Studies On Wrinkling Instability Behaviour Of Thin Film

Instability is widespread in nature and engineering,such as wrinkles on human skin,wrinkles in thin film spacecraft,dendrite phenomenon in solid electrolyte interphase of high-capacity lithium batteries,and buckling design of flexible electronic devices.How to understand the instability phenomenon and its mechanism in nature and engineering applications has become a hot issue in many fields,such as mechanics,materials and biology.On the one hand,the study of thin film instability helps to propose a strategy to suppress wrinkles and guide the structural design to avoide functional failure and life reduction of the product.On the other hand,instability investigation can help to design materials with new functions.This paper is focused on the analyses of the instability mechanism,the post-buckling morphology evolution and the correlation of various instability modes by theoretical analysis,numerical simulation and experimental testing.The results provide theoretical support for applications of thin film in high-capacity lithium batteries,flexible electronics,and thin film spacecraft.Torsional wrinkling behavior and vibrational characteristics of an annular thin film are investigated.Non-dimensional nonlinear von-Kármán buckling equations are established and solved by introducing compound series method and finite difference method to acquire the post-wrinkling characteristics.The proposed theoretical model can accurately predict the critical wrinkling load and post-wrinkling characteristics of the annular thin film.The non-dimensional Hamilton motion equation of a wrinkled annular thin film is established to obtain the vibration frequency and mode.Effects of geometric parameters on critical wrinkling load and vibration frequency under different torsions are investigated.All the results are verified by the experimental measurement based on the digital image correlation(DIC)technique.Global-local interactive wrinkling behaviour of an inflated beam is investigated.The global-local interactive buckling governing equation is established based on a Fourier series method.The critical wrinkling and failure moments of inflated beam are obtained.The effects of geometric parameters,internal pressure and boundary conditions on the buckling of inflated beams are investigated.The global and local deformation variables are introduced respectively to consider the sectional Brazier effect.The governing equations,which are fourth-order ordinary differential nonlinear equations with integral conditions,are solved by introducing a continuation algorithm.The relationships between the internal pressure and geometric parameters on the buckling behavior of the inflated beam are obtained.Global-local interactive buckling behavior and buckling-driven delamination of a stiff film resting on a compliant substrate under uniaxial compression are studyed.An analytical model is proposed to describe the instability phenoena from buckling to buckling-driven delamination.The resulting governing non-linear equations are then solved by introducing a continuation algorithm,which offers considerable advantages to detect multiple bifurcations and trace a complex post-buckling path.The critical condition for local and global buckling and respective post-buckling equilibrium paths are carefully studied.By introducing the Heaviside function,the critical conditions of global and local buckling-driven delamination are obtained.The effects of buckling on interlayer delamination and the evolution characteristics of buckling-driven delamination are analyzed.Wrinkling and ratcheting behaviours of a thin film resting on a plastic substrate are investigated.A linear perturbation analysis is performed to determine the critical wrinkling strain and wavenumber.The ratcheting behaviors in the system under cyclic eigenstrain loading are studied,and the critical conditions for ratcheting are determined.A phase diagram is plotted to characterize and predict different system behaviors,e.g.,elastic,elastic wrinkling,shakedown without wrinkling,shakedown with wrinkling,and ratcheting.A series of finite element simulations are performed to validate the theoretical predictions.Diffusion induced instability behavior of an elastic–viscoplastic core-shell structure is analyzed.A coupled diffusion and finite deformation framework is formulated and numerically implemented as a user-element subroutine(UEL)to describe transient lithium diffusion and accompanying elastic–viscoplastic deformation of the core.Surface instability is found in such a system under cyclic plastic deformation induced by diffusion.A wrinkled morphology may further lead to ratcheting and related failure under cycling.The critical wrinkling mode is predicted and the mechanism of wrinkling and ratcheting is analyzed.