Wave propagation in relaxed micromorphic continua: modeling metamaterials with frequency band-gaps

A Madeo, P Neff, ID Ghiba, L Placidi, G Rosi - Continuum Mechanics and …, 2015 - Springer
In this paper, the relaxed micromorphic model proposed in Ghiba et al.(Math Mech Solids,
2013), Neff et al.(Contin Mech Thermodyn, 2013) has been used to study wave propagation …

Geometry of logarithmic strain measures in solid mechanics

P Neff, B Eidel, RJ Martin - Archive for Rational Mechanics and Analysis, 2016 - Springer
We consider the two logarithmic strain measures=||\mathrm dev _n\mathrm log U||=||\mathrm
dev _n\mathrm log F^ TF||\quad and\quad\vol=|\mathrm tr (\mathrm log U)=|\mathrm tr …

Cosserat micropolar elasticity: classical Eringen vs. dislocation form

ID Ghiba, G Rizzi, A Madeo, P Neff - Journal of Mechanics of Materials and …, 2023 - msp.org
We give a comparative presentation of the linear isotropic Cosserat elastic model from two
perspectives: the classical Mindlin–Eringen–Nowacki description in terms of a microrotation …

Numerical treatment of a geometrically nonlinear planar Cosserat shell model

O Sander, P Neff, M Birsan - Computational Mechanics, 2016 - Springer
We present a new way to discretize a geometrically nonlinear elastic planar Cosserat shell.
The kinematical model is similar to the general six-parameter resultant shell model with …

Existence of minimizers in the geometrically non-linear 6-parameter resultant shell theory with drilling rotations

M Birsan, P Neff - Mathematics and Mechanics of Solids, 2014 - journals.sagepub.com
This paper is concerned with the geometrically non-linear theory of 6-parametric elastic
shells with drilling degrees of freedom. This theory establishes a general model for shells …

On Grioli's minimum property and its relation to Cauchy's polar decomposition

P Neff, J Lankeit, A Madeo - International Journal of Engineering Science, 2014 - Elsevier
In this paper we rediscover Grioli's important work on the optimality of the orthogonal factor
in the polar decomposition in an euclidean distance framework. We also draw attention to …

Regularity for a geometrically nonlinear flat Cosserat micropolar membrane shell with curvature

A Gastel, P Neff - Annales de l'Institut Henri Poincaré C, 2024 - ems.press
We consider the rigorously derived thin shell membrane-limit of a three-dimensional
isotropic geometrically nonlinear Cosserat micropolar model and deduce full interior …

Existence theorem for geometrically nonlinear Cosserat micropolar model under uniform convexity requirements

P Neff, M Bîrsan, F Osterbrink - Journal of Elasticity, 2015 - Springer
We reconsider the geometrically nonlinear Cosserat model for a uniformly convex elastic
energy and write the equilibrium system as a minimization problem. Applying the direct …

A logarithmic minimization property of the unitary polar factor in the spectral and Frobenius norms

P Neff, Y Nakatsukasa, A Fischle - SIAM Journal on Matrix Analysis and …, 2014 - SIAM
The unitary polar factor Q=U_p in the polar decomposition of Z=U_p\,H is the minimizer over
unitary matrices Q for both ‖\rmLog(Q^*Z)‖^2 and its Hermitian part ‖\rmsym__*\!(\rmLog …

Quadratic-stretch elasticity

E Vitral, JA Hanna - Mathematics and Mechanics of Solids, 2022 - journals.sagepub.com
A nonlinear small-strain elastic theory is constructed from a systematic expansion in Biot
strains, truncated at quadratic order. The primary motivation is the desire for a clean …