corresponding blast data alongside empirical injury reports presents a significant knowledge gap, particularly concerning the blast pressures propagating within trench spaces following nearby explosions. This absence hinders the correlation between blast parameters, trench geometry, and reported injury cases, limiting our understanding of blast-related risks within trenches.</div><div>This paper addresses the critical aspect of blast propagation within trench systems, essential for evaluating potential blast injury risks to individuals within these structures. Through advanced computational fluid dynamics (CFD) simulations, the study comprehensively investigates blast injury risks resulting from explosions near military trenches. Employing a sophisticated computational model, the research analyzes the dynamic blast effects within trenches, considering both geometrical parameters and blast characteristics influenced by explosive weight and scaled distance.</div><div>The numerical simulations yield valuable insights into the impact of these parameters on blast injury risks, particularly focusing on eardrum rupture, lung injury, and traumatic brain injury levels within the trench. The findings elucidate distinct patterns of high-risk zones, highlighting unique characteristics of internal explosions due to confinement and venting dynamics along the trench. This study underscores the significance of detailed numerical modeling in assessing blast injury risks and provides a novel knowledge base for understanding risks associated with explosives detonating near military trenches. The insights gained contribute to enhancing safety measures in both military and civilian contexts exposed to blast events near trench structures.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"40 ","pages":"Pages 91-104"},"PeriodicalIF":5.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140399346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Exploring the hygroscopic behavior of highly energetic oxidizer ammonium dinitramide (ADN) at different temperatures and humidities using an innovative hygroscopic modeling 利用创新吸湿模型探索高能氧化剂二硝胺铵（ADN）在不同温度和湿度下的吸湿行为

IF 5 Q1 ENGINEERING, MULTIDISCIPLINARY

Defence Technology(防务技术)

Pub Date : 2024-10-01 DOI: 10.1016/j.dt.2024.06.003

Ammonium dinitramide (ADN) is a new type of green energetic oxidizer with excellent energy density and low pollution combustion characteristics. However, the strong hygroscopicity has a significant impact on its practical application. To assist in the research on moisture-proof modification of ADN materials, an innovative hygroscopic modeling approach was proposed to evaluate the hygroscopicity of ADN at various temperatures and humidities. By investigating the diffusion coefficient of water molecules in molecular dynamics processes, a visual insight into the hygroscopic process of ADN was gained. Furthermore, analyzing the non-covalent interactions between ADN and water molecules, the hygroscopicity of ADN could be evaluated qualitatively and quantitatively. The energy analysis revealed that electrostatic forces play a dominant role in the process of water adsorption by ADN, whereas van der Waals forces impede it. As a whole, the simulation results show that ADN presents the following hygroscopic law: At temperatures ranging from 273 K to 373 K and relative humidity (RH) from 10% to 100%, the hygroscopicity of ADN generally shows an increasing trend with the rise in temperature and humidity based on the results of three simulations. According to the non-hygroscopic point (298 K, 52% RH) of ADN obtained by experiment in the literature, a non-hygroscopic range of temperature and humidity for ADN can be depicted when the simulation results in relative hygroscopicity is less than or equal to 17%. This study can provide effective strategies for screening anti-hygroscopic modified materials of ADN.

二硝胺铵（ADN）是一种新型绿色高能氧化剂，具有优异的能量密度和低污染燃烧特性。然而，强烈的吸湿性对其实际应用有很大影响。为了帮助研究 ADN 材料的防潮改性，研究人员提出了一种创新的吸湿性建模方法，用于评估 ADN 在不同温度和湿度下的吸湿性。通过研究分子动力学过程中水分子的扩散系数，可以直观地了解 ADN 的吸湿过程。此外，通过分析 ADN 与水分子之间的非共价相互作用，可以定性和定量地评估 ADN 的吸湿性。能量分析表明，静电力在 ADN 吸附水的过程中起主导作用，而范德华力则阻碍吸附。总的来说，模拟结果表明 ADN 呈现出以下吸湿规律：在温度为 273 K 至 373 K 和相对湿度（RH）为 10% 至 100% 的条件下，根据三次模拟结果，ADN 的吸湿性一般会随着温度和湿度的升高而呈上升趋势。根据文献中通过实验得到的 ADN 的非吸湿点（298 K，52% RH），当模拟结果中的相对吸湿性小于或等于 17% 时，可以描绘出 ADN 的非吸湿温度和湿度范围。这项研究可为筛选 ADN 的抗吸湿改性材料提供有效策略。

{"title":"Exploring the hygroscopic behavior of highly energetic oxidizer ammonium dinitramide (ADN) at different temperatures and humidities using an innovative hygroscopic modeling","authors":"","doi":"10.1016/j.dt.2024.06.003","DOIUrl":"10.1016/j.dt.2024.06.003","url":null,"abstract":"<div><div>Ammonium dinitramide (ADN) is a new type of green energetic oxidizer with excellent energy density and low pollution combustion characteristics. However, the strong hygroscopicity has a significant impact on its practical application. To assist in the research on moisture-proof modification of ADN materials, an innovative hygroscopic modeling approach was proposed to evaluate the hygroscopicity of ADN at various temperatures and humidities. By investigating the diffusion coefficient of water molecules in molecular dynamics processes, a visual insight into the hygroscopic process of ADN was gained. Furthermore, analyzing the non-covalent interactions between ADN and water molecules, the hygroscopicity of ADN could be evaluated qualitatively and quantitatively. The energy analysis revealed that electrostatic forces play a dominant role in the process of water adsorption by ADN, whereas van der Waals forces impede it. As a whole, the simulation results show that ADN presents the following hygroscopic law: At temperatures ranging from 273 K to 373 K and relative humidity (RH) from 10% to 100%, the hygroscopicity of ADN generally shows an increasing trend with the rise in temperature and humidity based on the results of three simulations. According to the non-hygroscopic point (298 K, 52% RH) of ADN obtained by experiment in the literature, a non-hygroscopic range of temperature and humidity for ADN can be depicted when the simulation results in relative hygroscopicity is less than or equal to 17%. This study can provide effective strategies for screening anti-hygroscopic modified materials of ADN.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"40 ","pages":"Pages 25-34"},"PeriodicalIF":5.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141416031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Data-driven prediction of dimensionless quantities for semi-infinite target penetration by integrating machine-learning and feature selection methods 通过整合机器学习和特征选择方法，以数据驱动预测半无限目标穿透的无量纲数量

IF 5 Q1 ENGINEERING, MULTIDISCIPLINARY

Defence Technology(防务技术)

Pub Date : 2024-10-01 DOI: 10.1016/j.dt.2024.04.012

This study employs a data-driven methodology that embeds the principle of dimensional invariance into an artificial neural network to automatically identify dominant dimensionless quantities in the penetration of rod projectiles into semi-infinite metal targets from experimental measurements. The derived mathematical expressions of dimensionless quantities are simplified by the examination of the exponent matrix and coupling relationships between feature variables. As a physics-based dimension reduction methodology, this way reduces high-dimensional parameter spaces to descriptions involving only a few physically interpretable dimensionless quantities in penetrating cases. Then the relative importance of various dimensionless feature variables on the penetration efficiencies for four impacting conditions is evaluated through feature selection engineering. The results indicate that the selected critical dimensionless feature variables by this synergistic method, without referring to the complex theoretical equations and aiding in the detailed knowledge of penetration mechanics, are in accordance with those reported in the reference. Lastly, the determined dimensionless quantities can be efficiently applied to conduct semi-empirical analysis for the specific penetrating case, and the reliability of regression functions is validated.

本研究采用数据驱动方法，将尺寸不变性原理嵌入人工神经网络，从实验测量结果中自动识别棒状射弹穿透半无限金属目标时的主要无量纲量。通过检查指数矩阵和特征变量之间的耦合关系，简化了无量纲量的数学表达式。作为一种基于物理学的维度缩减方法，这种方法将高维参数空间缩减为在穿透情况下只涉及几个物理上可解释的无量纲量的描述。然后，通过特征选择工程评估了四种撞击条件下各种无量纲特征变量对穿透效率的相对重要性。结果表明，通过这种协同方法，无需参考复杂的理论方程，也无需借助详细的穿透力学知识，所选择的关键无量纲特征变量与参考文献中的变量一致。最后，确定的无量纲量可以有效地应用于对特定穿透情况进行半经验分析，并验证了回归函数的可靠性。

{"title":"Data-driven prediction of dimensionless quantities for semi-infinite target penetration by integrating machine-learning and feature selection methods","authors":"","doi":"10.1016/j.dt.2024.04.012","DOIUrl":"10.1016/j.dt.2024.04.012","url":null,"abstract":"<div><div>This study employs a data-driven methodology that embeds the principle of dimensional invariance into an artificial neural network to automatically identify dominant dimensionless quantities in the penetration of rod projectiles into semi-infinite metal targets from experimental measurements. The derived mathematical expressions of dimensionless quantities are simplified by the examination of the exponent matrix and coupling relationships between feature variables. As a physics-based dimension reduction methodology, this way reduces high-dimensional parameter spaces to descriptions involving only a few physically interpretable dimensionless quantities in penetrating cases. Then the relative importance of various dimensionless feature variables on the penetration efficiencies for four impacting conditions is evaluated through feature selection engineering. The results indicate that the selected critical dimensionless feature variables by this synergistic method, without referring to the complex theoretical equations and aiding in the detailed knowledge of penetration mechanics, are in accordance with those reported in the reference. Lastly, the determined dimensionless quantities can be efficiently applied to conduct semi-empirical analysis for the specific penetrating case, and the reliability of regression functions is validated.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"40 ","pages":"Pages 105-124"},"PeriodicalIF":5.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141528353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0