Dynamic Properties of the Pressure Exerted on the Material Surface by Water Jet Impingements

It is interesting to know dynamic properties of the water jet pressure acting on the surface of a cutting object in order to clarify the cutting mechanism. This pressure includes wide range of frequency components that vary from the pulsation of a plunger pump to the water hammer pressure caused by impingements of droplets. In such case the transducers’ characteristics affect the detected wave seriously, and source wave of the pressure differs from detected wave. To eliminate the transducers characteristics and obtain the original wave form, special techniques, so called the deconvolution method or the source wave analysis method, are necessary. This paper presents the method to obtain the source wave of impingement pressure of water jets and demonstrates how it works correctly. Pressures acting on the material surface were measured directly by making water jets to impinge upon the pressure sensor. After experiments, detected wave data were processed by the deconvolution method. In addition, relationship between characteristics of the impingement pressure of water jet and flow structure of water jet is examined by flash photography using pulsed laser light. As a result, it becomes clear that dynamic property of the impingement pressure is closely related to the flow structure of water jet.