Abstract It is well known that the densification of oxide glass can occur at high contact pressure (typically >5 GPa) under normal indentation conditions. This study reports that when frictional shear is involved, the subsurface densification of glass can occur under low load conditions that would involve completely elastic deformation if the load is applied along the surface normal direction without any interfacial shear. This phenomenon was observed for a borosilicate glass rubbed with a smooth stainless-steel ball in liquid water at a nominal Hertzian contact pressure of ≤0.5 GPa. Under these frictional conditions, subsurface cracking is completely suppressed, and surface wear occurs through mechanochemical reactions. Since the mechanochemical wear track was sufficiently smooth, it was possible to employ a sub-glass transition temperature (sub-Tg) annealing method to measure the volume recovery of the densified subsurface region. The friction-induced subsurface densification of the wear track was also confirmed through nanoindentation measurements and dissolution tests in pH 13 aqueous solutions. Molecular dynamics (MD) simulations with a ReaxFF reactive force also suggested that the subsurface structural change can occur readily when friction is involved at low contact pressure conditions.

中文翻译：

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在远低于压痕损伤阈值的接触应力下摩擦引起的玻璃次表面致密化

摘要 众所周知，在正常压痕条件下，氧化物玻璃会在高接触压力（通常 >5 GPa）下发生致密化。该研究报告说，当涉及摩擦剪切时，如果沿表面法线方向施加载荷而没有任何界面剪切，则在低载荷条件下会发生玻璃的表面致密化，这将涉及完全弹性变形。在额定赫兹接触压力≤0.5 GPa 的液态水中用光滑的不锈钢球摩擦硼硅酸盐玻璃时观察到这种现象。在这些摩擦条件下，表面下裂纹被完全抑制，并且通过机械化学反应发生表面磨损。由于机械化学磨损轨迹足够光滑，可以采用亚玻璃化转变温度 (sub-Tg) 退火方法来测量致密的亚表面区域的体积恢复。通过纳米压痕测量和 pH 13 水溶液中的溶解测试也证实了磨损轨迹的摩擦引起的亚表面致密化。具有 ReaxFF 反作用力的分子动力学 (MD) 模拟还表明，当在低接触压力条件下涉及摩擦时，很容易发生地下结构变化。