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Mechanical properties of multi-scale germanium specimens from space solar cells under electron irradiation

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Chinese Journal of Aeronautics 2024年第1期37卷 173-185页

作者： Jian QIU Maliya HEINI Jusha MA Wenjia HAN Xunchun WANG Jun YIN Yan SHI cunfa gao State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China School of Chemistry and Civil Engineering Shaoguan UniversityShaoguan 512005China Key Laboratory of Functional Materials and Devices for Special Environments of Chinese Academy of Sciences Chinese Academy of SciencesUrumqi 830011China Shanghai Institute of Space Power-Sources Shanghai 200245China

During long-term service in space,Gallium Arsenide(GaAs)solar cells are directly exposed to electron irradiation which usually causes a dramatic decrease in their performance.In the multilayer structure of solar cells,the germanium(Ge)layer occupies the majority of the thickness as the substrate.Due to the intrinsic brittleness of semiconductor material,there exist various defects during the preparation and assembly of solar cells,the influences of which tend to be intensified by the irradiation effect.In this work,first,Ge specimens for mechanical tests were prepared at scales from microscopic to macroscopic.Then,after different doses of electron irradiation,the mechanical properties of the Ge specimens were investigated.The experimental results demonstrate that electron irradiation has an obvious effect on the mechanical property variation of Ge in diverse scales.The four-point bending test indicates that the elastic modulus,fracture strength,and maximum displacement of the Ge specimens all increase,and reach the maximum value at the irradiation dose of 1×10^(15)e/cm^(2).The micrometer scale cantilever and nanoindentation tests present similar trends for Ge specimens after irradiation.Atomic Force Microscope(AFM)also observed the change in surface roughness.Finally,a fitting model was established to characterize the relation between modulus change and electron irradiation dose.

关键词： Electron irradiation Germanium Mechanical properties Multi-scale Space solar cells

Theoretical analysis on elastic buckling of nanobeams based on stress-driven nonlocal integral model

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Applied Mathematics and Mechanics(English Edition) 2020年第2期41卷 207-232页

作者： Peng JIANG Hai QING cunfa gao State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Several studies indicate that Eringen's nonlocal model may lead to some inconsistencies for both Euler-Bernoulli and Timoshenko beams, such as cantilever beams subjected to an end point force and fixed-fixed beams subjected a uniform distributed load. In this paper, the elastic buckling behavior of nanobeams, including both EulerBernoulli and Timoshenko beams, is investigated on the basis of a stress-driven nonlocal integral model. The constitutive equations are the Fredholm-type integral equations of the first kind, which can be transformed to the Volterra integral equations of the first kind. With the application of the Laplace transformation, the general solutions of the deflections and bending moments for the Euler-Bernoulli and Timoshenko beams as well as the rotation and shear force for the Timoshenko beams are obtained explicitly with several unknown constants. Considering the boundary conditions and extra constitutive constraints, the characteristic equations are obtained explicitly for the Euler-Bernoulli and Timoshenko beams under different boundary conditions, from which one can determine the critical buckling loads of nanobeams. The effects of the nonlocal parameters and buckling order on the buckling loads of nanobeams are studied numerically, and a consistent toughening effect is obtained.

关键词： Laplace transformation Volterra integral equation Fredholm integral equation stress-driven nonlocal integral model

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多组分多层级3D打印材料研究进展

Transactions of Nanjing University of Aeronautics and Astronautics 2024年第1期41卷 1-34页

作者：张强师岩高存法南京航空航天大学航空航天结构力学及控制全国重点实验室南京210016

多组分多层级3D打印材料(McMl3DPMs)是一种新兴的先进材料,源于多孔材料、复合材料和增材制造的融合。由于增材制造赋予了Mc Ml3DPMs三维架构跨越广泛组分构成和结构类型的能力,Mc Ml3DPMs拥有杰出的机械性能,甚至是通常被认为相互排斥... 详细信息

多组分多层级3D打印材料(McMl3DPMs)是一种新兴的先进材料,源于多孔材料、复合材料和增材制造的融合。由于增材制造赋予了Mc Ml3DPMs三维架构跨越广泛组分构成和结构类型的能力,Mc Ml3DPMs拥有杰出的机械性能,甚至是通常被认为相互排斥的性能(例如高强度和高韧性)。本文重点介绍为了实现高性能结构用Mc Ml3DPMs所必须解决的科学挑战以及最近研究工作对此做出的努力,将从结构设计、制造过程建模、缺陷表征和性能评价3个方面对相关案例进行回顾。最后,本文指出了当前研究的不足之处,并展望了Mc Ml3DPMs的未来发展,包括讨论了进一步推进这一新兴领域发展的几个可能的研究方向。

关键词：多组分多层级3D打印材料结构设计制造过程建模缺陷表征和性能评价

Analytic solution for a circular nano-inhomogeneity in a finite matrix

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Nano Materials Science 2019年第2期1卷 116-120页

作者： Shuang Wang Zengtao Chen cunfa gao State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Department of Mechanical Engineering University of Alberta Edmonton AB T6G 1H9 Canada

The Gurtin-Murdoch model has found wide applications in analyzing the mechanical behaviors of nanocomposites with surface/interface effect. In the existing literature, the matrix is usually assumed to be infinite and the surface/interface effect is considered only at the inhomogeneity-matrix interface. This assumption is indeed valid as the matrix is usually at macroscale rather than nanoscale. However, if the size of the matrix decreases to the nanoscale too, the surface/interface effect will have to be considered at the outer boundary of the matrix. In this paper, the plane deformation of a circular nano-inhomogeneity embedded inside a finite circular matrix (which implies the matrix is also at nanoscale) is investigated. The stress boundary conditions are given at the inhomogeneity-matrix interface and the outer boundary of the matrix by the G-M model. The analytic solution for the stress field is finally obtained through the complex variable method. The results show that the stress field inside the inhomogeneity is still uniform (size-dependent) when the surface/interface effect is considered. In addition, the stress field inside the bulk (including the inhomogeneity and the matrix) can be influenced not only by the size and elastic constant of the inhomogeneity, but also by those of the matrix.

关键词： Plane problem Nanoscale inhomogeneity Finite matrix Surface/interface effect Complex variable methods

Effects of electric/magnetic impact on the transient fracture of interface crack in piezoelectric-piezomagnetic sandwich structure: anti-plane case

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Applied Mathematics and Mechanics(English Edition) 2020年第1期41卷 139-156页

作者： Xing ZHAO Zhenghua QIAN Jinxi LIU cunfa gao Department of Engineering Mechanics Shijiazhuang Tiedao UniversityShijiazhuang 050043China State Key Laboratory of Mechanics and Control of Mechanical Structures College of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China

Due to the incompatibility of the interlaminar deformations,the interface debonding or cracking usually happens in a layered magnetoelectric(ME)structure under an applied load.In this paper,the transient responses of the anti-plane interface cracks in piezoelectric(PE)-piezomagnetic(PM)sandwich structures are studied by the standard methods of the integral transform and singular integral equation.Discussion on the numerical examples indicates that the PE-PM-PE structure under electric impact is more likely to fracture than the PM-PE-PM structure under a magnetic impact.The dynamic stress intensity factors(DSIFs)are more sensitive to the variation of the active layer thickness.The effects of the material constants on the DSIFs are dependent on the roles played by PE and PM media during the deformation process.

关键词： piezoelectric(PE)-piezomagnetic(PM) sandwich structure interface crack transient response dynamic stress intensity factor(DSIF)

Semi-analytic solution of Eringen's two-phase local/nonlocal model for Euler-Bernoulli beam with axial force

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Applied Mathematics and Mechanics(English Edition) 2018年第12期39卷 1805-1824页

作者： Licheng MENG Dajun ZOU Huan LAI Zili GUO Xianzhong HE Zhijun XIE cunfa gao Facility Design and Instrumentation Institute China Aerodynamics Research and Development Center State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics

Eringen’s two-phase local/nonlocal model is applied to an Euler-Bernoulli nanobeam considering the bending-induced axial force, where the contribution of the axial force to bending moment is calculated on the deformed state. Basic equations for the corresponding one-dimensional beam problem are obtained by degenerating from the three-dimensional nonlocal elastic equations. Semi-analytic solutions are then presented for a clamped-clamped beam subject to a concentrated force and a uniformly distributed load, respectively. Except for the traditional essential boundary conditions and those required to be satisfied by transferring an integral equation to its equivalent differential form, additional boundary conditions are needed and should be chosen with great caution, since numerical results reveal that non-unique solutions might exist for a nonlinear problem if inappropriate boundary conditions are used. The validity of the solutions is examined by plotting both sides of the original integro-differential governing equation of deflection and studying the error between both sides. Besides, an increase in the internal characteristic length would cause an increase in the deflection and axial force of the beam.

关键词： nonlocal elasticity internal characteristic length size effect nanobeam axial force unique solution

Thermal stresses around a circular inclusion with functionally graded interphase in a finite matrix

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Science China(Physics,Mechanics & Astronomy) 2014年第10期57卷 1927-1933页

作者： YANG QuanQuan gao cunfa State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics & Astronautics

Based on the theory of the complex variable functions, the analysis of non-axisymmetric thermal stresses in a finite matrix containing a circular inclusion with functionally graded interphase is presented by means of the least square boundary collocation technique. The distribution of thermal stress for the functionally graded interphase layer with arbitrary radial material parameters is derived by using the method of piece-wise homogeneous layers when the finite matrix is subjected to uniform heat flow. The effects of matrix size, interphase thickness and compositional gradient on the interfacial thermal stress are discussed in detail. Numerical results show that the magnitude and distribution of interfacial thermal stress in the inclusion and matrix can be designed properly by controlling these parameters.

关键词：功能梯度圆形夹杂热应力基质复变函数论边界配点法非轴对称最小二乘

Stress concentration in a finite functionally graded material plate

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Science China(Physics,Mechanics & Astronomy) 2012年第7期55卷 1263-1271页

作者： YANG QuanQuan gao cunfa CHEN WenTao State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics&AstronauticsNanjing 210016China

This paper is to study the two-dimensional stress distribution of a finite functionally graded material (FGM) plate with a circular hole under arbitrary constant loads. Using the method of piece-wise homogeneous layers, the stress analysis of the finite FGM plate having radial arbitrary elastic properties is made based on the complex variable method combined with the least square boundary collocation technique. Numerical results of stress distribution around the hole are then presented for different loading conditions, different material properties and different plate sizes, respectively. It is shown that the stress concentration in the finite plate is generally enhanced compared with the case of an infinite plate, but it can be significantly reduced by choosing proper change ways of the radial elastic modulus.

关键词：功能梯度材料无限大板应力集中复变函数方法应力分布负载条件配置技术最小二乘

Partial discharge-induced crack growth in dielectric materials

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Science China(Physics,Mechanics & Astronomy) 2010年第5期53卷 886-891页

作者： LUO JiaCheng,gao cunfa & DAI XiangHua College of Aerospace Engineering,Nanjing University of Aeronautics & Astronautics,Nanjing 210016,China College of Aerospace Engineering Nanjing University of Aeronautics & Astronautics Nanjing China

Partial discharge(PD) of an air-filled semi-permeable crack in a dielectric material is studied based on the streamer-type discharge mechanism to explore the effects of applied mechanical-electric fields on crack growth.Within the frame of two-dimensional deformation,the electric field inside the crack is first derived by taking the crack deformation into account.Then,the effects of electric field before PD are discussed through considering the contribution of the induced electric field inside the deformed crack space to the total energy release rate.Finally,PD and its effects on crack growth are investigated.It is found that:(1) before PD,the applied electric field always retards crack growth;(2) during PD,the applied electric field can induce crack growth in dielectric materials.

关键词： crack dielectric materials partial discharge electric field effects