Pub Date : 2024-10-01DOI: 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.
{"title":"Research status and challenges in the manufacturing of IR conformal optics","authors":"","doi":"10.1016/j.dt.2024.04.015","DOIUrl":"10.1016/j.dt.2024.04.015","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"40 ","pages":"Pages 154-172"},"PeriodicalIF":5.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141528402","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}
Pub Date : 2024-10-01DOI: 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.
{"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}
Pub Date : 2024-10-01DOI: 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.
{"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}
Pub Date : 2024-10-01DOI: 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.
{"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}
Pub Date : 2024-10-01DOI: 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.
{"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}
Pub Date : 2024-10-01DOI: 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.
{"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}
Pub Date : 2024-10-01DOI: 10.1016/j.dt.2024.05.006
Long-term navigation ability based on consumer-level wearable inertial sensors plays an essential role towards various emerging fields, for instance, smart healthcare, emergency rescue, soldier positioning et al. The performance of existing long-term navigation algorithm is limited by the cumulative error of inertial sensors, disturbed local magnetic field, and complex motion modes of the pedestrian. This paper develops a robust data and physical model dual-driven based trajectory estimation (DPDD-TE) framework, which can be applied for long-term navigation tasks. A Bi-directional Long Short-Term Memory (Bi-LSTM) based quasi-static magnetic field (QSMF) detection algorithm is developed for extracting useful magnetic observation for heading calibration, and another Bi-LSTM is adopted for walking speed estimation by considering hybrid human motion information under a specific time period. In addition, a data and physical model dual-driven based multi-source fusion model is proposed to integrate basic INS mechanization and multi-level constraint and observations for maintaining accuracy under long-term navigation tasks, and enhanced by the magnetic and trajectory features assisted loop detection algorithm. Real-world experiments indicate that the proposed DPDD-TE outperforms than existing algorithms, and final estimated heading and positioning accuracy indexes reaches 5° and less than 2 m under the time period of 30 min, respectively.
{"title":"A data and physical model dual-driven based trajectory estimator for long-term navigation","authors":"","doi":"10.1016/j.dt.2024.05.006","DOIUrl":"10.1016/j.dt.2024.05.006","url":null,"abstract":"<div><div>Long-term navigation ability based on consumer-level wearable inertial sensors plays an essential role towards various emerging fields, for instance, smart healthcare, emergency rescue, soldier positioning et al. The performance of existing long-term navigation algorithm is limited by the cumulative error of inertial sensors, disturbed local magnetic field, and complex motion modes of the pedestrian. This paper develops a robust data and physical model dual-driven based trajectory estimation (DPDD-TE) framework, which can be applied for long-term navigation tasks. A Bi-directional Long Short-Term Memory (Bi-LSTM) based quasi-static magnetic field (QSMF) detection algorithm is developed for extracting useful magnetic observation for heading calibration, and another Bi-LSTM is adopted for walking speed estimation by considering hybrid human motion information under a specific time period. In addition, a data and physical model dual-driven based multi-source fusion model is proposed to integrate basic INS mechanization and multi-level constraint and observations for maintaining accuracy under long-term navigation tasks, and enhanced by the magnetic and trajectory features assisted loop detection algorithm. Real-world experiments indicate that the proposed DPDD-TE outperforms than existing algorithms, and final estimated heading and positioning accuracy indexes reaches 5° and less than 2 m under the time period of 30 min, respectively.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"40 ","pages":"Pages 78-90"},"PeriodicalIF":5.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141028479","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}
Pub Date : 2024-10-01DOI: 10.1016/j.dt.2024.05.008
To solve the problem of target damage assessment when fragments attack target under uncertain projectile and target intersection in an air defense intercept, this paper proposes a method for calculating target damage probability leveraging spatio-temporal finite multilayer fragments distribution and the target damage assessment algorithm based on cloud model theory. Drawing on the spatial dispersion characteristics of fragments of projectile proximity explosion, we divide into a finite number of fragments distribution planes based on the time series in space, set up a fragment layer dispersion model grounded in the time series and intersection criterion for determining the effective penetration of each layer of fragments into the target. Building on the precondition that the multilayer fragments of the time series effectively assail the target, we also establish the damage criterion of the perforation and penetration damage and deduce the damage probability calculation model. Taking the damage probability of the fragment layer in the spatio-temporal sequence to the target as the input state variable, we introduce cloud model theory to research the target damage assessment method. Combining the equivalent simulation experiment, the scientific and rational nature of the proposed method were validated through quantitative calculations and comparative analysis.
{"title":"A cloud model target damage effectiveness assessment algorithm based on spatio-temporal sequence finite multilayer fragments dispersion","authors":"","doi":"10.1016/j.dt.2024.05.008","DOIUrl":"10.1016/j.dt.2024.05.008","url":null,"abstract":"<div><div>To solve the problem of target damage assessment when fragments attack target under uncertain projectile and target intersection in an air defense intercept, this paper proposes a method for calculating target damage probability leveraging spatio-temporal finite multilayer fragments distribution and the target damage assessment algorithm based on cloud model theory. Drawing on the spatial dispersion characteristics of fragments of projectile proximity explosion, we divide into a finite number of fragments distribution planes based on the time series in space, set up a fragment layer dispersion model grounded in the time series and intersection criterion for determining the effective penetration of each layer of fragments into the target. Building on the precondition that the multilayer fragments of the time series effectively assail the target, we also establish the damage criterion of the perforation and penetration damage and deduce the damage probability calculation model. Taking the damage probability of the fragment layer in the spatio-temporal sequence to the target as the input state variable, we introduce cloud model theory to research the target damage assessment method. Combining the equivalent simulation experiment, the scientific and rational nature of the proposed method were validated through quantitative calculations and comparative analysis.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"40 ","pages":"Pages 48-64"},"PeriodicalIF":5.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141051229","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}
Pub Date : 2024-10-01DOI: 10.1016/j.dt.2024.05.014
Chi Zhang , Ge Song , Hui Guo , Jiafan Ren , Chunhua Bai
The stratification phenomenon resulting from differences in the physical properties of solid‒liquid components seriously affect the final combustion and explosion characteristics of mixed fuel under the action of oscillation. The effects of oscillation on the physical stability of mixed fuel with two solid‒liquid ratios and three liquid component distribution ratios have been investigated using a self-designed experimental system at oscillation frequencies of 60–300 r/min. The explosion characteristics of mixed fuel before and after oscillation are gained from a 20 L spherical explosion container system. When the mass ratio of liquid components is controlled at 66.9%, 64.7%, 62.6% the final explosion characteristics are stable, with a maximum difference of only 0.71%. The volume of liquid fuel precipitation increases with increasing oscillation frequency when the mass ratio of liquid components reaches 71.7%, 69.6%, 67.7%. The fuel explosion overpressure after oscillation decreases with increasing liquid precipitation volume, and the repeatability is poor, with a maximum standard deviation of 82.736, which is much higher than the ratio without stratification. Properly controlling the mass ratio of liquid components of the mixed fuel can effectively combat the impact of oscillation on the physical state and maintain the stability of the final explosion characteristics.
{"title":"Influences of oscillation on the physical stability and explosion characteristics of solid‒liquid mixed fuel","authors":"Chi Zhang , Ge Song , Hui Guo , Jiafan Ren , Chunhua Bai","doi":"10.1016/j.dt.2024.05.014","DOIUrl":"10.1016/j.dt.2024.05.014","url":null,"abstract":"<div><div>The stratification phenomenon resulting from differences in the physical properties of solid‒liquid components seriously affect the final combustion and explosion characteristics of mixed fuel under the action of oscillation. The effects of oscillation on the physical stability of mixed fuel with two solid‒liquid ratios and three liquid component distribution ratios have been investigated using a self-designed experimental system at oscillation frequencies of 60–300 r/min. The explosion characteristics of mixed fuel before and after oscillation are gained from a 20 L spherical explosion container system. When the mass ratio of liquid components is controlled at 66.9%, 64.7%, 62.6% the final explosion characteristics are stable, with a maximum difference of only 0.71%. The volume of liquid fuel precipitation increases with increasing oscillation frequency when the mass ratio of liquid components reaches 71.7%, 69.6%, 67.7%. The fuel explosion overpressure after oscillation decreases with increasing liquid precipitation volume, and the repeatability is poor, with a maximum standard deviation of 82.736, which is much higher than the ratio without stratification. Properly controlling the mass ratio of liquid components of the mixed fuel can effectively combat the impact of oscillation on the physical state and maintain the stability of the final explosion characteristics.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"40 ","pages":"Pages 191-198"},"PeriodicalIF":5.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141784823","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}
Pub Date : 2024-10-01DOI: 10.1016/j.dt.2024.04.004
In this work, comprehensive studies of 2,4-dinitroanisole (2,4DNAN) were carried out using powder thermorentgenography of the internal standard. The time of the complete polymorphic transition in the solid phase β→α in 2,4DNAN under various combinations of conditions has been determined. It has been established that, regardless of the season of manufacture of the substance, when it is stored for 8–9 months, with a change in ambient temperature from minus 30 °C to plus 30 °C, a complete polymorphic transition β→α occurs. When stored in conditions below minus 5 °C, polymorphic transition does not occur. When stored in conditions above plus 30 °C in a closed container, polymorphic transition occurs within 3 weeks. The polymorphic transition is accompanied by a decrease in density by 1.3%–1.5% and an increase in melting temperature by 10–12 °C, depending on the degree of purity of the starting substance. The activation energy of the molecular rearrangement was 68–70 kJ/mol (16.5 ± 3 kcal/mol). The mechanism of polymorphic transition has been evaluated, which is presumably based on internal homodiffusion and energy transfer to the surface of the mass of powder particles and the product. The average activation energy of the polymorphic transition process was 110 ± 6.2 kJ/mol (26.2 kcal/mol). In an open container, reactions proceed by a homogeneous mechanism, and in a closed container by a heterogeneous mechanism involving the gas phase.
{"title":"Kinetics and mechanism of the low-energy β-α phase transition of the second kind in 2,4-dinitroanisole","authors":"","doi":"10.1016/j.dt.2024.04.004","DOIUrl":"10.1016/j.dt.2024.04.004","url":null,"abstract":"<div><div>In this work, comprehensive studies of 2,4-dinitroanisole (2,4DNAN) were carried out using powder thermorentgenography of the internal standard. The time of the complete polymorphic transition in the solid phase β→α in 2,4DNAN under various combinations of conditions has been determined. It has been established that, regardless of the season of manufacture of the substance, when it is stored for 8–9 months, with a change in ambient temperature from minus 30 °C to plus 30 °C, a complete polymorphic transition β→α occurs. When stored in conditions below minus 5 °C, polymorphic transition does not occur. When stored in conditions above plus 30 °C in a closed container, polymorphic transition occurs within 3 weeks. The polymorphic transition is accompanied by a decrease in density by 1.3%–1.5% and an increase in melting temperature by 10–12 °C, depending on the degree of purity of the starting substance. The activation energy of the molecular rearrangement was 68–70 kJ/mol (16.5 ± 3 kcal/mol). The mechanism of polymorphic transition has been evaluated, which is presumably based on internal homodiffusion and energy transfer to the surface of the mass of powder particles and the product. The average activation energy of the polymorphic transition process was 110 ± 6.2 kJ/mol (26.2 kcal/mol). In an open container, reactions proceed by a homogeneous mechanism, and in a closed container by a heterogeneous mechanism involving the gas phase.</div></div>","PeriodicalId":58209,"journal":{"name":"Defence Technology(防务技术)","volume":"40 ","pages":"Pages 210-224"},"PeriodicalIF":5.0,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141197906","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}
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