In this study, investigated are the effects of tool rake angles and the change of cutting conditions on the specific cutting pressure in face milling. The cutting force in face milling is predicted from the double cutting edge model in3-dimensional cutting. Conventional specific cutting pressure model is modified by considering the variation of tool rake angles. Effectiveness of the modified cutting force model is verified by the experiments using special face milling cutters with different cutter pockets and various rake angles. From the comparison of the presented model and the specific cutting pressure, it is shown that the axial force can be predicted by the tangential force, radial force and geometric conditions. Also, the rela- tionship between specific cutting pressure and cutting conditions including feedrate, cutting velocity and depth of cut is studied.
The feasibility of electrochemical drilling and milling on stainless steel are investigated using tungsten microelectrode with in diameter. For the development of environmentally friendly and safe electrochemical process, citric acid solution is used as electrolyte. A few hundred nanoseconds duration pulses are applied between the microelectrode and work material for dissolution localization. Tool fracture by Joule heating, micro welding, capillary phenomenon, tool wandering by the generated bubbles are observed and their effects on micro ECM are discussed. Occasionally, complex textures including micro pitting corrosion marks appeared on the hole inner surface. Metal growth is also observed under the weak electric conditions and it hinders further dissolutions for workpiece penetration. By adjusting appropriate pulse and chemical conditions, micro holes of in diameter with in depth and 26Jim in diameter with in depth are drilled on stainless steel 304. Also, micro grooves with width and complex micro hand pattern are machined by electrochemical milling.
Machining accuracy is closely related with tool deflection induced by cutting forces. In this research, cutting forces and tool deflection in end milling are expressed as a closed form of tool rotational angle and cutting conditions. The discrete cutting fores caused by periodic tool entry and exit are represented as a continuous function using the Fourier series expansion. Tool deflection is predicted by direct integration of the distributed loads on cutting edges. Cutting conditions, tool geometry, run-outs and the stiffness of tool clamping part are considered together far cutting forces and tool deflection estimation. Compared with numerical methods, the presented method has advantages in prediction time reduction and the effects of feeding and run-outs on cutting forces and tool deflection can be analyzed quantitatively. This research can be effectively used in real time machining error estimation and cutting condition selection for error minimization since the form accuracy is easily predicted from tool deflection curve.
Photoacoustic Tomography (PAT) is a promising medical imaging modality by reason of its particularity. It combines optical imaging contrast with the spatial resolution of ultrasound imaging, and can distinguish changes in biological features in an image. For these reasons, many studies are in progress to apply this technique for diagnosis. But, real-time PAT systems are necessary to confirm biological reactions induced by external stimulation immediately. Thus, we have developed a real-time PAT system using a linear array transducer and a custom-developed data acquisition board (DAQ). To evaluate the feasibility and performance of our proposed system, two types of phantom tests were also performed. As a result of those experiments, the proposed system shows satisfactory performance and its usefulness has been confirmed.
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