The demand for increasing productivity when machining heat resistant alloys has resulted in the use of new tool materials such as cubic boron nitride (CBN) or ceramics. However, CBN tools are mostly used by the automotive industry in hard turning, and the wear of those tools is not sufficiently known in aerospace materials. In addition, the grade of these tools is not optimized for superalloys due to these being a small part of the market, although expanding (at 20% a year). So this investigation has been conducted to show which grade is optimal and what the wear mechanisms are during finishing operations of Inconel 718. It is shown that a low CBN content with a ceramic binder and small grains gives the best results. The wear mechanisms on the rake and flank faces were investigated. Through SEM observations and chemical analysis of the tested inserts, it is shown that the dominant wear mechanisms are adhesion and diffusion due to chemical affinity between elements from workpiece and insert.

Abstract:The thermal conductivity of straw bales is an intensively discussed topic in the international straw bale community. Straw bales are, by nature, highly heterogeneous and porous. They can have a relatively large range of density and the baling process can influence the way the fibres are organised within the bale. In addition, straw bales have a larger thickness than most of the insulating materials that can be found in the building industry. Measurement apparatus is usually not designed for such thicknesses, and most of the thermal conductivity values that can be found in the literature are defined based on samples in which the straw bales are resized. During this operation, the orientation of the fibres and the density may not be preserved. This paper starts with a literature review of straw bale thermal conductivity measurements and presents a measuring campaign performed with a specific Guarded Hot Plate, designed to measure samples up to 50 cm thick. The influence of the density is discussed thoroughly. Representative values are proposed for a large range of straw bales to support straw-bale development in the building industry.

The predictability of manufacturing process simulation is highly dependent on the accuracy of the constitutive model to describe the mechanical behavior of the work material. The model should consider the most relevant parameters affecting this behavior. In this study, a constitutive model for Ti6Al4V titanium alloy is proposed that considers both material plasticity and damage. It includes the effects of strain hardening, strain-rate and the state of stress to represent the mechanical behavior of Ti6Al4V titanium alloy in metal cutting simulation. To generate states of stress and strain rates representative of this process, mechanical tests were performed using a specific experimental setup. This included a specimen geometry designed to generate different states of stress, as well as a digital image correlation technique to obtain the strains during the mechanical tests. For the determination of the coefficients of the constitutive model, the yield stress and fracture locus obtained from these tests were used in an optimization-based procedure. To verify the accuracy of the proposed constitutive model to represent the mechanical behavior of the Ti6Al4V alloy under different states of stress, force-displacement curves obtained using this model and the Johnson-Cook model are compared with the curves obtained experimentally.

-High cutting speed machining processes have been used for about 10 years for metals. This technology presents many advantages related to output and surface quality. For timber machining, commonly used velocities are already high. However, literature about cutting velocity function during a machining process is rare. Nevertheless, some published results have shown the effect of speed on chip formation. In order to perform experiments at high cutting speeds, we used a prototype model of a CN routing machine, which allowed us to conduct machining from 3 m s -1 to 62 m s -1 . Surface analysis was carried out by an optical roughness measurement device. The wood species studied is beech. Tests have been performed with constant chip thickness value.wood / milling / cutting speed / surface quality Résumé -Utilisation des grandes vitesses de coupe dans le fraisage du bois. Depuis une dizaine d'années, l'industrie des métaux a recours au procédé d'usinage à grande vitesse. Ses principaux avantages résident dans l'augmentation du débit matière ainsi que l'amélioration des surfaces usinées. Dans le domaine de l'usinage du bois, les vitesses de coupe sont déjà très élevées de telle sorte que les limites techniques sont pratiquement atteintes. Concernant la vitesse de coupe, peu d'informations existent sur son effet au cours du procédé d'usinage. Cependant, certains travaux traitent de l'effet de la vitesse sur le mode de formation du copeau. Afin d'analyser ce rôle de la vitesse, nous avons acquis une défonceuse à commande numérique permettant une gamme de vitesses de coupe de 3 m s -1 à 62 m s -1 . Une première série d'essais de contournage sur du hêtre, parallèlement et perpendiculairement au sens des fibres est présentée ici. Les surfaces obtenues sont analysées à l'aide d'un rugosimètre à capteur optique.bois / défonçage / vitesse de coupe / état de surface

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The experimental results of orthogonal cutting of maple and the modeling of the cutting mechanics are presented. The tool cutting forces were measured for different feed rates. A set of equations relating the tangential and feed forces to the tool edge width and feed rate (chip thickness) to calculate the chip and edge cutting force coefficients was developed. Then the chip force and edge force coefficients were calculated from experimentally obtained cutting forces and were plotted in a polar-coordinate system with respect to the fiber orientation of the maple disk. The polar-coordinate presentation of the cutting force results and the calculated cutting force coefficients provides an excellent visual appreciation of the relation between the cutting forces and the wood fiber orientation. Chips were also collected from various sectors of the wood disk. This analysis further identified the effects of fiber orientation and cutting forces on the types of chip formed and hence the cutting mechanics involved. By applying the calculated cutting coefficients for each tool orientation (in respect to the grain) it is possible to predict the feed and tangential forces for any feed rates. There is good agreement between the predicted and measured cutting forces.

International audienceIn order to predict the characteristics of the machined part, such as geometry, surface roughness and fatigue or corrosion resistance, the cutting forces values should be known as precisely as possible. The edge discretisation methodology can be used to model the three components of the cutting forces. The results are generally considered as suitable, even if the considered cutting operation is complex, because the geometry is well described. Usually, the local cutting forces model is identified from orthogonal or oblique cutting tests and the local contributions are assumed to be independent of the orientation of the elementary edge in the reference plane Pr. However, when turning in the tool nose or with round inserts, the tool cutting edge angle Kr (or Side Cutting Edge Angle) evolves along the active cutting edge and the values of this angle are very small compared to that of 90° used in orthogonal/oblique cutting. For this study, a new elementary cutting operation, called "oriented cutting", has been tested. In this configuration, the active cutting edge is rectilinear, without inclination, but oriented by an angle Kr different from 90°. In addition, cylindrical turning tests have been done. The measurements, performed in pure copper, show an influence of the tool cutting edge angle on the cutting forces. An interaction between Kr and the workpiece radius is also highlighted

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. AbstractThe knowledge of cutting forces is of prime importance to ensure the success of cutting operations, the desired properties of the machined parts and therefore the functionality of the workpieces. Edge discretisation is one way to model cutting forces. Traditionally used in milling, this methodology enables local changes in uncut chip thickness or cutting geometry to be taken into account and then gives suitable results in the three directions. A key point of this method is the geometrical transformation that enables the description of various tool geometries. This study proposes a geometrical model based on homogeneous matrices, whose main interest is to decompose the transformations step-by-step. The method, generalisable to all machining operations, is detailed for turning operations. Inserted cutters are modelled considering both the positioning of the insert and the local geometry of the insert. The cutting geometry and the edge are described using the same model in the machine coordinates system, allowing forces and moments to be calculated easily.Keywords: Cutting force modelling, Edge discretisation, Tool geometry, Homogeneous matrix transformations, Turning operations Nomenclature α ne Working normal clearance angle; defined in P n [1] α P n Normal clearance angle given by the local preparation (P) of the insert; defined in P n α oe Working orthogonal clearance angle; defined inWorking normal rake angle; defined in P n [1] γ P n Normal rake angle given by the local preparation (P) of the insert; defined in P n ε E Tool included angle of the cutting edge (E); also denoted ε r if the cutting edge is included in P r [1] η Chip flow angle θ Polar angle defined in a coordinate system linked to the insert (parameterisation of the cutting edge) Θ Polar angle defined in a coordinate system linked to the machine (Θ = θ + κ r + ε r /2 − π/2) κ r Tool minor cutting edge angle; defined in