Factories of the Future (FoF) are expected to implement new integrated design-manufacturing appro... more Factories of the Future (FoF) are expected to implement new integrated design-manufacturing approaches to go towards so-called 'advanced manufacturing'. Actually, combination of additive manufacturing (AM, or 3D-printing) and topological optimization offer new opportunities to produce lighter products with lower environmental footprint. Fused Deposition Modeling (FDM) is a widely used AM process which is affordable with a free control of process parameters. This paper aims at improving the design of 3D-printed structures using topological optimization to define the external geometry and then either heterogeneous internal filling or multimaterials to achieve targeted usage properties. 22 ème Congrès Français de Mécanique Lyon, 24 au 28 Août 2015 2 Based on structural mechanics simulation, parts of the structures where stresses field is high are printed with high density internal filling, or alternatively a new material with improved mechanical properties is added. In the pres...
Thermoplastic shape memory polyurethane is a "smart" material that is able to return to... more Thermoplastic shape memory polyurethane is a "smart" material that is able to return to its original shape from a large strain deformed shape by exposing it to a thermal stimulus. This total reversibility is possible over several thermomechanical cycles. In order to explore this performance in a smart mechanical system, a finite strain thermo-viscoelastic model is proposed to describe the shape memory effect in large strain. The identification of the parameters of this model is carried out on the basis of thermomechanical tests (Dynamic Mechanical analysis DMA, tensile-relaxation in temperature, free and constrained recovery tests). The formulated constitutive model which decoupled the hyperelastic stress and the viscoelastic overstress is implemented in the numerical simulation software Comsol Multiphysics. The results of the simulation show a very good agreement with the experimental response of the material during several shape memory cycles.
World Academy of Science, Engineering and Technology, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, 2011
A transient finite element model has been developed to study the heat transfer and fluid flow dur... more A transient finite element model has been developed to study the heat transfer and fluid flow during sp ot Gas Tungsten Arc Welding (GTAW) on stainless steel. Temperature field, fluid velocity and electromagnetic fields are computed in side the cathode, arc-plasma and anode using a unified MHD formulatio n. The developed model is then used to study the influence of different helium-argon gas mixtures on both the energy transf erred to the workpiece and the time evolution of the weld pool d imensions. It is found that the addition of helium to argon increase s the heat flux density on the weld axis by a factor that can reach 6.5. This induces an increase in the weld pool depth by a factor of 3 . It is also found that the addition of only 10% of argon to helium de creases considerably the weld pool depth, which is due to t he electrical conductivity of the mixture that increases signific antly when argon is added to helium. Keywords—GTAW, Thermal plasmas, Fluid flow, Marangoni effect,...
Large-scale X-ray microcomputed tomography (μ-CT) is used to investigate microstructural features... more Large-scale X-ray microcomputed tomography (μ-CT) is used to investigate microstructural features of weld lines in a short glass fiber reinforced polymer. The main originality of this work is related to the evaluation of local structural and mechanical characteristics in zones of unmastered heterogeneities. Complete and incomplete injection molded plates are considered to investigate weld lines with and without process-induced porosity. Using a helical scanning trajectory, the full 3D microstructure is obtained at centimetric scale to cover a large zone including first contact between colliding fronts at a voxel size of 3 μm. Microstructure analyses show that weld line area is ill-ordered at the fiber and structure length scales. Near the first contact point, fiber orientations show the signature of vortexes, which mark the presence of repulsive forces. The presence of micrometric porosity is only confirmed in incomplete plates. μ-CT images are used as inputs to create a full-scale finite element model for assessing strain localization. Predicted principal strains are compared to digital image correlation measurements performed during uniaxial tensile tests. Full-scale modeling combined to 3D high-resolution imaging proves high potential to correlate local fiber heterogeneities with strain localization effects
We report a new approach to measure orthotropic properties of short glass fibre reinforced thermo... more We report a new approach to measure orthotropic properties of short glass fibre reinforced thermoplastics at the macroscopic scale taking into account all microstructural details. 3D imaging technique based on X-ray micro-tomography is used to assess fibrous architecture of an injected part at different positions characterised by different fibre flow histories. Finite element computation is used as a multiscale process, firstly by computing orthotropic parameters at a micro-scale for hundreds of bi-phasic 3D domains composing the macrostructure of the composite at all studied positions. Results are implemented in a second finite element computation as a collection of orthotropic material models composing the heterogeneous structure of the composite
Factories of the Future (FoF) are expected to implement new integrated design-manufacturing appro... more Factories of the Future (FoF) are expected to implement new integrated design-manufacturing approaches to go towards so-called 'advanced manufacturing'. Actually, combination of additive manufacturing (AM, or 3D-printing) and topological optimization offer new opportunities to produce lighter products with lower environmental footprint. Fused Deposition Modeling (FDM) is a widely used AM process which is affordable with a free control of process parameters. This paper aims at improving the design of 3D-printed structures using topological optimization to define the external geometry and then either heterogeneous internal filling or multimaterials to achieve targeted usage properties. 22 ème Congrès Français de Mécanique Lyon, 24 au 28 Août 2015 2 Based on structural mechanics simulation, parts of the structures where stresses field is high are printed with high density internal filling, or alternatively a new material with improved mechanical properties is added. In the pres...
Thermoplastic shape memory polyurethane is a "smart" material that is able to return to... more Thermoplastic shape memory polyurethane is a "smart" material that is able to return to its original shape from a large strain deformed shape by exposing it to a thermal stimulus. This total reversibility is possible over several thermomechanical cycles. In order to explore this performance in a smart mechanical system, a finite strain thermo-viscoelastic model is proposed to describe the shape memory effect in large strain. The identification of the parameters of this model is carried out on the basis of thermomechanical tests (Dynamic Mechanical analysis DMA, tensile-relaxation in temperature, free and constrained recovery tests). The formulated constitutive model which decoupled the hyperelastic stress and the viscoelastic overstress is implemented in the numerical simulation software Comsol Multiphysics. The results of the simulation show a very good agreement with the experimental response of the material during several shape memory cycles.
World Academy of Science, Engineering and Technology, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, 2011
A transient finite element model has been developed to study the heat transfer and fluid flow dur... more A transient finite element model has been developed to study the heat transfer and fluid flow during sp ot Gas Tungsten Arc Welding (GTAW) on stainless steel. Temperature field, fluid velocity and electromagnetic fields are computed in side the cathode, arc-plasma and anode using a unified MHD formulatio n. The developed model is then used to study the influence of different helium-argon gas mixtures on both the energy transf erred to the workpiece and the time evolution of the weld pool d imensions. It is found that the addition of helium to argon increase s the heat flux density on the weld axis by a factor that can reach 6.5. This induces an increase in the weld pool depth by a factor of 3 . It is also found that the addition of only 10% of argon to helium de creases considerably the weld pool depth, which is due to t he electrical conductivity of the mixture that increases signific antly when argon is added to helium. Keywords—GTAW, Thermal plasmas, Fluid flow, Marangoni effect,...
Large-scale X-ray microcomputed tomography (μ-CT) is used to investigate microstructural features... more Large-scale X-ray microcomputed tomography (μ-CT) is used to investigate microstructural features of weld lines in a short glass fiber reinforced polymer. The main originality of this work is related to the evaluation of local structural and mechanical characteristics in zones of unmastered heterogeneities. Complete and incomplete injection molded plates are considered to investigate weld lines with and without process-induced porosity. Using a helical scanning trajectory, the full 3D microstructure is obtained at centimetric scale to cover a large zone including first contact between colliding fronts at a voxel size of 3 μm. Microstructure analyses show that weld line area is ill-ordered at the fiber and structure length scales. Near the first contact point, fiber orientations show the signature of vortexes, which mark the presence of repulsive forces. The presence of micrometric porosity is only confirmed in incomplete plates. μ-CT images are used as inputs to create a full-scale finite element model for assessing strain localization. Predicted principal strains are compared to digital image correlation measurements performed during uniaxial tensile tests. Full-scale modeling combined to 3D high-resolution imaging proves high potential to correlate local fiber heterogeneities with strain localization effects
We report a new approach to measure orthotropic properties of short glass fibre reinforced thermo... more We report a new approach to measure orthotropic properties of short glass fibre reinforced thermoplastics at the macroscopic scale taking into account all microstructural details. 3D imaging technique based on X-ray micro-tomography is used to assess fibrous architecture of an injected part at different positions characterised by different fibre flow histories. Finite element computation is used as a multiscale process, firstly by computing orthotropic parameters at a micro-scale for hundreds of bi-phasic 3D domains composing the macrostructure of the composite at all studied positions. Results are implemented in a second finite element computation as a collection of orthotropic material models composing the heterogeneous structure of the composite
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Papers by Frederic ROGER