Estimation of characteristics of water jets by means of impact force measurement

近十年来，高压水射流作为岩石切割和钻孔工具的实际应用已经得到了人们的重视，水射流技术正处于实际应用的改进阶段。因此，人们对岩石切割机理的研究越来越感兴趣，需要一种精确的方法来评估冲击岩石表面的水射流结构，以澄清岩石的破裂机制。在本研究中，分析了水射流正常撞击固体目标所产生的合力，以估计水射流的特性。得到的结果如下：1)根据动量的低值，利用无蚀平靶测得的冲击力的时间平均值确定了入射射流的平均速度。2)地表侵蚀期中心深度与撞击时间成正比，侵蚀速度与入射速度的6次方成正比。3)理论和实验表明，狭缝深度是喷管直径、驱动压力、曝光时间、压力衰减常数和表征客观材料的标准侵蚀压力的函数。4)对于韧性材料（如金属），侵蚀速度与运动学能量成正比；对于脆性材料（如精细陶瓷），侵蚀速度与动量成正比。

Practical use of high pressure water jets as a tool for rock cutting and drilling has become seriously accepted within the last decade, and the water jet technology is in the improvement stage for practical application. Then, the interest in the cutting mechanism is growing greater, and the precise method to evaluate the structure of water jets impinging onto the rock surface is required for the clarification of the fracture mechanism of rock.In this research, the impact force that is the resultant force imposes upon a solid target by water jet impinging normally is analyzed to estimate the characteristics of water jet. The obtained results are as follows :1) The mean velocity of incident jet is determined from the time-average of the impact force measured using a flat target of erosionless, based on the low of momentum.2) The center depth in the surface erosion period is clarified to increase in direct proportion to the time of impinging, and the erosion speed is proportional to the 6th power of the incident velocity.3) The theory and experiments shows that the depth of the slot is a function of the nozzle diameter, the driving pressure, the time of exposure, the pressure attenuation constants and the standard erosion pressure that characterizes the objective materials.4) The erosion speed is proportional to the kinematic energy for ductile materials such as metals, and proportional to the momentum for brittle materials such as fine ceramics.