Studies On The Deformation Transfer Mechanism Of Film Structure And Its Influence On Resistance

With the rise of the microelectronics industry and thin-film technology,film structures are widely used in the electronics industry,aerospace,medical devices,bionic devices and other fields.Due to the complexity of the actual application environment as well as the difference in structure and function,film structure will be subjected to tensile loads during the working process,resulting in the deformation and even bifurcation of the film attached to the substrate.Meanwhile,the film structure will also be delaminated due to its insufficient transverse mechanical performance,resulting in an increase in its resistance.Therefore,revealing the resistance evolution mechanism of film structure due to tensile bifurcation and delamination behavior has become an urgent scientific fundamental problem to be solved.This thesis established a theoretical model to reveal the deformation mechanism of the film structure's tensile bifurcation and delamination behavior under the action of uniaxial stretching,based on which,the effect of tensile bifurcation and delamination of the film structure on its resistance was further studied.Firstly,based on the resistance law,an evolution model of film resistance under tensile bifurcation is established.The model starts from the bifurcation behavior of the film,and studies the variation of the geometric parameters of the film with the strain in the uniform deformation stage and the localized deformation stage.At the same time,the microscopic electron scattering effect of film resistivity is studied by considering the scattering effect of the film surface and the grain boundaries existing in the film on the conductive electrons.Combining the above effects,the influence of tensile bifurcation behavior of film on its resistance is revealed.Then,based on the interlaminar shear stiffness model,a deformation transfer theoretical model was established to study the delamination behavior of film structure.The model can quantify the distribution of stress and strain in each layer under elastic and plastic states and the distribution of interlaminar shear stress,calculate the interlaminar displacement difference and strain transfer rate,and further calculate the mechanical shear strength of the film structure.In order to study the effect of film structure delamination on its electrical conductivity,HTS tape was taken as an example for calculation.Then,the phenomenological model combining Ekin power law formula and Weibull distribution function was used to predict the critical current degradation of superconducting tapes,and the equivalent resistance was further calculated by using the E-J exponential constitutive model.To sum up,the thesis conducts a systematic study on the resistance evolution law of film structure under tensile bifurcation and delamination behavior,which provides a theoretical basis for predicting the degradation of the electrical conductivity of film structure,and then provides suggestions and references for optimizing its design,so as to ensure the safe service of the film structure and realize the effective control of its working state.