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Minimum Control Energy of Spatial Beam with Assumed Attitude Adjustment Target

Acta Mechanica Solida Sinica 2020年第1期33卷 51-60页

作者： Weipeng Hu Lingjun Yu zichen Deng School of Civil Engineering and Architecture Xi’an University of TechnologyXi’an 710048China State Key Laboratory of Eco-Hydraulics in Northwest Arid Region of China Xi’an University of TechnologyXi’an 710048China Department of Aeronautical Machinery Engineering of Army Aviation Institute Beijing 101123China School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 710072China

The dynamic analysis on the ultra-large spatial structure can be simplified drastically by ignoring the flexibility and damping of the ***,these simplifications will result in the erroneous estimate on the dynamic behaviors of the ultra-large spatial *** the spatial beam as an example,the minimum control energy defined by the difference between the initial total energy and the final total energy in the assumed stable attitude state of the beam is investigated by the structure-preserving method proposed in our previous studies in two cases:the spatial beam considering the flexibility as well as the damping effect,and the spatial beam ignoring both the flexibility and the damping *** the numerical experiments,the assumed simulation interval of three months is evaluated on whether or not it is long enough for the spatial flexible damping beam to arrive at the assumed stable attitude *** then,taking the initial attitude angle and the initial attitude angle velocity as the independent variables,respectively,the minimum control energies of the mentioned two cases are investigated in *** the numerical results,the following conclusions can be *** the fixed initial attitude angle velocity,the minimum control energy of the spatial flexible damping beam is higher than that of the spatial rigid beam when the initial attitude angle is close to or far away from the stable attitude *** the fixed initial attitude angle,ignoring the flexibility and the damping effect will underestimate the minimum control energy of the spatial beam.

关键词： Spatial beam Structure-preserving method Generalized multi-symplectic Minimum control energy Hamiltonian

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In-Plane Dynamic Crushing Behaviors of a Vertex-Based Hierarchical Auxetic Honeycomb

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Acta Mechanica Solida Sinica 2024年第1期37卷 53-62页

作者： Yichen Zan Xiuhui Hou zichen Deng School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi'an 710072China School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentDalian University of TechnologyDalian 116024China

Auxetic metamaterials,which exhibit the negative Poisson’s ratio(NPR)effect,have found wide applications in many engineering ***,their high porosity inevitably weakens their bearing capacity and impact *** improve the energy absorption efficiency of auxetic honeycombs,a novel vertex-based hierarchical star-shaped honeycomb(VSH)is designed by replacing each vertex in the classical star-shaped honeycomb(SSH)with a newly added self-similar *** analytical model is built to investigate the Young’s modulus of VSH,which shows good agreement with experimental results and numerical *** in-plane dynamic crushing behaviors of VSH at three different crushing velocities are investigated,and empirical formulas for the densification strain and plateau stress are *** results reveal more stable deformation modes for VSH,attributed to the addition of self-similar star-shaped ***,compared with SSH under the same relative densities,VSH exhibits better specific energy absorption and higher plateau ***,VSH is verified to be a better candidate for energy absorption while maintaining the auxetic *** study is expected to provide a new design strategy for auxetic honeycombs.

关键词： Vertex-based hierarchical star-shaped honeycomb Auxetic honeycomb Energy absorption Plateau stress Negative Poisson's ratio

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DESIGN OPTIMIZATION FOR TRUSS STRUCTURES UNDER ELASTO-PLASTIC LOADING CONDITION

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Acta Mechanica Solida Sinica 2006年第3期19卷 264-274页

作者： Liu Tao Deng zichen Department of Engineering Mechanics Northwestern Polytechnical University Xi＇an 710072 China State Key Laboratory of Structural Analysis of Industrial Equipment Dalian University of Technology Dalian 116024 China

In this paper, a method for the design optimization of elasto-plastic truss structures is proposed based on parametric variational principles （PVPs）. The optimization aims to find the minimum weight/volume solution under the constraints of allowable node displacements. The design optimization is a formulation of mathematical programming with equilibrium constraints （MPECs）. To overcome the numerical difficulties of the complementary constraints in optimization, an iteration process, comprising a quadratic programming （QP） and an updating process, is employed as the optimization method. Furthermore, the elasto-plastic buckling of truss mem- bers is considered as a constraint in design optimization. A combinational optimization strategy is proposed for the displacement constraints and the buckling constraint, which comprises the method mentioned above and an optimal criterion. Three numerical examples are presented to show the validity of the methods proposed.

关键词： parametric variational principles elasto-plasticity truss structure optimization elasto-plasticity buckling

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Structure-preserving properties of Strmer-Verlet scheme for mathematical pendulum

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Applied Mathematics and Mechanics(English Edition) 2017年第9期38卷 1225-1232页

作者： Weipeng HU Mingzhe SONG zichen DENG School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 710072China State Key Laboratory of Structural Analysis of Industrial Equipment Dalian University of TechnologyDalian 116023Liaoning ProvinceChina

The structure-preserving property, in both the time domain and the frequency domain, is an important index for evaluating validity of a numerical method. Even in the known structure-preserving methods such as the symplectic method, the inherent conser- vation law in the frequency domain is hardly conserved. By considering a mathematical pendulum model, a Stormer-Verlet scheme is first constructed in a Hamiltonian frame- work. The conservation law of the StSrmer-Verlet scheme is derived, including the total energy expressed in the time domain and periodicity in the frequency domain. To track the structure-preserving properties of the Stormer-Verlet scheme associated with the con- servation law, the motion of the mathematical pendulum is simulated with different time step lengths. The numerical results illustrate that the StSrmer-Verlet scheme can preserve the total energy of the model but cannot preserve periodicity at all. A phase correction is performed for the StSrmer-Verlet scheme. The results imply that the phase correction can improve the conservative property of periodicity of the Stormer-Verlet scheme.

关键词： Strmer-Verlet scheme symplectic mathematical pendulum structure-preserving Hamiltonian system phase correction

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Tailored energy absorption for a novel auxetic honeycomb structure under large deformation

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Science China(Physics,Mechanics & Astronomy) 2024年第5期67卷 63-80页

作者： Xiuhui Hou Bin Wang zichen Deng School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 710129China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi'an 710072China School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentDalian University of TechnologyDalian 116024China

In comparison to conventional hexagonal honeycomb structures,auxetic metamaterials with re-entrant configurations have exhibited superior mechanical properties in terms of energy *** further enhance the energy absorption capacity of these materials,a novel re-entrant honeycomb configuration,named novel auxetic re-entrant honeycomb(NARH),is developed by incorporating“”-shaped cell walls into the conventional auxetic re-entrant honeycomb(ARH).Two analytical models for the plateau stress are formulated to consider the plastic deformation of NARH during quasi-static compression and the dynamic impact using the linear momentum ***-static compression tests on 3D printed NARH honeycomb specimens and finite element simulations are performed to verify the effectiveness of the theoretical *** exhibits higher plateau stresses compared with ARH during compression,which can be attributed to the presence of more plastic hinges formed in *** hinges,the embedded parts with inclined cell walls,not only improve stability by forming stable triangles during compression but also enhance the energy absorption capacity.A parametric study is conducted to analyze the effect of impact velocity,thickness,and incline angle of cell walls on *** simulations demonstrate higher sensitivity of the mechanical properties to impact velocity and cell wall *** ribs to the“”-shaped cell walls in NARH further reduces the initial peak force during dynamic crushing while maintaining high energy *** research provides valuable guidelines for the design of energy absorption metamaterials.

关键词： absorption walls shaped

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Identification of Kinematic Errors of Five-axis Machine Tool Trunnion Axis from Finished Test Piece

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Chinese Journal of Mechanical Engineering 2014年第5期27卷 999-1007页

作者： ZHANG Ya FU Jianzhong CHEN zichen The State Key Lab of Fluid Power Transmission and Control Zhejiang University Zhejiang Industry Polytechnic College

Compared with the traditional non-cutting measurement,machining tests can more accurately reflect the kinematic errors of five-axis machine tools in the actual machining process for the ***,measurement and calculation of the machining tests in the literature are quite difficult and time-consuming.A new method of the machining tests for the trunnion axis of five-axis machine tool is ***,a simple mathematical model of the cradle-type five-axis machine tool was established by optimizing the coordinate system settings based on robot ***,the machining tests based on error-sensitive directions were proposed to identify the kinematic errors of the trunnion axis of cradle-type five-axis machine *** adopting the error-sensitive vectors in the matrix calculation,the functional relationship equations between the machining errors of the test piece in the error-sensitive directions and the kinematic errors of C-axis and A-axis of five-axis machine tool rotary table was established based on the model of the kinematic *** to our previous work,the kinematic errors of C-axis can be treated as the known quantities,and the kinematic errors of A-axis can be obtained from the *** method was tested in Mikron UCP600 vertical machining *** machining errors in the error-sensitive directions can be obtained by CMM inspection from the finished test piece to identify the kinematic errors of five-axis machine tool trunnion *** results demonstrated that the proposed method can reduce the complexity,cost,and the time consumed substantially,and has a wider *** paper proposes a new method of the machining tests for the trunnion axis of five-axis machine tool.

关键词： five-axis machine tool kinematic errors trunnion axis test piece error-sensitive directions

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Dynamic Crushing Strength Analysis of Auxetic Honeycombs

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Acta Mechanica Solida Sinica 2016年第5期29卷 490-501页

作者： Xiuhui Hou zichen Deng Kai Zhang School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical University State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology

The in-plane dynamic crushing behavior of re-entrant honeycomb is analyzed and compared with the conventional hexagon *** deformation modes along two orthogonal directions are examined,where a parametric study of the effect of impact velocity and cell wall aspect ratio is *** analytical formula of the dynamic crushing strength is then deduced based on the periodic collapse mechanism of cell *** with the finite element results validate the effectiveness of the proposed analytical *** results also reveal higher plateau stress of re-entrant honeycomb over conventional hexagon topology,implying better energy absorption *** underlying physical understanding of the results is emphasized,where the auxetic effect（negative Poisson＇s ratio） induced in the re-entrant topology is believed to be responsible for this superior impact resistance.

关键词： honeycomb topology collapse plateau emphasized perfectly directions deduced validate Poisson

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Effect of sodium alginate on phosphorus recovery by vivianite precipitation

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Journal of Environmental Sciences 2020年第7期32卷 164-169页

作者： Cong Zhang Dexiu Hu Ruijie Yang zichen Liu State Key Laboratory of Eco-hydraulics in Northwest Arid Region of China Xi’an University of TechnologyXi’an 710048China

There are good prospects for phosphorus recovery from excess sludge by vivianite crystallization while a large number of extracellular polymeric substances in sludge will have impact on vivianite *** this study,as a representative of extracellular polymeric substance,the effect of sodium alginate(SA)on phosphorus recovery by vivianite precipitation under different initial SA concentrations(0–800 mg/L),p H values(6.5–9.0)and Fe/P molar ratios(1:1–2.4:1)was investigated using synthetic *** results showed that SA in low concentrations(≤400 mg/L)had little inhibitory effect on the phosphorus recovery ***,when the concentration of SA was larger than 400 mg/L,the phosphorus recovery rate decreased significantly with increasing SA *** inhibition rate of 800 mg/L SA was about 3 times as large as that of 400 mg/L *** was worth noting that the inhibitory effect of SA on vivianite precipitation decreased with increasing initial p H and Fe/P molar ***,SA has no obvious influence on the composition of products,but the morphology of harvested crystals was transformed from branches to plates or rods in uneven sizes.

关键词： Phosphorus recovery Excess sludge Vivianite Sodium alginate

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Record-breaking High-temperature Outlook for 2023: An Assessment Based on the China Global Merged Temperature(CMST) Dataset

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Advances in Atmospheric Sciences 2024年第2期41卷 369-376页

作者： zichen LI Qingxiang LI Tianyi CHEN School of Atmospheric Sciences and Guangdong Province Key Laboratory for Climate Change and Natural Disasters SUN Yat-Sen UniversityZhuhai 519082China Research Center for Ecology and Environment of Central Asia Chinese Academy of SciencesUrumqi 830011China Southern Laboratory of Ocean Science and Engineering(Guangdong Zhuhai) Zhuhai 519082China

According to the latest version(version 2.0) of the China global Merged Surface Temperature(CMST2.0) dataset, the global mean surface temperature(GMST) in the first half of 2023 reached its third warmest value since the period of instrumental observation began, being only slightly lower than the values recorded in 2016 and 2020, and historically record-breaking GMST emerged from May to July 2023. Further analysis also indicates that if the surface temperature in the last five months of 2023 approaches the average level of the past five years, the annual average surface temperature anomaly in 2023 of approximately 1.26°C will break the previous highest surface temperature, which was recorded in 2016of approximately 1.25°C(both values relative to the global pre-industrialization period, i.e., the average value from 1850 to1900). With El Ni?o triggering a record-breaking hottest July, record-breaking average annual temperatures will most likely become a reality in 2023.

关键词： CMST2.0 global mean surface temperature record-breaking temperature El Ni?o

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Multi-resonator coupled metamaterials for broadband vibration suppression

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Applied Mathematics and Mechanics(English Edition) 2021年第1期42卷 53-64页

作者： Pengcheng ZHAO Kai ZHANG Cheng ZHAO zichen DENG School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an 710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an 710072China

In this study,multi-resonator coupled metamaterials(MRCMs)with local resonators are proposed to obtain the multiple and wide band *** models of the MRCMs are established,and the boundary conditions of the unit cell are obtained with Bloch's *** effects of structural parameters,including the mass of the resonator and the spring stiffness,on the distributions of the band gaps are ***,the frequency domain responses and the time domain responses are calculated for analyzing the structural vibration characteristics and the effects of damping on structural *** results show that the frequency domain response can accurately express the distributions of the band gaps of the MRCMs,and we can increase the number and the width of the band gaps by using the MRCMs for the superior vibration suppression capability.

关键词： multi-resonator coupled metamaterial(MRCM) band gap broadband vibration suppression

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