Prediction of distortion during cooling of steel rolled rings using thermal-mechanical-metallurgical finite element model

peer reviewedThis work takes place in the framework of a CRAFT European project gathering three universities, three companies who produce rings through the ring rolling process and a manufacturer of temperature and dimension measurement devices. The final goal of the project is to develop and set up a system, integrated in the industrial process, capable of predicting the geometrical characteristics of final pieces just after the ring rolling stage and to allow the rolling process to avoid dimensional defects through online adaption. In fact, ring rolling production does not imply only the rolling process, but also the cooling and quench stages of steel rings. During all these phases, the dimensions of the pieces change dramatically. In particular, due to the lack of symmetry in the cooling conditions, ring distortions include contraction and rotation of the ring section. The modeling of the cooling phase requires taking into account a large number of phenomena resulting from the coupling of thermal, mechanical and metallurgical effects. A numerical model has been implemented in the non-linear finite element code LAGAMINE, developed by the University of Liège. Such a model can help to better understand the evolution of the geometry during the cooling phase and also the effects of each physical and microstructural parameter implemented in the model on the ring final shape. Effectively, several parameters can affect the ring distortions and the model should take them into account; in particular, the mechanical and thermal behavior of each phase present in the material (metastable austenite, ferrite, pearlite, bainite and martensite). Phase transformation modeling implies the integration of a wide data base of material properties (thermo-physical and mechanical properties of the phases, TTT and CCT diagrams, enthalpy and strain of phase transformation, strain of transformation plasticity…) but only a few of these data are available in literature. Some of them have been found for the reference material (42CrMo4 steel), but additional laboratory experiments have been performed at the Universities of Padua and Liège in order to characterize thermal, mechanical and plastic behaviour of phases. Finally, this paper presents the model validation on an industrial case (measurements of temperature and dimensions of rings have been provided by the manufacturer). Then, some applications are presented, demonstrating the importance of some factors such as some material properties, the shape of the rings, the type of cooling (and the cooling rate) or the symmetry of the cooling scheme on final ring distortion

Comparison of residual stresses on long rolled profiles measured by X-ray diffraction,ring core and the sectioning methods and simulated by FE method

Sheet piles are produced by hot rolling, a cooling step and, if required, by a straightening operation. Numerical simulations indicate that the stress field is almost homogeneous through the thickness, justifying the comparison of X-ray diffraction, ring core and the sectioning methods applied after the cooling step and after the straightening process. The equipment, the steps of the experimental procedures and the results are detailed, showing the limits, the specificities and the advantages of each method. Moreover, the amplitude and the distribution of the stresses along the width of the sections present good agreement with results of numerical simulations

Effect of FEM choices in the modelling of incremental forming of aluminium sheets

peer reviewedThis paper investigates the process of single point incremental forming of an aluminium cone with a 50-degree wall angle. Finite element (FE) models are established to simulate the process. Different FE packages have been used. Various aspects associated with the numerical choices as well as the material and process parameters have been studied. The final geometry and the reaction forces are presented as the results of the simulations. Comparison between the simulation results and the experimental data is also made

Forming limit predictions for single-point incremental sheet metal forming

peer reviewedA characteristic of incremental sheet metal forming is that much higher deformations can be achieved than conventional forming limits. In this paper it is investigated to which extent the highly non-monotonic strain paths during such a process may be responsible for this high formability. A Marciniak-Kuczynski (MK) model is used to predict the onset of necking of a sheet subjected to the strain paths obtained by finite-element simulations. The predicted forming limits are considerably higher than for monotonic loading, but still lower than the experimental ones. This discrepancy is attributed to the strain gradient over the sheet thickness, which is not taken into account in the currently used MK model

Development of a 2.5D Representative Volume Element model of AlSi10Mg material produced by additive manufacturing

peer reviewe

Prediction of static properties of LPBFAlSi10Mg samples post-treated by Friction Stir Processing or thermal treatments

peer reviewedLongLifeA

Identification of a soft matrix-hard inclusion material by indentation

peer reviewedA new procedure for identifying the mechanical behavior of individual phases within a bi-material (matrix-particles) is presented. The case of AlSi10Mg (large globularized Si-rich particles surrounded by an α-Al phase) processed by additive manufacturing and post-treated is taken as a typical example. Grids of nano-indentation tests are performed at different locations on the nanocomposite using a Berkovich indenter and show an impact of the hard inclusions on the experimental curves. The elastoplastic properties of the matrix are identified based on the lowest load–indentation depth curves. Several representative finite element (FE) models demonstrate the influence of the particles on the nano-indentation response. The capacity of the FE model to predict the indentation curve of a cube corner indenter experiment and the Berkovich grid result scattering was checked. A representative volume element (RVE) based on a scanning electron microscope (SEM) image is defined. The identified material parameters of the α-Al phase and Si phase, it allows the prediction of the stress-strain curve of a macroscopic experimental tensile test.LongLifeA

Nanomechanical Characterization of the Deformation Response of Orthotropic Ti–6Al–4V

The nanoindentation‐induced mechanical deformation response is applied to identify the orthotropic elastic moduli using the Delafargue and Ulm method as well as to validate the asymmetric orthotropic CPB06 nonlinear plasticity model required in simulations of nonuniform macroscopic mechanical response of the Ti–6Al–4V alloy. Scanning electron microscope (SEM) technique allows to select the maximum penetration depth for the indentation in the deformed alpha phase and alpha–beta interphase, α and α/β, respectively. The apparent macromechanical response can be successfully derived from several residual imprints conducted at micro‐ and/or submicrometric length scale and distributed throughout samples of the investigated bulk alloy, as demonstrated by correlation with finite element simulations based on the orthotropic elastoplastic model. The accurate numerical response obtained validates the material model and the Delafargue and Ulm approach, opening a window for next generation identification methods of macromechanical plasticity models with hybrid experimental–numerical method based on instrumented indentation and the use of SEM technique

Development of a contact model adapted to incremental forming

peer reviewedThe objective of this article is to present the development of a new method for taking into account the contact between the tool and the blank during incremental forming. First, the need for such a model is justified. Then, the basic features of the adapted dynamic explicit scheme are presented, followed by the new algorithms proposed and their programming. Finally, some conclusions and perspectives are drawn

Back Analysis and optimisation method with Lagamine

Comparison of Back Analysis and Optimization Methods to characterize materials with LAGAMIN