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Energy absorption behaviors of a novel buffer lander-leg with Yoshimura core

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Chinese Journal of Aeronautics 2024年第4期37卷 333-342页

作者： Yan XU He HUANG Chao ZHANG Rongji FU school of Aeronautics and Astronautics Zhejiang UniversityHangzhou 310027China school of mechanics civil engineering and architecture Northwestern Polytechnical UniversityXi’an 710072China

In the current soft-landing system,the lander-leg and the buffer are two independent parts which may cause weight problem.The traditional mechanical buffers also have their own shortcomings such as small buffer stroke and being non-reusable.A Novel Buffer Lander-leg with Yoshimura core (NBLY) is proposed in this paper,inspired by the Buckling Restrained Brace(BRB).The design details of NBLY and parameter definitions of the core are presented.The finite element analysis modes have been employed to analyze the nonlinear mechanical behaviors of NBLY subjected to the cyclic loading.NBLY with four different core styles of hexagon,octagon,dodecagon and hexadecagon are analyzed and compared.The restraining ratio and cumulative dissipation energy ratio have been obtained to evaluate the energy absorption properties.The results show that the origami pattern has significant influences on the deformation ductility,plastic energy absorbing and axial load transferring to the core.The NBLY with octagon core has outstanding properties,especially the hysteretic energy dissipation and enhancement of compression capacity.The interaction mechanism between the core and encasing member constrains the deformation extensions and contributes to the frictional energy dissipation of the NBLYs.This paper provides a new conceptual design of buffer lander-leg for soft-landing missions.It can realize the reuse function as a buffer lander-leg with better loading-bearing and energy absorption behaviors.

关键词： Lander-leg structure Origami Energy absorption Cyclic loading Finite element analysis

Effect of Size Change on Mechanical Properties of Monolayer Arsenene

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Journal of Wuhan University of Technology(Materials Science) 2024年第1期39卷 206-212页

作者：郭娟刘贵立孙震宇 school of architecture and civil engineering Shenyang University of TechnologyShenyang 110870China

The Young's modulus, shear modulus and Poisson's ratio of monolayer arsenene with different sizes were calculated by finite element method, so as to explore the influence of dimension and orientation on the mechanical properties of monolayer arsenene. The calculation results show that the small size has a significant effect on the mechanical properties of the monolayer arsenene. The smaller the size, the larger the Young's modulus and Poisson's ratio of the monolayer arsenene. The size change has a great influence on the Young's modulus of the arsenene handrail direction, and the Young's modulus of the zigzag direction is not sensitive to the size change. Similarly, the size change has a significant effect on the shear modulus of arsenene in the handrail direction, while the shear modulus in the zigzag direction has no significant effect on its size change. For the Poisson's ratio, the situation is just the opposite, and the effect of the size change on the Poisson's ratio of the arsenene zigzag direction is greater than that of the handrail direction.

关键词： finite element method arsenene size change mechanical properties

2.5-dimension soil seismic response to oblique incident waves based on exact free-field solution

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Frontiers of Structural and civil engineering 2024年第2期18卷 216-235页

作者： Yeongbin Yang Zeyang Zhou Xiaoli Wang Xiongfei Zhang Zhilu Wang school of civil engineering Chongqing UniversityChongqing 400045China school of civil engineering and architecture Chongqing University of Science and TechnologyChongqing 401331China

With the three dimensional(3D)oblique incident waves exactly determined for the free field,the soil seismic responses in both frequency and time domains are studied by the 2.5 dimension(2.5D)finite/infinite element method.First,the free-field responses in frequency domain are solved exactly for 3D arbitrary incident P and SV waves,which requires no coordinate conversion or extra effort for SV waves with super-critical incident angles.Next,the earthquake spectra are incorporated by the concept of equivalent seismic forces on the near-field boundary,based only on the displacements input derived for unit ground accelerations of each frequency using the 2.5D approach.For the asymmetric 2.5D finite/infinite element model adopted,the procedure for soil seismic analysis is presented.The solutions computed by the proposed method are verified against those of Wolf’s and de Barros and Luco’s and for inversely calculated ground motions.Of interest is that abrupt variation in soil response occurs around the critical angle on the wave propagation plane for SV waves.In addition,the horizontal displacements attenuate with increasing horizontal incident angle,while the longitudinal ones increase inversely for 3D incident P and SV waves.

关键词： 3D oblique incident wave seismic response analysis 2.5D approach infinite element half-space

A Comprehensive Study on the Consequences of Gap-Graded Sands Considering the Loss of Fine Particles

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Journal of Earth Science 2024年第2期35卷 597-612页

作者： Weiping Liu Yu Gan Yunwei Cui Faming Huang Lina Hu school of civil engineering and architecture Nanchang UniversityNanchang330031China

Water and sand leakage disasters are likely to occur during construction in water-rich sand layer areas,resulting in ground collapse.The stress-strain action characteristics of discontinuous graded sand under different internal erosion degrees,and the evolution mechanism of water and sand leakage disasters caused by the internal erosion need to be further explored.Therefore,this paper takes the discontinuous graded sand in a water rich sand layer area in Nanchang City of China as the research object.Considering the influence of different fine particle losses(0,10%,20%and 30%)under the internal erosion of sand,the salt solution method is used to realize the specified loss of fine particles in the internal erosion.The stress-strain behavior after the loss of fine particles due to internal erosion is studied by triaxial shear test.Meanwhile,the physical model test and PFC-CFD method are both used to study the evolution rules of water and sand leakage disaster considered the influence of internal erosion degrees.Results show that:(1)under the same confining pressure,the peak failure strength of sand samples decreases along with the increase of fine particle loss.(2)In the water and sand leakage test of saturated sand,a natural filter channel is formed above the observed soil arch.The greater the loss of fine particles,the steeper and wider the collapse settlement area.(3)The relationship between the cumulative amount of water and sand leakage and time is nonlinear.The total mass loss of sand increases along with the increase of internal erosion degree.(4)After the soil arch is formed around the damaged opening,the sand continues to converge above the soil arch under the action of water flow,resulting in the dense convergence of contact force chains.

关键词： sandy soil internal erosion stress and strain water and sand leakage PFC3D engineering geology

The Role of the Spatial Network in Urban Disaster Risk Variations:Reimagining the Notion of Spatial Vulnerability at the Urban Scale

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International Journal of Disaster Risk Science 2024年第3期15卷 303-316页

作者： Monia Del Pinto Ksenia Chmutina Falli Palaiologou Lee Bosher school of architecture Building and Civil Engineering Loughborough University school of Business University of Leicester

The notion of “spatial vulnerability” is present in most disaster studies with a strong geographical connotation and accordingly is adopted at all scales, including the urban. While enabling mapping and visualizing risk patterns at macroscales, this geocentric foundation fails to capture disaster risk dynamics associated with the urban spatial network—an element that plays a significant role in the everyday and emergency functioning of cities, enabling users' movement and interaction. Yet,urban vulnerability assessment overlooks this aspect and thus leaves urban disaster risk mechanisms partially unexplored.This study investigated the role of the network of urban public open spaces(UPOS) in the creation and progression of urban disaster risk in earthquake-prone settlements. Through a multimethod approach that integrates quantitative and qualitative methods and explores spatial configuration, planning policies, and practices of use of UPOS in everyday and emergency scenarios, our study demonstrated that UPOS configuration plays an active role in urban disaster risk. Urban public open spaces impact risk by influencing the exposure of pedestrians and their capacity for self-protection. The study further reconceptualized spatial vulnerability at the urban scale, as the fraction of vulnerability associated to the spatial network, highlighting the interplay of planning policies and spatial practices in its production and progression. Our findings make the notion of spatial vulnerability less ambiguous at the urban scale, by viewing the variable as an imbalance in capacities and exposure that generates spatially unsafe conditions. This refined conceptualization of spatial vulnerability becomes a lens for a more granular approach to urban disaster risk reduction and city planning by identifying and integrating sociospatial considerations.

关键词： Central Italy Earthquakes Pedestrian evacuation Space syntax Spatial vulnerability Urban disaster risk

Experimental Investigation of the Operating Characteristics of a Pulsating Heat Pipe with Ultra-Pure Water and Micro Encapsulated Phase Change Material Suspension

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Journal of Thermal Science 2024年第2期33卷 457-468页

作者： SHI Weixiu SU Xiaoyang CHEN Hongdi PAN Lisheng Beijing engineering Research Center of Sustainable Energy and Buildings Beijing University of Civil Engineering and ArchitectureBeijing100044China school of Environment and Energy engineering Beijing University of Civil Engineering and ArchitectureBeijing100044China State Key Laboratory of High Temperature Gas Dynamics Institute of MechanicsChinese Academy of SciencesBeijing100190China

The specific heat capacity of working fluid is an important influence factor on heat transfer characteristic of the pulsating heat pipe(PHP).Due to the relatively large specific heat capacity of micro encapsulated phase change material(MEPCM) suspension,a heat transfer performance experimental facility of the PHP was established.The heat transfer characteristic with MEPCM suspension of different mass concentrations(0.5% and 1.0%) and ultra-pure water were compared experimentally.It was found that when the PHP uses MEPCM suspension as its working fluid,operating stability is impoverished under lower heating power and the operating stability is better under higher heating power.At the inclination angle of 90°,the temperature at heating side decreases compared to ultra-pure water and the temperature at heating side decreases with the raising of MEPCM suspension mass concentration.The heat transfer characteristic of the PHP is positively correlated with the inclination angle and the 90° is optimum.The unfavorable effect of the inclination angle decreases with heating power increasing.When the inclination angle is 90°,the PHP with MEPCM suspension at 1.0% of mass concentration has the lowest thermal transfer resistance and followed by ultra-pure water and MEPCM suspension at 0.5% of mass concentration has the highest thermal transfer resistance.When the inclination angles are 60° and30°,the effect of gravity on the flow direction is reduced to 86.6% and 50% of that on the inclination angle of 90°,respectively,and the promoting effect of gravity on the working fluid is further weakened as the inclination angle further decreases.Due to the high viscosity of MEPCM suspension,the PHP with ultra-pure water has the lowest heat transfer resistance.When the inclination angles is 60°,the thermal resistance with MEPCM suspension at0.5% of the mass concentration is lower than that at 1.0% at the heating power below 230 W.The thermal resistance of MEPCM suspension tends to be similar for heating power of 230-250 W.At the heating

关键词： pulsating heat pipe(PHP) micro encapsulated phase change material(MEPCM) heat transfer characteristic inclination angle

An Efficient Reliability-Based Optimization Method Utilizing High-Dimensional Model Representation and Weight-Point Estimation Method

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Computer Modeling in engineering & Sciences 2024年第5期139卷 1775-1796页

作者： Xiaoyi Wang Xinyue Chang Wenxuan Wang Zijie Qiao Feng Zhang school of Mechatronic engineering Lanzhou Jiaotong UniversityLanzhou730070China school of Electronic and Information engineering Lanzhou Jiaotong UniversityLanzhou730070China school of mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’anChina

The objective of reliability-based design optimization(RBDO)is to minimize the optimization objective while satisfying the corresponding reliability requirements.However,the nested loop characteristic reduces the efficiency of RBDO algorithm,which hinders their application to high-dimensional engineering problems.To address these issues,this paper proposes an efficient decoupled RBDO method combining high dimensional model representation(HDMR)and the weight-point estimation method(WPEM).First,we decouple the RBDO model using HDMR and WPEM.Second,Lagrange interpolation is used to approximate a univariate function.Finally,based on the results of the first two steps,the original nested loop reliability optimization model is completely transformed into a deterministic design optimization model that can be solved by a series of mature constrained optimization methods without any additional calculations.Two numerical examples of a planar 10-bar structure and an aviation hydraulic piping system with 28 design variables are analyzed to illustrate the performance and practicability of the proposed method.

关键词： Reliability-based design optimization high-dimensional model decomposition point estimation method Lagrange interpolation aviation hydraulic piping system

Impact Analysis of Microscopic Defect Types on the Macroscopic Crack Propagation in Sintered Silver Nanoparticles

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Computer Modeling in engineering & Sciences 2024年第4期139卷 441-458页

作者： Zhongqing Zhang Bo Wan Guicui Fu Yutai Su Zhaoxi Wu Xiangfen Wang Xu Long school of Reliability and Systems engineering Beihang UniversityBeijing100191China school of mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an710072China China Aerospace Components engineering Center Beijing100098China

Sintered silver nanoparticles(AgNPs)arewidely used in high-power electronics due to their exceptional properties.However,the material reliability is significantly affected by various microscopic defects.In this work,the three primary micro-defect types at potential stress concentrations in sintered AgNPs are identified,categorized,and quantified.Molecular dynamics(MD)simulations are employed to observe the failure evolution of different microscopic defects.The dominant mechanisms responsible for this evolution are dislocation nucleation and dislocation motion.At the same time,this paper clarifies the quantitative relationship between the tensile strain amount and the failure mechanism transitions of the three defect types by defining key strain points.The impact of defect types on the failure process is also discussed.Furthermore,traction-separation curves extracted from microscopic defect evolutions serve as a bridge to connect the macro-scale model.The validity of the crack propagation model is confirmed through tensile tests.Finally,we thoroughly analyze how micro-defect types influence macro-crack propagation and attempt to find supporting evidence from the MD model.Our findings provide a multi-perspective reference for the reliability analysis of sintered AgNPs.

关键词： Sintered silver nanoparticles defect types microscopic defect evolution macroscopic crack propagation molecular dynamics simulation cohesive zone model

Graph Convolutional Networks Embedding Textual Structure Information for Relation Extraction

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Computers, Materials & Continua 2024年第5期79卷 3299-3314页

作者： Chuyuan Wei Jinzhe Li Zhiyuan Wang Shanshan Wan Maozu Guo school of Electrical and Information engineering Beijing University of Civil Engineering and ArchitectureBeijing102616China

Deep neural network-based relational extraction research has made significant progress in recent years,andit provides data support for many natural language processing downstream tasks such as building knowledgegraph,sentiment analysis and question-answering systems.However,previous studies ignored much unusedstructural information in sentences that could enhance the performance of the relation extraction task.Moreover,most existing dependency-based models utilize self-attention to distinguish the importance of context,whichhardly deals withmultiple-structure information.To efficiently leverage multiple structure information,this paperproposes a dynamic structure attention mechanism model based on textual structure information,which deeplyintegrates word embedding,named entity recognition labels,part of speech,dependency tree and dependency typeinto a graph convolutional network.Specifically,our model extracts text features of different structures from theinput sentence.Textual Structure information Graph Convolutional Networks employs the dynamic structureattention mechanism to learn multi-structure attention,effectively distinguishing important contextual features invarious structural information.In addition,multi-structure weights are carefully designed as amergingmechanismin the different structure attention to dynamically adjust the final attention.This paper combines these featuresand trains a graph convolutional network for relation extraction.We experiment on supervised relation extractiondatasets including SemEval 2010 Task 8,TACRED,TACREV,and Re-TACED,the result significantly outperformsthe previous.

关键词： Relation extraction graph convolutional neural networks dependency tree dynamic structure attention