Blast effects and energy transfer in near-ground explosions differ significantly from underground scenarios,particularly in terms of ground shock propagation and energy coupling mechanisms across various geological co...Blast effects and energy transfer in near-ground explosions differ significantly from underground scenarios,particularly in terms of ground shock propagation and energy coupling mechanisms across various geological conditions.This study employs centrifuge modeling to simulate near-ground explosions in sandy soil,including surface explosions and airbursts.The focus was on blast-induced cratering,ground shock effects,and energy coupling in sandy foundations.Scaling laws for crater dimensions and ground shock parameters were established and validated based on experimental results.The"modeling of models"series showed good consistency in crater measurements,leading to an empirical formula for estimating crater radius in dry sand.For surface explosions,soil acceleration responses showed single peaks in the central zone(horizontal standoff distance<0.6 m/(kg)1/3)and dual peaks in the near-surface zone(0.79-1.2 m/(kg)1/3)due to combined effects of direct and airburst-induced ground shock.Empirical methods were developed to predict peak acceleration distributions in sandy foundations.Utilizing crater measurements and ground shock propagation laws,a computational approach for evaluating energy transmission in soil foundations was proposed.The study also developed prediction curves for ground shock energy coupling coefficients with scaled blast depth/height,providing a unified model for both underground and near-ground explosions in sandy foundations.The research findings can enhance the methodologies for simulating blast effects and offer a scientific basis for optimizing weapon effectiveness and protective engineering design.展开更多
The penetration resistance of aluminum plates against square projectiles has emerged as a critical research focus in impact engineering.In our study,experimental analyses were conducted using a ballistic gun system.Nu...The penetration resistance of aluminum plates against square projectiles has emerged as a critical research focus in impact engineering.In our study,experimental analyses were conducted using a ballistic gun system.Numerical simulations were performed using an advanced physical damage model incorporating dynamic void evolution.Our new model exhibited excellent prediction performances in ballistic limit velocity(the maximum error is 7.74%)and residual velocity(the lowest R-value is 0.8803).The effects of width-thickness ratio for square projectile,plate thickness,and material properties on ballistic performance were evaluated.The results revealed that localized shear plugging was the dominant failure mode in aluminum plates penetrated by square projectiles.Increasing the square projectile velocity led to a change in fracture morphology from square to circular,accompanied by a marked expansion of the penetration area.Comparative studies highlighted the high prediction accuracy in ballistic limit velocity of our proposed model compared to traditional phenomenological models(the maximum error is 14.99%)and physical models(the maximum error is 65.99%).Parametric investigations using our validated model examined the influence of projectile characteristics on penetration performance.Among projectiles with the same mass,cubic projectile exhibited the optimal penetration performances,while spherical projectile was the worst.Moreover,the penetration performance between square and cylindrical projectiles was solely determined by their contact area with the plate,and was independent of their cross-sectional shape.Our model provided an effective new method for analyzing penetration mechanisms.Our findings provided significant insights for damage assessment of warheads and the design of protective structures.展开更多
狙击瞄准点轨迹视觉测量系统是一种应用于现代化狙击训练领域的高精度光学测量装置,针对该系统高分辨率图像处理延迟与户外强光导致的轨迹定位困难问题,提出一种基于自适应阈值感兴趣区域(region of interest,ROI)投影法的瞄准点质心快...狙击瞄准点轨迹视觉测量系统是一种应用于现代化狙击训练领域的高精度光学测量装置,针对该系统高分辨率图像处理延迟与户外强光导致的轨迹定位困难问题,提出一种基于自适应阈值感兴趣区域(region of interest,ROI)投影法的瞄准点质心快速定位算法,并基于现场可编程门阵列(field programmable gate array,FPGA)平台硬件实现。该算法通过分析光斑像素个数在图像中的占比,结合相关场景参数动态计算ROI提取的自适应阈值,实现了ROI区域的高效精准提取,大幅减少了计算量。实验结果表明,对于2448×2048分辨率的图像,所提算法将处理数据量减少了98.7%。同时,自适应阈值机制有效克服了户外环境光照变化的影响,在不同射击场景下均能稳定提取质心,显著提升了系统的实时性与鲁棒性。展开更多
Hypervelocity rocket sled systems are critical for testing advanced military technologies,yet track damage at speeds exceeding Mach 5 remains a significant challenge for system reliability and performance.In this stud...Hypervelocity rocket sled systems are critical for testing advanced military technologies,yet track damage at speeds exceeding Mach 5 remains a significant challenge for system reliability and performance.In this study,we investigated the hypervelocity impact response and protection for highstrength U71 Mn or bainitic steel used in rocket sled tracks.Flyer plate impact experiments using a two-stage light-gas gun were conducted to study the hypervelocity collision response,followed by the microstructural characterization via optical microscope,scanning electron microscopy equipped with electron backscatter diffraction to reveal underlying damage mechanisms.Then,the calibrated thermalmechanical coupled finite element simulations using the Johnson-Cook constitutive model and MieGrüneisen equation of state were carried out.Results indicated that bainitic steel exhibits superior impact resistance with predominantly smooth scratch-dominated damage due to its higher ductility.In contrast,U71 Mn suffered significant material spallation and crack propagation arising from brittle fracture mechanisms.Zinc-rich epoxy primer coatings effectively mitigated stress concentration and temperature rise in the substrate at impacting velocities below 2.4 km/s,so as to suppress the microstructural damage such as adiabatic shear bands and dynamic recrystallization.However,coating protection diminished at ultra-high-speed impacts due to the coating failure.Dimensional analysis established quantitative relationships of the gouge damage size to projectile mass,impact velocity,and material yield strength.This study provides in-depth insights into damage mechanisms in hypervelocity rail systems,demonstrating that bainitic steel combined with protective coatings can significantly enhance impact resistance and system reliability,offering valuable guidance for the design and optimization of hypervelocity testing platforms.展开更多
The characterization of mechanical properties for high-dynamic,high-velocity target motion is essential in defense testing.It provides crucial data for validating weapon systems and precision manufacturing processes e...The characterization of mechanical properties for high-dynamic,high-velocity target motion is essential in defense testing.It provides crucial data for validating weapon systems and precision manufacturing processes etc.However,existing measurement methods face challenges such as limited dynamic range,discontinuous observations,and high costs.This paper presents a new approach leveraging an event-based multi-view photogrammetric system,which aims to address the aforementioned challenges.First,the monotonicity in the spatiotemporal distribution of events is leveraged to extract the target’s leading-edge features,eliminating the tailing effect that complicates motion measurements.Then,reprojection error is used to associate events with the target’s trajectory,providing more data than traditional intersection methods.Finally,a target velocity decay model is employed to fit the data,enabling accurate motion measurements via our multi-view data joint computation.In a light gas gun fragment test,the proposed method showed a measurement deviation of 4.47%compared to the electromagnetic speedometer.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52588202)under the project''Multiphase Media Evolution in Hypergravity''.
摘要Blast effects and energy transfer in near-ground explosions differ significantly from underground scenarios,particularly in terms of ground shock propagation and energy coupling mechanisms across various geological conditions.This study employs centrifuge modeling to simulate near-ground explosions in sandy soil,including surface explosions and airbursts.The focus was on blast-induced cratering,ground shock effects,and energy coupling in sandy foundations.Scaling laws for crater dimensions and ground shock parameters were established and validated based on experimental results.The"modeling of models"series showed good consistency in crater measurements,leading to an empirical formula for estimating crater radius in dry sand.For surface explosions,soil acceleration responses showed single peaks in the central zone(horizontal standoff distance<0.6 m/(kg)1/3)and dual peaks in the near-surface zone(0.79-1.2 m/(kg)1/3)due to combined effects of direct and airburst-induced ground shock.Empirical methods were developed to predict peak acceleration distributions in sandy foundations.Utilizing crater measurements and ground shock propagation laws,a computational approach for evaluating energy transmission in soil foundations was proposed.The study also developed prediction curves for ground shock energy coupling coefficients with scaled blast depth/height,providing a unified model for both underground and near-ground explosions in sandy foundations.The research findings can enhance the methodologies for simulating blast effects and offer a scientific basis for optimizing weapon effectiveness and protective engineering design.
基金supported by the National Natural ScienceFoundation of China(Grant No.12172054)。
摘要The penetration resistance of aluminum plates against square projectiles has emerged as a critical research focus in impact engineering.In our study,experimental analyses were conducted using a ballistic gun system.Numerical simulations were performed using an advanced physical damage model incorporating dynamic void evolution.Our new model exhibited excellent prediction performances in ballistic limit velocity(the maximum error is 7.74%)and residual velocity(the lowest R-value is 0.8803).The effects of width-thickness ratio for square projectile,plate thickness,and material properties on ballistic performance were evaluated.The results revealed that localized shear plugging was the dominant failure mode in aluminum plates penetrated by square projectiles.Increasing the square projectile velocity led to a change in fracture morphology from square to circular,accompanied by a marked expansion of the penetration area.Comparative studies highlighted the high prediction accuracy in ballistic limit velocity of our proposed model compared to traditional phenomenological models(the maximum error is 14.99%)and physical models(the maximum error is 65.99%).Parametric investigations using our validated model examined the influence of projectile characteristics on penetration performance.Among projectiles with the same mass,cubic projectile exhibited the optimal penetration performances,while spherical projectile was the worst.Moreover,the penetration performance between square and cylindrical projectiles was solely determined by their contact area with the plate,and was independent of their cross-sectional shape.Our model provided an effective new method for analyzing penetration mechanisms.Our findings provided significant insights for damage assessment of warheads and the design of protective structures.
基金financial support from the National Key Research and Development Program(Grant No.2024YFA1209801)the National Natural Science Foundation of China(Grant Nos.12302140,12325204)+4 种基金the China Postdoctoral Science Foundation(Grant No.2023M732794)the Fundamental Research Funds for the Central Universities of China(Grant No.sxzy012023213)the Scientific Research Program of Shaanxi Province(Grant No.2023JC-XJ-02)the Young Talent Support Program of Xi'an Science and Technology Association(Grant No.959202413069)Postdoctoral Fellowship Program(Grade B)of China Postdoctoral Science Foundation(Grant No.GZB20230575)。
摘要Hypervelocity rocket sled systems are critical for testing advanced military technologies,yet track damage at speeds exceeding Mach 5 remains a significant challenge for system reliability and performance.In this study,we investigated the hypervelocity impact response and protection for highstrength U71 Mn or bainitic steel used in rocket sled tracks.Flyer plate impact experiments using a two-stage light-gas gun were conducted to study the hypervelocity collision response,followed by the microstructural characterization via optical microscope,scanning electron microscopy equipped with electron backscatter diffraction to reveal underlying damage mechanisms.Then,the calibrated thermalmechanical coupled finite element simulations using the Johnson-Cook constitutive model and MieGrüneisen equation of state were carried out.Results indicated that bainitic steel exhibits superior impact resistance with predominantly smooth scratch-dominated damage due to its higher ductility.In contrast,U71 Mn suffered significant material spallation and crack propagation arising from brittle fracture mechanisms.Zinc-rich epoxy primer coatings effectively mitigated stress concentration and temperature rise in the substrate at impacting velocities below 2.4 km/s,so as to suppress the microstructural damage such as adiabatic shear bands and dynamic recrystallization.However,coating protection diminished at ultra-high-speed impacts due to the coating failure.Dimensional analysis established quantitative relationships of the gouge damage size to projectile mass,impact velocity,and material yield strength.This study provides in-depth insights into damage mechanisms in hypervelocity rail systems,demonstrating that bainitic steel combined with protective coatings can significantly enhance impact resistance and system reliability,offering valuable guidance for the design and optimization of hypervelocity testing platforms.
基金supported by the National Natural Science Foundation of China(Grant No.12372189)the Hunan Provincial Natural Science Foundation for Excellent Young Scholars(Grant No.2023JJ20045).
摘要The characterization of mechanical properties for high-dynamic,high-velocity target motion is essential in defense testing.It provides crucial data for validating weapon systems and precision manufacturing processes etc.However,existing measurement methods face challenges such as limited dynamic range,discontinuous observations,and high costs.This paper presents a new approach leveraging an event-based multi-view photogrammetric system,which aims to address the aforementioned challenges.First,the monotonicity in the spatiotemporal distribution of events is leveraged to extract the target’s leading-edge features,eliminating the tailing effect that complicates motion measurements.Then,reprojection error is used to associate events with the target’s trajectory,providing more data than traditional intersection methods.Finally,a target velocity decay model is employed to fit the data,enabling accurate motion measurements via our multi-view data joint computation.In a light gas gun fragment test,the proposed method showed a measurement deviation of 4.47%compared to the electromagnetic speedometer.