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Study on Dynamic Mechanical Behavior of Al-Mg-Si Alloy

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Journal of Wuhan University of Technology(Materials Science) 2024年第2期39卷 454-462页

作者：陶小旺 LIU Jibo LIU Xianbin CHEN Jianbin WANG Yonggang 汪小锋 key laboratory of impact and safety engineering Ministry of EducationNingbo UniversityNingbo 315211China Ningbo Zhanci New Material Co. Ltd.Ningbo 315338China

The dynamic mechanical behavior of Al-Mg-Si alloy was investigated under different strain rates by mechanical property and microstructure characterization,constitutive behavior analysis and numerical simulation in the present *** the strain rate increases,the yield strength,ultimate tensile strength and elongation increase first,then remain almost constant,and finally *** alloy always exhibits a typical ductile fracture mode,not depending on the strain ***,as the strain rate increases,the number of dimples gradually *** deformation can refine grains,however,the grain structure is slightly affected by the strain *** optimized Johnson-Cook constitutive equation was used to describe the mechanical behavior and obtained by fitting the true stress-strain *** parameter C was described by a function related to the strain *** fitting true stress-strain curves by the JC model agree very well with the experimental true stress-strain *** true stress-strain curves calculated by the finite element numerical simulation agree well with the experimental true stress-strain curves.

关键词： Al-Mg-Si alloy strain rate mechanical property microstructure Johnson-Cook model finite element simulation

Layered metastructure containing freely-designed local resonators for wave attenuation

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Defence Technology（防务技术） 2024年第2期32卷 23-31页

作者： Yu Li Huguang He Jiang Feng Hailong Chen Fengnian Jin Hualin Fan State key laboratory for Disaster Prevention&Mitigation of Explosion&impact Army Engineering University of PLANanjing 210007China Rocket Force University of engineering Xi'an 710025China Henan International Joint laboratory of Dynamics of impact and Disaster of engineering Structures Department of Civil EngineeringNanyang Institute of TechnologyNanyang 473004China Guangxi key laboratory of Disaster Prevention and engineering safety and Key Laboratory of Disaster Prevention and Structural Safety of Ministry of EducationCollege of Civil Engineering and ArchitectureGuangxi UniversityNanning 530004China Research Center of Lightweight Structures and Intelligent Manufacturing State Key Laboratory of Mechanics and Control of Mechanical StructuresNanjing University of Aeronautics and AstronauticsNanjing 210016China

Combining periodic layered structure with three-dimensional cylindrical local resonators,a hybrid metastructure with improved wave isolation ability was designed and investigated through theoretical and numerical *** metastructure is composed of periodic rubber layers and concrete layers embedded with three-dimensional resonators,which can be freely designed with multi local resonant frequencies to attenuate vibrations at required frequencies and widen the attenuation *** metastructure can also effectively attenuate seismic *** with layered rubber-based structures,the metastructure has more excellent wave attenuation effects with greater attenuation and wider bandgap.

关键词： Layered metastructure Local resonator Wave attenuation

Experimental investigation of engineered geopolymer composite for structural strengthening against blast loads

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Defence Technology（防务技术） 2024年第2期32卷 496-509页

作者： Shan Liu Chunyuan Liu Yifei Hao Yi Zhang Li Chen Zhan Li key laboratory of Coast Civil Structure safety of Ministry of Education Tianjin UniversityTianjin 300072China Tianjin key laboratory of Prefabricated Buildings and Intelligent Construction Hebei University of TechnologyTianjin 300400China Institute of Defense engineering AMSPLABeijing 100850China engineering Research Center of safety and Protection of Explosion&impact of Ministry of Education Southeast UniversityNanjing 211189JiangsuChina State key laboratory of Disaster Prevention&Mitigation of Explosion&impact Army Engineering University of the PLANanjing 210007JiangsuChina

The recent increase in blast/bombing incidents all over the world has pushed the development of effective strengthening approaches to enhance the blast resistance of existing civil *** geopolymer composite(EGC)is a promising material featured by eco-friendly,fast-setting and strain-hardening characteristics for emergent strengthening and ***,the fiber optimization for preparing EGC and its protective effect on structural elements under blast scenarios are *** this study,laboratory tests were firstly conducted to evaluate the effects of fiber types on the properties of EGC in terms of workability,dry shrinkage,and mechanical properties in compression,tension and *** experimental results showed that EGC containing PE fiber exhibited suitable workability,acceptable dry shrinkage and superior mechanical properties compared with other types of *** that,a series of field tests were carried out to evaluate the effectiveness of EGC retrofitting layer on the enhancement of blast performance of typical *** tests include autoclaved aerated concrete(AAC)masonry walls subjected to vented gas explosion,reinforced AAC panels subjected to TNT explosion and plain concrete slabs subjected to contact *** was found that EGC could effectively enhance the blast resistance of structural elements in different *** AAC masonry walls and panels,with the existence of EGC,the integrity of specimens could be maintained,and their deflections and damage were significantly *** plain concrete slabs,the EGC overlay could reduce the diameter and depth of the crater and spallation of specimens.

关键词： Engineered geopolymer composites Fiber optimization Strengthening material Blast resistance Masonry wall Reinforced AAC panel Plain concrete slab

Modified Sadowski formula-based model for the slope shape amplification effect under multistage slope blasting vibration

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International Journal of Mining Science and Technology 2024年第5期34卷 631-641页

作者： Xiaogang Wu Mingyang Wang Hao Lu Yongjun Zhang Wen Nie State key laboratory of Disaster Prevention&Mitigation of Explosion&impact Army Engineering University of PLANanjing 210007China State key laboratory of Metal Mine safety and Health Ma’anshan 243000China School of Civil engineering Qingdao University of TechnologyQingdao 266520China

Blasting operations,which are crucial to open-pit mine production due to their simplicity and efficiency,require precise control through accurate vibration velocity *** conventional Sadowski formula mainly focuses on blast center distance but neglects the amplification effect of blasting vibration waves by terraced terrain,from which the calculated blasting vibration velocities are smaller than the actual values,affecting the safety of the *** address this issue,our model introduces the influences of slope and time into Sadowski formula to measure safety through blast vibration *** the northern section of the open-pit quartz mine in Jinchang City,Gansu Province,China,the data of a continuous blasting slope project are referred *** findings reveal a noticeable vibration amplification effect during blasting when a multi-stage slope platform undergoes a sudden cross-sectional change near the upper overhanging *** amplification vibration coefficient increases with height,while vibration waves within rocks decrease from bottom to ***,platforms without distinct crosssectional changes exhibit no pronounced amplification during *** addition,the vibration intensity decreases with distance as the rock height difference change *** results obtained by the proposed blast vibration displacement equation incorporating slope shape influence closely agree with real-world *** to Pearson correlation coefficient(PPMCC)analysis,the average accuracy rate of our model is 88.84%,which exceeds the conventional Sadowski formula(46.92%).

关键词： Multistage slope Slope shape influence factor Continuous blasting Sadowski formula Amplification effect

Nano-frictional mechano-reinforcing porous nanowires scaffolds

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Friction 2024年第5期12卷 968-980页

作者： Licheng HUA Conghu HU Jingkang ZHANG Jin LI Chenjie GU Bin HUANG Guangyong LI Jianke DU Wanlin GUO Smart Materials and Advanced Structures laboratory School of Mechanical Engineering&MechanicsNingbo UniversityNingbo315211China key laboratory for Intelligent Nano Materials and Devices of Ministry of Education Nanjing University of Aeronautics and AstronauticsNanjing210016China key laboratory of impact and safety engineering Ministry of EducationSchool of mechanical Engineering and MechanicsNingbo UniversityNingbo315211China Department of Microelectronics and engineering Ningbo UniversityNingbo315211China

Artificial biomaterials with dynamic mechano-responsive behaviors similar to those of biological tissues have been drawing great *** this study,we report a TiO_(2)-based nanowire(TiO_(2)NWs)scaffolds,which exhibit dynamic mechano-responsive behaviors varying with the number and amplitude of nano-deformation *** is found that the elastic and adhesive forces in the TiO_(2)NWs scaffolds can increase significantly after multiple cycles of *** nanofriction experiments show the triboelectric effect of increasing elastic and adhesive forces during the nano-deformation cycles of TiO_(2)NWs *** properties allow the TiO_(2)NW scaffolds to be designed and applied as intelligent artificial biomaterials to simulate biological tissues in the future.

关键词： TiO_(2)NWs scaffolds nano-deformation mechano-reinforcing triboelectric effect intelligent artificial biomaterials

Lunar In Situ Large-Scale Construction:Quantitative Evaluation of Regolith Solidification Techniques

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engineering 2024年第8期39卷 204-221页

作者： Charun Bao Daobo Zhang Qinyu Wang Yifei Cui Peng Feng MOE key laboratory of Civil engineering safety and Durability Department of Civil EngineeringTsinghua UniversityBeijing 100084China State key laboratory of Hydroscience and engineering Tsinghua UniversityBeijing 100084China

Lunar habitat construction is crucial for successful lunar exploration *** to the limitations of transportation conditions,extensive global research has been conducted on lunar in situ material processing techniques in recent *** aim of this paper is to provide a comprehensive review,precise classification,and quantitative evaluation of these approaches,focusing specifically on four main approaches:reaction solidification(RS),sintering/melting(SM),bonding solidification(BS),and confinement formation(CF).Eight key indicators have been identified for the construction of low-cost and highperformance systems to assess the feasibility of these methods:in situ material ratio,curing temperature,curing time,implementation conditions,compressive strength,tensile strength,curing dimensions,and environmental *** scoring thresholds are determined by comparing the construction requirements with the actual *** the evaluated methods,regolith bagging has emerged as a promising option due to its high in situ material ratio,low time requirement,lack of hightemperature requirements,and minimal shortcomings,with only the compressive strength falling below the neutral *** compressive strength still maintains a value of 2–3 *** proposed construction scheme utilizing regolith bags offers numerous advantages,including rapid and large-scale construction,ensured tensile strength,and reduced reliance on equipment and *** this study,guidelines for evaluating regolith solidification techniques are provided,and directions for improvement are *** proposed lunar habitat design based on regolith bags is a practical reference for future research.

关键词： Lunar habitats Lunar in situ construction Regolith bag Solidification and formation In situ materials Evaluation method

Numerical Study on the Aerodynamic and Fluid−Structure Interaction of An NREL-5MW Wind Turbine

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China Ocean engineering 2024年第3期38卷 363-378页

作者： ZHAO Mi YU Wan-li WANG Pi-guang QU Yang DU Xiu-li key laboratory of Urban Security and Disaster engineering of Ministry of Education Beijing University of TechnologyBeijing 100124China State key laboratory of Bridge engineering safety and Resilience Beijing University of TechnologyBeijing 100124China

A 5-MW wind turbine has been modeled and analyzed for fluid-structure interaction and aerodynamic *** this study, a full-scale model of a 5-MW wind turbine is first developed based on a computational fluid dynamics(CFD) approach, in which the unsteady, noncompressible Reynolds Averaged Navier-Stokes(RANS) method is used. The main focus of the study is to analyze the tower shadow effect on the aerodynamic performance of the wind turbine under different inlet flow conditions. Subsequently, the finite element model is established by considering fluid/structure interactions to study the structural stress, displacement, strain distributions and flow field information of the structure under the uniform wind speed. Finally, the fluid-structure interaction model is established by considering turbulent wind and the tower shadow effect. The variation rules of the dynamic response of the one-way and two-way fluid-structure interaction(FSI) models under different wind speeds are analyzed, and the numerical calculation results are compared with those of the centralized mass model. The results show that the tower shadow effect and structural deformation are the main factors affecting the aerodynamic load fluctuation of the wind turbine, which in turn affects the aerodynamic performance and structural stability of the blades. The structural dynamic response of the coupled model shows significant similarity, while the structural displacement response of the former exhibits less fluctuation compared with the conventional centralized mass model. The one-way fluid-structure interaction(FSI)model shows a higher frequency of stress-strain and displacement oscillations on the blade compared with the two-way FSI model.

关键词： computational fluid dynamics methods(CFD) tower shadow effect aerodynamic performance fluidstructure interaction space flow field

An extended social force model on unidirectional flow considering psychological and behavioral impacts of hazard source

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Chinese Physics B 2024年第2期33卷 567-576页

作者：邓凯丰李梦胡祥敏陈涛 Institute of Public safety Research Department of Engineering PhysicsTsinghua UniversityBeijing 100084China Anhui Province key laboratory of Human safety Hefei 230601China Beijing key laboratory of Comprehensive Emergency Response Science Beijing 100084China

An accurate assessment of the evacuation efficiency in case of disasters is of vital importance to the safety design of buildings and street *** sources not only physically but psychologically affect the pedestrians,which may further alter their behavioral *** effect is especially significant in narrow spaces,such as corridors and *** study aims to integrate a non-spreading hazard source into the social force model following the results from a previous experiment and simulation,and to simulate unidirectional pedestrian flows over various crowd densities and clarity–intensity properties of the hazard *** integration include a virtual repulsion force from the hazard source and a decay on the social force *** simulations reveal(i)that the hazard source creates virtual bottlenecks that suppress the flow,(ii)that the inter-pedestrian push forms a stabilisation phase on the flow-density curve within medium-to-high densities,and(iii)that the pedestrians are prone to a less orderly and stable pattern of movement in low clarity–intensity scenarios,possibly with lateral collisions passing the hazard source.

关键词： evacuation social force model hazard source unidirectional pedestrian flow

Non-dimensional analysis on blast wave propagation in foam concrete:Minimum thickness to avoid stress enhancement

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Defence Technology（防务技术） 2024年第6期36卷 30-46页

作者： Ya Yang Xiangzhen Kong Qin Fang State key laboratory of Disaster Prevention&Mitigation of Explosion&impact Army Engineering University of PLANanjing 210007JiangsuChina

Foam concrete is a prospective material in defense engineering to protect structures due to its high energy absorption capability resulted from the long plateau ***,stress enhancement rather than stress mitigation may happen when foam concrete is used as sacrificial claddings placed in the path of an incoming blast *** investigate this interesting phenomenon,a one-dimensional difference model for blast wave propagation in foam concrete is firstly proposed and numerically solved by improving the second-order Godunov *** difference model and numerical algorithm are validated against experimental results including both the stress mitigation and the stress *** difference model is then used to numerically analyze the blast wave propagation and deformation of material in which the effects of blast loads,stress-strain relation and length of foam concrete are *** particular,the concept of minimum thickness of foam concrete to avoid stress enhancement is ***,non-dimensional analysis on the minimum thickness is conducted and an empirical formula is proposed by curve-fitting the numerical data,which can provide a reference for the application of foam concrete in defense engineering.

关键词： Foam concrete Blast wave propagation Non-dimensional analysis Stress enhancement