The partial knowledge of the physical properties of metals in liquid state is today a lack in the understanding of physical phenomena and a key issue for the development of multiphysics models. This information, very difficult to access, is required in many sectors: automotive, aerospace, naval, energy, wherever metal alloys are strongly used. Unfortunately, the current literature is incomplete or temperature limited. For example, metal additive manufacturing makes it possible to create parts by depositing exclusively molten metal. The development of this technology is based on thermo-hydrodynamic modelling and experimental research, both requiring extensive knowledge of the thermophysical properties of molten metal in order to understand the appearance of defects and analyse the observed physical phenomena (example : Marangoni).. The CarameLL project aims to establish a breakthrough in the measurement of thermophysical properties of molten metals by using a non-contact aerodynamic levitation device allowing high temperature measurements of surface tension, viscosity or specific heat of molten metals. This method, rather well known and already used at IRDL, will be coupled, for the first time in the CarameLL project, with a new methodology consisting in measuring under very high pressure in order to reduce as much as possible the phenomena of evaporation of alloying elements and of base metal. This idea will make it possible to reach much higher temperatures and to keep intact the chemical composition of alloys characterized. It will also make it possible to study more fundamentally the evaporation of alloying elements. Another originality, the project will be based on multiphysics modeling allowing the lifting of the last locks.

In the field of virtual mechanical design, the robustness and reliability of a mechanical model depends strongly on the experimental database used for the calibration, I.e., the richness/completeness of the database and the closeness to the material used in production. At the moment, within an industrial context, the link between the virtual material and the real one used in production is not strong enough, and at the best, is obtained on other batches, in different aged states or thicknesses. The aim of the AutoMeCal project is to provide, rapidly and efficiently, a calibration of advanced mechanical models from the batch used in production. To this end, an automated mechanical characterization and model calibration will be developed, to provide, by an inverse methodology, the material parameters needed for the virtual design of the forming process and/or the structural design.

Polycyclic fatigue is an aspect of the mechanical behavior of materials, which is particularly insidious due to its progressive and masked nature. Although significant progress has been made since the first works on fatigue in the 19th century, the fatigue resistance of industrial parts under service conditions remains a major current problem. Indeed, even if exact numbers are not available, it is expected that at least half of all mechanical failures are due to fatigue. The relative cost of these failures constitutes approximately 4% of the gross national product of the US. For this reason, it is essential to understand the physics of fatigue, in order to create a cause and effect relationship in an effort to reduce the probability of such failures. However, the development of predictive models for fatigue remains difficult, for at least three reasons: 1. The fatigue properties of materials depend on a large number of parameters such as the nature of the loading, the microstructure of the material, the environment, the manufacturing process... 2. The HCF fatigue life durations of materials and engineering parts are scattered. 3. The times for characterizing the fatigue properties, in a given configuration and using conventional methods, are prohibitive. The SELF-HEATING project therefore relates to the rapid characterization and prediction of the high cycle fatigue properties of materials from a new experimental methods based on thermometric measurements coupled with modeling. Metallic and composite materials will be studied in the proposed project. The main challenge is to propose robust and rapid characterization method of the fatigue properties of materials in order to better design the mechanical parts that use them. Thus the SELF-HEATING project is in relation with strong societal challenges such as reducing energy costs through the lightening of structures, reducing the risk of failure of mechanical systems, development of decision support tools for preventive maintenance... The ANR industrial chair project SELF-HEATING is based on a common need expressed by two internationally renowned French industrial groups, Safran and Naval Group, and brings together the skills of the IRDL (UMR CNRS 6027) concerning the rapid characterization of fatigue properties materials and structures from self-heating tests under cyclic loading and those of the Pprime institute (UPR CNRS 3346) in the field of HCF and VHCF fatigue of materials. The ANR industrial chair intends to amplify and perpetuate the numerous collaborations between the two industrial groups and these two research institutes. This consortium was set up to deal with all the issues of the ANR industrial chair SELF-HEATING in order to not only propose a new approach that breaks with current practices in the fatigue community, to train specialists in these methods who tomorrow will diffuse them, but also, to introduce, in the environment of industrial partners, new procedures for characterizing the fatigue properties of materials. Finally, before the end of the project, we plan to initiate a standardization process. The person proposed to be the chair holder, Sylvain Calloch, is a professor at ENSTA Bretagne since 2004 and a researcher at the Institut de Recherche Dupuy de Lôme (IRDL, UMR CNRS 6027). He is an experienced scientist in the field of mechanics of materials with strong connection with industry. Expert in fatigue of materials and structures, he has been working for twenty years with his team on the rapid characterization of HCF fatigue properties of materials using self-heating method. The other involved researchers complete the large competency spectrum needed to achieve that ambitious project. Fundamental works (experimental and numerical developments, theoretical tools) will help solving efficiently and originally the industrial issues treated in the works in direct connection with industrial concerns.

The development and shaping of structural components as well as their assembly generate significant residual stress fields in the structures. These stresses are superimposed on the in-service loads and have an influence on structures fatigue durability and buckling. When these residual stresses are not known, the implementation of a conservative design approach will lead to an oversizing which can be both costly and limiting in terms of performance, with a particular increase in the weight of the structures. Beyond the optimization of existing designs, the use of new materials and innovative manufacturing processes (additive manufacturing in particular) also makes it necessary to characterize the residual constraints generated. Finally, the improvement of the knowledge of the internal stresses of components already in service may allow their in-service life extension. Residual stress fields are by nature heterogeneous and most often multiaxial. Therefore, their knowledge requires the characterization at different points and in different directions in space. For this purpose, there are different techniques that differ in the possible directions of measurement, the volume of measurement, and the depth of measurement. The standardized and controlled methods are currently reserved for measurements close to the surface. Few methods can be used to characterize the stresses in the core of thick and large structures such as submarine hulls or nuclear reactor containments. If the contour method is now relatively widespread in the research community, including in France, it is limited to the measurement of small parts (< 1m). Only the deep hole drilling method can be applied on real parts but this method is currently mastered by only a few foreign organizations. The development of this method in France is therefore of strategic interest, particularly in the field of defense and nuclear energy (civil and military). The objective of the ASTRID RESISTANCE (RESIdual STress ANalysis for Critical Elements) project is to combine the results of in-depth stress measurements in order to allow the reconstruction of stress fields in the core of thick components. Several technical and scientific obstacles will have to be overcome in the RESISTANCE project. Experimentally and during an 18-month post-doctoral fellowship, it will first be necessary to develop an expertise on the deep hole drilling method and to validate its application. For this, at some reference structures will be designed and produced with different levels of complexity ranging from a 2D flat structure allowing to study the repeatability of the measurements towards more complex structures with strong stress gradients in the 3 directions representative of the targeted structures. Numerically, it will be necessary to adapt the principle of the reconstruction method by deformation, inherent to an incomplete mechanics problem in the sense that it will not be possible to have experimentally all the information at every point. The available information may be contradictory due to the different precision of each measurement and the biases associated with each technique (in particular the appearance of plastic deformation during trepanning). An innovative reconstruction method will be developed through a PhD thesis, and will integrate the consideration of measurement uncertainties in order to reconstruct a compatible averaged field. Finally, an original approach will aim at enriching the method with the measurement of the strain hardening profile which will allow improving the spatial distribution of the introduced deformation fields.

The setting up of the CoLoRe joint laboratory, associating the Institut de Rrecherche Dupuy de Lome (IRDL) of the University of Southern Brittany and the company Laboratoire CBTP, a subsidiary of the Pigeon Group, is fully in line with the strategic axes of the Pigeon Group with the objective of reducing the company's overall environmental footprint by optimising the use of currently unexploited natural resources and by developing innovative materials with lower impacts based on local resources from the mineral, plant and/or marine world. This initiative aims to amplify the active collaboration between the two entities, which have been interacting effectively for the past three years. The acquired skills of the IRDL Joint Research Unit in these scientific fields and especially the experience of partnership research are indisputable assets in the success of such a joint public/private research structure. The ambition of the Pigeon group for the coming years is to begin its transformation in order to optimise the natural resources extracted, particularly those currently not exploited and considered as co-products or even waste from the extractive industries, and to offer the construction and public works sectors less impactful materials. Three lines of research are more specifically targeted. The first concerns the development of raw earth-based construction products. Indeed, one of the solutions that is gaining ground in order to limit the impact of human construction on climate change is to use natural materials that have been little transformed. Thus, there is a strong revival of interest in the use of raw earth in the construction sector. Through its activities, the Pigeon Group generates large volumes of excavated materials that could be integrated into this recovery process. Currently, the development of the use of these materials in the field of construction comes up against the difficulty of producing standardised construction elements with guaranteed target performances. With regard to its activities, the Pigeon group has the industrial know-how to prepare this type of material (extraction, sorting) and to shape it (prefabrication factory for blocks in the short term, or for massive and complete structural elements in the longer term). The LabCom should make it possible to identify the mechanisms at work at the scale of the structure of the material, in order to propose the best material/process pairing for the industrial development of these solutions. The second line of research concerns construction products based on hydraulic binders. Concrete is currently an essential material for the construction of civil engineering infrastructures. However, its environmental impact is significant, both through the mobilisation of non-renewable natural resources (alluvial sands) and through the significant carbon impact of the manufacture of the Portland type binders currently most widely used. For this axis, two development paths are planned. The first aims to optimise the introduction of natural crushed resources extracted on the Pigeon group's sites as a substitute for alluvial resources. The second is to develop new binders that are lower in carbon than the traditional binders (Portland cement) currently used. In particular, it is planned to develop new binders incorporating the washing fines from the group's extraction sites, which are currently considered as co-products. Finally, the third line of research will focus on materials with bituminous binders. For these materials, the objective is to develop solutions that limit the use of carbon-based binders. The objective is to develop plant-based (or seaweed-based) binder solutions to replace bituminous binders.