An abrasive air jet, which is sufficiently powerful to break rock, has significant potential in the field of assisted rock breaking, such as assistive tunnel excavation using a tunnel boring machine. To make its application more efficient and beneficial, a clear and definite erosion mechanism of an abrasive air jet is necessary. However, the present erosion mechanisms of an abrasive air jet have mostly neglected the secondary erosion of rebounding particles. The effect of rebounding particles on rock erosion was analyzed by numerical simulation and scanning electron microscopic images. We obtained a variety of stresses and the distribution when a perpendicular abrasive air jet erodes rock through smoothed particle hydrodynamics (SPH). In addition, the particle trajectory and a variety of velocities were also obtained, which provide the data necessary to analyze the formation and characteristics of the erosion pits. It can be concluded that the rebounding abrasive particles play an indispensable role in the stress formation and distribution of rock, and are also the primary cause of a particular erosion pit feature, that is, a semi sphere-like bottom, under an annular platform. The incident abrasive at the center of an air jet deepens the erosion pit with a large impact force and its energy propagates into the rock with a stress wave. Meanwhile, the rebounding abrasive enlarges the diameter of both the erosion pits and the semi sphere-like bottom. Because the diameter of an erosion pit is larger than that of a semi sphere-like bottom, an annular platform is formed. The incident abrasive at the jet boundary involves the formation of an annular platform. The incident and rebounding abrasives have different roles in the erosion wear of rock. The main wear characteristics of the rock are cutting and deformation wear. The incident abrasive with a high velocity induces the deformation and cutting wear at the semi sphere-like bottom. Only a cutting wear can be induced at an annular platform by an incident abrasive with a lower velocity. The rebounding abrasive induces the cutting wear of the rock only. However, the features of an erosion rock surface vary depending on the eroding angle of the rebounding abrasive.

中文翻译：

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90°冲击角喷砂冲蚀岩石的冲蚀磨损特性

具有足以破碎岩石的强大动力的磨料空气射流在辅助岩石破碎领域具有巨大潜力，例如使用隧道掘进机进行辅助隧道开挖。为了使其应用更加有效和有益，需要一个清晰明确的磨料空气射流侵蚀机制。然而，目前磨料空气射流的侵蚀机制大多忽略了回弹颗粒的二次侵蚀。通过数值模拟和扫描电镜图像分析了回弹粒子对岩石侵蚀的影响。当垂直磨料空气射流通过平滑粒子流体动力学 (SPH) 侵蚀岩石时，我们获得了各种应力和分布。此外，还得到了粒子轨迹和各种速度，为分析侵蚀坑的形成和特征提供必要的数据。可以得出结论，回弹磨粒在岩石的应力形成和分布中起着不可或缺的作用，也是环形台下形成特定冲蚀坑特征即半球状底部的主要原因。空气射流中心的入射磨料以较大的冲击力加深侵蚀坑，其能量以应力波传播到岩石中。同时，回弹磨料扩大了侵蚀坑和半球状底部的直径。由于侵蚀坑的直径大于半球形底部的直径，因此形成了环形平台。射流边界处的入射磨料涉及环形平台的形成。入射磨料和回弹磨料在岩石冲刷磨损中的作用不同。岩石的主要磨损特征是切削磨损和变形磨损。高速的入射磨料引起半球形底部的变形和切削磨损。在环形平台上，只有较低速度的磨料会引起切削磨损。回弹磨料仅引起岩石的切削磨损。然而，侵蚀岩石表面的特征取决于回弹磨料的侵蚀角度。在环形平台上，只有速度较低的磨料会引起切削磨损。回弹磨料仅引起岩石的切削磨损。然而，侵蚀岩石表面的特征取决于回弹磨料的侵蚀角度。在环形平台上，只有较低速度的磨料会引起切削磨损。回弹磨料仅引起岩石的切削磨损。然而，侵蚀岩石表面的特征取决于回弹磨料的侵蚀角度。