Scientific direction Development of key enabling technologies
Transfer of knowledge to industry

PhD : selection by topics

Technological challenges >> Additive manufacturing, new routes for saving materials
7 proposition(s).

Additive manufacturing of a high temperature strain jauge

DLORR (CTReg)

Autre DLORR

01-10-2020

SL-DRT-20-0217

manuel.fendler@cea.fr

Additive manufacturing, new routes for saving materials (.pdf)

The Internet of Things brings intelligence and connectivity within industrial tools. It gathers a real-time knowledge of the equipment parameters, which allows optimizing the processes by a better control and monitoring of the manufacturing conditions. The accumulation of data allows statistical processing by machine learning to improve the process and control in real time thanks to more connectivity and embedded intelligence. At the heart of data collection in the tools, many sensors are designed based on a common sensing element: the strain gauge. However, the operating conditions in the industrial environment are extremely severe; the major degradation stimulus is temperature, with values commonly exceeding 400 ° C, eliminating the use of gauges that are performed exclusively on plastic substrates. The aim of this thesis is to develop high temperature gauge sensors, leveraging additive techniques for both the fabrication and integration of gauges on topologically optimized test bodies.

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Realization by additive manufacturing of a 3D ceramic / metal device, applied to remote power transfer and to remote control.

DMIPY (CTReg)

Autre DMIPY

01-09-2020

SL-DRT-20-0282

regis.delsol@cea.fr

Additive manufacturing, new routes for saving materials (.pdf)

CEA Tech's materials platform focuses on the shaping of advanced ceramics and offers R&D partnerships in additive manufacturing involving ceramics parts. The proposed thesis aims the increase of the knowledge and expertise needed to design and realize ceramic / metal devices. The chosen application is the remote control and the remote power transfer of a mechatronic system consisting of one or several sensors. The first phase of the thesis of a duration of 9 months will consist in a bibliography study and a dimensioning study in order to choose the best ceramic / metal couple with respect to the application case. The second phase of a duration of 9 months will consist in additive manufacturing and metallization of planar prototypes and will consist in mechanical, morphological and dielectric characterization. The third phase of a duration of 12 months will lead to additive manufacturing and metallization of the final 3D prototype. Eventually, the performance of the prototype will be evaluated though functional testing.

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Advanced nanocomposites for additive manufacturing

Département des Technologies des NanoMatériaux (LITEN)

Laboratoire Synthèse et Intégration des Nanomatériaux

01-10-2020

SL-DRT-20-0419

thomas.pietri@cea.fr

Additive manufacturing, new routes for saving materials (.pdf)

The proposed scientific objectives are at the crossroads of nanomaterials and additive manufacturing. Various 3D printing technologies of polymeric matrices have been developed, allowing a conversion of a numerical model with a great precision. But, due to the very recent development of these technologies, the currently available materials appear insufficiently mature and require significant improvements. A great chance of success for properties enhancement could certainly come from the fabrication of advanced nanocomposites (through inclusion of nanomaterials within a polymeric matrix). The work that will be carried out during his PhD will take advantage of the synthesis and functionalization of one-dimensionnal nanomaterials (nanowires, nanotubes). After characterization of the intrinsic properties of the nanocomposites, printable wires will be produced and used with 3D printers. High performance nanocomposites will be used for the fabrication of 3D elements with high conduction of electricity and/or heat. Applications for health will also be considered.

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Microstructural changes in additive manufacturing materials during Hot Isostatic Pressing: modelling and experimental study

Département Thermique Biomasse et Hydrogène (LITEN)

Laboratoire Conception et Assemblages

01-10-2020

SL-DRT-20-0470

emmanuel.rigal@cea.fr

Additive manufacturing, new routes for saving materials (.pdf)

Additive manufacturing (AM) processes are promising techniques for manufacturing metallic components from powder or wire feedstock. AM materials exhibit microstructures very different from cast or forged equivalent materials. They are out of equilibrium, sometimes anisotropic, with specific features like a high dislocation density and defects (unmelted particles, pores) which may be detrimental to mechanical properties (creep, fatigue resistance). Defects can be mitigated using a heat treatment under high gas pressure (hot isostatic pressing HIP), at the expense of material softening. The objective of the PhD thesis is to model the microstructural évolutions during HIP in order to optimise the HIP cycle for a given AM microstructure: defects shall be decreased enough while softening shall be limited. A detailed characterisation of the initial microstructure will be done (defects, grain size, dislocation density, precipitates, texture?) in order to provide data for the DIGIMU software. This software uses the level set method to simulate, by finite element calculation, the evolution of a volumic element representative of a microstructure during thermomechanical loading. This software will be enriched. The comparison between modelled evolution and experimentally observed ones will be used to assess the relevancy of the modelling (HIP will be applied on samples). Furthermore, attention will be paid to the evaluation of the impact of the HIP treatment on mechanical properties of AM material (316L steel will be used).

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Embedding of high temperature resistant Fiber Bragg Gratings into metal structures obtained by additive manufacturing processes

Département Métrologie Instrumentation et Information (LIST)

Laboratoire Capteurs Fibres Optiques

01-10-2020

SL-DRT-20-0645

guillaume.laffont@cea.fr

Additive manufacturing, new routes for saving materials (.pdf)

LCFO laboratory from the Technological Research Division at CEA List, in partnership with the LISL laboratory from the CEA DEN, specialized in metal additive layer manufacturing processes, proposes a PhD thesis aiming at developing methods to integrate optical fiber sensors (OFS) based on high temperature resistant Fiber Bragg Gratings (FBGs) in metallic components obtained thanks to metal additive layer manufacturing processes either for the aerospace or for the nuclear industry. Thanks to recent developments, ultra-stable FBGs have been realized using direct writing processes into silica optical fibers with femtosecond lasers. These temperature and strain transducers combined with special optical fibers designed for very high temperature environments will be considered for the instrumentation of components obtained by metal additive layer manufacturing. This project aims at contributing to the adoption of in situ monitoring of 3D-printed metallic components, paving the way for their Structural Health Monitoring (SHM) to anticipate failures in the fabrication process and to optimize operating costs thanks to the development of predictive and conditional maintenance-based procedures.

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Microstructure control of additive manufacturing parts by generation and detection of ultrasound by laser

Département Imagerie Simulation pour le Contrôle (LIST)

Laboratoire Instrumentation et Capteurs

01-01-2020

SL-DRT-20-0757

jerome.laurent2@cea.fr

Additive manufacturing, new routes for saving materials (.pdf)

The metal additive manufacturing (AM) processes show a great potential still growing, and those in very varied applications fields. However, existing systems have limitations, in particular on the ability to adapt the microstructures and to detect online the melting defects [1]. To overcome these limitations, it is necessary to develop new manufacturing strategies that could make it possible to adapt the solidification conditions as well as online non-destructive testing (NDT) inspection methods. Direct energy deposition (DED) or selective laser melting (SLM) processes use metallic powder and a locally concentrated energy source, which generates strong thermal gradients, which most often lead to highly oriented microstructures and relatively rough surfaces, both making NDT inspection and physical interpretations more tricky. The microstructures produced are out of thermodynamic equilibrium and possess coarse grains structure; they are characterized by the entanglement of columnar and equiaxed grains. This type of microstructure influences significantly the mechanical behavior and elastic waves propagation; the size distribution of heterogeneities are close to the acoustic wavelengths, having for effect the attenuation and scattering of elastic waves. One of the major challenges in AM is to reduce/prevent the formation of columnar grains during manufacturing, as their presence within the microstructure is the most unfavorable for the use properties. By controlling the thermal conditions during the solidification/crystallization (cooling rate, temperature gradients), it is a priori possible to favorably induce the formation of equiaxed grains. It is also known that, by insonification of the molten metal with high intensity ultrasound, it is possible to perform a ?grain refinement-like?, or also to generate other effects (cavitation, flow, mixing, spraying, dislocation, scattering and phase transformation [2]). Indeed, when an elastic vibration is applied directly to molten metal, it would be possible to control-like the solidified grain structure, i.e. to change locally the direction of growth and morphology of the microstructure during the solidification phase. Therby perturbating the solidification conditions, then, it is conceivable to cause the formation of equiaxial grains, and, potentially, the number of flaws (microporosities, cracks). This observation sets the objective of this thesis, which aims to shape more optimally the AM microstructures by vibrating the melting pool and to conduct either offline or online monitoring by ultrasonic-laser (LU) technique. On the one hand, the work, in the CEA-DEN-LISL Lab. [3], will consist of controlling the microstructural evolution of AM parts by contactless vibration of the melting pool. Thus, it will seek to modify the dynamics of the melt, for example, by destabilizing the dendritic growth in the solidification front due to elastic waves generation with a continuous-wave modulated or pulsed laser source. The control parameters will be assessed in laboratory conditions using an existing experimental prototype, which will be improve by adding several other instruments (fast/thermal/Schlieren cameras, pyrometer) to generate ?enhanced microstructures? and by improving the coaxial manufacturing nozzle. On the other hand, the work in the CEA-DRT-LIST Lab., will consist to inspect online AM samples by employing a LU method. Thus, it will seek to generate and detect ultrasound by laser in the melt, to monitored, for example, the evolution of solidification front, keyhole outbreak, optical penetration evolution, and so on, by measuring acoustic precursors [4]. Ultrasonic characterization measurements, under laboratory conditions, will also be carried out in order to determine the elastic properties by LU [5], whether using surface waves (Rayleigh) or zero-group velocity modes (local Poisson's ratio, anisotropy, thickness), and other NDT methods available from the LIST lab., which can then be compared to EBSD (homogenization method) and metallurgical cuts. FDTD or Finite Elements simulations of ultrasound in these rough and heterogeneous media will also be considered. References: [1] Zhao et al, Phys. Rev. X, 9, 02052, (2019), Wolff et al, Sci. Rep., 9, 962, (2019), Martin et al., Nat. Com., 10, 1987, (2019), Wei, Mazumder & DebRoy, Sci. Rep., 5, 16446, (2015). [2] G. I. Eskin & D. G. Eskin, ?Ultrasonic melt treatment of light alloy melts', 2nd edn, Boca Raton, FL, CRC Press, (2014), M. C. Flemings, ?Solidification processing', McGraw-HilI press, (1974), T.T. Roehling et al., Acta Materialia 128, 197, (2017), M.J. Matthews et al., Optics Express 25, 11788, (2017). [3] P. Aubry et al., J. Laser Appl., 29(2), (2017) [4] Walter & Telschow, QNDE, 15, (1996), Walter, Telschow & Haun, Proc COM, (1999), Carlson and Johnson, WJ, (1998), He, Wu, Li & Hao, Appl. Phys. Lett., 89, (2006). [5] Clorennec, Prada & Royer, Murray, Appl. Phys. Lett., 89, (2006), Laurent, Royer & Prada, Wave Motion 51(6), (2014) Laurent, Royer, Hussain, Ahmad & Prada, J. Acoust. Soc. Am. 137(6), (2015).

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Iterative Computed Tomography reconstruction from prior information for additive mafufactured components

Département Imagerie Simulation pour le Contrôle (LIST)

Laboratoire Méthodes CND

01-10-2018

SL-DRT-20-1025

caroline.vienne@cea.fr

Additive manufacturing, new routes for saving materials (.pdf)

Among the various non-destructive testing (NDT) methods, X-ray computed tomography (CT) is a powerful tool to characterize and localize inner flaws and to verify the geometric conformity of an object. For this reason, micro CT has been established as the most promising way of control for Additive Manufactured specimens in view of its unique capability for the inspection of complex internal structures and geometries without destroying the part. In classical industrial CT systems, X-ray projections are obtained through the rotation of the object, which is put on a turntable placed between the X-ray source and the image detector. However, to increase the flexibility in the acquisition trajectory and therefore a valued adaptability to object and environment constraints, robotized CT inspection is one of the acknowledged new trends in X-ray NDT. In this context, CEA List is developing an advanced X-ray inspection platform, which consists in moving the X-ray source and the detector around a fixed object, thanks to two synchronized robotic arms. In order to perform CT inspection with such equipment, it is essential to develop new reconstruction algorithms and the objective of the thesis consists in optimizing the acquisition trajectory and an existing iterative algorithm by injecting prior information from the additive manufactured object (its material and 3D model).

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