[SSS15-P14] Effects of ambient temperature on the frictional strength and frictional heating of dolerite
Keywords:frictional strength, frictional heating, temperature dependence, dolerite
Experiments were performed on dolerite (Belfast, Northern Ireland) using a rotary shear deformation apparatus at Chiba University. Samples were displaced up to about 20 m at a normal stress of 1 MPa, slip velocities V of 3–300 mm/s, and ambient temperatures Ta of ~20–500oC in an argon atmosphere with an oxygen concentration of 0.3 %. Temperature adjacent to the slip surface Ts was also measured by a thermocouple placed near the slip surface.
At V = 3–30 mm/s, dolerite showed steady-state friction coefficients µss of 0.46–0.54 at Ta = 20–100oC. Whereas at Ta = 200–500oC, µss increased to 0.64–0.71. At V = 100 mm/s, dolerite showed clear velocity-strengthening with µss up to 0.58–0.64 at Ta = 20–100oC, almost constant values with µss = 0.65–0.69 at Ta = 200oC and 300oC, and clear velocity-weakening with µss = 0.45–0.46 at Ta = 400oC and 500oC. At V = 300 mm/s, dolerite showed strong velocity-weakening at all Ta investigated. In addition, slip-weakening distance (Dc) at V = 100 mm/s and 300 mm/s was smaller at higher Ta. Ts increased with increasing V. The amount of Ts increase (ΔTs) due to frictional heating was almost the same at all Ta tested at V = 3–30 mm/s (ΔTs was ~1oC at V = 3 mm/s and ~30oC at V = 30 mm/s). At V = 100 mm/s and 300mm/s, on the other hand, ΔTs was notably smaller at higher Ta. Thus, the frictional properties and frictional heating of dolerite are affected not only by V but also by Ta. Estimations of temperature distribution during experiments based on three-dimensional finite element modeling are also in progress.