Characterization and Modelling of the Rough Turning Process of Large-scale Parts: Tribological Behaviour and Tool Wear Analyses

AbstractMachining large-scale parts in several industries (nuclear, naval, energy…) is a challenge for machine tools operators. Various problems are encountered, like respecting specified dimensions, deformation of the workpiece during machining, limit of the cutting speed, excessive tool wear, etc. All these difficulties are related to the large size of the machined part, which may have several meters and weigh several hundred kilograms. This study focuses on analysis of the rough turning process of a shell component, having few meters, as a part of steam generators of nuclear power plants. During the rough turning step, a high material removal rate (moderate cutting speed, but high depth-of-cut and feed rate) is necessary to achieve the workpiece in reasonable time. Experimental and theoretical analyses are conducted to highlight the intense thermomechanical loading at the tool–workmaterial interface. Revealed physical phenomena at the tool rake face, like adhesion and abrasive wear types, using various characterization techniques, are reproduced by a numerical model developed to simulate the cutting process. As an interest result, contact discontinuities at the tool–chip interface as well as where the wear is highly localized are well predicted as observed on scanning electron microscope. These contact discontinuities are attributed to the grooved rake face of the insert, designed with a chip breaker to reduce the tool–chip contact area and to promote the chip fragmentation. This study can be helpful for the design of rough turning inserts, by analysing the effectiveness of the rake face geometry (contact area, chip breaker…)

Microstructural and Mechanical Characterizations of Natural Long Alfa Fibers Obtained with Different Extractions Processes

This study investigates the morphological changes and tensile properties of Alfa fibers extracted mechanically after two treatments namely water retting and alkali treatment. The Scanning Electron Microscopy technique is used in this experimental work. The main observation reveals the decrease of noncellulosic component in the fibers which is inversely proportional to the concentration of sodium hydroxide solution in the case of the alkali treatment. Tensile tests were carried out using tensile machine for determining the tensile properties mainly the tensile strength and the elastic modulus. The tensile strength and young’s modulus of retted fibers are assumed constant. The results relative to the alkalized fibers show an improvement of tensile strength and young’s modulus and are proportional to the sodium hydroxide concentration up to 14%

Identification des propriétés effectives d’élasticité d’un polymère obtenu par fabrication additive SLS à partir d’une modélisation du volume élémentaire représentatif

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