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Stress distribution and surface instability of an inclined granular layer

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Chinese Physics B 2013年第4期22卷 205-212页

作者：郑鹤鹏蒋亦民彭政 School of Physics and Electronics Central South University School of Basic Medical Sciences Guilin Medical University

Static granular materials may avalanche suddenly under continuous quasi-static drives. This phenomenon, which is important in many engineering applications, can be explained by analyzing the stability of the elastic solutions. We show this for a granular layer driven by its inclination angle in gravity, where the elastic problem can be solved generally and analytically. It is found that a loss of stability may occur only at the free surface of the layer. This result is considered to be relevant for understanding surface avalanches and the flows observed experimentally.

关键词： granular matter nonlinear elasticity stress surface instability

Prediction and Regulation of Delamination at Flexible Film/Finite-Thickness-Substrate Structure Interfaces

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Acta Mechanica Solida Sinica 2024年第2期37卷 238-251页

作者： Yutang Zhou Yunlong Xu Haoran Gong Chenyu Wang Department of Engineering Mechanics Northwestern Polytechnical UniversityXi’an710072China School of Instrumentation Science and Opto-Electronics Engineering Beihang UniversityBeijing100191China

Regulating the surface instability of thin film/substrate structures has been successfully applied to prepare new ductile electronic ***,such electronic devices need to be subjected to external loads during operation,which can easily induce delamination of the thin-film electronic device from the *** study aims to investigate the instability characteristics of hard films on flexible substrate surfaces from theoretical analysis and numerical simulation *** finite-thickness substrates,this paper establishes theoretical models for pure bending,bent wrinkle,partial delamination,and total delamination buckling of film/substrate structures based on the nonlinear Euler–Bernoulli beam theory and the principle of minimum energy;then the effects of material and geometric parameters of the structure,interfacial adhesion strength,and pre-strain on the evolutionary path of the four patterns are *** study results show that:the greater Young’s modulus of the substrate is,the larger the parameter region where partial delamination of the film/substrate structure occurs,and the smaller the parameter region where bent wrinkle *** varying Young’s modulus,thickness of the film and substrate,interfacial adhesion coefficient,and pre-strain,the buckling pattern of the structure can be predicted and *** parametric design intervals for each pattern are summarized in the phase *** results of this paper provide theoretical support for the design and reliability evaluation of flexible electronic devices.

关键词： Thin film/finite-thickness-substrate structure Delamination surface instability Pattern evolution

Bioinspired Multiscale Wrinkling Patterns on Curved Substrates:An Overview

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Nano-Micro Letters 2020年第8期12卷 130-171页

作者： Yinlong Tan Biru Hu Jia Song Zengyong Chu Wenjian Wu College of Liberal Arts and Science National University of Defense TechnologyChangsha 410073People’s Republic of China

The surface wrinkling of biological tissues is ubiquitous in *** evidence suggests that the mechanical force plays a significant role in shaping the biological *** wrinkling has been demonstrated to be able to spontaneously form rich multiscale patterns,on either planar or curved *** surface wrinkling on planar substrates has been investigated thoroughly during the past ***,most wrinkling morphologies in nature are based on the curved biological surfaces and the research of controllable patterning on curved substrates still remains *** study of wrinkling on curved substrates is critical for understanding the biological growth,developing threedimensional(3D)or four-dimensional(4D)fabrication techniques,and creating novel topographic *** this review,fundamental wrinkling mechanics and recent advances in both fabrications and applications of the wrinkling patterns on curved substrates are *** mechanics behind the wrinkles is compared between the planar and the curved *** the film thickness,modulus ratio,and mismatch strain,the substrate curvature is one more significant parameter controlling the surface *** substrates can be both solid and hollow with various 3D geometries across multiple length *** to date,the wrinkling morphologies on solid/hollow core-shell spheres and cylinders have been simulated and selectively *** applications of the curved topographic patterns have been found in smart wetting surfaces,cell culture interfaces,healthcare materials,and actuators,which may accelerate the development of artificial organs,stimuli-responsive devices,and micro/nano fabrications with higher dimensions.

关键词： surface instability Wrinkling patterns Substrate curvature Micro/nano fabrications Low-dimensional materials

BIOMECHANICAL MODELING OF surface WRINKLING OF SOFT TISSUES WITH GROWTH-DEPENDENT MECHANICAL PROPERTIES

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Acta Mechanica Solida Sinica 2012年第5期25卷 483-492页

作者： Yanping Cao Yi Jiang Bo Li Xiqiao Feng Institute of Biomechanics and Medical Engineering Department of Engineering MechanicsTsinghua UniversityBeijing 100084China

This paper explores growth induced morphological instabilities in biological soft materials. In view of that the growth of a living tissue not only changes its geometry but also can alter its mechanical properties, we suggest a refined volumetric growth model incorporating the effects of growth on the mechanical properties of materials. Analogy between this volumetric growth model and the conventional thermal stress model is addressed for both small and finite de- formation problems, which brings great ease for the finite element analysis based on the suggested model. Examples of growth induced surface wrinkling behavior in soft composites, including core- shell soft cylinders and three-layered soft tissues, are explored. The results and discussions foresee possible applications of the model in understanding the correlation between the morphogenesis and growth of soft biological tissues （e.g. skins and tumors）, as well as in evaluating the defor- mation and surface instability behavior of soft artificial materials induced by swelling/shrinkage.

关键词： volumetric growth soft tissues surface instability morphogenesis