INELASTIC RESPONSE OF CONFINED ALUMINUM-OXIDE UNDER DYNAMIC LOADING CONDITIONS

Previous efforts to explore the compressive strength of ceramics as a function of confining pressure at high strain rates have been limited by the maximum hydrostatic pressure that could be achieved within the experimental apparatus. An alternate procedure, using an autofrettaged confinement ring, has been designed to achieve higher confining press ures. A 6.2 GPa stress pulse, of approximately 20 mu s duration, was u sed to load a 99.5% pure cylindrical aluminium oxide specimen under a hydrostatic load of approximately 650 MPa. The specimen remained intac t and showed no evidence of fracture under scanning electron microscop y (SEM). Transmission electron microscopy (TEM), however, showed exten sive evidence of plastic flow; the microcracks that were observed were associated with dislocation arrays. Static and dynamic yield strength s as a function of strain rate are compared. (C) 1998 Chapman & Hall.