Viscoelastic Fields Near Interface Edge And Crack

With the development of material science, new materials such as epoxy resin composite, polymer and solders, have been widely applied in industries, forming bonded dissimilar materials. Because these materials exhibit viscoelastic behavior under some service conditions, the singular stress fields near interface edge and crack, which always lead to structure failure, are time-dependent. The conventional analyses and evaluation methods for elastic bi-material interface seem helpless. To set up new evaluation methods for viscoelastic interface fracture, it is of great importance to clarify the characteristics of viscoelastic singular stress fields near the interface edge and crack.This thesis mainly includes the following two parts: (1) Derivation of the analytical solutions for the singular fields near viscoelastic interface edge, with the help of correspondence principle combined with quasi-static approximate method, and verifying its validity by FEA analysis. The time-dependent singular order and the stress intensity coefficient, which represent the characteristics of viscoelastic interface edge, are investigated carefully. (2) For an interface crack problem, firstly, the solutions are obtained with the classic interface crack model, which includes the interface overlapping contradiction. With the applied remote uniform constant stress and strain loadings, creep and stress relaxation properties near the crack tip are studied. Secondly, under remote mixed mode loadings, a viscoelastic interface crack is analyzed with the Comninou's contact model. The contact zone near the crack tip, as well as its influence on singularity of stress fields, is studied. The solutions are compared with classic results. Both results from classic model and contact model are verified with FEA.