Ricardo Lebensohn

Abstract: Crystal plasticity (CP) models are increasingly used in scale-bridging applications to obtain microstructure-sensitive mechanical response of polycrystalline materials. These models require a proper consideration of the single crystal deformation mechanisms, a representative description of the microstructure, and an appropriate scheme to connect the microstates with the macroscopic response. FFT-based methods, originally proposed by Moulinec and Suquet for composites [1] and extended to polycrystals [2] (the most recent formulation, including non-local large-strain elastoviscoplasticity reported in [3]) are attractive due their higher efficiency compared with CP-Finite Elements, and their direct use of voxelized microstructural images. In this talk, we will report recent progress on FFT-based polycrystal plasticity, with emphasis in novel implementations, including: strain-gradient plasticity, achieving geometric accuracy working with voxelized images, non-periodic extensions, and dynamic effects. We will show applications of these methods to: micromechanics of nano-metallic laminates, wave propagation in heterogeneous materials, multiscale coupling with Lagrangian hydrocodes, integration with 3-D characterization methods, and use for training and validation of machine-learning methods. [1] Moulinec, H., Suquet, P., A numerical method for computing the overall response of nonlinear composites with complex microstructure. CMAME 157, 69, (1998). [2] Lebensohn, R.A., N-site modelling of a 3D viscoplastic polycrystal using Fast Fourier Transform. Acta Mater. 49, 2723 (2001). [3] Zecevic M., Lebensohn R.A., Capolungo L., Non-local large-strain FFT-based formulation and its application to interface-dominated plasticity of nano-metallic laminates. JMPS 173, 105187 (2023).

Bio: Ricardo Lebensohn is a senior scientist of Los Alamos National Laboratory’s (LANL) Theoretical Division, Fluid Dynamics and Solid Mechanics Group. He has worked in the area of structure/property relationships of materials for more than 30 years. He is an expert in crystal plasticity modelling. His contributions include the viscoplastic selfconsistent (VPSC) formulation, a simulation tool for the prediction of mechanical response and microstructure evolution of crystalline aggregates, and the Fast Fourier Transform (FFT)-based formulation specialized to polycrystalline materials, ideally suited for numerical simulations with direct input from microstructural images. Among several distinctions, he received Germany's Humboldt Research Award for Senior US Scientists (2010); NNSA Defense Programs Award of Excellence (2011); TMS Structural Materials Division Distinguished Scientist/Engineer Award (2019), and he was inducted as LANL’s Laboratory Fellow in 2022.