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effects of surface energy and substrate on modulus determination of biological films by conical indentation

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Science China Technological Sciences 2024年第6期67卷 1757-1764页

作者： DING Yue LI Cheng-Ya NIU XinRui WANG Gang-Feng Department of Engineering Mechanics SVLXi'an Jiaotong University Department of Mechanical Engineering City University of Hong Kong

Micro-/nano-indentation has become prevalent in evaluating the mechanical characteristics of biological samples, such as cells and tissues. However, the existing contact models describing conical indentation ignore the joint effects of surface energy and substrate, and consequently cannot accurately extract the Young's modulus of biological samples deposited on substrate.Through finite element methods, we examine the conical indentation of biological films on substrates while taking surface energy into account. Based on the dimensional analysis, the explicit relationship between load and indentation depth is achieved for films with their moduli varying from 0.001 to 100 times that of the substrate. If the classical Sneddon's model was employed to analyze the load-depth data, the measured modulus could reach 18 times the real modulus for films on harder substrates, but only 4% of the real modulus for films on softer substrates. Meanwhile, in micro-/nano-indentations, neglecting the contribution of surface energy would result in an overestimation of the Young's modulus of films depending on the contact size. The analytical expression provided here can be utilized to precisely deduce the mechanical characteristics of biological films deposited on substrate from the load and indentation depth data of a conical indentation.

关键词： biological film surface effect substrate effect indentation

Closed-Form Solution for a Circular Nanohole with surface effects Under Uniform Heat Flux

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Acta Mechanica Solida Sinica 2024年第1期37卷 43-52页

作者： Jieyao Tang Jieyan Zhao Haibing Yang Cunfa Gao State Key Laboratory of Mechanics and Control for Aerospace Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China School of Civil Engineering and Transportation South China University of TechnologyGuangzhou 510641China College of Mechanics and Materials Hohai UniversityNanjing 211100China

This paper investigates the steady-state thermoelastic problem of a circular nanohole embedded in an infinitely large elastic plane subjected to a uniform far-field heat flux.A lowly conductive surface model is used to account for the effects of surface phonon scattering,while the complete Gurtin–Murdoch model is utilized to characterize the effects of surface tension and surface elasticity.The closed-form solution to the temperature and stress field surrounding the hole is derived in the context of complex variable methods.Several numerical examples are presented to analyze the influence of surface effects on thermal stress fields.It is shown that surface effects induce notable increases in normal and shear stresses around the hole.Specifically,all three stress components(hoop,normal,and shear)in the vicinity of the hole exhibit substantial augmentation with increasing surface tension and surface modulus.In particular,it is found that the presence of surface effects amplifies the variation in stress gradients and intensifies stress concentration around the hole.

关键词： Circular nanohole surface effect Thermal stress Heat flux

surface effect induced phase transformation by Mn removal during annealing and its textures in cold-rolled high manganese transformation-induced plasticity steel

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Journal of Iron and Steel Research(International) 2022年第3期29卷 494-502页

作者： Li-ying Liu Ping Yang Dan-dan Ma Xin-fu Gu School of Materials Science and Engineering University of Science and Technology BeijingBeijing100083China

The surface effect induced transformation texture during vacuum annealing of cold-rolled high manganese transformation-induced plasticity(TRIP)steels was studied.Due to Mn removal occurring at the surface layer,γ→δdiffusional phase transformation leads to the formation of hard pancake-shaped ferrite grains due to solution strengthening at the surface and the centre layer remains as austenite+martensite after annealing.In the case of slow heating,{112}/{111}textures for the surface ferrite were strengthened with the increase in temperature and holding time,indicating an inheritance of rolling textures.By increasing the heating rate of annealing,the rotated cube texture was developed in surface ferrite.This kind of multiphase sandwich structure with hard ferrite surface layer and tough austenite dominant centre can increase tensile strength and should also improve deep drawing properties,therefore providing new possibility of controlling properties for the application of high manganese TRIP steel.

关键词： High manganese transformation-induced plasticity steel surface effect Texture Microstructure Vacuum annealing

surface effect on band structure of magneto-elastic phononic crystal nanoplates subject to magnetic and stress loadings

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Applied Mathematics and Mechanics(English Edition) 2022年第2期43卷 203-218页

作者： Shunzu ZHANG Qianqian HU Wenjuan ZHAO School of Civil and Hydraulic Engineering Ningxia UniversityYinchuan750021China

This paper presents a theoretical model for the size-dependent band structure of magneto-elastic phononic crystal(PC)nanoplates according to the Kirchhoff plate theory and Gurtin-Murdoch theory,in which the surface effect and magneto-elastic coupling are considered.By introducing the nonlinear coupling constitutive relation of magnetostrictive materials,Terfenol-D/epoxy PC nanoplates are carried out as an example to investigate the dependence of the band structure on the surface effect,magnetic field,pre-stress,and geometric parameters.The results show that the surface effect has promotive influence on dispersion curves of the band structure,and the band gaps can be improved gradually with the increase in the material intrinsic length.Meanwhile,the band gaps exhibit obvious nonlinear coupling characteristics owing to the competition between the magnetic field and the pre-stress.By considering the surface effect and magneto-elastic coupling,the open and closed points of band gaps are found when the lattice constant to thickness ratio increases.The study may provide a method for flexible tunability of elastic wave propagation in magneto-elastic PC nanoplates and functional design of highperformance nanoplate-based devices.

关键词： magneto-elastic phononic crystal nanoplate surface effect magnetic field band gap

Analytic solution of quasicrystal microsphere considering the thermoelectric effect and surface effect in the elastic matrix

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Applied Mathematics and Mechanics(English Edition) 2023年第8期44卷 1331-1350页

作者： Yunzhi HUANG Wenqing ZHENG Xiuhua CHEN Miaolin FENG Department of Engineering Mechanics School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China Marine Design and Research Institute of China Shanghai 200011China School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai 200240China

The incorporation of the quasicrystalline phase into the metal matrix offers a wide range of potential applications in particle-reinforced metal-matrix composites.The analytic solution of the piezoelectric quasicrystal(QC)microsphere considering the thermoelectric effect and surface effect contained in the elastic matrix is presented in this study.The governing equations for the QC microsphere in the matrix subject to the external electric loading are derived based on the nonlocal elastic theory,electro-elastic interface theory,and eigenvalue method.A comparison between the existing results and the finite-element simulation validates the present approach.Numerical examples reveal the effects of temperature variation,nonlocal parameters,surface properties,elastic coefficients,and phason coefficients on the phonon,phason,and electric fields.The results indicate that the QC microsphere enhances the mechanical properties of the matrix.The results are useful for the design and understanding of the characterization of QCs in micro-structures.

关键词： quasicrystal(QC)microsphere thermoelectric effect surface effect

Nonlinear magneto-mechanical-thermo coupling characteristic analysis for transport behaviors of carriers in composite multiferroic piezoelectric semiconductor nanoplates with surface effect

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Applied Mathematics and Mechanics(English Edition) 2022年第9期43卷 1323-1338页

作者： Wenjun WANG Feng JIN Tianhu HE Yongbin MA School of Science Lanzhou University of TechnologyLanzhou 730050China State Key Laboratory for Strength and Vibration of Mechanical Structures School of AerospaceXi’an Jiaotong UniversityXi’an 710049China MOE Key Laboratory for Multifunctional Materials and Structures School of AerospaceXi’an Jiaotong UniversityXi’an 710049China

In this paper,to better reveal the surface effect and the screening effect as well as the nonlinear multi-field coupling characteristic of the multifunctional piezoelectric semiconductor(PS)nanodevice,and to further improve its working performance,a magneto-mechanical-thermo coupling theoretical model is theoretically established for the extensional analysis of a three-layered magneto-electro-semiconductor coupling laminated nanoplate with the surface effect.Next,by using the current theoretical model,some numerical analyses and discussion about the surface effect,the corresponding critical thickness of the nanoplate,and the distributions of the physical fields(including the electron concentration perturbation,the electric potential,the electric field,the average electric displacement,the effective polarization charge density,and the total charge density)under different initial state electron concentrations,as well as their active manipulation via some external magnetic field,pre-stress,and temperature stimuli,are performed.Utilizing the nonlinear multi-field coupling effect induced by inevitable external stimuli in the device operating environment,this paper not only provides theoretical support for understanding the size-dependent tuning/controlling of carrier transport as well as its screening effect,but also assists the design of a series of multiferroic PS nanodevices.

关键词： composite multiferroic piezoelectric semiconductor(PS)nanoplate nonlinear multi-field coupling characteristic surface effect screening effect active manipulation of carrier transport

surface effect of nanocrystals doped with rare-earth ions enriched on surface and its application in upconversion luminescence

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Chinese Physics B 2012年第7期21卷 241-249页

作者：何恩节刘宁章毛连秦炎福官邦贵李勇郭明磊 Department of Physical and Electronics Anhui Science and Technology University

By employing a certain proportion of hydrogen peroxide, ammonia, ammonium fluoride, and ethylene diamine tetraacetic acid （EDTA） as precipitator, well-crystallized LaOF：Eu3＋ and LaOF：Yba＋, Era＋ nanocrystals are synthe- sized by using the chemical co-precipitation method. The structural properties of these samples are characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and Fourier transform infrared spectroscopy （FTIR） spectra. The results show that all the samples have an average size below 70 nm, which decreases gradually with the increase of the EDTA content, and a certain number of EDTA molecules are coupled with doped ions on the surfaces of nanocrystals. Most of the doped ions are proved to be enriched on the surfaces of nanocrystals and surrounded by the high energy vibration groups and bonds in EDTA molecules. The observed differences in upconversion emission spectrum among the different LaOF：Yba＋, Er3＋ nanocrystals are explained by the different two-photon upconversion mechanisms. Especially, in the LaOF：Yba＋, Era＋ nanocrystals with EDTA, the two-photon processes that contain several special cross-relaxation processes are introduced to analyse the corresponding upconversion mechanisms.

关键词： surface effect nanocrystals cross relaxation

surface effect and non-local elasticity in wave propagation of functionally graded piezoelectric nano-rod excited to applied voltage

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Applied Mathematics and Mechanics(English Edition) 2016年第3期37卷 289-302页

作者： M.AREFI Department of Solid Mechanics Faculty of Mechanical EngineeringUniversity of Kashan

A non-local solution for a functionally graded piezoelectric nano-rod is pre- sented by accounting the surface effect. This solution is used to evaluate the charac- teristics of the wave propagation in the rod structure. The model is loaded under a two-dimensional （2D） electric potential and an initially applied voltage at the top of the rod. The mechanical and electrical properties are assumed to be variable along the thick- ness direction of the rod according to the power law. The Hamilton principle is used to derive the governing differential equations of the electromechanical system. The effects of some important parameters such as the applied voltage and gradation of the material properties on the wave characteristics of the rod are studied.

关键词： wave propagation non-local elasticity surface effect Love rod model non-homogeneous index voltage

surface effect IN PROCESSING CHINASTONE

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Journal of Wuhan University of Technology(Materials Science) 1997年第Z1期12卷 69-73页

作者：宋振东 Wuhan University of Technology

As one of main raw materials in ceramic industry, chinastone mostly contains minerals such as quartz and sericite. In ultrafine processing of chinastone, the aggregation and adhesion of micropowders caused by surface effect lower the efficiency of ultrafine comminution. In this paper, a kind of grinding aid for chinastone delaminating has been developed by the author to change the surfacial electronic property of particles and decrease the viscosity of pulp. Experiments about delaminating-comminuting chinastone ores from Ningcun and Shangzhu (Jiangxi Province, China) reveal that the contents of 2 um grade particles are increased from 23. 0% and 27. 1% to 42. 7% and 45. 3% respectively, the products reach the index at first-class chinastone.

关键词： chinastone ultrafine comminution surface effect grinding aid