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Processing,microstructure,and properties of porous ceramic composites with directional channels

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Journal of Materials Science & Technology 2024年第1期168卷 1-15页

作者： Bo Zhang Yang Yang Xueling Fan key laboratory of Service Performance and Protection Technology in Extreme Environments Xi’an Jiaotong UniversityXi’an 710049China state key laboratory for strength and vibration of mechanical structures School of Aerospace EngineeringXi’an Jiaotong UniversityXi’an 710049China

Porous ceramic composites with directional microchannels from micrometer to dozens of micrometer levels have attracted more and more attention in various fields including aerospace,biomedicines,and thermal insulation due to their excellent fluid permeability,mechanical properties,etc.In this article,we summarize the recent directional porous ceramics developments including their main processing routes and respective properties.Meanwhile,the properties get from different processing routes have been com-pared and analyzed in terms of microstructures,mechanical properties,and permeability.Emphasis has been given to the deeper understanding which can allow one to control the microstructural features of these porous ceramic composites to obtain the desired characteristics.This work can provide a useful reference for the development and application of porous ceramic composites with directional microchan-nels.

关键词： Porous ceramic composites Directional microchannels Processing routes Permeability

Aerodynamic optimization of an adaptive flap for next-generation green aircraft

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Chinese Journal of Aeronautics 2024年第2期37卷 100-122页

作者： Tianlong LIN Rosario PECORA Danilo CILIBERTI Wei XIA Shuling HU state key laboratory for strength and vibration of mechanical structures School of Aerospace EngineeringXi’an Jiaotong UniversityXi’an 710049China Deparment of Industrial Engineering Aerospace DivisionUniversity of Naples"FEDERICO II"Napoli 80125Italy

Adaptive,morphing flaps are taking ever-increasing attention in civil aviation thanks to the expected benefits this technology can bring at the aircraft level in terms of high-lift performance improvement and related fuel burnt reduction per flight.Relying upon morphing capabilities,it is possible to fix a unique setting for the flap and adapt the flap shape to match the aerodynamic requirements for take-off or landing.The proper morphed shapes can assure better high-lift performances than those achievable by referring to a conventional flap.Moreover,standing the unique flap setting for take-off and landing,a dramatic simplification of the flap deployment systems may be achieved.As a consequence of this simplification,the deployment system can be fully hosted in the wing,thus avoiding under-wing nacelles with significantly better aerodynamics and fuel consumption.The first step for a rational design of an adaptive flap consists in defining the target morphed shapes and the unique optimal flap setting in the take-off and landing phases.In this work,aerodynamic optimization analyses are carried out to determine the best flap setting and related morphed shapes in compliance with the take-off and landing requirements of a reference civil transport aircraft.Four different initial conditions are adopted to avoid the optimization falling into local optima,thus obtaining four groups of optimal candidate configurations.After comparing each candidate’s performance through 2D and 3D simulations,the optimal configuration has been selected.2D simulations show that the optimal configuration is characterized by a maximum lift increase of 31.92%in take-off and 9.04%in landing.According to 3D simulations,the rise in maximum lift equals 22.26%in take-off and 3.50%in landing.Numerical results are finally verified through wind tunnel tests,and the aerodynamic mechanism behind the obtained improvements is explained by carefully analyzing the flow field around the flap.

关键词： Morphing wings High-lift system Adaptive flap Computational Fluid Dynamics(CFD) Wind tunnel tests

Snap-through behaviors and nonlinear vibrations of a bistable composite laminated cantilever shell:an experimental and numerical study

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Applied Mathematics and Mechanics(English Edition) 2024年第5期45卷 779-794页

作者： Lele REN Wei ZHANG Ting DONG Yufei ZHANG state key laboratory of mechanical System and vibration Shanghai Jiao Tong UniversityShanghai 200240China Department of Mechanics Guangxi UniversityNanning 530004China Beijing key laboratory of Nonlinear vibrations and strength of mechanical structures College of Mechanical EngineeringBeijing University of TechnologyBeijing 100124China School of mechanical Engineering Beijing Institute of TechnologyBeijing 100081China

The snap-through behaviors and nonlinear vibrations are investigated for a bistable composite laminated cantilever shell subjected to transversal foundation excitation based on experimental and theoretical approaches.An improved experimental specimen is designed in order to satisfy the cantilever support boundary condition,which is composed of an asymmetric region and a symmetric region.The symmetric region of the experimental specimen is entirely clamped,which is rigidly connected to an electromagnetic shaker,while the asymmetric region remains free of constraint.Different motion paths are realized for the bistable cantilever shell by changing the input signal levels of the electromagnetic shaker,and the displacement responses of the shell are collected by the laser displacement sensors.The numerical simulation is conducted based on the established theoretical model of the bistable composite laminated cantilever shell,and an off-axis three-dimensional dynamic snap-through domain is obtained.The numerical solutions are in good agreement with the experimental results.The nonlinear stiffness characteristics,dynamic snap-through domain,and chaos and bifurcation behaviors of the shell are quantitatively analyzed.Due to the asymmetry of the boundary condition and the shell,the upper stable-state of the shell exhibits an obvious soft spring stiffness characteristic,and the lower stable-state shows a linear stiffness characteristic of the shell.

关键词： bistable composite laminated cantilever shell snap-through behavior nonlinear vibration nonlinear stiffness characteristic chaos and bifurcation

Deployment analysis of composite thin-walled lenticular tubes with effect of storage time and temperature

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Chinese Journal of Aeronautics 2024年第1期37卷 162-172页

作者： Jinfeng DENG Ning AN Qilong JIA Xiaofei MA School of Aeronautics and Astronautics Sichuan UniversityChengdu 610065China state key laboratory for strength and vibration of mechanical structures School of AerospaceXi’an Jiaotong UniversityXi’an 710049China state key laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116024China Xi’an Institute of Space Radio Technology Xi’an 710100China

Composite Thin-walled Lenticular Tube(CTLT)is increasingly utilized in small satellites missions as a lightweight,foldable,and rollable structural material that facilitates the construction of large deployable systems.The CTLT is initially flattened and coiled around a central hub for storage before launch,during which elastic energy is stored as deformation energy,allowing it to be self-deployed on demand for use in orbit.This work presents a comprehensive investigation into the coiling,storage and deployment behaviors of CTLT that wraps around a central hub.A nonlinear explicit dynamic finite element model was developed with both deformable CTLT and rigidbodies mechanisms including the central hub and guide rollers,as well as the complex interactions among them.The coiling mechanics characteristics such as stored strain energy and rotational moment were presented and validated against experimental data in the literature.Then,the dynamic deployment behaviors were analyzed in terms of two different deployment methods,namely,controlled deployment and free deployment.The effect of material property change during storage was also discussed through numerical experiments.

关键词： Composite deployable structures Deployment dynamics Finite element method Stress relaxation Thin-walled booms

Performance enhancement of a viscoelastic bistable energy harvester using time-delayed feedback control

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Chinese Physics B 2024年第6期33卷 142-154页

作者：黄美玲杨勇歌刘洋 School of Mathematics and Statistics Guangdong University of TechnologyGuangzhou 510520China state key laboratory for strength and vibration of mechanical structures Xi'an Jiaotong UniversityXi'an 710049China Exeter Small-Scale Robotics laboratory Engineering DepartmentUniversity of ExeterNorth Park RoadExeter EX44QFUK

This paper focuses on the stochastic analysis of a viscoelastic bistable energy harvesting system under colored noise and harmonic excitation, and adopts the time-delayed feedback control to improve its harvesting efficiency. Firstly, to obtain the dimensionless governing equation of the system, the original bistable system is approximated as a system without viscoelastic term by using the stochastic averaging method of energy envelope, and then is further decoupled to derive an equivalent system. The credibility of the proposed method is validated by contrasting the consistency between the numerical and the analytical results of the equivalent system under different noise conditions. The influence of system parameters on average output power is analyzed, and the control effect of the time-delayed feedback control on system performance is compared. The output performance of the system is improved with the occurrence of stochastic resonance(SR). Therefore, the signal-to-noise ratio expression for measuring SR is derived, and the dependence of its SR behavior on different parameters is explored.

关键词： energy harvesting bistability stochastic averaging method stochastic resonance time-delayed feedback control

Space truss construction modeling based on on-orbit assembly motion feature

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Chinese Journal of Aeronautics 2024年第3期37卷 365-379页

作者： Changjie ZHAO Weizhong GUO Meng CHEN Jiaxing HU Youcheng HAN Rongfu LIN state key lab of mechanical System and vibration Shanghai Jiao Tong UniversityShanghai 200240China Institute of Aerospace System Engineering Shanghai Shanghai 201109China

More space truss construction has been planned to develop and utilize space resources.These trusses are designed in the way of large-scale,complex,modular,and on-orbit assembly.To meet the upcoming challenge of large-scale space infrastructure construction,it is necessary to study space truss automation design and robotic construction.This paper proposes an ordinal finite screw adjacency matrix model(OFSAMM),focusing on the relationship between assembly motions,to express and compute a space truss structure.In this model,a space truss is abstracted as a set of ordered assembly motions,each of which is recorded as a finite screw as the basic element of the truss and its assembly.The operation of truss transformation is also derived under this model.Therefore,the truss configuration,the assembly sequence,the truss sub-assembly,the truss components,and the on-orbit assembly task can be expressed and calculated in a unified model,which is calculated and stores the truss topology and assembly with the minimum storage cost.At the end of this paper,we introduce how to synthesize and optimize space truss design through two cases.The study will help to improve design efficiency.Furthermore,it provides a theoretical basis for the automatic construction of space truss structures,especially in the next stage.

关键词： Adjacency matrix Finite screw On-orbit construction modeling Space applications Space trusses Topology design

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非高斯过程下混合式能量采集系统的方程识别

Acta Mechanica Sinica 2024年第2期40卷 182-198页

作者：孙亚辉曾远辉杨勇歌 School of Mathematics and Statistics Guangdong University of TechnologyGuangzhou510520China state key laboratory for strength and vibration of mechanical structures Xi’an Jiaotong UniversityXi’an710049China

混合式能量采集系统由于提高采集效率的优点被广泛地应用于许多领域.在实际环境中,许多表现为跳跃、飞行、罕见跃迁以及间歇性特征的现象能够被非高斯Lévy过程所描述.但有时候精确地建立复杂条件下的混合式能量采集系统方程是较为困难... 详细信息

混合式能量采集系统由于提高采集效率的优点被广泛地应用于许多领域.在实际环境中,许多表现为跳跃、飞行、罕见跃迁以及间歇性特征的现象能够被非高斯Lévy过程所描述.但有时候精确地建立复杂条件下的混合式能量采集系统方程是较为困难的,尤其是由非高斯Lévy噪声驱动的系统.近年来,随着仿真能力和观测技术的发展,大量的噪声测量数据以及仿真数据能够被收集,并且已有许多研究致力于从大量数据中提取控制法则.本文采用数据驱动的方法,从受非高斯Lévy噪声影响的观测数据中提取系统方程.利用Fokker-Planck方程和非局部Kramers-Moyal公式,获得漂移项、扩散项和Lévy参数的近似表达式,并利用稀疏回归方法识别近似表达式中的系数.本文给出了三个算例,验证了该方法的有效性.结果表明,该方法不仅适用于高斯布朗过程下的混合能量收集系统,也适用于非高斯Lévy过程下的混合能量收集系统.此外,还分析了不同时间步长下区间划分参数与指标Ratio的关系.结果表明,该指标可以作为选择合适的划分参数的标准.

关键词：近似表达式非高斯过程数据驱动仿真能力收集系统区间划分采集效率能量采集系统

mechanical behavior of nanorubber reinforced epoxy over a wide strain rate loading

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Nano Materials Science 2024年第1期6卷 106-114页

作者： Yinggang Miao Jianping Yin Wenxuan Du Lianyang Chen Joint International Research laboratory of Impact Dynamics and Its Engineering Applications School of AeronauticsNorthwestern Polytechnical UniversityXi'anShaanxi710072China state key laboratory for strength and vibration of mechanical structures Xi'an Jiaotong UniversityXi'anShaanxi710049China Shaanxi key laboratory of Impact Dynamics and Its Engineering Application School of AeronauticsNorthwestern Polytechnical UniversityXi'anShaanxi710072China

Nanorubber/epoxy composites containing 0,2,6 and 10 wt%nanorubber are subjected to uniaxial compression over a wide range of strain rate from 8×10^(-4) s^(-1) to~2×10^(4) s^(-1).Unexpectedly,their strain rate sensitivity and strain hardening index increase with increasing nanorubber content.Potential mechanisms are proposed based on numerical simulations using a unit cell model.An increase in the strain rate sensitivity with increasing nanorubber content results from the fact that the nanorubber becomes less incompressible at high strain,generating a higher hydro-static pressure.Adiabatic shear localization starts to occur in the epoxy under a strain rate of 22,000 s^(-1) when the strain exceeds 0.35.The presence of nanorubber in the epoxy reduces adiabatic shear localization by preventing it from propagating.

关键词： Strain rate Strain hardening Nano rubber Epoxy Adiabatic shearing localization

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Experimental Investigation of the Anisotropic Thermal Conductivity of C/SiC Composite Thin Slab

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Chinese Physics Letters 2024年第3期41卷 48-60页

作者：毋克凡张虎唐桂华 state key laboratory for strength and vibration of mechanical structures School of Aerospace EngineeringXi’an Jiaotong UniversityXi’an 710049China MOE key laboratory of Thermo-Fluid Science and Engineering School of Energy and Power EngineeringXi’an Jiaotong UniversityXi’an 710049China

Fiber-reinforced composites possess anisotropic mechanical and heat transfer properties due to their anisotropic fibers and structure distribution.In C/Si C composites,the out-of-plane thermal conductivity has mainly ... 详细信息

关键词： composites C/Si anisotropic