Frictional experiments of dolerite at intermediate slip rates with controlled temperature: Rate weakening or temperature weakening?
Frictional experiments of dolerite at intermediate slip rates with controlled temperature: Rate weakening or temperature weakening?
复制标题
DOI：
10.1029/2010jb007945
复制
发表时间：
2011-07
影响因子：
--
通讯作者：
H. Noda;K. Kanagawa;T. Hirose;A. Inoue
中科院分区：
文献类型：
--
作者：
H. Noda;K. Kanagawa;T. Hirose;A. Inoue
千叶大学新建立的旋转剪切装置，可以将滑动表面附近的温度T_meas控制在1000°C以下，而不受滑移率v的影响。在0.010 m/s， 1 MPa法向应力和变T_meas下对白云石的摩擦系数f有显著的影响。随着T_meas的增加，f在室温下从0.7 ~ 0.8开始，在400℃时下降到0.5 ~ 0.6，增加到800℃。然后再次减小。我们还对磨损材料（主要是亚微米颗粒）进行了XRD分析，并研究了在不同温度t_mes下形成的滑动表面的微观结构，我们发现除了在RT和1000°C时，f与非晶材料的数量呈负相关。非晶态相的产生可能是导致弱化的原因。在1000°C时，样品没有识别出非晶态相，它是圆形晶体的集合。EBSD分析表明，在1000℃时，滑动表面的材料含有随机取向的赤铁矿颗粒，结合观察到的微观结构特征，表明发生了颗粒流动。我们还证明了f不仅取决于温度的瞬时值，而且取决于它的历史。通过与常规无温度控制的旋转剪切摩擦实验比较，我们得出结论，在没有温度主动控制的高速摩擦实验中观察到的强烈的“速率弱化”是温度效应的重要贡献。
A rotary shear apparatus has been newly set up in Chiba University which can control the temperature near a sliding surface, T_meas, up to 1000°C independently from slip rate, V. Frictional experiments at 0.010 m/s, 1 MPa normal stress, and variable T_meas for dolerite have revealed a remarkable effect of temperature on the friction coefficient, f. With increasing T_meas, f starts from 0.7 to 0.8 at room temperature (RT), decreases down to 0.5–0.6 at 400°C, increases until 800°C, and then decreases again. We have also conducted XRD analyses of the wear materials (mainly submicron particles) and investigated microstructures of the sliding surfaces developed at different temperatures T_meas, and we found that there is a negative correlation between f and the amount of amorphous material except at RT and 1000°C. The generation of the amorphous phase probably causes the weakening. There is no amorphous phase recognized for a sample at 1000°C which is an aggregate of rounded crystals. EBSD analyses show that the material on the sliding surface at 1000°C contains randomly oriented hematite grains, which together with the observed microstructural features suggests that granular flow was taking place. We have also demonstrated that f depends not only on the instantaneous value of temperature, but also on its history. By comparing with conventional rotary shear friction experiment for the same dolerite without temperature control, we conclude that strong “rate weakening” as recently observed in high-velocity frictional experiments without an active control of the temperature has a significant amount of contribution from the temperature effect.