| Among the various advanced machining methods, abrasive waterjet (AWJ) is increasingly used as a versatile tool for drilling difficult-to-machine materials such as glass, ceramics, titanium and metal matrix composites due to its numerous advantages like, capability to achieve higher depth to diameter ratios, absence of heat affect zone and absence of thermal distortion. Apart from critical process parameters such as stand-off distance, pump pressure, abrasive flow rate, abrasive material/size, jet impact angle, and drilling time, drilling performance in terms of depth of drilling or material removal rate is influenced by the material properties and back flow of the jet from bottom of blind hole. The mechanisms of these phenomena and the role of material properties in defining the material removal process need to be studied in detail in order to understand the abrasive waterjet drilling process.; In the first phase of this study an analytical model is developed to predict depth of drilling and drilled hole shape using the constitutive equations for millions of particle impacts. This theoretical model considers damping effect of the abrasive waterjet drilling process which occurs as the depth of penetration increases. Different workpiece materials such as glass, titanium and polycarbonate were used to verify the analytical model. The top surface quality of drilled hole in polycarbonate material is also investigated. High pressures (above 100 MPa) produced chipping in the top surface.; In the second phase acoustic emission sensing technique is used here to understand more about material removal mechanisms involved in abrasive waterjet drilling process. Feasibility to monitor abrasive waterjet drilling depth on-line using AE-RMS is investigated. Stochastic modeling of the time domain and frequency domain analysis of the acoustic emission signals provide more insight into the physics of the process. |
