高压磨料水射流加工中材料去除机理研究

本文根据脆、塑性断裂理论,通过高压纯水射流和磨料水射流对石材冲蚀试验,对冲蚀凹坑成型机理进行了研究。结果表明,高压纯水射流只有不发散的中心射流对材料具有去除作用。高压磨料水射流对材料表面冲击时形成"倒钟"型孔,材料去除机理是在成穴力、剪切应力和水楔的共同作用下,以脆性和塑性断裂方式实现去除。磨料水射流对材料的冲蚀区分为中心射流区、成穴区和喷砂区,材料的主要体积去除量处在成穴区。磨料水射流加工孔的直径和深度随靶距的增加而增加。磨料水射流从射流中心沿径向至射流边缘流速逐渐降低,磨料浓度逐渐增大,但射流能量最高的部位既不在射流中心也不在磨粒集中的射流边缘,而是在成穴区。

Mechanism of material removal by high pressure abrasive water-jet

High pressure abrasive water jet machining is considered as a promising technique in hard and brittle material processing. In this paper,the mechanism of hole formation on stone by high pressure water jet （HPWJ） and high pressure abrasive water jet （HPAWJ） are studied based on brittle and plastic fracture theories. It is shown that only the center core of HPWJ has the ability to remove materials. The cross-section of the hole is characterized by a ＂reverse-bell＂ shape on stone by a HPAWJ,and the material is eroded by an action of indenting forces,shearing forces and water-wedge action,in a brittle and plastic fracture mode. The eroded area by HPAWJ is constituted by a center-jet impact zone,an indenting zone and a sand-spraying zone ,and the main material removal is found in the indenting zone. The diameter and depth of the holes eroded by HPAWJ increase with the increase of stand-off-distance. The jet velocity of HPAWJ gets lower from the center to the margin of the jet,and the concentration of abrasive grits becomes higher from the center to the margin of the jet. The largest kinetic energy is located neither in the center nor in the margin of the jet,but in the indenting zone.