Search results for "optics"
showing 10 items of 10033 documents
The numerical simulation of heat transfer during a hybrid laser–MIG welding using equivalent heat source approach
2014
International audience; The present study is dedicated to the numerical simulation of an industrial case of hybrid laser-MIG welding of high thickness duplex steel UR2507Cu with Y-shaped chamfer geometry. It consists in simulation of heat transfer phenomena using heat equivalent source approach and implementing in finite element software COMSOL Multiphysics. A numerical exploratory designs method is used to identify the heat sources parameters in order to obtain a minimal required difference between the numerical results and the experiment which are the shape of the welded zone and the temperature evolution in different locations. The obtained results were found in good correspondence with …
Impact des conditions d'usinage sur la zone du matériau affectée par le procédé
2007
Colloque avec actes et comité de lecture. Internationale.; International audience; Les procédés d'usinage peuvent créer des contraintes résiduelles à la surface des pièces usinées et ainsi modifier la microstructure et la texture de la matière proche de la surface. De tels changements sont importants pour l'étude du comportement des pièces au cours du temps. Il est alors nécessaire de quantifier les contraintes résiduelles, les composantes de texture et de déterminer la microstructure induite par l'usinage pour comprendre et prédire le comportement des surfaces considérées. Dans cette étude, le matériau cuivre pur a été choisi et considéré comme un "système modèle". En tournage, l'influence…
Optimisation of refractory coatings realised with cored wire addition using a high-power diode laser
2005
Laser; Cladding; Refractory alloys; Factorial experiments; International audience; The objective or our research was to obtain refractory alloys using the high-power diode laser (HPDL) coating technique. After optimisation using factorial experiments, two different cladding regimes were clearly distinguished. It was also shown that a very narrow transition zone exists between the two regimes, and, inside this zone, clad layers having a satisfactory compromise between the response functions (surface aspect and cavity presence) were obtained. The main objective of our study, namely, the control of the operating parameters (geometrical and kinematical) to realise adequate coatings, without cav…
Through-transmission laser welding of polymers – temperature field modeling and infrared investigation
2007
The purpose of the present study is to estimate the weldability of a polymeric material couple according to their thermal and optical properties. A first model based on Mie theory and Monte Carlo method describes the laser beam behavior in semi-transparent media and makes it possible to approximate the laser power distribution at the interface of the two materials. A second model based on finite element method permits the temperature field estimation into both parts to be welded. The results are validated by infrared thermography.
Laser-assisted narrow gap arc welding of an 18MND5 steel thick plate
2020
Abstract Narrow gap arc welding is a common solution for the welding of thick structures. In this study, a defocused laser beam is used to pre-melt the narrow gap walls in front of an arc-welding bath. Such a welding configuration can be referred to a hybrid welding configuration. In the present work, a particular attention is given to evaluation of the interaction between an arc plasma and a defocused laser beam. High-speed imaging of the metal transfer through arc plasma is achieved thanks to a diode laser illumination system. Electrical arc parameters are logged, synchronously, in order to perform a correlation analysis and to make a diagnosis of the interaction level between laser beam …
Decorous combinatorial lower bounds for row layout problems
2020
Abstract In this paper we consider the Double-Row Facility Layout Problem (DRFLP). Given a set of departments and pairwise transport weights between them the DRFLP asks for a non-overlapping arrangement of the departments along both sides of a common path such that the weighted sum of the center-to-center distances between the departments is minimized. Despite its broad applicability in factory planning, only small instances can be solved to optimality in reasonable time. Apart from this even deriving good lower bounds using existing integer programming formulations and branch-and-cut methods is a challenging problem. We focus here on deriving combinatorial lower bounds which can be compute…
Online dimensional control of rolled steel profiles using projected fringes
2020
AbstractFringe projection is a versatile method for mapping the topography of surfaces. In this paper, it is used to measure the defects on the head of railroad rails while the rails are moving. Railroad rails are made by hot rolling. The quality of the finished product is generally good, but surface texture will deteriorate with increasing temperature. A method for online inspection therefore is very desirable. In the present experiment, dimensional inspection of the railroad rails was made online while moving at a speed of 1–2 m/s. Therefore, it is important to minimize the registration time. To achieve this, we apply a method of fringe location with sub-pixel accuracy that requires only …
Improved Active Disturbance Rejection Control for Trajectory Tracking Control of Lower Limb Robotic Rehabilitation Exoskeleton.
2020
Neurological disorders such as cerebral paralysis, spinal cord injuries[acronym](SCI), and strokes, result in the impairment of motor control and induce functional difficulties to human beings like walking, standing, etc. Physical injuries due to accidents and muscular weaknesses caused by aging [english]affectsaffect people and can cause them to lose their ability to perform daily routine functions. In order to help people recover or improve their dysfunctional activities and quality of life after accidents or strokes, assistive devices like exoskeletons and orthoses are developed. Control strategies for control of exoskeletons are developed with the desired intention of improving the qual…
Diode laser welding of ABS: Experiments and process modeling
2009
International audience; The laser beam weldability of acrylonitrile/butadiene/styrene (ABS) plates is determined by combining both experimental and theoretical aspects. In modeling the process, an optical model is used to determine how the laser beam is attenuated by the first material and to obtain the laser beam profile at the interface. Using this information as the input data to a thermal model, the evolution of the temperature field within the two components can be estimated. The thermal model is based on the first principles of heat transfer and utilizes the temperature variation laws of material properties. Corroborating the numerical results with the experimental results, some impor…
A Comprehensive Survey of Indoor Localization Methods Based on Computer Vision
2020
Computer vision based indoor localization methods use either an infrastructure of static cameras to track mobile entities (e.g., people, robots) or cameras attached to the mobile entities. Methods in the first category employ object tracking, while the others map images from mobile cameras with images acquired during a configuration stage or extracted from 3D reconstructed models of the space. This paper offers an overview of the computer vision based indoor localization domain, presenting application areas, commercial tools, existing benchmarks, and other reviews. It provides a survey of indoor localization research solutions, proposing a new classification based on the configuration stage…