An Innovative Experimental Study of Corner Radius Effect on Cutting Forces

The cutting forces are often modelled using edge discretisation methodology. In finish turning, due to the smaller corner radii, the use of a local cutting force model identified from orthogonal cutting tests poses a significant challenge. In this paper, the local effect of the corner radius on the forces is investigated using a new experimental configuration: corner cutting tests involving the tool nose. The results are compared with inverse identifications based on cylindrical turning tests and elementary cutting tests on tubes. The results obtained from these methods consistently show the significant influence of the corner radius on the cutting forces

A force model for superfinish turning of pure copper with rounded edge tools at low feed rate

International audienceThis paper presents a model for force prediction of superfinish turning operation on pure copper. The model is divided in two parts. The first part computes the forces acting on the rake face of the tool. The second part computes the forces on the clearance face that are much more important in superfinish machining than in conventional machining

From large-scale to micro machining: a review of force prediction models

International audienceIn this paper, a reviewof work performed in the area of force modelling in metal cutting processes is presented. Past and present trends are described and criticised to compare their relevance with current requirements. Several approaches are reviewed, such as empirical, mechanistic and analytical models. The models' ability to predict forces, from rough machining to finish machining, is analysed

Identification d'un modèle d'efforts de coupe mécanistique et application dans le cas d'un contournage de cuivre pur

L'obtention des caractéristiques des pièces usinées ainsi que la bonne maîtrise du procédé d'usinage sont liées aux efforts de coupe. De nombreux modèles d'efforts de coupe ont déjà été développés, mais ils sont souvent appliqués dans le cas d'opérations d'usinage élémentaires (coupe orthogonale ou oblique), ce qui limite leur utilisation à la communauté scientifique. La méthode de discrétisation d'arête permet de généraliser les applications de ces modèles à des géométries d'outils plus complexes. Néanmoins, les applications restent généralement limitées à des opérations d'usinage simples (chariotage, dressage, fraisage flanc...) plutôt éloignées des besoins industriels. D'autre part, les modèles mécanistiques sont généralement critiqués car nécessitant d'être calibrés à partir d'un trop grand nombre d'essais. La présente étude propose de minimiser le nombre d'essais nécessaires à l'identification. Pour cela, les coefficients d'un modèle mécanistique ont été estimés par identification inverse, à partir de différents nombres d'essais de chariotage. Le modèle ainsi identifié est comparé, pour chaque couple de coefficients, à des essais couvrant une large plage de conditions de coupe. Ce modèle est ensuite appliqué dans le cas d'une opération de contournage. Les résultats obtenus par modélisation à partir de la trajectoire théorique, mais aussi de la trajectoire mesurée à vide sur la machine, sont comparés avec les efforts mesurés lors de l'opération de contournage

Large-field high-resolution X-ray microscope for studying laser plasmas

International audienceIn 1948, P. Kirkpatrick and A. V. Baez developed an x-ray microscope (energy range about 100 eV-10 keV) composed of two concave spherical mirrors working at grazing incidence. That device, named KB microscope, presents a 3-5 μm resolution within a field having a radius about 100 μm; outside that field, its resolution lowers rapidly when the object point recedes from the center. The adjunction of two similar mirrors can notably increase the useful field (typically, the resolution can be better than 10 μm within a 2-mm-diam field of view), which is necessary for studying laser plasmas. Its main advantage with respect to more simple optics, as the pinhole, is that it can be located far enough from the plasma to avoid any destruction during the shot. We describe such a microscope that we call KBA microscope and present some images of fine metallic grids. Those grids were backlighted by x-raysources, either a cw one or a series of laser plasmas from the Octal-Héliotrope facility. Examining the films in detail shows that the experimental results are very close to the theoretical characteristics; hence the interest of this device for the x-raydiagnostics on the future powerful laser facilities

A generalised geometrical model of turning operations for cutting force modelling using edge discretisation

The 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

Towards cutting force evaluation without cutting tests

Mechanistic cutting force modelling generally involves coefficients identification from machining tests. In order to develop multi-material cutting force models avoiding identification, several studies have tried to link cutting forces to mechanical properties from databases, whose relevance remains questionable. In this study, the cutting coefficients obtained by inverse identification from turning tests are compared with properties obtained from several mechanical tests.The correlations show that cutting forces can be estimated, without cutting tests, using hat-shaped shear tests.The originality of the approach is the behaviour proximity of the five machined materials used: thermal and mechanical treated pure coppers, brass and bronze

TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution

The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolution, to provide a reference spectrum for future reactor neutrino experiments, and to provide a benchmark measurement to test nuclear databases. A spherical acrylic vessel containing 2.8 ton gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full coverage. The photoelectron yield is about 4500 per MeV, an order higher than any existing large-scale liquid scintillator detectors. The detector operates at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The detector will measure about 2000 reactor antineutrinos per day, and is designed to be well shielded from cosmogenic backgrounds and ambient radioactivities to have about 10% background-to-signal ratio. The experiment is expected to start operation in 2022

Potential of Core-Collapse Supernova Neutrino Detection at JUNO

JUNO is an underground neutrino observatory under construction in Jiangmen, China. It uses 20kton liquid scintillator as target, which enables it to detect supernova burst neutrinos of a large statistics for the next galactic core-collapse supernova (CCSN) and also pre-supernova neutrinos from the nearby CCSN progenitors. All flavors of supernova burst neutrinos can be detected by JUNO via several interaction channels, including inverse beta decay, elastic scattering on electron and proton, interactions on C12 nuclei, etc. This retains the possibility for JUNO to reconstruct the energy spectra of supernova burst neutrinos of all flavors. The real time monitoring systems based on FPGA and DAQ are under development in JUNO, which allow prompt alert and trigger-less data acquisition of CCSN events. The alert performances of both monitoring systems have been thoroughly studied using simulations. Moreover, once a CCSN is tagged, the system can give fast characterizations, such as directionality and light curve

Detection of the Diffuse Supernova Neutrino Background with JUNO

As an underground multi-purpose neutrino detector with 20 kton liquid scintillator, Jiangmen Underground Neutrino Observatory (JUNO) is competitive with and complementary to the water-Cherenkov detectors on the search for the diffuse supernova neutrino background (DSNB). Typical supernova models predict 2-4 events per year within the optimal observation window in the JUNO detector. The dominant background is from the neutral-current (NC) interaction of atmospheric neutrinos with 12C nuclei, which surpasses the DSNB by more than one order of magnitude. We evaluated the systematic uncertainty of NC background from the spread of a variety of data-driven models and further developed a method to determine NC background within 15\% with {\it{in}} {\it{situ}} measurements after ten years of running. Besides, the NC-like backgrounds can be effectively suppressed by the intrinsic pulse-shape discrimination (PSD) capabilities of liquid scintillators. In this talk, I will present in detail the improvements on NC background uncertainty evaluation, PSD discriminator development, and finally, the potential of DSNB sensitivity in JUNO