References of "Habraken, Anne"
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See detailPhase-Field Simulations of Coarsening Kinetics of Si Precipitates in AlSi10Mg Processed by Selective Laser Melting
Delahaye, Jocelyn ULiege; Vertruyen, Bénédicte ULiege; Mertens, Anne ULiege et al

Conference (2020, October 28)

AlSi10Mg processed by Selective Laser Melting (SLM) exhibits fine microstructure due to the very high cooling rate reached during the process. The microstructure consists in submicron Al cells surrounded ... [more ▼]

AlSi10Mg processed by Selective Laser Melting (SLM) exhibits fine microstructure due to the very high cooling rate reached during the process. The microstructure consists in submicron Al cells surrounded by a tight Al-Si eutectic network. Due to the heat input accompanying the deposition of a new layer, the Si precipitates coarsen and the eutectic network loosen to form a Heat Affected Zone (HAZ) at the melt-pool boundary. During a tensile test, the rupture preferentially occurs in the HAZ by decohesion between coarse Si precipitates and the Al matrix [1]. Knowing the coarsening kinetic of the Si precipitates in the HAZ with respect to the process parameters is thus of great interest to improve the mechanical properties of AlSi10Mg SLM. With this aim in mind, the phase-field method is a powerful technique to model microstructural evolution [2]. The method describes concentrations and phases by a set of conserved and non-conserved fields with diffuse interfaces. Microstructural evolution is predicted by solving governing equations of the fields. We propose to study the coarsening kinetics of Si precipitates in the HAZ using phase-field simulations. In the model, the initial conditions i.e. Si precipitate size and spatial distribution as well as the Si concentration in the super-saturated Al matrix are set according to experimental observations performed by X-Ray and Scanning Electron Microscope (SEM) analysis. The thermal history in the HAZ with respect to the process parameters is obtained by a calibrated thermal finite element model. The size and the morphology of the heat affected zone observed by SEM is then compared with the ones given by the phase-field model. [1] J. Delahaye et al., Acta Mater. 175 (2019) 160–170. [2] I. Bellemans et al., Crit. Rev. Solid State 43 (2018) 417–454. [less ▲]

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See detail2D thermal finite element analysis of laser cladding of 316L+WC Composite coatings
El Fetni, Seifallah ULiege; Maurizi-Enrici, Tommaso ULiege; Niccolini, Tobia et al

in Procedia Manufacturing (2020)

In this work, a 2D-thermal model of laser cladding (also called Directed Energy Deposition) of composite coating (316L stainless steel reinforced by hard WC carbide particles) was developed. The ... [more ▼]

In this work, a 2D-thermal model of laser cladding (also called Directed Energy Deposition) of composite coating (316L stainless steel reinforced by hard WC carbide particles) was developed. The temperature field and its time evolution were computed by the Finite Element software Lagamine and then compared to experimental measurements. Indeed, in a related work, the effects of the high temperatures on the WC particles in contact with the molten metal and the resulting microstructure at the end of the fabrication were evaluated by means of different experimental techniques. Thus, correlations between simulated thermal histories and microscopic analysis as well as thermocouple records were established. The temperature distribution in the substrate allows the prediction of the depths of the melt pool as well as the thermal histories of the different parts of the clad. Such a model is of great interest and can be applied in situ-calculations to offer quick data about the influences of the process parameters on the properties of the built part. [less ▲]

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See detailIdentification of metal sheet parameters (Levenberg-Marquardt algorithm) and identifiability method
Betaieb, Ehssen ULiege; Habraken, Anne ULiege

Report (2020)

Knowing the material parameters in advance and simulating the process seems something trivial in the numerical modelling. Here, the challenge is starting with the reference result in order to find the ... [more ▼]

Knowing the material parameters in advance and simulating the process seems something trivial in the numerical modelling. Here, the challenge is starting with the reference result in order to find the material parameters: it is the inverse modelling. In my current work, the chosen algorithm is the well-known Levenberg-Marquardt algorithm. This algorithm allows us to obtain a numerical solution of a problem of minimization function, often nonlinear and depending on several variables. This method was developed by Kenneth Levenberg and published after by Donald Marquardt. Implementaion and an application of LM algorithm are presented in this report. This original contribution consists to use several tests with different type of numerical results to identify the same set of parameters. [less ▲]

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See detailMicrostructure and properties of SLM AlSi10Mg: Understanding the influence of the local thermal history
Mertens, Anne ULiege; Delahaye, Jocelyn ULiege; Dedry, Olivier ULiege et al

in Procedia Manufacturing (2020, April 26), 47

Selective Laser Melting (SLM) is an Additive Manufacturing technique that is widely used to produce AlSi10Mg parts with a good strength-to-weight ratio. Indeed, strongly refined microstructures are ... [more ▼]

Selective Laser Melting (SLM) is an Additive Manufacturing technique that is widely used to produce AlSi10Mg parts with a good strength-to-weight ratio. Indeed, strongly refined microstructures are obtained due to the ultra-fast cooling rates reached in this process, conferring high strength to the parts, even in the as-built state. However, microstructural heterogeneities at the scale of the melt pool may exert a detrimental influence on the mechanical properties e.g. by causing a loss in ductility. This study thus aims at a better understanding of the influence of the local thermal history on local variations of microstructure and mechanical properties. Microscopy (i.e. SEM+EDS) and nanoindentation have been combined to reach a detailed knowledge of the local microstructure and properties. In particular, the solute Si content in the -Al matrix, the volume fraction and the size of Si precipitates have been quantified by microscopy analysis. These local microstructural parameters are correlated with the matrix hardness as revealed by nanoindentation. Finally, the results of this detailed characterization are linked with the local thermal history that is approached in two different ways i.e. (i) an analytical description of thermal gradients inside the melt pool based on Rosenthal’s and Matyja’s equations and (ii) a simple Finite Element model for the deposition of a few layers in the SLM process. [less ▲]

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See detailThermal Analysis of Solidifying Steel Shell in Continuous Casting Process
Tran, Hoang Son ULiege; Castiaux, Etienne; Habraken, Anne ULiege

in Procedia Manufacturing (2020, April), 47

A finite element simulation of the steel shell formation in continuous casting has been developed. The current research is focused on the solidification of molten steel during the initial stages of the ... [more ▼]

A finite element simulation of the steel shell formation in continuous casting has been developed. The current research is focused on the solidification of molten steel during the initial stages of the mould cooling. The model allows predicting the temperature field throughout the process: temperature gradient, solidification front, cooling rates. In stationary state, the prediction of shell thickness reasonably agrees with analytical models and experimental observations. The simulation tool is used to study the alteration of the mould thermal field in case of sticking defects encountered in industrial practice. A numerical analysis increases the understanding of the phenomena. [less ▲]

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See detailAlternative experimental method for characterizing the deformation behavior of Ti6Al4V at constant strain rates over the full elastoplastic range
Tuninetti, Víctor; Flores, Paulo; Valenzuela, Marian et al

in International Journal of Material Forming (2020)

range constant strain rate tests are required for accurately characterizing initial yield point, strength differential effect and direct identification of constitutive laws describing the plastic behavior ... [more ▼]

range constant strain rate tests are required for accurately characterizing initial yield point, strength differential effect and direct identification of constitutive laws describing the plastic behavior of materials. These tests require the use of a closed-loop control in order to achieve the constant strain rate, however this feature is not available in many laboratories. An alternative method is proposed here for full range constant strain rate with testing machines that can be configured for user-defined displacements of the cross head prior to testing. Tests performed at a constant die speed include a variable strain rate response for the specimen involved. Significant deformation rate variation occurs between the elastic and plastic range with consequences for initial yield point identification. To overcome this drawback, appropriate user-defined displacements can be computed and applied, allowing for both tensile and compression tests to be performed at a constant strain rate. The method is validated using a compression test of Ti6Al4V alloy at room temperature, as well as a 3D digital image correlation (DIC) system exhibiting a constant strain rate value equal to 10-3 s-1, for both elastic and plastic ranges. A non-negligible inhomogeneous strain field was measured on the surface of the compression specimen using DIC and was corroborated by numerical modeling. Results identified the source of the non-homogeneous strain field, thereby proposing a quantitative indicator of plastic anisotropy. The initial yield stress and strain hardening rates of the alloy at several temperatures were obtained with both testing method, conventional constant cross-head speed, and the constant strain rate; these were then used to determine the influence of the small strain rate variations on the mechanical response of Ti6Al4V alloy. [less ▲]

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See detailTunable surface boundary conditions in strain gradient crystal plasticity model
Yuan, Sibo ULiege; Duchene, Laurent ULiege; Keller, C. et al

in Mechanics of Materials (2020), 145

The behavior of dislocations in the neighborhood of a metallurgical interface or a free surface can be totally different depending on the boundary conditions. Dislocations cease to move and accumulate ... [more ▼]

The behavior of dislocations in the neighborhood of a metallurgical interface or a free surface can be totally different depending on the boundary conditions. Dislocations cease to move and accumulate around impermeable interfaces, such as grain boundaries or hard (i.e. coated or oxidized) external surfaces. On the contrary, dislocations annihilate on free surfaces, as supported by the image force concept. However the behavior of dislocations depends on the true surface permeability, which falls between these two idealized cases. In this paper, two different numerical methods are applied to model the intermediate surface behaviors: the virtual image geometrically necessary dislocation approach and the generalized elastic foundation approach while a strain gradient crystal plasticity constitutive law simulates the response of a Ni single crystal. It is demonstrated that a uniform dislocation density field on the surface can only be obtained by a variant of the generalized elastic foundation approach. © 2020 Elsevier Ltd [less ▲]

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See detail2D thermal finite element analysis of sticker breakout in continuous casting.
Tran, Hoang Son ULiege; Castiaux, Etienne; Habraken, Anne ULiege

in Procedia Manufacturing (2020)

The sticker breakout is an accident in continuous casting which could frequently occur without a correct process monitoring. The breakout of the sticker has become one of the main factors limiting the ... [more ▼]

The sticker breakout is an accident in continuous casting which could frequently occur without a correct process monitoring. The breakout of the sticker has become one of the main factors limiting the development of the continuous casting technology at high speed and wide-thick-plate. In this work, finite element models of the steel shell formation in continuous casting have been developed. The thermal parameters such as conductivity of mold, convection due to cooling system, thermal contact resistance were calibrated. The model allows to predict the temperature field throughout the process. The prediction of shell thickness reasonably agrees with experimental observations. Then, a 2D-thermal model of sticker breakout is established. The new algorithm allows for prediction of hot tearing due to sticking phenomena and its propagation. Current simulations are useful to define the model sensitivity and they increase the understanding of this phenomena. [less ▲]

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See detailMicrostructure prediction in additive manufacturing(TA6V, AlSi10Mg, AISI M4 materials)
Habraken, Anne ULiege; Mertens, Anne ULiege; Duchene, Laurent ULiege et al

Scientific conference (2019, December 06)

Bilan des travaux depuis 3 ans sur 3 matériaux en additive manufacturing

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See detailIdentification and identifiability methods of metal sheet parameters
Betaieb, Ehssen ULiege; Duchene, Laurent ULiege; Habraken, Anne ULiege

Poster (2019, September 19)

The identification of accurate law parameters for metal sheets in the whole range of their deformation field by just one or two tests would be an interesting progress for the efficiency of forming ... [more ▼]

The identification of accurate law parameters for metal sheets in the whole range of their deformation field by just one or two tests would be an interesting progress for the efficiency of forming simulations and manufacturing processes. The final aim of this project is to replace classical experimental homogeneous tests by a few tests performed by single point incremental forming process able to reach very large plastic strains. The identifiability method consists to measure the capacity of a test to identify a material parameter by analysing the sensitivity matrix. In this work, as a first step, this method is just applied on in-plane mechanical tests. Lagamine finite element software developed by MSM team is used to perform the simulation. [less ▲]

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See detailImpact of distortional hardening and the strength differential effect on the prediction of large deformation behavior of the Ti6Al4V alloy
Tuninetti, Victor; Gilles, Gaetan; Flores, Paulo et al

in Meccanica (2019), 54(11-12), 18231840

The ability of three plasticity models to predict the mechanical behavior of Ti6Al4V until fracture is presented. The first model is the orthotropic yield criterion CPB06 developed by Cazacu et al. (Int J ... [more ▼]

The ability of three plasticity models to predict the mechanical behavior of Ti6Al4V until fracture is presented. The first model is the orthotropic yield criterion CPB06 developed by Cazacu et al. (Int J Plast 22:1171–1194, 2006) with a distortional hardening, allowing for the description of material anisotropy and the strength differential effect. The second model is the anisotropic Hill’48 yield criterion with distortional hardening, describing the material anisotropy with quadratic functions but is unable to model the strength differential effect. Finally, the third model is the classical Hill’48 yield locus with isotropic hardening. Distortional hardening is modeled through five yield surfaces associated with five levels of plastic work. Each model is validated by comparing the finite element predictions with experimental results, such as the load and displacement field histories of specimens subjected to different stress triaxiality values. Tensile tests are performed on round bars with a V-notch, a through-hole, and two different radial notches; compression tests are performed on elliptical cross-section samples. The numerical results show that none of the models can perfectly predict both the measured load and the sample shape used for validation. However, the CPB06 yield criterion with distortional hardening minimizes the global error of the model predictions. The results provide a quantification of the influence of mechanical features such as hardening phenomenon, plastic anisotropy, and tension–compression asymmetry. The impact of these features on the prediction of the post-necking deformation behavior of the Ti6Al4V alloy is explored. [less ▲]

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See detailInfluence of Si precipitates on fracture mechanisms of AlSi10Mg parts processed by Selective Laser Melting
Delahaye, Jocelyn ULiege; Tchuindjang, Jérôme Tchoufack ULiege; Lecomte-Beckers, Jacqueline ULiege et al

in Acta Materialia (2019), 175

While it is generally accepted that the rupture of SLM AlSi10Mg tensile specimens occurs at the melt pool boundary, the exact zone and microstructural features responsible for the rupture have not been ... [more ▼]

While it is generally accepted that the rupture of SLM AlSi10Mg tensile specimens occurs at the melt pool boundary, the exact zone and microstructural features responsible for the rupture have not been clearly identified. In this study, the microstructures and local mechanical properties at the melt pool boundary are thus analyzed in details. The Si phase fraction and the Si precipitate spacing are measured by image analysis and SEM-EDS analysis. Hardness tests are performed by nanoindentation. Fracture features are observed on broken samples. It is found that the Heat Affected Zone (HAZ) exhibits low hardness due to coarse non-coherent Si precipitates. Void nucleation occurs at the interface between the coarse Si precipitates and the Al matrix by dislocations piling up. For that reason, the HAZ is found to be the preferential region where fracture is likely to occur. This analysis is confirmed by the matching of Si precipitate spacing within the HAZ with dimple spacing observed in fracture surfaces. Moreover, a simple analytical approach of the thermal history during manufacturing, using Rosenthal’s equation, allows elucidating the mechanisms by which the processing conditions affect the fracture behavior. [less ▲]

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See detailStudy of High Purity Nickel with Various Grain Sizes Using Shear Tests
Yuan, Sibo ULiege; Habraken, Anne ULiege; Milis, Olivier ULiege et al

in AIP Conference Proceedings (2019, July 02)

In this paper, an experimental campaign is described. The high purity Nickel sheet with a thickness of 500 microns is tested at low triaxiality. Thanks to a novel geometry, the axial tensile force is ... [more ▼]

In this paper, an experimental campaign is described. The high purity Nickel sheet with a thickness of 500 microns is tested at low triaxiality. Thanks to a novel geometry, the axial tensile force is converted to shear the material in a local region. Different series of tests are carried out in function of grain sizes. A strong influence on the global mechanical response can be observed due to different numbers of grains through the thickness of sample. The experimental curves are reproduced by finite element simulations with an isotropic macroscopic Hollomon constitutive law relying on different sets of parameters. Next, a small representative volume is considered. Using the identified parameters for each grain size, a sandwich approach is applied. The results of the single constitutive law approach and the sandwich approach are compared. [less ▲]

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See detailNumerical analysis of thermal stress in laser cladding technology of M4 High Speed Steel
Tomé Jardin, Ruben Antonio ULiege; Tchuindjang, Jérôme Tchoufack ULiege; Duchene, Laurent ULiege et al

in Korkolis, Yannis; Kinsey, Brad; Knezevic, Marko (Eds.) et al Proceedings of NUMIFORM 2019: The 13th International Conference on Numerical Methods in Industrial Forming Processes (2019, June 23)

Directed Energy Deposition also called laser cladding process involves high thermal gradients resulting in important stress fields, distortions and possibly cracks. Using the academic non-linear finite ... [more ▼]

Directed Energy Deposition also called laser cladding process involves high thermal gradients resulting in important stress fields, distortions and possibly cracks. Using the academic non-linear finite element code LAGAMINE developed by Uliege, fully coupled thermo-mechanical simulations of laser cladding process of a thin wall in High Speed Steel are performed. A thermo-elasto-plastic constitutive law is used. The thermal model is validated by comparisons between predicted and measured substrate temperatures. The sensitivity of the predicted stresses to the use of simple or multilinear hardening law coupled or not to numerical annealing temperature is demonstrated. [less ▲]

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See detailImproved Temperature Dependence of the Material Parameters in a Visco-plastic Chaboche Law for an Accurate Cyclic Hardening Modelling
Duchene, Laurent ULiege; Morch, Hélène ULiege; Habraken, Anne ULiege

Conference (2019, June 04)

In various industrial applications, the thermo-mechanical behaviour of the load bearing materials must be accurately modelled for a proper design of the key components. In this respect, a visco-plastic ... [more ▼]

In various industrial applications, the thermo-mechanical behaviour of the load bearing materials must be accurately modelled for a proper design of the key components. In this respect, a visco-plastic Chaboche type model [1] with advanced features such as kinematic and cyclic hardening, static and dynamic recovery, was implemented in a finite element code. Additionally, this constitutive model was coupled with a damage model in order to predict the lifetime of the material. Concerning the coupling in such thermo-mechanical model, beside the modelling of the elongation associated with temperature variations and the heat generated by plastic strains, it is very important to accurately reproduce the influence of the temperature on the mechanical behaviour. This can be conveniently achieved by varying the mechanical parameters as a function of the current temperature at the material point. In a first attempt to reproduce the temperature dependence of the material parameters, we calculated them by piecewise linear interpolations between values at pre-defined specific temperatures. A first drawback of this method is the large amount of parameters to be identified, as a complete determination of all the material parameters has to be performed at each specific temperature. A second and more important drawback is the discontinuity of the mechanical behaviour around the specific temperatures. Indeed, with piecewise interpolations, C0 continuity is fulfilled but not C1, which can be a significant issue during finite element simulations. [2] proposed to improve the temperature dependence of the material parameters by replacing the linear interpolations by a continuous analytical expression. In order to reproduce accurately the effects of the temperature, they used an exponential expression with 3 adjustable coefficients. Based on this idea, the present contribution proposes to use the sum of 2 exponential expressions. The influence of the temperature in the range of interest for each material parameter is therefore defined by 5 coefficients (instead of 3). The interest of such improvement is to be able to reproduce accurately the evolution of the cyclic hardening during high cycle loading, which was not possible with the method proposed by [2]. For instance, this is necessary when one wants to track the evolution of the stress amplitude as a function of the cycles in a strain imposed cyclic loading at various temperatures. REFERENCES [1] R. Ahmed, P.R. Barrett and T. Hassan, " Unified viscoplasticity modeling for isothermal low-cycle fatigue and fatigue-creep stress–strain responses of Haynes 230", Int. J. Solids Struct., Vol. 88-89, pp. 131-145, (2016). [2] E. Hosseini, S.R. Holdsworth, I. Kühn and E. Mazza, "Temperature dependent representation for Chaboche kinematic hardening model", Mater. High Temp., Vol. 32, pp. 404-411, (2015). [less ▲]

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See detailInfluence of Processing Routes on the Micro-mechanical behavior of alpha’-martensite in Ti-6Al-4V alloy
Tchuindjang, Jérôme Tchoufack ULiege; Paydas, Hakan ULiege; Maurizi-Enrici, Tommaso ULiege et al

Conference (2019, May 28)

In this work, the micro-mechanical behavior of alpha’ martensite obtained from different manufacturing conditions is studied. One sample obtained from Direct Metal Deposition (DMD) process is compared to ... [more ▼]

In this work, the micro-mechanical behavior of alpha’ martensite obtained from different manufacturing conditions is studied. One sample obtained from Direct Metal Deposition (DMD) process is compared to two other heat treated (HT) samples. The DMD sample manufactured with a low incident energy exhibits a martensitic matrix within wavy columnar grains (Fig. 1). The two HT samples exhibit fully martensite structure within equiaxed grains obtained after 30’ of solution treated annealing at 1000°C and 1050°C respectively, followed by water quenching. The micro-mechanical behavior is obtained while carrying out hardness tests at different scales. Each scale level (macro, meso, micro or nano) highlights related local contributions (prior grain size, martensite lath, lath joint, dislocations or crystal orientation). The complete characterization of HT samples serves as a basis for comparison with equivalent results obtained on the DMD sample. The indentation size effect is established. Difference between HT and DMD samples are discussed thus highlighting the effects of both process and metallurgical features on the hardness. This work is useful not only to better understand the micro-mechanical behavior of martensite, but it can also serve as a reference for setting thermo-kinetics models describing microstructure evolution under Additive manufacturing processing. [less ▲]

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See detailEffect of small strain rate variations on the identification of the compressive behaviour of Ti6Al4V
Tuninetti, Victor; Flores, Paulo; Medina, C et al

in Proceedings og Giens 2019 (2019, May 13)

Ti6Al4V is an hcp material that exhibits a strain rate sensitive behaviour and the tension compression asymmetry yielding known as the Strength Differential (SD). To quantify the SD effect of this alloys ... [more ▼]

Ti6Al4V is an hcp material that exhibits a strain rate sensitive behaviour and the tension compression asymmetry yielding known as the Strength Differential (SD). To quantify the SD effect of this alloys, initial yield compressive stress at different temperatures are computed by performing two type of tests, the conventional constant die speed and the constant strain rate compression tests. The results [less ▲]

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See detailPrediction of cracks within cones processed by single point incremental forming
Betaieb, Ehssen ULiege; Yuan, Sibo ULiege; Guzman, Carlos Felipe et al

in Procedia Manufacturing (2019, April 16), 29(2019), 96-104

Plane stress tests such as tensile tests on smooth and notched samples as well as shear tests are used to identify the set of material parameters associated with two damage models: a micromechanically ... [more ▼]

Plane stress tests such as tensile tests on smooth and notched samples as well as shear tests are used to identify the set of material parameters associated with two damage models: a micromechanically-based Gurson model and a continuum Lemaitre and Chaboche model. Finite element simulations and inverse modelling are applied on these tests to characterize the mechanical behavior of a DC01 steel sheet. The capabilities of these two damage models to predict the maximum wall angle before failure of cones formed by single point incremental forming are analyzed, showing that the Lemaitre and Chaboche model appears to be more reliable when applied on this steel sheet. [less ▲]

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See detailOptimal use of high strength steel grades within bridge (OPTIBRI)
Habraken, Anne ULiege; Duchene, Laurent ULiege; Bouffioux, Chantal ULiege

Report (2019)

The project aims to generate guide lines for welded bridges using High Strength Steel. The quantification of the advantage of using HSS within bridges is performed on a 21.5 m wide highway bridge, with a ... [more ▼]

The project aims to generate guide lines for welded bridges using High Strength Steel. The quantification of the advantage of using HSS within bridges is performed on a 21.5 m wide highway bridge, with a typical 80 m long inner span and a composite steel-concrete twin plate girder deck. It presents clear fatigue and stability issues. An extensive experimental and numerical campaign of fatigue on HSS samples, welded plates and welded beams as well as an experimental and numerical study of multiaxial stressed plates allow a better understanding of HSS material and HSS welded joint behaviour with or without weld post treatment. The results enhance the need of an Eurocode review. Three designs of this bridge are compared: the first bridge design (A) uses only standard S355 steel grade whereas the second design (B) uses also HSS S690 QL steel but relies on current state of Eurocodes. Finally, the third design (C) is performed based on the real measured behaviour of HSS S690 QL steel and post treated welded joints. Through different variants of the design (C), the project results demonstrate the need of updating of Eurocode to take into account the enhanced material properties of HSS and the buckling of multiaxial stressed plates. The use of S690 QL in design B (C) enables reductions of steel weight of 25% (32%) on the steel deck and 34% (39%) on main girder compared to Design A and these designs save about 50% on full penetration welding volume compared to design A [less ▲]

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