"Nowadays, the forming process steps and the design phases of real parts are most of the time unrelated. The mechanical design of these components under service conditions does not account for the thermomechanical and microstructural history of the materials used. This leads sometimes to approximate estimations of their mechanical strengths and to too high safety coefficients. Recently, some numerical simulation forming process codes allow to estimate the mechanical properties of a component after the forming process. They also give information on the microstructure with regard to the thermomechanical conditions used during the process. The damage fatigue models (low cycle and high cycle fatigue regimes, uniaxial and multiaxial loading conditions) and the related design codes, do not yet use these informations as input data. It is now important to identify the principal mechanical and microstructural characteristics induced by the forming process and playing a role in the fatigue strength. This knowledge will make possible the increase of the fatigue model predictivity and will lead to consider the process phase as the previous step of the fatigue design approach. The DEFISURF project main objective is to carefully study the effects of the surface defects and microstructural heterogeneities on the fatigue damage mechanisms of forged components in order to give better predictions of their mechanical properties and conduct the best possible design. It is more exactly planed to analyze and model the influence of the surface state (microgeometry, gradient of microstructure, residual stresses intensity and distribution) on the fatigue behavior of forged parts generally highly loaded. This project is composed of several tasks dealing with: 1. The assessment of the principal defects (geometrical and metallurgical) occurring in forged parts together with their origins 2. The estimation by relevant techniques (that can be used in the industrial framework) of the defects distribution in a component 3. The use of advanced experimental devices (tomography, EBSD 3D, nanoindentation …) to characterize surface geometrical and metallurgical defects 4. The fatigue testing under different loading modes and path of three steels showing different defect contents and shot-peening conditions (residual stresses distribution, surface hardening …) 5. The numerical modeling, at the microscopic and the macroscopic scales, of the nucleation and growth of different defects along the forming process steps 6. The numerical modeling, at the microscopic and the macroscopic scales, of the fatigue response of different steels showing several defect and microstructural heterogeneities content. Different loading conditions will be applied like very high compressive loading for the rod."

The goal of this project is to implement a process of analysis, control and optimisation of a surface induction heat treatment process followed by a quenching stage. The part which will be used in this project if an automotive crankshaft, which is one of the most critical parts in the future powertrains prescribed by the EURO6 regulations. This part may be reinforced in the most mechanically loaded areas by burnishing or by induction. If induction has become largely used for large-size engines, its use for automobiles is scarcer, mostly due to badly mastered process and costs. Indeed, small crankshafts are more sensitive to deformation after induction hardening due to their geometry (weaker massiveness). These distortions make the use of induction hardening quite delicate and increase the global cost of the part. The analysis, study approach and results of this project will not be limited to crankshaft production, but may alos be reused for studying the induction hardening of other parts with a complex geometry subject to distortions The scientific approach will be based on the use of complementary approaches to reach the prescribed goals: - accurate understanding of material behaviour during fast heating - modelling of multiphyssics couplings between electromagnetism, heat transfer, solid mechanics and metallurgical phases transformation - experimental validation of the optimised solutions The complementarity between consortium partners (laboratories in the field of numerical modelling of processes and in material science, automotive industry, steel industry, experts in electromagnetic processing of materials) will help to make this project to a success. Project benefits are manifold - Scientific: improve knowledge of metallurgical behaviour for fats heating, fine analysis of thermal-mechanical-metallurgical couplings, progress towards process optimisation through an accurate predictive multphysics computational model - Process and material optimisation (structure, hardness, residual stresses, deformation,..) with the help of computational modelling (predictive aspects) to better take it into account in the part design process - Technological: induction heat treatment is an economic process easily implementable on a new production line, and which can potentially lead to very good in-use properties - Economical: enable manufacturing of small automotive crankshafts with minimal and reproducible deformation. We need to recall here that straightening of induction heat treated crankshafts cannot be carried out – since it leads either to unfavourable residual stresses, or worse to breaking - Environmental; reduction of energy consumption during manufacturing processes complies with sustainable development goals.

During casting of bottom-poured ingots, the metallic alloy is protected by a layer of mineral powder, called casting powder, which partially melts to form an airtight liquid slag film on top of the liquid metal. The layers of liquid slag and remaining powder play a paramount role in casting by its chemical and thermal insulation properties. Despite clear evidence of impact on both the skin quality and the internal metallurgical soundness of the ingots, the evolving thermochemical properties of the powder are not known and researches in this field remain mainly empirical. TheCAP projects to understand the thermochemical mechanisms that drive the melting of casting powders and their consequences on the liquid metal and the final ingot quality. The ambitious are to get scientific expertise in an almost unexplored field, to improve numerical tools and to significantly optimize the metal yield of the casting route of bottom-poured ingots by eliminating grinding, its resulting scraps, as well as by accelerating the development of new grades of metallic alloys and casting powders. For this purpose, experimental and numerical approaches will be concomitantly considered. Innovative experimental set-ups working at very high temperature and dedicated new instrumented trials will be developed, together with a comprehensive modelling of the powder thermochemistry including melting. The consortium is based on well established and proven effective collaborations among the partners who gather their forces in order to progress on the Thermochemistry of ingot CAsting Powders.

The principal objective of project FLUOTI consists in simulating the spin forming process of TA6V at room temperature to produce long tubes by successive work hardening and local large deformation stages. The advantage lies in the high geometrical precision for obtaining thick tubes used in aeronautics for instance. The material behaviour of the a+ß microstructure of TA6V under large "cold" deformation is still a challenge. However, and this is how the project is original in its purpose, the spin forming process could allow, for successive incremental deformations, to push the limits of the standard formability of the material. Indeed, preliminary tests at ROXEL with repeated deformations up to 30% have already been obtained but the industrial interest is above 70%. Despite this, there is no certainty that an industrial solution exists. Today there are no cold scale spin formed tubes in TA6V produced at an industrial scale. However, room temperature is certainly less favourable to deformation but allows for better reproducibility and less distortion and oxidation during step by step operations. Accordingly the quality of the tubes will be better assured during an easier cycle and the processing cost to form the tube will be less expensive. Furthermore the quality of the tube at the end of the processes must be known throughout its whole length and thickness because many of theses pieces are parts of class 1 for aeronautics. Therefore the company ROXEL wishes to continue these preliminary investigations and implement the means necessary to obtain a 1st prototype tube realised by cold spin forming of TA6V. If one combines the high cost of material, multiple settings of spin forming conditions and the many possibilities of heat treatments, we soon realize that the number of trial and error would be prohibitive for ROXEL. Therefore the numerical simulations of the process are then proposed to try to minimize the number of tests on industrial site by identifying and optimizing the operating conditions and status of the tube after the forming operation. The simulation will also incorporate changes in the material behaviour from its raw supply state to the finished piece. A blocking point of numerical simulations of flow forming is computing time. Indeed, like all processes of incremental forming, spin forming is an unsteady process which leads to time-intensive computing. The flow zones are located in contact with the wheels and are always in motion. We must therefore optimize the size of the mesh in adequacy with both the geometry reproduction and the level of distortion experienced by the material. The detailed managements of free surfaces and the contact are also important numerical issues. More accurate representation of the kinematics of tools (mandrels and rollers) is complex. Its influence on the quality of simulation results is very important. Many parameters come into play when evaluating the processing of the tube during the cold spin forming operation. There is of course the influence of operating conditions (kinematics and geometries of the tools) and geometries (initial, intermediate and final) of the tube on the rheology and behaviour of the material. There is also the influence of thermal treatments between two pass of spin forming that will help to push the material to its very far limit of deformation. Improving the cold formability of TA6V is going through a series of cross linked steps of analyses and characterizations of the influence of strain paths with respect to evolutions of mechanical properties and microstructure.

Numerical modelling is less frequently used in industry for simulation of welding than for simulation of other transformation procedures, like plastic deformation or melting. This is due to the multiphysical nature of the welding process, involving arc plasma, fluid flow in the melted area, strongly coupled mechanics, thermal effects and metallurgy. This complexity penalizes the setting up of innovative welding process, such as arc-laser hybrid welding. The industrial stake is big in sense of quality and productivity (no reliable predictive tool of the operative and metallurgical weldability exists). The aim of the SISHYFE project is to create this kind of tool, especially for the thick steel welding. Hence, four main aims are defined: 1. To develop methods of direct simulation of welding procedure, by modelling, in particular, laser-plasma interaction in case of hybrid welding, as well as the strong convective fluid flow of the liquid metal in the melted area. This should increase the predictability of these models. 2. In addition to direct simulation, to develop and to customize for hybrid welding (two power sources - arc and laser beam) a methodology consistent in identifying the thermal power sources using an automatic inversed finite elements method. 3. To evaluate the performance of these two methods, and particularly the contribution of the direct simulation, in sense of mechanical and metallurgical predictions (shape of the seam, properties of the melted area and the heat affected area, structure distortions and residual stresses). 4. To develop predictive simulations of the laser-arc hybrid welding procedure, that can also be applied to other procedures, such as arc, laser or electron beam welding. The methodology suggested is: A. Instrumented welding experiments performed for three configurations typical for hybrid welding will serve as reference throughout the project. Emphasis will be put on instrumentation with the aim to obtain a precise and consistent experimental database: thermocouples, high speed video camera, IR camera, distortion and deformation measurements using an image stereo-correlation device, ... B. For a development of numerical models three softwares will be used: COMSOL, SYSWELD and TRANSWELD. A verification of the numerical methods, on one hand, and the performances of each software, on the other hand, will be possible by comparing the obtained numerical results with the experimental results from corresponding reference configurations. C. These new softwares will be used for welding-tests by three industrial users. They would enable determination of experimental windows for operative and metallurgical weldability. The consortium is compact, reliable and well-balanced. It comprises all adequate expertises: 3 industrials, 1 technical center, 2 software companies and 2 research laboratories. All of them are major contributors to each of industrial, technical or scientific problematic. The project can contribute significant innovations in several fields of theme 4 of the request for proposals: - To develop innovative numerical tools for the comprehension of multiphysical phenomena typical for hybrid welding: plasma-laser interaction, fluid-structure coupling (hydrodynamics of melted area/solid part) - To verify the theoretical predictions using a serious experimental approach - To optimize the industrial development of the hybrid welding process