The PIs will study of the physics and mechanics of the brittle-ductile transition and of the effects of pressure, temperature, grain-size, and second-phase content on the strength of dunite, diabase, and marble. Strength and axial and volumetric strain will be measured during tests at temperatures of up to 1300o C and pressures of up to 600 MPa in either of three fluid confining-medium, triaxial testing machines presently available. The data will be used to determine the effect of pressure and temperature on strain hardening, dilation rates, and the localization process. Both creep tests and constant strain- rate tests will be done. Acoustic emission measurements will be made during some of the tests to obtain frequency of acoustic events as a function of strain.
