CALIBRATION OF CAPACITIVE SENSORS AND ELECTRONIC LEVELS FOR THE STRAIGHTNESS MEASUREMENTS USING MULTIPROBE METHOD

In this work, the straightness length 300 mm measurement under nanometer uncertainty. The proposed methodology represents a process known as propagation using the assumption of small displacement which leads to solving an overdetermined linear system. The experimental studies were carried out on the capacitive sensors and electronic levels. The least squares mathematic method is apply to calculate the optimal solution. This method requires taking into account the uncertainties of the two different types of sensors leads to method of weighted least squares. The first step is to calibrate the sensors and to estimate the effect on the calculated straightness

An expert system to characterize the surface morphological properties according to their functionalities

In this paper we propose a new methodology to characterize the morphological properties of a surface in relation with its functionality (tribological properties, surface coating adhesion, brightness, wettability…). We create a software based on experimental design and surface profile recording. Using an appropriate database structure, the roughness parameters are automatically computed at different scales. The surface files are saved in a hard disk directory and roughness parameters are computed at different scales. Finally, a statistical analysis system proposes the roughness parameter (or the pair of roughness parameters) that better describe(s) the functionality of the surface and the spatial scales at which the parameter(s) is (are) the more relevant

An expert system to characterise the surfaces morphological properties according to their tribological functionalities: The relevance of a pair of roughness parameters

Knowing that a surface or profile can be characterized by numerous roughness parameters, the objective of this investigation was to present a methodology which aims to determine quantitatively and without preconceived opinion the most relevant pair of roughness parameters that describe an abraded surface. The methodology was firstly validated on simulated fractal profiles having different amplitudes and Hölder exponents and it was secondly applied to characterise different worn regions of a retrieved metallic femoral head articulated against an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup containing an embedded metallic fibber into its surface. The methodology consists in combining the recent Bootstrap method with the usual discriminant analysis. It was validated on simulated fractal profiles showing that, among more than 3000 pairs tested, the total amplitude Rt and the fractal dimension Δ is the most relevant pair of roughness parameters; parameters corresponding to the variables modulated in the analytical expression of the fractal function. The application of this methodology on a retrieved metallic femoral head shows that the most relevant pair of parameters for discriminating the different investigated worn regions is the arithmetic roughness parameter Ra paired with the mean peak height Rpm. This methodology finally helps in a better understanding of the scratch mechanism of this orthopedic bearing component

Modelisation de la courbe de decharge en indentation instrumentee

Lors d’un essai d’indentation instrumentée, la courbe de décharge force – déplacement, qui correspond à un retour élastique du matériau pendant le retrait de l’indenteur, est utilisée pour estimer le module d’Young du matériau étudié. Un premier modèle proposé par Doerner et Nix en assumaient la décharge comme linéaire, en supposant que l’aire de contact était constante pendant la décharge, mais le modèle le plus utilisé est celui proposé par Oliver et Pharr pour décrire la courbe à la décharge selon une relation puissance. La présence de trois paramètres utilisés pour décrire le retour élastique ainsi que la relation puissance impliquent que ces paramètres ne sont pas indépendants et qu’ils sont reliés par une relation comme rapporté pour les essais de traction, de fatiguefissuration , de dureté ou de fluage

LNE Activies in Nanometrology: flatness reference calibration algorithm

The Laboratoire National de Métrologie et d’Essais (LNE) has developed an innovative ultra precision coordinate measuring machine [LAH07] traceable to the national length standard to measure three-dimensional objects with nanometric uncertainties (figure 1). The measuring range is 300 mm x 300 mm x 50 μm. The objective in term of uncertainty is to reach 30 nm in X and Y directions for a displacement of 300 mm and about few nanometers for a vertical displacement of 50 μm. On this machine, we use four capacitive sensors to measure the position along z direction. These sensors target the flat surface of cylinders (300 mm diameter) used as flatness references. To measure the shape of these aluminum references with nanometric uncertainties, we propose a measurement method based on a propagation process in which we introduce an angular measurement to compensate the curvature error inherent in this method. The measurement process uses the same sensor technology (capacitive sensor) we use on the machine. This paper presents the measurement method, its validation and the first results

Estimation of the constitutive law by dual Small Punch Test and Instrumented Indentation

The authors thank Mrs. G. Starzyk, F. Baratto, N. Charoy and M. Moura for the projects they realised to develop the SPT equipment and to realize the tests presented here. Moreover we thank Drs. S. Allain and J.-Ph. Masse (ArcelorMittal, Maizières-lès-Metz) for the DP steel sheets supplied and discussions on the DP characterization. We also thank J.C. Vervisch for its valuable help in experimental activities.In this paper an inverse finite element procedure was developed to assess the true- stress strain relationship of a DP dual phase. Experiments were performed both by means of instrumented indentation and small punch tests on small samples cut in the same steel sheet. Tests are developed on a Zwick macro-hardness tester. Single test are first proposed in order to estimate the parameters of the constitutive law (K,n). We propose to conduct SPT tests using PTFE lubricant and hard (WC / Co) ball. An inverse method based on the Nelder and Mead algorithm has been developed in order to found experimental curves. Nevertheless we show that this method lead to poor estimation of the parameter of the constitutive law. We propose to improve these estimations by cross-mechanical tests. Indeed we show that the estimation of the low-error (K,n) domains deduced from each single test can be crossed. This method leads to a better estimation of the constitutive law. Moreover both load/displacement curves of SPT and macrohardness can be found again.contrat ARTS avec ArcelorMitta

An expert system to characterize the surface morphological properties according to their functionalities

In this paper we propose a new methodology to characterize the morphological properties of a surface in relation with its functionality (tribological properties, surface coating adhesion, brightness, wettability…). We create a software based on experimental design and surface profile recording. Using an appropriate database structure, the roughness parameters are automatically computed at different scales. The surface files are saved in a hard disk directory and roughness parameters are computed at different scales. Finally, a statistical analysis system proposes the roughness parameter (or the pair of roughness parameters) that better describe(s) the functionality of the surface and the spatial scales at which the parameter(s) is (are) the more relevant

Nouvelle méthode d’évaluation du taux de pénétration linéaire et du volume d'usure d'explants en polyethilène

Il est reconnu que l’usure des composants articulaires de prothèses totales de hanche (PTH) est un des principaux facteurs à l’origine de la limitation de la durée de vie de ces dispositifs médicaux. En pratique, les chirurgiens estiment cette usure en effectuant une mesure du taux de pénétration linéaire sur des clichés radiographiques lors du suivi médical des patients. Cette mesure est ensuite utilisée pour faire un calcul de volume d’usure à partir d’une équation analytique relative à un modèle. L’objectif de notre étude est de présenter une nouvelle méthode d’évaluation du taux de pénétration linéaire et du volume d’usure à partir de l’analyse in vitro d’explants en polyéthylène. Ne faisant appel à aucun modèle analytique, notre méthode s’appuie sur le traitement de mesures d’explants sur Machine à Mesurer Tridimensionnelle. La pertinence de notre méthode est validée par simulation

Nouvelle méthode d’évaluation du taux de pénétration linéaire et du volume d'usure d'explants en polyethilène

Il est reconnu que l’usure des composants articulaires de prothèses totales de hanche (PTH) est un des principaux facteurs à l’origine de la limitation de la durée de vie de ces dispositifs médicaux. En pratique, les chirurgiens estiment cette usure en effectuant une mesure du taux de pénétration linéaire sur des clichés radiographiques lors du suivi médical des patients. Cette mesure est ensuite utilisée pour faire un calcul de volume d’usure à partir d’une équation analytique relative à un modèle. L’objectif de notre étude est de présenter une nouvelle méthode d’évaluation du taux de pénétration linéaire et du volume d’usure à partir de l’analyse in vitro d’explants en polyéthylène. Ne faisant appel à aucun modèle analytique, notre méthode s’appuie sur le traitement de mesures d’explants sur Machine à Mesurer Tridimensionnelle. La pertinence de notre méthode est validée par simulation

Study of the Influence of the Fabrication Process Imperfections on the Performances of a Claw Pole Synchronous Machine Using a Stochastic Approach

In mass production, fabrication processes of electrical machines are not perfectly repeatable with time, leading to dispersions on the dimensions which are not equal to their nominal values. The issue is then to link the dispersions on the dimensions which are uncertain to the performances of electrical machines in order to evaluate their influence. To deal with uncertainty, there is a growing interest in the stochastic approach, which consists in modelling the uncertain parameters with random variables. In fact, this approach enables to quantify the influence of the variability of the uncertain parameters on the variability of the quantities of interest. In this paper, a stochastic approach coupled with a 3D Finite Element model is used to study the influence of the fabrication process imperfections like the rotor eccentricity and the stator deformation on the performances of a claw pole synchronous machine