The Research On Interface Crack And Buckling Problems In Film/substrate System

As a kind of surface technology, film/substrate system is developed quickly and widely used in several engineering fields. Film/substrate system belongs to multilayered structure. The obvious differences between layers in mechanical properties and the surfaces are important characters for this type of structure. So the mechanical behaviors exhibited in this structure are different from that in conventional material structure in working time. Such as, plastic deformation, debonding, buckling, spalling and cracking and so on. All of these will affect the working efficiency and life of film/substrate system. With the exploitation and application of the thin-film devices, it is more and more important to research the mechanical properties of film and film/substrate systems.With regard to this problem, the main research items in this dissertation are as follows:1. The interface static propagating crack was detailedly studied firstly. Through the asymptotic analysis of the crack-tip field, the exponents of singularity of stress and strain in interface static propagating crack-tip field were determined. Embarking from the fundamental equation and combining with the analysis on the singularity of crack-tip fields, the asymptotic governing equations were deduced. With soluting-deterimining conditions, the stress, strain and displacement fields near the tip of mode I and II crack were also obtained by using the shooting method, and the variation trend of the fields with different parameters was discussed. From the asymptotic solution of the crack-tip fields, the parameters controlling the partial cracking were searched. The results can provide theoretical base for establishing of the damage criterion.2. The buckling problems were researched secondly, and the delamination phenomenon was researched further using the results based on the linear elastic fracture mechanics.The study of the paper will provide a beneficial exploration for the final solutions of the asymptotic crack-tip field of the interface cracks and the buckling problems for film/substrate system, as well as theoretical references for the corresponding problems encountered in engineering practices and building the materil's fracture rule.