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Damage-ignition mechanism studies on modified propellant with different crosslinking density under dynamic loading

Defence Technology（防务技术） 2023年第10期28卷 155-164页

作者： Hong-zheng Duan Yan-qing Wu Xiao Hou Kun Yang Feng-lei Huang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081PR China School of Aerospace Engineering Beijing Institute of TechnologyBeijing100081PR China The Fourth Institute of China Aerospace Science and Technology Corporation Xi'an710025PR China

The study of high-energy and low-vulnerability propellants is important for the power performance and safety of solid propellant rocket motors.The modified split Hopkinson pressure bar(SHPB)tests are performed on two kinds of propellant with different crosslinking density to study the dynamic mechanical responses and damage-ignition mechanism.SHPB apparatus is equipped with a highperformance infrared camera and high-speed camera to capture the deformation,damage-ignition feature and temperature evolution images in the impact process.The results suggested that the mechanical responses and damage-ignition mechanism of the propellants were affected by the strain rates and crosslinking density.The damage-ignition degree is more intense and the reaction occurs earlier with the increase of strain rates.For propellant 1 with higher crosslinking density,the critical ignition strain rate is 4500 s^(-1).Two kinds of propellants show different ignition mechanism,i.***.crack generation,propagation and final fracture for propellant 1 while viscous shear flow for propellant 2.Meanwhile,the SEM images also reveal the difference of damage-ignition mechanism of the two kinds of propellants.Finally,the ignition mechanism under different strain rates and critical ignition strain rate of propellants are further explained by the theoretical calculation of temperature variations.

关键词： The modified propellants dynamic loading Mechanical property Damage-ignition mechanism Experimental and theoretical calculation

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Mesoscopic Modeling Approach and Application for Steel Fiber Reinforced Concrete under dynamic loading:A Review

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Engineering 2022年第9期16卷 220-238页

作者： Jinhua Zhang Zhangyu Wu Hongfa Yu Haiyan Ma Bo Da School of Civil Engineering Southeast UniversityNanjing 210096China Department of Civil and Airport Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China Science and Technology on Near-Surface Detection Laboratory Wuxi 214035China College of Harbour Coastal and Offshore EngineeringHohai UniversityNanjing 210098China

Steel fiber reinforced concrete(SFRC)has drawn extensive attention in recent years for its superior mechanical response to dynamic and impact loadings.Based on the existing test results,the highstrength steel fibers embedded in a concrete matrix usually play a strong bridging effect to enhance the bonding force between fiber and the matrix,and directly contribute to the improvement of the post-cracking behavior and residual strength of SFRC.To gain a better understanding of the action behavior of steel fibers in matrix and further capture the failure mechanism of SFRC under dynamic loads,the mesoscopic modeling approach that assumes SFRC to be composed of different mesoscale phases(i.e.,steel fibers,coarse aggregates,mortar matrix,and interfacial transition zone(ITZ))has been widely employed to simulate the dynamic responses of SFRC material and structural members.This paper presents a comprehensive review of the state-of-the-art mesoscopic models and simulations for SFRC under dynamic loading.Generation approaches for the SFRC mesoscale model in the simulation works,including steel fiber,coarse aggregate,and the ITZ between them,are reviewed and compared systematically.The material models for different phases and the interaction relationship between fiber and concrete matrix are summarized comprehensively.Additionally,some example applications for SFRC under dynamic loads(i.e.,compression,tension,and contact blast)simulated using the general mesoscale models are given.Finally,some critical analysis on the current shortcomings of the mesoscale modeling of SFRC is highlighted,which is of great significance for the future investigation and development of SFRC.

关键词： Steel fiber reinforced concrete Mesoscale modeling dynamic loading Materials model Interfacial characteristic

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dynamic loading Vulnerability Detection for Android Applications Through Ensemble Learning

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Chinese Journal of Electronics 2017年第5期26卷 960-965页

作者： YANG Tianchang CUI Haoliang NIU Shaozhang Beijing Key Lab of Intelligent Telecommunication Software and Multimedia Beijing University of Posts and Telecommunications

Valid authentication and security protection measures are not provided for external code and resources executed by dynamic loading technology during the runtime in Android.In this paper,a new method of detecting vulnerabilities related to dynamic loading technology is proposed.Two phases are included in the detection process.Static analysis phase determines the location information of the loading point and extracts the feature vector for each loading procedure.Identification phase classifies the extracted feature vector by means of constructed multilabel classification ensemble learning algorithm.According to the examination result on 4464 Android applications,37.8% of all applications use the dynamic loading technology,and more than 12% of total test applications are detected with related security deficiencies.Experimental result shows that the detection method can detect vulnerabilities of dynamic loading effectively and is more comprehensive.

关键词： dynamic loading Android application Vulnerability Ensemble learning

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Spalling characteristics of high-temperature treated granitic rock at different strain rates

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第4期16卷 1280-1288页

作者： L.F.Fan Q.H.Yang X.L.Du The Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education Beijing University of TechnologyBeijing100124China

The dynamic spalling characteristics of rock are important for stability analysis in rock engineering.This paper presented an experimental investigation on the dynamic spalling characteristics of granite with different temperatures and strain rates.A series of dynamic spalling tests with different impact velocities were conducted on thermally treated granite at different temperatures.The dynamic spalling strengths of granite with different temperatures and strain rates were determined.A model was proposed to correlate the dynamic spalling strength of granite,high temperature and strain rate.The results show that the spalling strength of granite decreases with increasing temperature.Moreover,the spalling strength of granite with a higher strain rate is larger than that with a lower strain rate.The proposed model can describe the relationship among dynamic spalling strength of granite,high temperature and strain rate.

关键词： dynamic spalling characteristics High temperature Strain rate dynamic loading Granite

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dynamic Biaxial Compression of CFRP Laminates Using Electromagnetic loading

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Acta Mechanica Solida Sinica 2022年第5期35卷 891-900页

作者： Huaipu Kang Jintao Liang Yi Li Hao Cui Yulong Li NPU Yangtze River Delta Research Institute Suzhou215400China School of Aeronautics Northwestern Polytechnical UniversityXi’an710072China School of Civil Aviation Northwestern Polytechnical UniversitySuzhou215400China

The dynamic biaxial compression test for carbon-fiber-reinforced polymer(CFRP)laminates was carried out via synchronous electromagnetic loading in this study.During the experiments,four stress pulses transmitted along four incident bars,loading the square specimen simultaneously from four directions to keep the center of the specimen still.The dynamic mechanical behavior of CFRP was obtained employing the one-dimensional wave propagation theory,and the deformation and failure processes of the specimens were recorded by a high-speed camera.The effects of various biaxial stresses on the compressive strength were investigated in three biaxial and one uniaxial loading cases.For the CFRP laminates,the dynamic transverse compressive stress showed little effect on the longitudinal ultimate compressive strength.Numerical simulations were performed to understand the dynamic stress wave propagation.It showed that the employed loading device could guarantee good biaxial loading conditions until the ultimate failure of the specimens.This approach allows for the dynamic biaxial compression testing of various materials,which is of great significance in evaluating the dynamic impact performance of aeronautical composites.

关键词： Carbon-fiber-reinforced polymer(CFRP) dynamic loading Biaxial testing Electromagnetic loading

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Microstructure evolution of ultra-high-strength twinning-induced plasticity(TWIP)steel under dynamic loading

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Journal of Iron and Steel Research(International) 2021年第1期28卷 66-75页

作者： Qi‑hang Pang Mei Xu Zhen‑li Mi Juan Cui Jing Guo School of Materials and Metallurgy University of Science and Technology LiaoningAnshan 114051LiaoningChina State Key Laboratory of Metal Material for Marine Equipment and Application Anshan 114009LiaoningChina State Key Laboratory of Advanced Stainless Steel Materials Taiyuan Iron and Steel Group Co.Ltd.Taiyuan 030003ShanxiChina Institute of Engineering Technology University of Science and Technology BeijingBeijing 100083China Beijing Jianlong Heavy Industry Group Co. Ltd.Beijing 100070China

To prepare ultra-high-yield strength twinning-induced plasticity(TWIP)steel and reveal its work hardening mechanism at different strain rates from the microcosmic range,the microstructure evolution mechanism of Fe–20Mn–0.6C TWIP steel was investigated at strain rates of 10^(-4)–10^(3)s^(-1)using a high-speed tensile testing machine and a transmission electron microscope.The results show that the strain rate and deformation had a significant effect on the twin morphology of TWIP steels.At a strain rate of 10^(2)s^(-1),secondary deformation twins were developed,which intersected with the initial deformation twins and increased the resistance of dislocation movement,as well as the plasticity.TWIP steel at a strain rate of 10^(2)s^(-1)had a higher twin formation speed than that at 10^(0)s^(-1).At the same amount of deformation,the twin boundary fraction was higher and increased linearly at a strain rate of 10^(2)s^(-1),while the rule of twin growth at 10^(0)s^(-1)was conformed to S-curve change of DoseResp model.

关键词： Twinning-induced plasticity steel Electron backscattered diffraction,Microstructure dynamic loading Strain rate Work hardening

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NMR-based damage characterisation of backfill material in host rock under dynamic loading

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International Journal of Mining Science and Technology 2020年第3期30卷 329-335页

作者： Binglei Li Jiquan Lan Guangyao Si Guopeng Lin Liuqing Hu College of Zijin Mining Fuzhou UniversityFuzhou 350108China School of Minerals and Energy Resources Engineering University of New South WalesSydney 2205Australia

It is not uncommon that backfill material used in underground mining being exposed to repetitive dynamic stresses induced by blasting operations or rockburst events. Understanding the strength and fracture evolution of backfilled stopes is critical to maintain the long-term stope stability and ensure safe mining activities. This paper aims to study the damage evolution of the backfill material and its host rock behaviour under three-dimensional(3D) dynamic loading. Using a true-triaxial testing machine, multiple samples of backfill material enclosed by country rock were fabricated and tested under various dynamic loadings with different true-triaxial confining stress conditions. In addition, the nuclear magnetic resonance(NMR) measurement was conducted on the samples before and after exerting static and dynamic loading to obtain their porosity distribution changes. The experiment results suggested that with the increase of the dynamic loading, the porosity of the backfill sample goes through a two-stage process,which shows a slightly linear decrease and then followed by an exponential increase. The research findings can help understand the damage mechanism and fracture development of backfilled stopes and its host rock in deep underground mines, which are constantly subject to the combination of 3D static confining stress and dynamic loading.

关键词： dynamic loading Backfill-country rock system True triaxial test Coupled static and dynamic loads Nuclear magnetic resonance(NMR) Damage evolution

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Evaluation on Fracture Toughness at dynamic loading for Welded Joint Based on the Local Approach

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Journal of Materials Science & Technology 2004年第1期20卷 113-117页

作者： Hongyang JING, Lianyong XU, Lixing HUO and Yufeng ZHANGSchool of Materials Science and Engineering, Tianjin University, Tianjin 300072, China Sch. of Mat. Sci. and Eng. Tianjin Univ. Tianjin 300072 China

The changes in mechanical properties and fracture toughness by dynamic loading were investigated with experiments. The parameter R, which can reflect the effect of the loading rate and the temperature rising during the high loading rate, could be employed to describe the constituent relation for the typical structure steel and its weld metal. The dynamic loading effect on the stress/strain fields and the temperature variation in the vicinity of the crack tip was analyzed by the finite element method, the dynamic fracture behavior was evaluated based on the local approach. It has been found that the Weibull stress is an effective fracture parameter, independent of the temperature and the loading rate.

关键词： Fracture toughness dynamic loading Welded joint

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Effective Virtual Reality Based Building Navigation Using dynamic loading and Path Optimization

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International Journal of Automation and computing 2009年第4期6卷 335-343页

作者： Qing-Jin Peng Xiu-Mei Kang Ting-Ting Zhao Department of Mechanical and Manufacturing Engineering University of Manitoba Winnipeg R3T 5V6 Canada

Although computer capabilities have been improved significantly, a large-scale virtual reality （VR） system demands much more in terms of memory and computation than the current computer systems can offer. This paper discusses two important issues related to VR performance and applications in building navigation. These are dynamic loading of models based on cell segmentation for the optimal VR operation, and the route optimization based on path planning for easy navigation. The VR model of engineering and information technology complex （EITC） building at the University of Manitoba is built as an example to show the feasibility of the proposed methods. The reality, enhanced by three-dimensional （3D） real-time interactivity and visualization, leads navigators into a state of the virtual building immersion.

关键词： Virtual reality （VR） virtual environments （VEs） building navigation dynamic loading cell segmentation path planning

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Principal axes of M-DOF structures PartⅡ:dynamic loading

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Earthquake Engineering and Engineering Vibration 2003年第1期2卷 39-50页

作者： Zach Liang GeorgeC.Lee Department of Civil Structural and Environmental Engineering University at BuffaloState University of New YorkBuffaloNew YorkUSA Research Associate Professor Multidisciplinary Center for Earthquake Engineering Research University at BuffaloState University of New YorkBuffaloNew YorkUSA Samuel P.Capen Professor of Engineering

This paper is the second in a two-part series that discusses the principal axes of M-DOF structures subjected to static and dynamic loads.The primary purpose of this series is to understand the magnitude of the dynamie response of structures to enable better design of structures and response modification devices/systems.Under idealized design condi- tions,the structural responses are obtained by using single directinn input ground motions in the direction of the intended response modification devices/systems,and by assuming that the responses of the structure is deconpleable in three mutual- ly perpendicular directions.This standard practice has been applied to both new and retrofitted structures using various seis- mic protective systems.Very limited information is available on the effects of neglecting the impact of directional couplings (cross effects of which torsion is a component)of the dynamic response of structures.In order to quantify such effects,it is necessary to examine the principal axes of structures under both static and dynamic loading.In this twn-part series,the first paper is concerned with static loading,which provides definitions and fundamental formulations,with the conclusion that cross effects of a statically loaded M-DOF structure resulting from the lack of principal axes are of insignificant magnitude. However,under dynamic or earthquake loading,a relatively small amount of energy transferred across perpendicular direc- tions is accumulated,which may result in significant enlargement of the structural response.This paper deals with a formu- lation to define the principal axes of M-DOF structures under dynamic loading and develops quantitative measures to identify cross effects resuhing from the non-existence of principal axes.

关键词： principal axes of M-DOF structures structural response couplings cross effect theoretical base dynamic loading peak response estimation

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