5:15 PM - 7:15 PM
[SCG62-P06] Development of a new liquid cell for solid-medium deformation apparatus: Reduction of internal friction for precise stress measurements
Keywords:rheology, deformation experiments, solid-medium apparatus, differential stress, internal friction, confining medium
Solid-medium apparatus of the Griggs type has been widely used for deformation experiments at high-pressures and high-temperatures, but low accuracy in stress measurements due to friction in the solid confining medium has been a long-standing issue. To reduce internal friction in the sample assembly, a molten salt cell has been also used for the inner sleeve that covers the sample and a part of the inner pistons. To examine the measurement errors in Griggs apparatus using solid NaCl and molten salt cells, Holyoke and Kronenberg (2010) performed a series of calibration tests using pure Ni and Mo samples, and compared the results with those precisely determined by a gas-medium apparatus. It turned out that even the molten salt cell was used, differential stress was overestimated about several hundred of megapascals. It should be noted that confining pressure (Pc) is limited up to 300 MPa in the experiments using gas-medium apparatus. Hence, direct comparison between solid and gas medium apparatus is restricted within this pressure range.
Focusing accurate stress measurements, Kumazawa-type deformation apparatus was designed so that the axial stress and the confining pressure can be measured by two pairs of load cells set above and below the pressure vessel. In principle, internal friction can be corrected real-time by averaging the upper and lower load cell data (Shimizu and Michibayashi, 2022) but its performance has not well been verified. In this study, we made calibration tests using a Kumazawa-type apparatus and evaluated its performance in friction correction. Following Holyoke and Kronenberg (2010), we used high-purity Ni and Mo purchased from the same company, and conducted the calibration tests at the same conditions, i.e., temperatures of 600℃ and 700℃, Pc of 300 MPa, and strain rate of 1.6 ×10-4 sec-1. Talc, NaCl and BN were tested for solid confining media. Instead of the molten salt cell, which is chemically active and potentially corrosive, we developed a new liquid cell using two kinds of glass flits with softening points of 415℃ and 600℃. The differential stress determined with talc and NaCl assemblies lead to overestimation of about 200 MPa and 110 MPa, respectively. The former value is comparable with the previous results using a NaCl assembly in Griggs apparatus, and the latter is even better than 150 MPa of the Griggs apparatus with a molten salt cell. Using BN and low softening-point glass cell at the 600℃ runs, the difference between the yield stresses observed in this study and those determined by the gas-medium apparatus were almost diminished.
References
Holyoke, C. W. and Kronenberg, A. K. (2010) Accurate differential stress measurement using molten salt cell and solid salt assemblies in the Griggs apparatus with applications to strength, parameters and rheology, Tectonophysics, 494, 17–31, doi:10.1016/j.tecto.2010.08.001.
Shimizu, I. and Michibayashi, K. (2022) Steady-state microstructures of quartz revisited: Evaluation of stress states in deformation experiments using a solid-medium apparatus, Minerals, 12, 329, doi:10.3390/min12030329
Focusing accurate stress measurements, Kumazawa-type deformation apparatus was designed so that the axial stress and the confining pressure can be measured by two pairs of load cells set above and below the pressure vessel. In principle, internal friction can be corrected real-time by averaging the upper and lower load cell data (Shimizu and Michibayashi, 2022) but its performance has not well been verified. In this study, we made calibration tests using a Kumazawa-type apparatus and evaluated its performance in friction correction. Following Holyoke and Kronenberg (2010), we used high-purity Ni and Mo purchased from the same company, and conducted the calibration tests at the same conditions, i.e., temperatures of 600℃ and 700℃, Pc of 300 MPa, and strain rate of 1.6 ×10-4 sec-1. Talc, NaCl and BN were tested for solid confining media. Instead of the molten salt cell, which is chemically active and potentially corrosive, we developed a new liquid cell using two kinds of glass flits with softening points of 415℃ and 600℃. The differential stress determined with talc and NaCl assemblies lead to overestimation of about 200 MPa and 110 MPa, respectively. The former value is comparable with the previous results using a NaCl assembly in Griggs apparatus, and the latter is even better than 150 MPa of the Griggs apparatus with a molten salt cell. Using BN and low softening-point glass cell at the 600℃ runs, the difference between the yield stresses observed in this study and those determined by the gas-medium apparatus were almost diminished.
References
Holyoke, C. W. and Kronenberg, A. K. (2010) Accurate differential stress measurement using molten salt cell and solid salt assemblies in the Griggs apparatus with applications to strength, parameters and rheology, Tectonophysics, 494, 17–31, doi:10.1016/j.tecto.2010.08.001.
Shimizu, I. and Michibayashi, K. (2022) Steady-state microstructures of quartz revisited: Evaluation of stress states in deformation experiments using a solid-medium apparatus, Minerals, 12, 329, doi:10.3390/min12030329