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Topology optimization of chiral metamaterials with application to underwater sound insulation

Applied Mathematics and Mechanics(English Edition) 2024年第7期45卷 1119-1138页

作者： Chao WANG Honggang ZHAO Yang WANG Jie ZHONG Dianlong YU Jihong WEN Laboratory of Science and Technology on Integrated Logistics Support National University of Defense TechnologyChangsha410073China

Chiral metamaterials have been proven to possess many appealing mechanical phenomena,such as negative Poisson's ratio,high-impact resistance,and energy *** work extends the applications of chiral metamaterials to underwater sound *** chiral metamaterials with low acoustic impedance and proper stiffness are inversely designed using the topology optimization *** acoustic impedance enables the metamaterials to have a high and broadband sound transmission loss(STL),while proper stiffness guarantees its robust acoustic performance under a hydrostatic *** proof-of-concept demonstrations,two specimens are fabricated and tested in a water-filled impedance *** results show that,on average,over 95%incident sound energy can be isolated by the specimens in a broad frequency range from 1 k Hz to 5 k Hz,while the sound insulation performance keeps stable under a certain hydrostatic *** work may provide new insights for chiral metamaterials into the underwater applications with sound insulation.

关键词： chiral metamaterial topology optimization underwater sound insulation low acoustic impedance sound transmission loss(STL)

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Nonlinear metamaterial enabled aeroelastic vibration reduction of a supersonic cantilever wing plate

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Applied Mathematics and Mechanics(English Edition) 2024年第10期45卷 1749-1772页

作者： Peng SHENG Xin FANG Dianlong YU Jihong WEN Laboratory of Science and Technology on Integrated Logistics Support College of Intelligence Science and TechnologyNational University of Defense TechnologyChangsha 410073China

The violent vibration of supersonic wings threatens aircraft *** paper proposes the strongly nonlinear acoustic metamaterial(NAM)method to mitigate aeroelastic vibration in supersonic wing *** employ the cantilever plate to simulate the practical behavior of a *** aeroelastic vibration model of the NAM cantilever plate is established based on the mode superposition method and a modified third-order piston *** aerodynamic properties are systematically studied using both the timedomain integration and frequency-domain harmonic balance *** presenting the flutter and post-flutter behaviors of the NAM wing,we emphasize more on the preflutter broadband vibration that is prevalent in *** results show that the NAM method can reduce the low-frequency and broadband pre-flutter steady vibration by 50%-90%,while the post-flutter vibration is reduced by over 95%,and the critical flutter velocity is also slightly *** clarified,the significant reduction arises from the bandgap,chaotic band,and nonlinear resonances of the NAM *** reduction effect is robust across a broad range of parameters,with optimal performance achieved with only 10%attached *** work offers a novel approach for reducing aeroelastic vibration in aircraft,and it expands the study of nonlinear acoustic/elastic metamaterials.

关键词： nonlinear acoustic metamaterial(NAM) hypersonic aeroelastic vibration vibration reduction fluid-structure interaction

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Mechanical properties and flow stress constitutive relationship of Ti–6Al–4V alloy with equiaxed microstructure at cryogenic temperatures

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Chinese Journal of Aeronautics 2025年第1期38卷 365-379页

作者： Jingwen HU Xun CHEN Yashun WANG Chen YANG College of Intelligence Science and Technology National University of Defense TechnologyChangsha 410073China Laboratory of Science and Technology on Integrated Logistics Support National University of Defense TechnologyChangsha 410073China

This paper investigates the uniaxial tensile mechanical properties and flow behavior of Ti-6Al-4V alloys with equiaxed microstructure at cryogenic temperatures ranging from 77 K to298 K and strain rates from 10^(-4)/s to 10^(-2)/*** electron microscopy is utilized to analyze the fracture morphology,aiming to reveal the fracture behavior at various *** applicability of the Zener-Hollomon parameter and the Johnson-Cook model in describing the flow stress of Ti-6Al-4V at cryogenic temperatures is ***,a constitutive relationship modeling method based on the variational recurrent networks is *** test results show a significant increase in the strength of equiaxed Ti-6Al-4V alloy under cryogenic conditions while the plastic deformation process is ***,the fracture analysis indicates that even at 77 K,the fracture process is still dominated by ductile fracture,and brittle fracture does not occur within the range of 77 K to 298 *** fitting results validate the performance of the Zener-Hollomon parameter and the Johnson-Cook model in describing the deformation flow stress of Ti-6Al-4V alloy at cryogenic *** results also indicate that the proposed constitutive relationship modeling method based on the variational recurrent network performs better,making it a potential method for widespread applications.

关键词： Titanium alloys Mechanical properties Cryogenics Fracture testing Flow behavior

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Local resonance metamaterial-based integrated design for suppressing longitudinal and transverse waves in fluid-conveying pipes

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Applied Mathematics and Mechanics(English Edition) 2024年第10期45卷 1821-1840页

作者： Donghai HAN Qi JIA Yuanyu GAO Qiduo JIN Xin FANG Jihong WEN Dianlong YU Laboratory of Science and Technology on Integrated Logistics Support National University of Defense TechnologyChangsha 410073China College of Intelligence Science and Technology National University of Defense TechnologyChangsha 410073China

To solve the problem of low broadband multi-directional vibration control of fluid-conveying pipes,a novel metamaterial periodic structure with multi-directional wide bandgaps is ***,an integrated design method is proposed for the longitudinal and transverse wave control of fluid-conveying pipes,and a novel periodic structure unit model is constructed for vibration *** on the bandgap vibration reduction mechanism of the acoustic metamaterial periodic structure,the material parameters,structural parameters,and the arrangement interval of the periodic structure unit are *** finite element method(FEM)is used to predict the vibration transmission characteristics of the fluid-conveying pipe installed with the vibration reduction periodic ***,the wave/spectrum element method(WSEM)and experimental test are used to verify the calculated results ***,the vibration attenuation characteristics of the structure under different conditions,such as rubber material parameters,mass ring material,and fluid-structure coupling effect,are *** results show that the structure can produce a complete bandgap of 46 Hz-75 Hz in the low-frequency band below 100 Hz,which can effectively suppress the low broadband vibration of the fluidconveying *** addition,a high damping rubber material is used in the design of the periodic structure unit,which realizes the effective suppression of each formant peak of the pipe,and improves the vibration reduction effect of the fluid-conveying ***,the structure has the effect of suppressing both bending vibration and longitudinal vibration,and effectively inhibits the transmission of transverse waves and longitudinal waves in the *** research results provide a reference for the application of acoustic metamaterials in the multi-directional vibration control of fluid-conveying pipes.

关键词： fluid-conveying pipe acoustic metamaterial multi-directional vibration reduction local resonance

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Mission-oriented capability evaluation for combat network based on operation loops

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Defence technology（防务技术） 2024年第12期42卷 156-175页

作者： Yang Wang Junyong Tao Xiaoke Zhang Guanghan Bai Yunan Zhang Laboratory of Science and Technology on Integrated Logistics Support College of Intelligence Science and TechnologyNational University of Defense TechnologyChangsha 410073China National Key Laboratory for Complex Systems Simulation Beijing 100101China

With continuous growth in scale,topology complexity,mission phases,and mission diversity,challenges have been placed for efficient capability evaluation of modern combat *** at the problems of insufficient mission consideration and single evaluation dimension in the existing evaluation approaches,this study proposes a mission-oriented capability evaluation method for combat systems based on operation ***,a combat network model is given that takes into account the capability properties of combat ***,based on the transition matrix between combat nodes,an efficient algorithm for operation loop identification is proposed based on the Breadth-First *** the mission-capability satisfaction of nodes,the effectiveness evaluation indexes for operation loops and combat network are proposed,followed by node importance *** a case study of the combat scenario involving space-based support against surface ships under different strategies,the effectiveness of the proposed method is *** results indicated that the ROI-priority attack method has a notable impact on reducing the overall efficiency of the network,whereas the O-L betweenness-priority attack is more effective in obstructing the successful execution of enemy attack missions.

关键词： Combat network Operation loop identification Mission-oriented Network reliability Network effectiveness evaluation Strike strategies

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Collision enhanced hyper-damping in nonlinear elastic metamaterial

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Chinese Physics B 2022年第6期31卷 459-469页

作者： Miao Yu Xin Fang Dianlong Yu Jihong Wen Li Cheng Laboratory of Science and Technology on Integrated Logistics Support National University of Defense TechnologyChangsha 410073China

Nonlinear elastic metamaterial,a topic which has attracted extensive attention in recent years,can enable broadband vibration reduction under relatively large *** combination of damping and strong nonlinearity in metamaterials may entail extraordinary effects and offer the capability for low-frequency and broadband vibration ***,there exists a clear lack of proper design methods as well as the deficiency in understanding properties arising from this *** tackle this problem,this paper numerically demonstrates that the nonlinear elastic metamaterials,consisting of sandwich damping layers and collision resonators,can generate very robust hyper-damping effect,conducive to efficient and broadband vibration *** collision-enhanced hyper damping is persistently presented in a large parameter space,ranging from small to large amplitudes,and for small and large damping *** achieved robust effects greatly enlarge the application scope of nonlinear *** report the design concept,properties and mechanisms of the hyper-damping and its effect on vibration *** paper reveals new properties offered by nonlinear elastic metamaterials,and offers a robust method for achieving efficient low-frequency and broadband vibration suppression.

关键词： nonlinear elastic metamaterial hyper-damping vibration suppression

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Dynamic Investigations on the Wear Behavior of a 3D Revolute Joint Considering Time-Varying Contact Stiffness: Simulation and Experiment

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Chinese Journal of Mechanical Engineering 2023年第6期36卷 230-246页

作者： Li Zhang Yining Fang Guanghan Bai Junyong Tao College of Information and Communication National University of Defense TechnologyWuhan 430010China Laboratory of Science and Technology on Integrated Logistics Support College of Intelligence Science and TechnologyNational University of Defense TechnologyChangsha 410073China

The existence of the relative radial and axial movements of a revolute joint’s journal and bearing is widely *** three-dimensional(3D)revolute joint model considers relative radial and axial clearances;therefore,the freedoms of motion and contact scenarios are more realistic than those of the two-dimensional *** paper proposes a wear model that integrates the modeling of a 3D revolute clearance joint and the contact force and wear depth ***-varying contact stiffness is first considered in the contact force ***,a cycle-update wear depth calculation strategy is presented.A digital image correlation(DIC)non-contact measurement and a cylindricity test are *** measurement results are compared with the numerical simulation,and the proposed model’s correctness and the wear depth calculation strategy are *** results show that the wear amount distribution on the bearing’s inner surface is uneven in the axial and radial directions due to the journal’s stochastic *** maximum wear depth locates where at the bearing’s edges the motion direction of the follower *** find-ings help to seek the revolute joints’wear-prone parts and enhance their durability and reliability through improved design.

关键词： Multibody dynamics 3D revolute joint Wear prediction Digital image correlation

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Modelling and Prediction of Oil Monitoring Data for Power System Based on Grey Theory

Modelling and Prediction of Oil Monitoring Data for Power Sy...

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UNIfied Conference of International Workshop on Defence Applications of Multi-Agent Systems, DAMAS 2023, International Conference on Maintenance Engineering, IncoME-V 2023, International conference on the Efficiency and Performance Engineering Network, TEPEN 2023

作者： Yang, Dingxin Liu, Xiaorong Laboratory of Science and Technology on Integrated Logistics Support National University of Defense Technology Changsha410073 China

ISBN: (纸本)9783031494123

In order to realize the modeling and prediction of oil monitoring parameters for unequal interval sampling of equipment power system, an improved two-step non-equidistance GM (1,1) modeling method is studied. This method is not only suitable for high growth sequence, but also has high model accuracy. Based on this method, the grey prediction model of oil wear particle number is established, and the prediction accuracy is compared with that of the non-equidistance modeling accuracy of data transformation method. The results show that the former has higher accuracy and is more suitable for the short-term prediction of oil wear particle number trend. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.

关键词： Forecasting

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VIBRATION SUPPRESSION OF GRADIENT LOCALLY MULTIRESONANT CYLINDRICAL META-SHELLS 30

VIBRATION SUPPRESSION OF GRADIENT LOCALLY MULTIRESONANT CYLI...

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30th International Congress on Sound and Vibration, ICSV 2024

作者： Yibo, Ke Jianfei, Yin Li, Cai Lixin, Yang Zhoufu, Zheng Dianlong, Yu Jihong, Wen Laboratory of Science and Technology on Integrated Logistics Support National University of Defense Technology Changsha410073 China

ISBN: (纸本)9789090390581

Vibration reduction of shell-type structures is widely required across various industries, including automobile, aerospace, civil, and ocean engineering. Acoustic or elastic metamaterials have been extensively studied for their extraordinary abilities to manipulate wave propagation at the deep sub-wavelength scale. In this research, we investigate a meta-structure with spring-mass resonators periodically attached onto a cylindrical shell to achieve low-frequency, broadband vibration suppression. The dispersive behavior of unit cells is studied by finite element method (FEM). The effects of resonant frequencies of the resonators on bandgaps are investigated. The vibration transmissions in meta-shells are studied using the FEM and the attenuation of vibration energies are demonstrated in the frequency range of the bandgap. To further improve the vibration suppression performance, we propose a new design method for resonator arrays. Overall, the insights gleaned from the analysis results presented in this study offer valuable references for implementing broadband vibration suppression strategies in practical applications involving cylindrical shell structures. © 2024 Proceedings of the International Congress on Sound and Vibration. All rights reserved.

关键词： Shells (structures)

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Application of HMM in Fault Diagnosis of Permanent Magnet DC Motors 15

Application of HMM in Fault Diagnosis of Permanent Magnet DC...

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15th IEEE Global Reliability and Prognostics and Health Management Conference, PHM-Beijing 2024

作者： Hu, Jiangtao Hu, Niaoqing Yang, Yi Yin, Zhengyang Lin, Xiaosong Laboratory of Science and Technology on Integrated Logistics Support College of Intelligence Science and Technology National University of Defense Technology Changsha China

ISBN: (数字)9798350354010

ISBN: (纸本)9798350354010

In order to solve the problem of fault diagnosis of permanent magnet DC (PMDC) motors, this paper applies Hidden Markov Model (HMM) to the fault identification and classification of motor. In this paper, based on the dynamic differential equation of the PMDC motors, the current simulation data of four motor states are obtained, including normal, inter-turn short circuit, brush wear and resistance increase. Then, the HMM is constructed, and the HMM is used to identify and classify the fault of the current simulation data. The results show that when the PMDC motors are faulty, its current signal characteristics will be abnormal, and the use of HMM to identify and classify the current signal of the motor has achieved good results, reflecting the advantages of HMM in the analysis of time-domain signals. The research results have certain reference value for the fault diagnosis of PMDC motors. © 2024 IEEE.

关键词： Permanent magnets

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