Oxy-fuel welding and cutting

Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding, or gas welding in the United States) and oxy-fuel cutting are processes that use fuel gases (or liquid fuels such as gasoline or petrol, diesel, bio diesel, kerosene, etc) and oxygen to weld or cut metals. French engineers Edmond Fouché and Charles Picard became the first to develop oxygen-acetylene welding in 1903. Pure oxygen, instead of air, is used to increase the flame temperature to allow localised melting of the workpiece material (e.g. steel) in a room environment. A common propane/air flame burns at about , a propane/oxygen flame burns at about , an oxyhydrogen flame burns at and an acetylene/oxygen flame burns at about . During the early 20th century, before the development and availability of coated arc welding electrodes in the late 1920s that were capable of making sound welds in steel, oxy- acetylene welding was the only process capable of making welds of exceptionally high quality in virtually

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Experimental study of residual stresses in thick steel plates

Jean-Paul Lebet, Raphaël Thiébaud

Residual stresses must be taken into account when evaluating the stability of a steel bridge girder. Residual stresses are unavoidable, as manufacturing processes for steel plates introduce thermal residual stresses in the material. For welded built-up sections, such as those commonly used in large steel plate girders, these thermal residual stresses are due to 1) cooling after rolling, 2) flame cutting of the flanges, and 3) welding between the web and the flange. Residual stresses can influence the lateral torsional buckling resistance of structural steel members and need to be considered in design. This paper experimentally investigates residual stresses due to flame cutting using the sectioning method. In this study, residual stresses are measured after flame cutting and welding 60 mm thick steel (S355N) flanges, a typical size used in the fabrication of bridge girders. Results from flame cutting confirm the findings of previous studies which reveal that residual stress distributions have a high tensile component at the flame cut edge. Procedures and testing of welding residual stresses are also presented. Residual stress measurements from this study could be used to develop a longitudinal and through-thickness residual stress model for thick flame-cut plates and welded plates used in bridge I-girder construction. Such a model could serve as an initial state in non-linear finite element analyses to predict the residual stress influence on the LTB of steel bridge girders.

2012

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Resistance to LTB of steel bridge girders

Jean-Paul Lebet, Raphaël Thiébaud

Lateral torsional buckling (LTB), a complex phenomenon of instability, occurs when a beam is solicited by a bending force. In the area of steel and composite bridges girders which are characterised by slender plate girders, few experimental and theoretical studies exist in order to evaluate their structural security particularly with respect to LTB. Therefore, bridge girder resistance models refer to those existing for beams destined for buildings, by applying nevertheless a high level of conservatism. Steel bridge girders are three-dimensional structures, the behaviour of which is influenced by a number of parameters such as: cross bracing, variable geometry of cross sections, loading effects or even aspects related to manufacturing and to material. In fact, the manufacturing procedure of plate girders consists of flame cutting and then welding thin web to thick steel sheets. This results in geometric imperfections on the elements as well as in residual stresses inside the material, the effect of which on the behaviour of the structure is not to be neglected. This paper presents the actual results of experimental and theoretical studies carried out on the subject of LTB of steel bridge girders.

ECCS European Convention for Constructional Steelwork2014

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Experimental and numerical characterisation of heat flow during flame cutting of thick steel plates

Jean-Paul Lebet, Raphaël Thiébaud

This paper concentrates on the characterization of the heat flow present during flame cutting of 60 mm thick steel (S355N) flanges, a typical size used in the fabrication of bridge girders. Experimental results are associated with a finite element analysis of the process. Temperature measurements around the flame and extensions of the fusion and heat affected zones are used to determine the input parameters of a 3-D thermal model of flame cutting. For the sake of simplicity, the volumetric heat input within the plate is modelled using only two parameters. The heat loss associated with the air gap that forms behind the flame is adjusted to reproduce the measured cooling curves. Such a thermal model is the first step in a better understanding of thermally induced stresses during flame cutting.

2012

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Soudage

Le soudage est un procédé d'assemblage permanent qui assure la continuité de la matière à assembler ; la soudure est le résultat obtenu (mais le terme est souvent utilisé pour le procédé). Cette co

Arc welding

Arc welding is a welding process that is used to join metal to metal by using electricity to create enough heat to melt metal, and the melted metals, when cool, result in a binding of the metals. It

Oxygène

L'oxygène est l'élément chimique de numéro atomique 8, de symbole O. C'est la tête de file du groupe des chalcogènes, souvent appelé groupe de l'oxygène. Découvert indépendamment en 1772 par le Suéd

MSE-464: Assembly techniques

Introduction to the assembly of materials by homogeneous or heterogeneous joints (welding, bonding, mechanical assembly). Mechanical and environmental resistance of joints.

MSE-704: 3D Electron Microscopy and FIB-Nanotomography

The principles of 3D surface (SEM) reconstruction and its limitations will be explained. 3D volume reconstruction and tomography methods by electron microscopy (SEM/FIB and TEM) will be explained and compared with x-ray tomography.

CIVIL-330: Bridge design

Introduction à la conception et au dimensionnement des ponts routiers en construction mixte, en béton armé et précontraint. Ce cours porte sur le choix du type de pont, des principales dimensions des éléments structuraux, du matériau, du mode de construction et sur les exigences à satisfaire.