Thomas Tancogne-Dejean

Last Name

Tancogne-Dejean

First Name

Thomas

ORCID

0000-0001-7160-7019

Organisational unit

09473 - Mohr, Dirk / Mohr, Dirk

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Publications 1 - 10 of 29

3D Plate‐Lattices: An Emerging Class of Low‐Density Metamaterial Exhibiting Optimal Isotropic Stiffness
Tancogne-Dejean, Thomas; Diamantopoulou, Marianna; Gorji, Maysam B.; et al. (2018)
Advanced Materials
Heterogeneous random medium plasticity and fracture model of additively-manufactured Ti-6A1-4V
Gorji, Maysam B.; Tancogne-Dejean, Thomas; Mohr, Dirk (2018)
Acta Materialia
The third Sandia fracture challenge: predictions of ductile fracture in additively manufactured metal
Kramer, Sharlotte L.B.; Jones, Amanda; Mostafa, Ahmed; et al. (2019)
International Journal of Fracture
Tracking Microstructure Evolution in Complex Biaxial Strain Paths: A Bulge Test Methodology for the Scanning Electron Microscope
Plancher, Emeric; Qu, K.; Vonk, Niels H.; et al. (2020)
Experimental Mechanics
In this work, a novel method is presented to track site-specific microstructure evolution in metallic materials deformed biaxially along proportional and complex strain paths. A miniaturized bulge test setup featuring a removable sample holder was designed to enable incremental measurements to be performed in a scanning electron microscope, by probing the same position on the sample at different deformation levels, with electron backscatter diffraction (EBSD), electron channeling contrast imaging (ECCI) and other imaging modes. Validation experiments were performed at room temperature on samples prepared from commercial sheet metal (dual-phase steel) and foils (stainless steel). Local strain measurements with the digital image correlation technique confirmed that proportional strain paths with a strain ratio up to 5 can be investigated using elliptical dies in the bulge test holder. It is also shown how complex strain paths can be obtained using a combination of overlapping elliptical dies. Incremental EBSD and ECCI were conducted in configurations relevant for the multi-scale investigation of localized plasticity and damage mechanisms in dual-phase steel. Quantitative information regarding microstructure evolution (phase fractions, orientation fields, dislocation structures, etc.) and regarding local strain distributions could be successfully obtained. This type of data sheds light on underlying deformation mechanisms and provides opportunities to calibrate crystal plasticity models.
Plasticity and Fracture of Cast and SLM AlSi10MG: High-througput Testing and Modelling
Roth, Christian C.; Tancogne-Dejean, Thomas; Mohr, Dirk (2021)
Additive Manufacturing
Both additively-manufactured and cast metals are known to exhibit stochastic mechanical properties at the macroscopic level. Using a robot-assisted mechanical testing system, more than 360 experiments are performed on flat specimens extracted from AlSi10Mg components that are either cast or made through laser powder bed fusion (LPBF), commonly known as selective laser melting (SLM). Aside from basic EBSD analysis of the respective microstructures, micro-computed tomography is performed revealing a significantly higher porosity and pore size for the cast material. The results from uniaxial tension experiments reveal a 10% higher yield strength (on average) and an about 20% higher ultimate tensile strength for the SLM made AlSi10Mg. The tracking of the specimen origin within the SLM component shows a clear location dependence of the observed hardening response on the build height. The shear and tension fracture experiments revealed a strong stress-state dependence and significantly higher fracture strains for the cast material as compared to its SLM-made counterpart. To facilitate the computer aided engineering of structures with additively-manufactured AlSiMg alloys, a build height dependent hardening model is proposed along with a probabilistic plasticity and fracture modeling framework.
Hosford-Coulomb ductile failure model for shell elements: Experimental identification and validation for DP980 steel and aluminum 6016-T4
Pack, Keunhwan; Tancogne-Dejean, Thomas; Gorji, Maysam B.; et al. (2018)
International Journal of Solids and Structures
Additively-manufactured metallic micro-lattice materials for high specific energy absorption under static and dynamic loading
Tancogne-Dejean, Thomas; Spierings, Adriaan B.; Mohr, Dirk (2016)
Acta Materialia
Strain rate dependent plasticity of Lithium-ion pouch cells: Experiments and Simulations
Tancogne-Dejean, Thomas; Grolleau, Vincent; Mohr, Dirk (2022)
International Journal of Impact Engineering
The safety of electric vehicles under crash event depends on the mechanical behavior of Lithium-ion cells under large deformation at high strain rates. Here, an extensive experimental campaign is performed on large-format pouch cells under out-of-plane indentation with two indenter shapes and speeds ranging from a few millimeters per minute up to ten meters per seconds, spanning six decades of strain rates. It reveals that the displacement at the onset of short circuit decreases with increasing strain rates, while a non-monotonic relationship is observed between the strain rate and the maximum force as well as the macroscopic cell tangent stiffness. Based on the experimental results, a phenomenological constitutive model is proposed making use of a Deshpande-Fleck yield locus and strain-rate dependent hardening. An internal variable is introduced to capture the softening at intermediate strain rates. The calibrated model is able to accurately reproduce the experimental data and is further validated on a hemispherical indentation performed at two meters per seconds.
Non-symmetric plate-lattices: Recurrent neural network-based design of optimal metamaterials
Meyer, Paul P.; Tancogne-Dejean, Thomas; Mohr, Dirk (2024)
Acta Materialia
The elastic response of plate-lattices with cubic symmetry can reach the upper, isotropic Hashin-Shtrikman bound. Here, our primary objective is the design of stiff lattices with tailored properties beyond any symmetry or isotropy. We propose a general construction method of plate-lattices, defined as a sequence of plates. We present the large elastic property space, accessible via the geometric control offered by our construction method. Building upon this general formulation, we provide a large-scale comparison to the property spaces of truss- and shell-lattices. Additionally, we observe a distinct correlation between plate orientation and stiffness. To tailor the properties of plate-lattice, we employ a recurrent neural network mapping from a given property to the corresponding structure. Our results highlight the effectiveness of this inverse model in creating plate-lattices with desired properties. We believe that this work holds a paradigm shift in field of inverse design by enabling the efficient customization of the stiffest family of metamaterials.
High Strain Rate Response of Additively-Manufactured Plate-Lattices: Experiments and Modeling
Tancogne-Dejean, Thomas; Li, Xueyang; Diamantopoulou, Marianna; et al. (2019)
Journal of Dynamic Behavior of Materials
Plate-lattices are a new emerging class of isotropic cellular solids that attain the theoretical limits for the stiffness of porous materials. For the same mass, they are significantly stiffer than random foams or optimal truss-lattice structures. Plate-lattice structures of cubic symmetry are fabricated from stainless steel 316L through selective laser melting. A special direct impact Hopkinson bar system is employed to perform dynamic compression experiments at strain rates of about 500/s. In addition, tensile specimens are manufactured for characterizing the stress–strain response of the additively-manufactured cell wall material for strain rates ranging from 10⁻³ to 10³/s. The results show that plate-lattices of a relative density of 23% crush progressively when subject to large strain compression. Their specific energy absorption increases by about 8% when increasing the applied strain rate from 0.001 to 500/s, which is primarily attributed to the strain rate sensitivity of the base material. Good quantitative and qualitative agreement between the experiments and the simulations is observed when using a detailed finite element model of the plate structures in conjunction with a modified Johnson–Cook model. The comparison of the simulation results for plate- and truss-lattices of the equal-density reveal a 45% increase in specific energy absorption. Compression experiments on Ti–6Al–4V lattices revealed a low energy absorption due to the early fracture of the additively-manufactured cell wall material.

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Thomas Tancogne-Dejean

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