Milling is today the most effective, productive and flexiblemanufacturing method for machining complicated or sculptured surfaces. Ball-end tools are used for machining 3D freeform surfaces for dies, moulds, and various parts, such as aerospace components, etc. Milling data, such as surface topomorphy, surface roughness, non-deformed chip dimensions, cutting force components and dynamic cutting behaviour, are very helpful, especially if they can be accurately produced by means of a simulation program. This paper presents a novel simulation model, the so-called MSN-Milling Software Needle program, which is able to determine the surface produced and the resulting surface roughness, for ball-end milling. The model simulates precisely the tool kinematics and considers the effect of the cutting geometry on the resulting roughness. The accuracy of the simulation model has been thoroughly verified, with the aid of a wide variety of cutting experiments. Many roughness measurements were carried out on workpieces, which were cut using a 5-axis machining centre. The calculated roughness levels were found to be in agreement with the experimental ones. The proposed model has proved to be suitable for determining optimal cutting conditions, when finishing complex surfaces. The software can be easily integrated into various CAD-CAM systems.
The photoacoustic response of the YBCO high Tc superconductor has been monitored in order to investigate the interaction of the XeCl excimer laser nanosecond pulses with bulk YBCO targets. The detection and monitoring via a piezoelectric transducer of the compression of the laser induced pressure waves propagating into the bulk YBCO samples provides information regarding the vaporization and ablation thresholds, the velocity of the pressure wave and the etching rate.
Four stable and 12 unstable trochanteric fractures were produced in human cadavers and fixed with either a sliding screw-plate or the Bousquet nail-plate. Axial cyclic loading showed that both implants were satisfactory for stable fractures. The sliding screw-plate withstood increased loads and the system failed at a later cycle in unstable fractures. Central placement of both the sliding screw or nail enhances stability, especially against torsional forces.
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