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Aerospace China 2016年第3期17卷 44-47页

作者： XIONG Ke state key laboratory of mechanics and control of mechanical structures College of Aerospace Enigeering Nanjing University of Aeronauticsand Astronautics

·Prof.XIONG,could you please give us a brief introduction to SKLMCMS?Director XIONG Ke:The state key laboratory of mechanics and control of mechanical structures(SKLMCMS)was established with the approval of the Ministry of Science and Technology of the People’s Republic of China in October 2011.The laboratory is located at Nanjing University of Aeronautics and Astronautics(NUAA).The research areas of

关键词：实验室主任结构力学控制机械中华人民共和国国家重点实验室民族南京大学

A Lamb wave signal reconstruction method for high-resolution damage imaging

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Chinese Journal of Aeronautics 2019年第5期32卷 1087-1099页

作者： Xiaopeng WANG Jian CAI Zhiquan ZHOU state key lab of mechanics and control of mechanical structures Nanjing University of Aeronautics and Astronautics

In Lamb wave-based Structural Health Monitoring(SHM), a high-enough spatial resolution is highly required for Lamb wave signals to ensure the resolution and accuracy of damage detection. However, besides the dispersion characteristic, the signal spatial resolution is also largely restricted by the space duration of excitation waveforms, i.e., the Initial Spatial Resolution(ISR)for the signals before travelling. To resolve the problem of inferior signal spatial resolution of Lamb waves, a Lamb Wave Signal Reconstruction(LWSR) method is presented and applied for highresolution damage imaging in this paper. In LWSR, not only a new linearly-dispersive signal is reconstructed from an original Lamb wave signal, but also the group velocity at the central frequency is sufficiently decreased. Then, both dispersion compensation and ISR improvement can be realized to achieve a satisfying signal spatial resolution. After the frequency domain sensing model and spatial resolution of Lamb wave signals are firstly analyzed, the basic idea and numerical realization of LWSR are discussed. Numerical simulations are also implemented to preliminarily validate LWSR. Subsequently, LWSR-based high-resolution damage imaging is developed. An experiment of adjacent multiple damage identification is finally conducted to demonstrate the efficiency of LWSR and LWSR-based imaging methods.

关键词： Damage imaging Dispersion compensation High resolution Lamb waves Signal reconstruction

Free vibration of functionally graded sandwich plates in thermal environments

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International Journal of mechanical System Dynamics 2023年第1期3卷 39-47页

作者： Dongdong Li Zongbai Deng Guoping Chen state key laboratory of mechanics and control of mechanical structures Nanjing University of Aeronautics and AstronauticsNanjingChina

This paper presents an analytical solution for the free vibration of functionally graded material(FGM)sandwich plates in a thermal environment.An equivalentsingle‐layer(ESL)plate theory with four variables is used to obtain the solution.Two types of sandwich plates are examined in this study:one with FGM face sheets and a homogeneous core and the other with an FGM core and homogeneous face sheets.The governing equations of motion are derived based on Hamilton's principle and then solved using the Navier method.The results of natural frequencies of simply supported FGM sandwich plates are compared with the available solutions in the literature.The effects of volume fraction distribution,geometrical parameters,and temperature increments on the free vibration characteristics are discussed in detail.

关键词： functionally graded material sandwich plate equivalent‐single‐layer theory free vibration

Geometry independent C^(*)-T_(z) dominance of three-dimensional quasistatic growing crack-tip fields in creeping solids

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Science China(Physics,mechanics & Astronomy) 2022年第1期65卷 22-32页

作者： PengFei Cui WanLin Guo state key laboratory of mechanics and control of mechanical structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China

In creeping solids,plane stress and plane strain solutions for asymptotic singular crack-tip fields have been first put forward by Riedel and Rice with C^(*)as the dominating parameter and developed by Xiang and Guo into three-dimensional solution(3D)for stationary cracks under the domination of C^(*)with the constraint factor Tz.However,how to characterize the 3D crack-tip fields under creep damage-induced quasistatic growing conditions remains challenging.In this study,we reveal that,for 3D quasistatic growing cracks,the leading singular solution can effectively characterize the crack-tip stress distributions with relative errors less than 10.8%for relative creep time up to 0.8 in various specimens with finite thickness.For a given relative time,Tz distributions can be unified by the equivalent thickness concept,Beq.The results show that C^(*)-T_(z) can effectively quantify both the load and constraint effects on the crack-tip fields.Such geometry independent dominance can considerably simplify the treatments of load and constraint effects,thereby promoting the application of fracture mechanics in high-temperature damage tolerance designs.

关键词： quasistatic growing crack-tip fields C^(*)-T_(z)solution geometry independence constraints creep damage

Well-posedness of two-phase local/nonlocal integral polar models for consistent axisymmetric bending of circular microplates

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Applied Mathematics and mechanics(English Edition) 2022年第5期43卷 637-652页

作者： Hai QING state key laboratory of mechanics and control of mechanical structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Previous studies have shown that Eringen’s differential nonlocal model would lead to the ill-posed mathematical formulation for axisymmetric bending of circular microplates.Based on the nonlocal integral models along the radial and circumferential directions,we propose nonlocal integral polar models in this work.The proposed strainand stress-driven two-phase nonlocal integral polar models are applied to model the axisymmetric bending of circular microplates.The governing differential equations and boundary conditions(BCs)as well as constitutive constraints are deduced.It is found that the purely strain-driven nonlocal integral polar model turns to a traditional nonlocal differential polar model if the constitutive constraints are neglected.Meanwhile,the purely strain-and stress-driven nonlocal integral polar models are ill-posed,because the total number of the differential orders of the governing equations is less than that of the BCs plus constitutive constraints.Several nominal variables are introduced to simplify the mathematical expression,and the general differential quadrature method(GDQM)is applied to obtain the numerical solutions.The results from the current models(CMs)are compared with the data in the literature.It is clearly established that the consistent softening and toughening effects can be obtained for the strain-and stress-driven local/nonlocal integral polar models,respectively.The proposed two-phase local/nonlocal integral polar models(TPNIPMs)may provide an efficient method to design and optimize the plate-like structures for microelectro-mechanical systems.

关键词： softening effect toughening effect circular microplate nonlocal integral model general differential quadrature method(GDQM)

Flutter analysis of rotating beams with elastic restraints

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Applied Mathematics and mechanics(English Edition) 2022年第5期43卷 761-776页

作者： Lüsen WANG Zhu SU Lifeng WANG state key laboratory of mechanics and control of mechanical structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The aeroelastic stability of rotating beams with elastic restraints is investigated.The coupled bending-torsional Euler-Bernoulli beam and Timoshenko beam models are adopted for the structural modeling.The Greenberg aerodynamic model is used to describe the unsteady aerodynamic forces.The additional centrifugal stiffness effect and elastic boundary conditions are considered in the form of potential energy.A modified Fourier series method is used to assume the displacement field function and solve the governing equation.The convergence and accuracy of the method are verified by comparison of numerical results.Then,the flutter analysis of the rotating beam structure is carried out,and the critical rotational velocity of the flutter is predicted.The results show that the elastic boundary reduces the critical flutter velocity of the rotating beam,and the elastic range of torsional spring is larger than the elastic range of linear spring.

关键词： rotating beam modified Fourier series method elastic restraint flutter

Design,construction,and modeling of aircraft door sealing plate based on SMAs

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International Journal of Smart and Nano Materials 2022年第3期13卷 481-503页

作者： Chen Zhang Renhao Liu Chongcong Tao Chao Zhang Hongli Ji Jinhao Qiu state key laboratory of mechanics and control of mechanical structures Nanjing University of Aeronautics and AstronauticsNanjingJiangsuChina

In this work,a novel aircraft door sealing structure driven by shape memory alloys(SMAs)is proposed that offers much improved seal-ing capability than traditional sealing plates.The two-way shape memory effect(TWSME)of SMAs is utilized so that the proposed sealing plate can change its shape through heating and cooling of the driving SMA unit.Considering the inhomogeneous temperature and recovery strain field the SMA exhibits while being trained,a modified finite element(FE)model of the sealing structure is established to predict the deflection of the SMA-based sealing plate.Finally,verification experiments are carried out.The experi-mental results show good agreement with the FE predictions,indicating good accuracy of the modified FE model as well as the effectiveness of the proposed sealing structure.

关键词： Aircraft door sealing plate shape memory alloy inhomogeneous strain

Exit problem of stochastic SIR model with limited medical resource

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Theoretical & Applied mechanics Letters 2023年第1期13卷 8-13页

作者： Y.C.Mao X.B.Liu State Key Lab of Mechanics and Control for Mechanical Structures College of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China

Nonlinearity and randomness are both the essential attributes for the real world,and the case is the same for the models of infectious diseases,for which the deterministic models can not give a complete picture of the evolution.However,although there has been a lot of work on stochastic epidemic models,most of them focus mainly on qualitative properties,which makes us somewhat ignore the original meaning of the parameter value.In this paper we extend the classic susceptible-infectious-removed(SIR)epidemic model by adding a white noise excitation and then we utilize the large deviation theory to quantitatively study the long-term coexistence exit problem with epidemic.Finally,in order to extend the meaning of parameters in the corresponding deterministic system,we tentatively introduce two new thresholds which then prove rational.

关键词： Stochastic epidemic model Stochastic dynamical system Large deviation theory Exit problem

Improving accuracy of damage quantification based on two-level consistency control of PZT layers

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Chinese Journal of Aeronautics 2023年第3期36卷 241-253页

作者： Yuanqiang REN Qiuhui XU Shenfang YUAN Research Center of Structural Health Monitoring and Prognosis State Key Lab of Mechanics and Control of Mechanical StructuresNanjing University of Aeronautics and AstronauticsNanjing 210016China

Structural health monitoring-based quantitative damage diagnosis technique plays a key role in real-time condition monitoring.Among the current research,piezoelectric(PZT)sensor and Guided Wave(GW)based damage quantification methods are promising,which normally establish a calibration model between GW feature and damage degree by experiments on batch specimens,and then conduct the calibration model on the monitored specimen.However,the accuracy of PZT and GW based damage quantification is affected by dispersion introduced by sensor network performance,structural material,and damage propagation among the adopted batch specimens.For improving the accuracy of damage quantification,this paper adopts PZT layer as sensor network and creatively implements theoretical and experimental research on batch PZT layers consistency control.On one hand,a two-level consistency control method based on multidimensional features-Euclidean distance is proposed to ensure the performance consistency of PZT layers placed on different specimens.On the other hand,experimental research on typical aircraft lug structures is also carried out to evaluate the requirement on performance consistency of PZT layers when performing quantitative damage diagnosis,and further verify the proposed two-level consistency control method.Experimental results show that the accuracy of damage quantification raises by 38% when the dispersion of different PZT layers is controlled within 5%.

关键词： Consistency control Guided waves PZT layer Quantitative damage diagnosis Structural health monitoring

Nonlinear hysteresis identification and compensation based on the discrete Preisach model of an aircraft morphing wing device manipulated by an SMA actuator

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Chinese Journal of Aeronautics 2019年第4期32卷 1040-1050页

作者： Yuchen CHEN Xing SHEN Jiefeng LI Jinjin CHEN state key laboratory of mechanics and control of mechanical structures Nanjing University of Aeronautics and Astronautics

The conception of aircraft morphing wings thrives in aeronautics since the appearance of shape memory alloys(SMAs). An aircraft morphing wing device, manipulated by an SMA actuator, inherits the intrinsic nonlinear hysteresis from the SMA actuator, ending up with control disadvantages. Conventionally, systems with SMA actuators are constrained to bi-stable states to bypass the hysteresis region. Rather than retreating a morphing wing device to bi-stable states, this paper is dedicated to transcend the morphing wing device beyond the customary limit. A methodology of discrete Preisach modeling, which identifies the hysteresis of the morphing wing device, is proposed herein. An array of discrete equal-distance points is applied to the Preisach plane in order to derive the Preisach density over the partitioned unit of the Preisach plane. Discrete Preisach modeling is fulfilled by the discrete first-order reversible curve(DFORC). By utilizing the discrete Preisach model, the aircraft morphing wing device is simulated; the validity and accuracy of discrete Preisach modeling are demonstrated by contrasting the simulated outcome with experimental data of the major hysteretic loop and the wingspan-wise displacement over time; a comparison between simulation and experimental results exhibits consistency. Afterwards, a hysteresis compensation strategy put forward in this paper is implemented for quasi-linear control of the aircraft morphing wing device, which manifests a compensated shrinking hysteresis loop and attains the initiative of extending the morphing range to the intrinsic hysteretic region.

关键词： Actuator Compensation Hysteresis Morphing wing Preisach model Shape memory effect