Crack-tip Fields In Creep Damage Materials And Acoustic Detection Of Mesodamage

This dissertation includes two parts.In the first part, the kachanov's creep damage coupling constitutive model is adopted in the adymptotic analysis of fields near a growing crack-tip and a stationary crack-tip. For antiplane shear problem(Modeâ…¢), plane stress and plane strain problems(Modeâ… ), the adymptotic eguations and conditions of determining solutions are derived respectively. Thus, the asymptotic solutions to the fields of stress, strain and damage are obtained. The results are compared with those without considering damage effect, and the influnce of damage on the fields is discussed.In the second part, the mesodamage and macrodefect in some materials are detected by means of Scanning Acoustic Microscope(SAM), and the acoustic images in the different depth of the materials under different loading conditions are obtained. The information from the images is analysed in detail.