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On the material constants measurement method of a fluid-saturated transversely isotropic poroelastic medium

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Science China(Physics,mechanics & Astronomy) 2019年第1期62卷 69-75页

作者： Yue Gao ZhanLi Liu Zhuo Zhuang Keh-Chih Hwang AML Department of Engineering Mechanics Tsinghua University center for mechanics and Materials Tsinghua University

The fluid-saturated transversely isotropic poroelastic medium could be widely found in nature, e.g., the sedimentary rocks underground. To determine the eight independent material constants for the transversely isotropic poroelastic medium, a series of tests are discussed. Two undrained tests and one drained test are suggested as a set of tests of the least amount. For the verification purpose, two additional drained tests are also introduced as an option. The atmospheric dried test is discussed as a replacement of the traditional infiltrated drained test to save the time waiting for an equilibrium state. Some microscopic material constants, i.e.,the unjacketed bulk coefficients, the porosity, and the compressibility of porous fluid, are measurable but unnecessary to determine the independent material constants of a poroelastic medium.

关键词： poroelastic constitutive model material constants measurement transversely isotropic medium

Electro-mechanically controlled assembly of reconfigurable 3D mesostructures and electronic devices based on dielectric elastomer platforms

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National Science Review 2020年第2期7卷 342-354页

作者： Wenbo Pang xu Cheng Haojie Zhao xiaogang Guo Ziyao Ji Guorui Li Yiming Liang Zhaoguo xue Honglie Song Fan Zhang Zheng xu Lei Sang Wen Huang Tiefeng Li Yihui Zhang Applied mechanics Laboratory Department of Engineering Mechanics Tsinghua University center for Flexible Electronics Technology Tsinghua University School of Microelectronics Soft Membrane Electronic Technology Laboratory Hefei University of Technology Zhejiang Lab State Key Laboratory for Manufacturing and Systems Engineering School of Mechanical Engineering Xi'an Jiaotong University center for x-mechanics Zhejiang University

The manufacture of 3D mesostructures is receiving rapidly increasing attention, because of the fundamental significance and practical applications across wide-ranging areas. The recently developed approach of buckling-guided assembly allows deterministic formation of complex 3D mesostructures in a broad set of functional materials, with feature sizes spanning nanoscale to centimeter-scale. Previous studies mostly exploited mechanically controlled assembly platforms using elastomer substrates, which limits the capabilities to achieve on-demand local assembly, and to reshape assembled mesostructures into distinct 3D configurations. This work introduces a set of design concepts and assembly strategies to utilize dielectric elastomer actuators as powerful platforms for the electro-mechanically controlled 3D assembly. Capabilities of sequential, local loading with desired strain distributions allow access to precisely tailored 3D mesostructures that can be reshaped into distinct geometries, as demonstrated by experimental and theoretical studies of30 examples. A reconfigurable inductive–capacitive radio-frequency circuit consisting of morphable 3D capacitors serves as an application example.

关键词： 3D assembly buckling reconfigurable structures dielectric elastomers reconfigurable RF circuits

Decohesion of graphene from a uniaxially-stretched substrate:Failure analysis of a frictional adhesive interface

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Friction 2024年第3期12卷 510-521页

作者： Bo PENG Chaochen xU Qingao WANG Pei ZHAO xiqiao FENG Qunyang LI AML Department of Engineering MechanicsTsinghua UniversityBeijing 100084China State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China center for x-mechanics and Institute of Applied mechanics Zhejiang UniversityHangzhou 310027China State Key Laboratory of Fluid Power and M

Composite structures consisting of two-dimensional(2D)materials deposited on elastic substrates have a wide range of potential applications in flexible *** such devices,robust 2D film/substrate interfacial adhesion is essential for their reliable performance when subjected to external thermal and mechanical *** better understand the strength and failure behavior of the 2D film/substrate interfaces,two types of graphene/polymer samples with distinct interfacial adhesion properties are fabricated and tested by uniaxially stretching the *** on the interfacial adhesion,two drastically different debonding rates are observed,i.e.,rapid snap-through debonding and more progressive crack *** by the experimental observation,we propose an improved shear-lag model with a trapezoidal-shaped cohesive zone to derive an analytical solution for the decohesion *** theoretical model reveals that the decohesion behavior of the frictional adhesive interface is governed by three dimensionless ***,the dimensionless length of the film essentially determines the decohesion rate;while the other two parameters affect the critical substrate strain to initiate *** fitting the experimental data with the theoretical model,the intrinsic adhesion properties of the two samples are obtained with physically meaningful *** work offers an analytical solution to describing the decohesion behavior of general thin film/substrate systems with a frictional adhesive interface,which is beneficial for characterizing and optimizing the mechanical properties of various thin film/polymer devices.

关键词： film/substrate systems adhesion frictional sliding interface decohesion cohesive-zone model

Fatigue‑Resistant and Hysteresis‑Free Composite Fibers with a Heterogeneous Hierarchical Structure

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Advanced Fiber Materials 2023年第5期5卷 1643-1656页

作者： Siming Li Junwei xu Yan Mu Peng Wang Heng Zhu Binhong Liu Zhe Chen Zilong Han Shaoxing Qu Eye center of the Second Affiliated Hospital State Key Laboratory of Fluid Power&Mechatronic SystemKey Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceCenter for X‑Mechanicsand Department of Engineering MechanicsZhejiang UniversityHangzhou 310027China

Fatigue-resistant and hysteresis-free composite fibers hold great promise for the next generation of wearable electronic *** this study,a novel approach for the fabrication of composite fibers with outstanding elasticity and mechanical stability is *** design incorporates a heterogeneous hierarchical structure(HHS),which mimics the structure of arteries,to achieve enhanced fatigue resistance and hysteresis-free *** composite fibers,Ecoflex-polyacrylamide fibers(EPFs),are created through the combination of heterogeneous elastomers and strong interfacial *** results show that the EPFs exhibit exceptional fatigue resistance,being able to withstand up to 10,000 load–unload cycles at strains of 300%without any noticeable changes in their mechanical *** potential applications of these EPFs are demonstrated through their use as strain sensors for monitoring human motion in both air and water,as well as in energyharvesting e-textiles.

关键词： Heterogeneous hierarchical structure Composite fibers Fatigue resistance Hysteresis free Wearable electronic devices

Understanding the link between type 2 diabetes mellitus and Parkinson's disease:role of brain insulin resistance

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Neural Regeneration Research 2025年第11期20卷 3113-3123页

作者： Theodora Ntetsika Sergiu-Bogdan Catrina Ioanna Markaki Department of Clinical Neuroscience Karolinska InstituteStockholmSweden Department of Neurology Karolinska University HospitalStockholmSweden Department of Molecular Medicine and Surgery Karolinska InstituteStockholmSweden center for Diabetes Academic Specialist CenterStockholmSweden center for Neurology Academic Specialist CenterStockholmSweden

Type 2 diabetes mellitus and Parkinson's disease are chronic diseases linked to a growing pandemic that affects older adults and causes significant socio-economic *** data supporting a close relationship between these two aging-related diseases have resulted in the investigation of shared pathophysiological molecular *** insulin signaling in the brain has gained increasing attention during the last decade and has been suggested to contribute to the development of Parkinson's disease through the dysregulation of several pathological *** contribution of type 2 diabetes mellitus and insulin resistance in neurodegeneration in Parkinson's disease,with emphasis on brain insulin resistance,is extensively discussed in this article and new therapeutic strategies targeting this pathological link are presented and reviewed.

关键词： brain insulin resistance brain insulin signaling diabetes type 2 GLP-1 receptor agonists GLP-1 signaling insulin resistance insulin signaling neurodegeneration Parkinson's disease targeted therapy

On the energy conservation and critical velocities for the propagation of a "steady-shock" wave in a bar made of cellular material

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Acta Mechanica Sinica 2013年第3期29卷 420-428页

作者： Li-Li Wang Li-Ming Yang Yuan-Yuan Ding mechanics and Material Science Research center Ningbo University

The propagation of shock waves in a cellular bar is systematically studied in the framework of continuum solids by adopting two idealized material models, viz. the dynamic rigid, perfectly plastic, locking （D-R-PP-L） model and the dynamic rigid, linear hardening plastic, locking （D-R-LHP-L） model, both considering the effects of strain-rate on the material properties. The shock wave speed relevant to these two models is derived. Consider the case of a bar made of one of such material with initial length L 0 and initial velocity v i impinging onto a rigid target. The variations of the stress, strain, particle velocity, specific internal energy across the shock wave and the cease distance of shock wave are all determined analytically. In particular the ＂energy conservation condition＂ and the ＂kinematic existence condition＂ as proposed by Tan et al. （2005） is re-examined, showing that the ＂energy conservation condition＂ and the consequent ＂critical velocity＂, i.e. the shock can only be generated and sustained in R-PP-L bars when the impact velocity is above this critical velocity, is incorrect. Instead, with elastic deformation, strain-hardening and strain-rate sensitivity of the cellular materials being considered, it is appropriate to redefine a first and a second critical impact velocity for the existence and propagation of shock waves in cellular solids. Starting from the basic relations for shock wave propagating in D-R-LHP-L cellular materials, a new method for inversely determining the dynamic stress-strain curve for cellular materials is proposed. By using e.g. a combination of Taylor bar and Hopkinson pressure bar impact experimental technique, the dynamic stress-strain curve of aluminum foam could bedetermined. Finally, it is demonstrated that this new formulation of shock theory in this one-dimensional stress state can be generalized to shocks in a one-dimensional strain state, i.e. for the case of plate impact on cellular materials, by simply making proper

关键词： Cellular solids 1D shock theory D-R-PP-L model D-R-SHP-L model Energy conservation across shock Critical velocities

Dynamic compressive behavior and constitutive relations of lanthanum metal

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Journal of Rare Earths 2012年第5期30卷 473-479页

作者：王焕然蔡灿元陈大年马东方邓高涛 mechanics and Materials Science Research center Ningbo University

The dynamic compressive behavior and constitutive relations of Lanthanum（La） metal was determined by using the first compression in split Hopkinson pressure bar（SHPB） tests at different strain rates and *** constitutive relation of La metal determined in a certain range of strains was employed and adjusted in numerically simulating large deformations of La metal specimens generated by multi-compression in SHPB tests and recorded by a high-speed *** dynamic compressive behavior and constitutive relations of La metal under multiple SHPB tests loading was also *** results of scanning electron microscope（SEM） investigation of the recovered La metal specimens for typical tests showed that there was a variety of deformation microstructures depending on strain rate,temperature and stress state.

关键词： lanthanum metal dynamic compression constitutive relation multi-compression multiple impact SHPB rare earths

Inhomogeneous ablation behaviors and failure mechanism of copper cathode in air

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Science China(Technological Sciences) 2020年第11期63卷 2384-2394页

作者： GUAN WeiMian YUAN Jie WANG YongFeng ZHANG HuanYu LV Hao YANG Hong ZHU Tao FANG YouTong LIU JiaBin WANG HongTao YANG Wei School of Materials Science and Engineering Zhejiang UniversityHangzhou 310027China center for x-mechanics Faculty of EngineeringZhejiang UniversityHangzhou 310027China China Aerodynamic Research&Development center Mianyang 621000China

The copper cathode ablation limits the maximum power and operating time of arc heaters *** this work,copper cathodes were tested in an ablation testing system to investigate the ablation behaviors and mechanism of copper cathode in *** microstructure of the ablated cathodes was analyzed,and the ablation rate was *** maximum depth and ablation rate increased with the electronic *** mean ablation rate was compared with the prediction by a thermophysical theoretical *** ablation pits formed in the ablated surface and evolved into crater-like structures with unexpected depth as the ablation time was *** presence of ablation pits and crater-like structures suggested an inhomogeneous ablation behavior of the copper cathode in *** underlying mechanism is proposed to explain the ablation failure of copper cathode in the high-power arc *** attention to improving the service life of copper cathode could be focused on the surface modification to reduce the ablation inhomogeneity.

关键词： ablation arc copper cathode microstructure

Discrete Numerical Study on Type II Fracture of Partially Detached Concrete Panels in Cold Region

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Structural Durability & Health Monitoring 2025年第1期19卷 167-191页

作者： Huayi Zhang Maobin Song Lei Shen Nizar Faisal Alkayem Maosen Cao College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing210024China Haihe River Huaihe River and Xiaoqinghe River Basin Water Conservancy Management and Service Center of Shandong ProvinceJinan250100China College of mechanics and Engineering Science Hohai UniversityNanjing211100China

When the upper chord beam of the beam-string structure(BSS)is made of concrete-ﬁlled steel tube(CFST),its overall stiffness will change greatly with the construction of concrete placement,which will have an impact on the design of the tensioning plans and selection of control measures for the *** order to accurately obtain the bending stiffness of CFST beam and clarify its impact on the mechanical properties of composite BSS during con-struction,the inﬂuence of some factors such as height-width ratio,wall thickness of steel tube,elasticity modulus of concrete,and friction coefﬁcient on the bending stiffness are analyzed parametrically by the numerical simula-tion technology based on an actual *** calculation formula of the equivalent bending stiffness of CFST is also established through mathematical statistical ***,the equivalent bending stiffness is introduced into the construction and use stages of the composite BSS,respectively,and the mechanical properties such as prestress-tensioning control value,structural deformation,and internal force of key members are comparatively analyzed when adopting two different construction ***,the optimal construction plan of concrete placementﬁrst and then prestress-tensioning is proposed.

关键词： Beam-string structure(BSS) concrete-ﬁlled steel tube(CFST) bending stiffness timing of concrete placement prestress-tensioning