The Critical Impact Velocity in Particles Impact Erosion

固体颗粒对金属材料的冲击腐蚀主要经历两种损伤过程。一种是由于反复塑性变形而去除材料，另一种是切割。这些过程是同时发生的，它们对总损伤的贡献率不仅取决于撞击角度，而且取决于撞击速度。当冲击速度下降时，固体颗粒倾向于不滑过目标材料表面，这随后减少了通过切割造成的损伤。在一定的低速下，颗粒不发生滑移，不产生切削损伤，只产生塑性变形损伤。这一速度被定义为“临界撞击速度”。在这项研究中的方法来确定临界速度，通过建立一个测量的摩擦系数，即在滑动过程中的动摩擦系数和滚动时没有打滑的静摩擦系数。为了测量coe ...更多信息 利用粒子撞击时的摩擦效率，研制了一种旋转靶装置。由此确定的临界冲击速度取决于材料和颗粒的硬度，以及固体颗粒的形状和尺寸。通过分析球形固体颗粒撞击靶材表面的行为，从理论上推导出了临界撞击速度：在斜撞击的瞬间，靶材表面形成压痕，同时材料在颗粒运动方向上与表面相切地产生应变。当应变超过弹性极限时，受冲击的固体颗粒在表面上发生滑移，从而引起切削磨损。临界应变是冲击速度、旋转速度以及颗粒表面接触时间的函数。这些表征冲击行为的参数来自摩擦系数和回弹系数，所有这些都是从目标材料和颗粒的机械性能以及与颗粒有关的其他因素获得的。因此，临界撞击速度的理论值仅作为目标和颗粒的机械性能的函数给出。实验确定的临界流速与理论公式预测的临界流速之间有很好的相关性。少

Solid particles impact erosion of metallic materials proceed through two kinds of damage processes. One is the removal of material due to repeated plastic deformation, and the other is cutting. These processes occcur simultaneously and the ratio of their contribution to the total damage depends not only on the impact angle but also on the impact velocity. As the impact velocity goes down, a solid particle tends not to skid over the target material surface, which subsequently decreases the damage through cutting. At a certain lower velocity, the particle does not skid at all, which results in no cutting damage but plastic deformation damage only. This velocity was defined as the ""critical impact velocity". In this study the methodology to determine the critical velocity through a measurement of the coefficient of friction established, that is the dynamic friction coefficient during skidding and the static friction coefficient during rolling without skidding. In order to measure the coe … More fficient of friction at the moment of particle impact, a rotating target apparatus was developed. The critical impact velocity thus determined depended on the hardness of both material and particle, as well as on the shape and size of the solid particles. Furthermore, the critical impact velocity was theoretically derived through analyzing the behavior of the target material surface impacted by a spherical solid particle : at the moment of oblique impact, an indentation is formed ; at the same time, the material is strained tangentially to the surface in the direction of particle movement. As the extent of strain goes over the elastic limit, the impacted solid particle does skid over the surface, which brings about wear to the surface by cutting. The threshold strain was derived as a function of the impact velocity, the rotating velocities as well as the duration of particle surface contact. Those parameters which characterized the impact behavior were derived from the coefficient of friction and the rebounding coefficient, all of which were obtained from the mechanical properties of the target material and particle, and other factors concerning the particle. Consequently, the theoretical value of the critical impact velocity was given solely as a function of the mechanical properties of the target and the particle. A good correlation was found between the critical velocity determined by experiment and that predicted by the theoretical equation. Less