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Science China(Physics,mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 156-168页

作者： Yifeng Li Zhuoran Yang Ziming Yan Huibin Shi Zhanli Liu Kaijie Wang department of engineering mechanics School of Aerospace Engineering Tsinghua University Beijing Tongren Eye Center Beijing Tongren Hospital Capital Medical University Beijing Ophthalmology & Visual Sciences Key Lab

Orthokeratology(OK) is widely used for effective myopia correction and control. However, the incomplete understanding of its biomechanical mechanisms makes OK lens fitting rely heavily on clinician judgment, complicating accurate predictions of treatment outcomes. In this paper, we performed clinical experiments and numerical analysis to study corneal deformation modes and long-term changes in central corneal thickness. Clinical experiments were conducted on 194 Chinese myopic patients under OK treatment for 3 months. Based on the experimental data, a patient-specific computational biomechanical model for OK was established and validated. Specifically, the anisotropic mechanical properties of the cornea were incorporated into the model to describe the significant difference between its shear modulus(29.5 kPa) and tensile modulus(768.4 kPa). Additionally, a viscohyperelastic material model with a prolonged corneal relaxation time of 5.6 h was developed to capture the long-term deformation response. The results show that corneal thickness reduction in OK is primarily due to out-of-plane shear deformation,influenced by the cornea's low shear resistance. Modeling the extended corneal relaxation time is crucial for predicting long-term biomechanical responses. The computational model effectively captures long-term changes in central corneal thickness, potentially improving OK lens fitting accuracy.

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ARNOLD CIRCULATION AND MULTI-OPTIMAL DYNAMIC CONTROLLING MECHANISMS IN DRAGONFLY WINGS

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Acta Mechanica Solida Sinica 2013年第3期26卷 237-244页

作者： Hongxiao Zhao Yajun Yin Zheng Zhong School of aerospace engineering and applied mechanics Tongji University School of aerospace Department of Engineering MechanicsTsinghua University

This paper aims to reveal the multi-optimal mechanisms for dynamic control in drag- onfly wings. By combining the Arnold circulation with such micro/nano structures as the hollow inside constructions of the pterostigma, veins and spikes, dragonfly wings can create variable mass, variable rotating inertia and variable natural frequency. This marvelous ability enables dragonflies to overcome the contradictory requirements of both light-weight-wing and heavy-weight-wing, and displays the multi-optimal mechanisms for the excellent flying ability and dynamic control capac- ity of dragonflies. These results provide new perspectives for understanding the wings＇ functions and new inspirations for bionic manufactures.

关键词： dragonfly wings veins and pterostigma Arnold circulation multi-optimal control-ling mechanism

NONLINEAR VIBRATION OF THE COUPLED STRUCTURE OF SUSPENDED-CABLE-STAYED BEAM-1:2 INTERNAL RESONANCE

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Acta Mechanica Solida Sinica 2014年第5期27卷 467-476页

作者： Kun Huang Qi Feng Yajun Yin School of aerospace engineering and applied mechanics Tongji University department of engineering mechanics School of Aerospace Tsinghua University

Through the Galerkin method the nonlinear ordinary differential equations （ODEs） in time are obtained from the nonlinear partial differential equations （PDEs） to describe the mo- tion of the coupled structure of a suspended-cable-stayed beam. In the PDEs, the curvature of main cables and the deformation of cable stays are taken into account. The dynamics of the struc- ture is investigated based on the ODEs when the structure is subjected to a harmonic excitation in the presence of both high-frequency principle resonance and 1：2 internal resonance. It is found that there are typical jumps and saturation phenomena of the vibration amplitude in the struc- ture. And the structure may present quasi-periodic vibration or chaos, if the stiffness of the cable stays membrane and frequency of external excitation are disturbed.

关键词： the coupled structure of suspended-cable-stayed beam the multiscale method 1:2internal resonance Hopf bifurcation chaos

Targets capture by distributed active swarms via bio-inspired reinforcement learning

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Science China(Physics,mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 210-221页

作者： Kun Xu Yue Li Jun Sun Shuyuan Du Xinpeng Di Yuguang Yang Bo Li Institute of Biomechanics and Medical engineering Applied Mechanics Laboratory Department of Engineering MechanicsTsinghua University Institute of Nuclear and New Energy Technology Tsinghua University Shanghai aerospace Control Technology Institute Shanghai Key Laboratory of aerospace Intelligent Control Technology College of Automation engineering Nanjing University of Aeronautics and Astronautics

Natural swarms arranged from cells to herds are usually decentralized but display intriguing collective intelligence in coordinating individuals across large scales to efficiently achieve their common goals. Learning from nature may provide new strategies for controlling collective dynamics of synthetic swarms to accomplish specific functions. Here, we present a bioinspired computational framework that steers distributed active swarms to collectively capture and merge targets via reinforcement learning. We exploit collective milling structures of natural herds to cage the targets, and adopt a switching control policy inspired by sperms' chiral dynamics to optimize the trajectories of individuals, through which the active swarms can selforganize to enclose single or multiple distant targets in a dynamical, adaptive and scalable manner. There exists a critical swarm size, beyond which the excessive competition between agents would generate large mechanical forces, leading to capture instability but enabling the transition from short-distance to long-distance merging capture of multiple targets. This work provides physical insights into distributed active swarms and could offer a multilevel, decentralized strategy toward controlling swarm robotics in wide applications such as bio-medical devices, machine immunity, and target clearance.

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Bi-stable states of initially stressed elastic cylindrical shell structures with two piezoelectric surface layers

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Acta Mechanica Sinica 2015年第5期31卷 653-659页

作者： Bin Wang Guo-Hua Nie Institute of applied mechanics School of Aerospace Engineering and Applied MechanicsTongji University

A theoretical model is proposed in this paper to predict the bi-stable states of initially stressed cylindrical shell structures attached by surface anisotropic piezoelectric *** condition for existence of bi-stability of the shell structural system is presented and analytical expressions for corresponding rolled-up radii of the stable shell are given based on the principle of minimum strain *** resulting solution indicates that the shell system may have two stable configurations besides its initial state under a combined action of the actuating electric field and initial stresses characterized by the bending *** the piezoelectric layer materials act as only sensor materials without the actuating electric field,initial stresses may produce the bi-stable states,but one corresponding to its initial *** the shell without initial stresses,the magnitude in the actuating electric field determines the number of the stable states,one or two stable configurations besides the initial *** theoretical prediction for the bi-stable states is verified by finite element method（FEM） simulation by using the ABAQUS code.

关键词： Bi-stable Initial stress Cylindrical shell Piezoelectric layer Elastic potential energy Rolled-up radius Finite element

Heat Transfer and Thermal Characteristics Effects on Moving Plate Impinging from Cu-Water Nanofluid Jet

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Journal of Thermal Science 2020年第1期29卷 182-193页

作者： DATTA Abanti KUMAR Sonal HALDER Pabitra department of aerospace engineering and applied mechanics Indian Institute of Engineering Science and Technology

The present article is focused on modelling of flow and heat transfer behaviour of Cu-water nanofluid in a confined slot jet impingement on hot moving *** parameters such as various moving plate velocities,nanoparticles at various concentrations,variation in turbulent Reynolds number and jet nozzle to plate distance have been considered to study the flow field and convective heat transfer performance of the *** of distribution of local and average Nusselt number and skin friction coefficients at the plate surface are shown to elucidate the heat transfer and fluid flow *** analysis of both stream function and isotherm contours are carried out to perceive the flow pattern and heat transfer mechanism due to moving *** results revealed that average Nusselt number significantly rises with plate velocity in addition with jet inlet Reynolds *** of the average Nusselt numbers are presented.

关键词： Cu-water nanofluid,multiphase mixture model moving plate jet impingement CFD

Analysis and design for the comprehensive ballistic and blast resistance of polyurea-coated steel plate

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Defence Technology（防务技术） 2023年第1期19卷 35-51页

作者： Dongyang Chu Yigang Wang Shanglin Yang Zhijie Li Zhuo Zhuang Zhanli Liu applied mechanics Laboratory Department of Engineering MechanicsSchool of Aerospace EngineeringTsinghua UniversityBeijing100084China

Fragments and blast waves generated by explosions pose a serious threat to protective *** this paper,the impact resistance of polyurea-coated steel plate under complex dynamic loading is analyzed and designed for improving comprehensive ballistic and blast resistance using the newly established computational evaluating ***,according to the thickness and placement effects of the coating on the impact resistance,the steel-core sandwich plates are designed,which are proved to own outstanding comprehensive ballistic and blast ***,the distribution diagram of ballistic and blast resistance for different polyurea-coated steel plates is given to guide the design of protective structures applying in different explosion ***,the dynamic response of designed plates under two scenarios with combined fragments and blast loading is *** results show that the synergistic effect of the combined loading reduces both the ballistic and blast resistance of the polyurea-coated steel ***,the acting sequence of the fragments and blast affects the structural protective performance *** is found that the first loading inducing structural large deformation or damage is *** fragments impact first,the excellent unit-thickness ballistic performance of the structural front part is strongly needed for improving the comprehensive ballistic and blast resistance.

关键词： Polyurea Ballistic and blast resistance Combined fragments and blast loading

Sliding state stepping algorithm for solving impact problems of multi-rigid-body system with joint friction

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applied Mathematics and mechanics(English Edition) 2007年第12期28卷 1621-1627页

作者：姚文莉陈滨刘才山徐鉴 School of aerospace engineering and applied mechanics Tongji University department of mechanics and engineering Peking University

Impact dynamics of multi-rigid-body systems with joint friction is considered. Based on the traditional approximate assumption dealing with impact problem, a general numerical method called the sliding state stepping algorithm is introduced. This method can avoid difficulties in solving differential equations with variable scale and its result can avoid energy inconsistency before and after impact from considering complexily of tangential sliding mode. An example is given to describe details using this algorithm.

关键词： multi-rigid-body system joint friction sliding state stepping algorithm

THE EFFECTIVE ELECTROMECHANICAL PROPERTIES OF CELLULAR PIEZOELECTRET FILM:FINITE ELEMENT MODELING

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Acta Mechanica Solida Sinica 2013年第1期26卷 1-8页

作者： Yongping Wan Liangliang Fan Zheng Zhong School of aerospace engineering and applied mechanics Tongji University

Cellular space-charge polymer film, also called cellular piezoelectret, has very large piezoelectric effect due to their unique microvoid structure. In this article, the cellular piezoelectret film is considered to be a periodic composite material with closed-cell microvoids aligned periodically. Three dimensional finite element modeling is carried out to obtain the effective elastic modulus and piezoelectric coefficients. Sensitivity analysis was presented by modeling the effec- tive electromechanical properties with different individual variable, including material constants and void shape parameters. By assuming a relation between void shape and void volume fraction, the finite element model can simulate quite well the inflation experiments of the voided charged Polypropylene film published in literature. Finally, the finite element model is used to explore the voided charge polymer film with non-uniform distribution of the trapped charges on the internal surface of voids. It was found that the resultant overall piezoelectric coefficients will be more significant if charges are closely gathered in the central area, and sparse in the around area of the internal surface of voids.

关键词： piezoelectret electromechanical finite element methods

Effective properties of coated fibrous piezoelectric composites with spring-type interfaces under anti-plane mechanical and in-plane electrical loads

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Science China(Physics,mechanics & Astronomy) 2016年第10期59卷 58-65页

作者： Yin Shi YongPing Wan Zheng Zhong School of aerospace engineering and applied mechanics Tongji University

In this paper,we investigate the effective properties of three-phase(matrix/coating/fiber)cylindrical piezoelectric composites with imperfect interfaces under anti-plane mechanical and in-plane electrical *** using the electromechanically coupling spring-type interface model and the generalized self-consistent method(GSM),we analytically derived the effective electroelastic *** present solutions include as special cases the three-phase cylindrical piezoelectric composites with perfect interfaces as well as the two-phase(matrix/fiber)case with imperfect or perfect *** calculations are graphically shown to demonstrate dependence of the effective moduli on the interfacial *** particular size-dependent characteristic due to the interfacial imperfection is also discussed.

关键词： effective moduli piezoelectric composites spring-type interface generalized self-consistent method size effect