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C J Warren - One of the best experts on this subject based on the ideXlab platform.

  • crustal structure a key constraint on the mechanism of ultra high pressure rock exhumation
    Earth and Planetary Science Letters, 2009
    Co-Authors: Christopher Beaumont, J.p. Butler, Rebecca Anne Jamieson, C J Warren
    Abstract:

    Abstract The distribution of ultra-high-pressure (UHP) metamorphic rocks demonstrates that burial (to > 100 km) and rapid exhumation (> 1 cm a − 1 ) of continental crust is a normal part of early (∼ 10 Ma) continental collision. Currently, there is no comprehensive model for this fundamental tectonic process that also satisfactorily explains the upper-crustal structures resulting from early collisional UHP rock exhumation. Characteristic features requiring explanation include: structural domes that are cored by UHP nappes; associated medium- to high-pressure nappes displaying a distinct “pressure gap”; overlying lower-grade rocks, including suture zone ophiolites; and, coeval foreland-directed thrust-faults and syn-exhumation normal faults. We present a geodynamical model involving crustal burial and exhumation in a subduction channel below an accretionary wedge. Competition between down-channel shear traction and up-channel buoyancy forces, expressed as the exhumation number, E , controls burial and exhumation, leading to rapid up-channel flow when E  > 1. Exhuming UHP Material Forms a nappe stack and structural dome as it penetrates and destabilises the overlying wedge, driving thrusting and extension. This solution is compelling because it explains both the geology and the petrology of the Tso Morari and other UHP complexes, and because it demonstrates that pulse-like buoyant exhumation from deep in the subduction channel creates observed upper crustal structures. This places constraints on the exhumation mechanism and provides a test of alternative models. Other proposed mechanisms, such as continuous circulation in a lithospheric-scale wedge or overpressured subduction channel, predict different types of upper-crustal structures and are therefore unsatisfactory explanations for early collisional exhumation of UHP terranes.

  • deep subduction and rapid exhumation role of crustal strength and strain weakening in continental subduction and ultrahigh pressure rock exhumation
    Tectonics, 2008
    Co-Authors: C J Warren, Christopher Beaumont, Rebecca Anne Jamieson
    Abstract:

    [1] The exhumation of crustal ultra-high-pressure (UHP) Material depends on temporal and spatial variations in its detachment within the subduction channel. This dependence is investigated using numerical models with variable initial crustal strengths, representing a range of initial crustal compositions, and parameterized strain weakening, representing a range of processes that reduce effective crustal viscosity during deformation. Competition between down-channel shear traction, favoring subduction, and up-channel buoyancy, favoring exhumation, is expressed as the exhumation number, E, which can vary with time and position along the channel. Exhumed lower strength crust, which resists subduction owing to weak down-channel traction, records peak conditions 38 kbar. Given sufficient strain weakening, exhumation proceeds at >60 km Ma−1, indicating that buoyancy (E ≫ 1) drives exhumation in these models. In all models, exhuming UHP Material Forms a deforming ductile plume, with a range of possible structural relationships predicted between exhumed UHP and HP Materials.

Rebecca Anne Jamieson - One of the best experts on this subject based on the ideXlab platform.

  • crustal structure a key constraint on the mechanism of ultra high pressure rock exhumation
    Earth and Planetary Science Letters, 2009
    Co-Authors: Christopher Beaumont, J.p. Butler, Rebecca Anne Jamieson, C J Warren
    Abstract:

    Abstract The distribution of ultra-high-pressure (UHP) metamorphic rocks demonstrates that burial (to > 100 km) and rapid exhumation (> 1 cm a − 1 ) of continental crust is a normal part of early (∼ 10 Ma) continental collision. Currently, there is no comprehensive model for this fundamental tectonic process that also satisfactorily explains the upper-crustal structures resulting from early collisional UHP rock exhumation. Characteristic features requiring explanation include: structural domes that are cored by UHP nappes; associated medium- to high-pressure nappes displaying a distinct “pressure gap”; overlying lower-grade rocks, including suture zone ophiolites; and, coeval foreland-directed thrust-faults and syn-exhumation normal faults. We present a geodynamical model involving crustal burial and exhumation in a subduction channel below an accretionary wedge. Competition between down-channel shear traction and up-channel buoyancy forces, expressed as the exhumation number, E , controls burial and exhumation, leading to rapid up-channel flow when E  > 1. Exhuming UHP Material Forms a nappe stack and structural dome as it penetrates and destabilises the overlying wedge, driving thrusting and extension. This solution is compelling because it explains both the geology and the petrology of the Tso Morari and other UHP complexes, and because it demonstrates that pulse-like buoyant exhumation from deep in the subduction channel creates observed upper crustal structures. This places constraints on the exhumation mechanism and provides a test of alternative models. Other proposed mechanisms, such as continuous circulation in a lithospheric-scale wedge or overpressured subduction channel, predict different types of upper-crustal structures and are therefore unsatisfactory explanations for early collisional exhumation of UHP terranes.

  • deep subduction and rapid exhumation role of crustal strength and strain weakening in continental subduction and ultrahigh pressure rock exhumation
    Tectonics, 2008
    Co-Authors: C J Warren, Christopher Beaumont, Rebecca Anne Jamieson
    Abstract:

    [1] The exhumation of crustal ultra-high-pressure (UHP) Material depends on temporal and spatial variations in its detachment within the subduction channel. This dependence is investigated using numerical models with variable initial crustal strengths, representing a range of initial crustal compositions, and parameterized strain weakening, representing a range of processes that reduce effective crustal viscosity during deformation. Competition between down-channel shear traction, favoring subduction, and up-channel buoyancy, favoring exhumation, is expressed as the exhumation number, E, which can vary with time and position along the channel. Exhumed lower strength crust, which resists subduction owing to weak down-channel traction, records peak conditions 38 kbar. Given sufficient strain weakening, exhumation proceeds at >60 km Ma−1, indicating that buoyancy (E ≫ 1) drives exhumation in these models. In all models, exhuming UHP Material Forms a deforming ductile plume, with a range of possible structural relationships predicted between exhumed UHP and HP Materials.

S Brusethaug - One of the best experts on this subject based on the ideXlab platform.

  • tribological behavior of al si sicp composites automobile brake pad system under dry sliding conditions
    Tribology International, 2007
    Co-Authors: R K Uyyuru, M K Surappa, S Brusethaug
    Abstract:

    Tribological behavior of stir-cast $Al-Si/SiC_p$ composites against automobile brake pad Material was studied using Pin-on-Disc tribo-tester. The Al-metal matrix composite (Al-MMC) Material was used as disc, whereas the brake pad Material Forms the pin. It has been found that both wear rate and friction coefficient vary with both applied normal load and sliding speed. With increase in the applied normal load, the wear rate was observed to increase whereas the friction coefficient decreases. However, both the wear rate and friction coefficients were observed to vary proportionally with the sliding speed. During the wear tests, formation of a tribo-layer was observed, presence of which can affect the wear behavior, apart from acting as a source of wear debris. Tribo-layer formed over the worn disc surfaces was found to be heterogeneous in nature. Morphology and topography of worn surfaces and debris were studied using scanning electron microscope (SEM). Chemical composition of different wear products was obtained using electron probe micro analyzer (EPMA) and X-ray diffraction (XRD) techniques. Possible wear mechanisms operative in Al-MMC-brake pad tribo-couple have been discussed.

  • tribological behavior of al si sicp composites automobile brake pad system under dry sliding conditions
    Tribology International, 2007
    Co-Authors: R K Uyyuru, M K Surappa, S Brusethaug
    Abstract:

    Tribological behavior of stir-cast $Al-Si/SiC_p$ composites against automobile brake pad Material was studied using Pin-on-Disc tribo-tester. The Al-metal matrix composite (Al-MMC) Material was used as disc, whereas the brake pad Material Forms the pin. It has been found that both wear rate and friction coefficient vary with both applied normal load and sliding speed. With increase in the applied normal load, the wear rate was observed to increase whereas the friction coefficient decreases. However, both the wear rate and friction coefficients were observed to vary proportionally with the sliding speed. During the wear tests, formation of a tribo-layer was observed, presence of which can affect the wear behavior, apart from acting as a source of wear debris. Tribo-layer formed over the worn disc surfaces was found to be heterogeneous in nature. Morphology and topography of worn surfaces and debris were studied using scanning electron microscope (SEM). Chemical composition of different wear products was obtained using electron probe micro analyzer (EPMA) and X-ray diffraction (XRD) techniques. Possible wear mechanisms operative in Al-MMC-brake pad tribo-couple have been discussed.

Christopher Beaumont - One of the best experts on this subject based on the ideXlab platform.

  • crustal structure a key constraint on the mechanism of ultra high pressure rock exhumation
    Earth and Planetary Science Letters, 2009
    Co-Authors: Christopher Beaumont, J.p. Butler, Rebecca Anne Jamieson, C J Warren
    Abstract:

    Abstract The distribution of ultra-high-pressure (UHP) metamorphic rocks demonstrates that burial (to > 100 km) and rapid exhumation (> 1 cm a − 1 ) of continental crust is a normal part of early (∼ 10 Ma) continental collision. Currently, there is no comprehensive model for this fundamental tectonic process that also satisfactorily explains the upper-crustal structures resulting from early collisional UHP rock exhumation. Characteristic features requiring explanation include: structural domes that are cored by UHP nappes; associated medium- to high-pressure nappes displaying a distinct “pressure gap”; overlying lower-grade rocks, including suture zone ophiolites; and, coeval foreland-directed thrust-faults and syn-exhumation normal faults. We present a geodynamical model involving crustal burial and exhumation in a subduction channel below an accretionary wedge. Competition between down-channel shear traction and up-channel buoyancy forces, expressed as the exhumation number, E , controls burial and exhumation, leading to rapid up-channel flow when E  > 1. Exhuming UHP Material Forms a nappe stack and structural dome as it penetrates and destabilises the overlying wedge, driving thrusting and extension. This solution is compelling because it explains both the geology and the petrology of the Tso Morari and other UHP complexes, and because it demonstrates that pulse-like buoyant exhumation from deep in the subduction channel creates observed upper crustal structures. This places constraints on the exhumation mechanism and provides a test of alternative models. Other proposed mechanisms, such as continuous circulation in a lithospheric-scale wedge or overpressured subduction channel, predict different types of upper-crustal structures and are therefore unsatisfactory explanations for early collisional exhumation of UHP terranes.

  • deep subduction and rapid exhumation role of crustal strength and strain weakening in continental subduction and ultrahigh pressure rock exhumation
    Tectonics, 2008
    Co-Authors: C J Warren, Christopher Beaumont, Rebecca Anne Jamieson
    Abstract:

    [1] The exhumation of crustal ultra-high-pressure (UHP) Material depends on temporal and spatial variations in its detachment within the subduction channel. This dependence is investigated using numerical models with variable initial crustal strengths, representing a range of initial crustal compositions, and parameterized strain weakening, representing a range of processes that reduce effective crustal viscosity during deformation. Competition between down-channel shear traction, favoring subduction, and up-channel buoyancy, favoring exhumation, is expressed as the exhumation number, E, which can vary with time and position along the channel. Exhumed lower strength crust, which resists subduction owing to weak down-channel traction, records peak conditions 38 kbar. Given sufficient strain weakening, exhumation proceeds at >60 km Ma−1, indicating that buoyancy (E ≫ 1) drives exhumation in these models. In all models, exhuming UHP Material Forms a deforming ductile plume, with a range of possible structural relationships predicted between exhumed UHP and HP Materials.

R K Uyyuru - One of the best experts on this subject based on the ideXlab platform.

  • tribological behavior of al si sicp composites automobile brake pad system under dry sliding conditions
    Tribology International, 2007
    Co-Authors: R K Uyyuru, M K Surappa, S Brusethaug
    Abstract:

    Tribological behavior of stir-cast $Al-Si/SiC_p$ composites against automobile brake pad Material was studied using Pin-on-Disc tribo-tester. The Al-metal matrix composite (Al-MMC) Material was used as disc, whereas the brake pad Material Forms the pin. It has been found that both wear rate and friction coefficient vary with both applied normal load and sliding speed. With increase in the applied normal load, the wear rate was observed to increase whereas the friction coefficient decreases. However, both the wear rate and friction coefficients were observed to vary proportionally with the sliding speed. During the wear tests, formation of a tribo-layer was observed, presence of which can affect the wear behavior, apart from acting as a source of wear debris. Tribo-layer formed over the worn disc surfaces was found to be heterogeneous in nature. Morphology and topography of worn surfaces and debris were studied using scanning electron microscope (SEM). Chemical composition of different wear products was obtained using electron probe micro analyzer (EPMA) and X-ray diffraction (XRD) techniques. Possible wear mechanisms operative in Al-MMC-brake pad tribo-couple have been discussed.

  • tribological behavior of al si sicp composites automobile brake pad system under dry sliding conditions
    Tribology International, 2007
    Co-Authors: R K Uyyuru, M K Surappa, S Brusethaug
    Abstract:

    Tribological behavior of stir-cast $Al-Si/SiC_p$ composites against automobile brake pad Material was studied using Pin-on-Disc tribo-tester. The Al-metal matrix composite (Al-MMC) Material was used as disc, whereas the brake pad Material Forms the pin. It has been found that both wear rate and friction coefficient vary with both applied normal load and sliding speed. With increase in the applied normal load, the wear rate was observed to increase whereas the friction coefficient decreases. However, both the wear rate and friction coefficients were observed to vary proportionally with the sliding speed. During the wear tests, formation of a tribo-layer was observed, presence of which can affect the wear behavior, apart from acting as a source of wear debris. Tribo-layer formed over the worn disc surfaces was found to be heterogeneous in nature. Morphology and topography of worn surfaces and debris were studied using scanning electron microscope (SEM). Chemical composition of different wear products was obtained using electron probe micro analyzer (EPMA) and X-ray diffraction (XRD) techniques. Possible wear mechanisms operative in Al-MMC-brake pad tribo-couple have been discussed.