Michel Mousseigne

Low-frequency chatter genesis during inclined surface copy-milling with ball-end mill: Experimental study

ABSTRACT In this study low-frequency chatter during machining of inclined surfaces with ball-end mills is experimentally investigated. An explanation of genesis of low-frequency vibrations have been proposed for various conditions: cutting direction, lead angle values, spindle speed, depth of cut. As a result, it has been proven that low-frequency chatter has more significant effect on machined surface than usual chatter. Low-frequency chatter occurs during downward milling, rather than upward milling, especially when lead angle increases. Furthermore, low-frequency chatter takes place in the beginning of cutting process, thereafter develops into steady state of usual chatter, which has no such significant effect on machined surface, as it has been shown. The results are in line with the supposition that low frequency vibrations are caused by sudden and irregular nature of shearing process, when magnitude is small.

Orthogonal cutting of TA6V alloys with chamfered tools: Analysis of tool–chip contact lengths

In aerospace industry, the materials constituting aircraft evolved considerably in recent decades. The choice of composite materials (carbon fiber–reinforced plastic or multi-material) reduces the weight of structures, but for critical parts that support important forces or temperature, the indicated materials are alloys based on nickel or titanium. Consumption of titanium for the aerospace industry is growing rapidly, and the new generations of aircraft show an increase in the percentage of titanium. The TA6V is mostly used for structural parts, especially for engine pylon. Due to its low thermal properties, it shows a poor machinability, leading tools to undergo severe wears. The aim of this work is to understand the relation between cutting conditions and chamfered tool geometries on chip formation and tool wear. Based on a model dedicated to the understanding of cutting process with chamfered tool and on experimental tests, this work will show the influence of feed, cutting speed, chamfer length and rake angle on tool–chip contact lengths. It will also show the influence of these parameters on the variability of these contacts within a same geometry or cutting condition. This will lead to another interpretation of tool wears and pressures on the rake face.

Comparison of the chip formations during turning of Ti64 β and Ti64 α+β

For a number of years, the rise in the number of titanium alloy grades and therefore of microstructures has hampered the productivity of titanium parts. In order to understand the phenomena involved, this study presents a comparison of the chip formations between two microstructures obtained from the same alloy. The first part presents the two alloys, their microstructures and their methods of production. The chip formation of each material is then presented and shows two completely different processes. The first process is classical, for which shear mechanisms appear to be cyclical. Conversely, the second process depends on the orientation of the microstructure when the shear occurs. For a better understanding of the phenomena, the effect of cutting speed and feed is also discussed. Finally, in the last section, chip formations for the two microstructures are summarized and perspectives are presented.