Creep failure in linear and nonlinear viscoelastic materials
Abstract
For high reliability structures and structural components the residual strength must be estimated on the basis of Theoretical Fracture Mechanics. This evaluation procedure, coupled with the NDE, i.e., nondestructive evaluation techniques such as X rays, neutron diffraction and acoustic emission (AE), and other nondestructive methods of inspection, allows one to avoid catastrophic failures due to the metal fatigue, stress corrosion or other time dependent mechanisms leading to deterioration of strength and other pertinent mechanical properties which influence delayed fracture of structural components. Examples of integration of the equation of motion of a preexisting crack contained either in a linear or nonlinear viscoelastic polymer are provided for several crack and load configurations. The double logarithmic representation of the creep compliance function is used for both linear and nonlinear range of material behavior. The influence of stress level on such a loglog representation in the nonlinear range is accounted for through a modified power law of Gordon Williams. Finally, the approach of continuum mechanics is combined with certain microstructural considerations and used to derive the fundamental relationships between the rate of fracture growth, geometry of the component and the material characteristics of the solid.
 Publication:

Ph.D. Thesis
 Pub Date:
 September 1992
 Bibcode:
 1992PhDT.........7E
 Keywords:

 Creep Properties;
 Failure;
 Metal Fatigue;
 Residual Strength;
 Stress Corrosion;
 Viscoelasticity;
 Continuum Mechanics;
 Equations Of Motion;
 Fracture Mechanics;
 Fractures (Materials);
 Fracturing;
 Nondestructive Tests;
 Structural Design;
 Time Dependence;
 Structural Mechanics