Publications

2023

• Homogenized transition conditions for plasmonic metasurfaces
  
  • Lebbe Nicolas
  • Maurel Agnes
  • Pham Kim
  Physical Review B, American Physical Society, 2023, 107 (8), pp.085124. The present study aims to model the optical response of plasmonic metasurfaces made of a periodic arrangement of metallic particles with arbitrary shape and subwavelength dimensions. By combining homogenization with quasistatic plasmonic eigenmode expansion, the metasurface is replaced by a zero-thickness interface associated with frequency-dependent effective susceptibilities. The resulting discontinuities of the fields are responsible for strong interaction with the incoming light at the resonances when the complex permittivity of the metal passes close to the real permittivity of an eigenmode. Our modeling provides a physical picture of resonances in plasmonic metasurfaces, and it allows for a huge decrease in the numerical cost of their computations. In addition, comparisons with direct numerics in two dimensions evidence its predictive force at any incidence, particle shape, and arrangement. (10.1103/PhysRevB.107.085124)
  DOI : 10.1103/PhysRevB.107.085124
• Effect of the deposition direction on fracture propagation in a Duplex Stainless Steel manufactured by Directed Energy Deposition
  
  • Roucou David
  • Corre Thomas
  • Rolland Gilles
  • Lazarus Véronique
  Materials Science and Engineering: A, Elsevier, 2023. Dense volumes of duplex stainless steel are manufactured by directed energy deposition. Compact tension specimens are machined from these volumes in order to evaluate the fracture toughness in two directions : parallel or perpendicular to the deposited layers. Different values are measured in the two cases. In order to understand this anisotropy, additional analyzes are performed on the cracked specimens post-mortem. A classical metallography analysis reveals the highly oriented structure of the material, as well as phase localization. The study of the fracture surface reveals several points. At the macroscale, while the crack surfaces are flat in the parallel case, pronounced shear lips cover half of the fracture surface in the perpendicular case. At the microscale, fracture is ruled by microvoid coalescence. The mesoscale, which is inherited from the deposition strategy, is found to pilot the crack growth. The border between the primary solidified melt pools and the heat-affected zones, which corresponds to the interface between the deposited layers, is the preferred area for crack growth. Analyzing the crack surface roughness confirms the dominance of the mesoscale, as its characteristic lengthscale is retrieved. This explains the differences observed for the two tested directions of fracture: in the parallel case, the crack is aligned with the weak interfaces between layers, which channel the crack growth; in the orthogonal one, out-of-plane excursion of the crack becomes possible allowing the crack to follow a tortuous three-dimensional path that results in a higher toughness than in the parallel situation. (10.1016/j.msea.2023.145176)
  DOI : 10.1016/j.msea.2023.145176