Annual Technical Progress Report for 1975/76
CORNELL UNIV ITHACA NY MATERIALS SCIENCE CENTER
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Significant efforts are now underway in the area of non-destructive testing, grain matrix deformation processes, grain boundary deformation and fracture processes, and flaw top processes. The non-destructive testing NDT area has been developed from essentially a zero base to a very significant experimental effort using ultrasonic pulse spectroscopy, holographic interferometry, and acoustic emission. The Grain Matrix Deformation area continues to build on the continuing success of the mechanical equation of state approach. A phenomenological model of the processes described by the mechanical equation of state is under development, which may point the way to a better understanding of the microscopic processes. A new project has been started to evaluate the usefulness of mechanical equation of state concepts in describing the high-pressure creep deformation of ceramics. Possible areas of application include analysis of hot pressing processing techniques and of deformation of mantle materials in the earth. A new area of Grain Boundary Deformation and Fracture Processes has developed with new projects started on grain boundary crack initiationdamage in creep-fatique loading of ceramics hot pressed silicon nitride and metals stainless steels. Environmental effects are under study both in the creep-fatigue problem and in a program to characterize hydrogen attack at grain boundaries in steel methane bubble attack. In the flaw tip processes area the emphasis upon crazing at crack tips in glassy polymers continues, but new efforts have been initiated on crack tip deformation processes in metallic glasses and on slow crack growth in metals at elevated temperatures.
- Test Facilities, Equipment and Methods