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M. Shaat's picture

Metamaterials with Giant and Tailorable Nonreciprocal Elastic Moduli

Natural nonlinear materials, e.g., biological materials and polymers, are mechanically weak. It has been amajor challenge to develop a nonlinear material with potentialmechanical applications. Here, we develop a nonlinear elastic metamaterial with giant and tailorable-nonreciprocal elastic moduli. The metamaterial is designed with a microstructural axial asymmetry, which activated nonlinear microstructural deformations in the axial direction and microstructural residual moments.

M. Shaat's picture

Review on nonlocal continuum mechanics: Physics, material applicability, and mathematics

The classical continuum mechanics assumes that a material is a composition of an infinite number of particles each of which is a point that can only move and interact with its nearest neighbors. This classical mechanics has limited applications where it fails to describe the discrete structure of the material or to reveal many of the microscopic phenomena, e.g., micro-deformation and micro-dislocation.

M. Shaat's picture

A New Beam Theory: A Micromorphic Beam Theory for Beams with Elongated Microstructures

A novel micromorphic beam theory that considers the exact shape and size of the beam’s microstructure is developed. The new theory complements the beam theories that are based on the classical mechanics by modeling the shape and size of the beam’s microstructure. This theory models the beam with a microstructure that has shape and size and exhibits microstrains that are independent of the beam’s macroscopic strains.

M. Shaat's picture

On postbuckling mode distortion and inversion of nanostructures due to surface roughness

In this paper, we investigate the surface roughness-dependence of buckling of beam-nanostructures. A new variational formulation of buckling of Euler-Bernoulli rough beams is developed based on the Hamil- ton’s principle. The equation of motion of the beam is obtained with a coupling term that depends on the beam surface roughness. Exact solutions are derived for the buckling configurations and the pre-buckling and postbuckling vibrations of simply supported structures.

M. Shaat's picture

Hinged-3D metamaterials with giant and strain-independent Poisson’s ratios

Current designs of artificial metamaterials with giant Poisson’s ratios proposed microlattices that secrete the transverse displacement nonlinearly varies with the longitudinal displacement, and the Poisson’s ratio depends on the applied strain (i.e., tailorable Poisson’s ratio). Whereas metamaterials with tailorable Poisson’s ratios would find many important applications, the design of a metamaterial with a giant Poisson’s ratio that is constant over all the material deformation range has been a major challenge.

M. Shaat's picture

Fluidity and phase transitions of water in hydrophobic and hydrophilic nanotubes

In this paper, we put water flow under scrutiny to report radial distributions of water viscosity within hydrophobic and hydrophilic nanotubes as functions of the water-nanotube interactions, surface wettability, and nanotube size using a proposed hybrid continuum-molecular mechanics. Based on the computed viscosity data, phase diagram of the phase transitions of confined water in nanotubes is developed.

How to determine the reference rate of shearing and rate sensitivity for power-law rate dependent crystal plasticity formulation?

In single crystal plasticity, the material strain hardening is specified by the slip system strain hardness which is determined from the strain hardness function (Eqn 1, see attached). Its parameters can be determined by fitting the equation to the experimental stress-strain curve.

Ajeet Kumar's picture

Geometrically exact elastoplastic rods -determination of yield surface in terms of stress resultants

This work addresses the determination of yield surfaces for geometrically exact elastoplastic rods. Use is made of a formulation where the rod is subjected to an uniform strain field along its arc length, thereby reducing the elastoplastic problem of the full rod to just its cross-section. By integrating the plastic work and the stresses over the rod's cross-section, one then obtains discrete points of the yield surface in terms of stress resultants. Eventually, Lamé curves in their most general form are fitted to the discrete points by an appropriate optimisation method.

Emilio Martínez Pañeda's picture

A phase field formulation for dissolution-driven stress corrosion cracking

Dear iMechanicians, I hope that our latest JMPS paper is of interest to you. We show how the phase field paradigm can be extended to model localised corrosion (aqueous electrolyte-solid interface) and the associated damage mechanisms. 

C. Cui, R. Ma, E. Martínez-Pañeda. A phase field formulation for dissolution-driven stress corrosion cracking. Journal of the Mechanics and Physics of Solids 147, 104254 (2021)

Arash_Yavari's picture

The mathematical foundations of anelasticity: Existence of smooth global intermediate configurations

A central tool of nonlinear anelasticity is the multiplicative decomposition of the deformation tensor that assumes that the deformation gradient can be decomposed as a product of an elastic and an anelastic tensor. It is usually justified by the existence of an intermediate configuration. Yet, this configuration cannot exist in Euclidean space, in general, and the mathematical basis for this assumption is on unsatisfactory ground.

Patnaik's picture

Call for Papers - Bioengineering (ISSN 2306-5354) - PubMed Indexed

Excited to announce that Anthony Lau and I are editing a special issue for Bioengineering (ISSN 2306-5354)- Pubmed Indexed - Quantification of Biological and Mechanical Changes Due to Radiation Exposure. Deadline for manuscript submissions: 30 June 2021.

Link : 

Special Issue Editors

ChangyongCao's picture

Journal Club for December 2020: 3D Printing of Batteries: Fabrication, Materials and Challenges

3D Printing of Batteries: Fabrication, Materials and Challenges 

Yaokun Pang, Changyong Cao*

Laboratory for Soft Machines & Electronics, Michigan State University


1. Introduction

Fan Xu's picture

Oblique wrinkling patterns on liquid crystal polymer core–shell cylinders under thermal load

Smart soft materials, which can flexibly respond to external multi-physics stimuli, have attracted considerable attention over the past few years. Here, we present tunable wrinkling patterns in cylindrical core-shell systems under thermal load via the orientation of director in nematic liquid crystal polymer (LCP). To quantitatively analyze mechanical behavior and morphological evolution of LCP core-shell cylinders, we develop a core-shell model that accounts for director-induced anisotropic spontaneous strains.

Xiaoding Wei's picture

A new continuum model for metallic glass based on thermodynamics

My group at Peking University proposed a novel mechano-chemical continuum model based on the framework of thermodynamics that can describe the microstructural evolution in metallic glass, and connect it with the macroscopic plastic deformation. The model successfully simulated the shear band instability and dilatancy effects of metallic glass under uniaxial tension and simple shear.

surot's picture

VUMAT viscoelasticity (Maxwell model)

Dear all,

I would like to ask you for advice. I am about to simulate a pull-through test (see attached picture) of a cladding panel made of a material with highly viscoelastic behaviour. I have parameters for Maxwell model (Prony series) obtained from test. I expect large deformation and probably cone failure (or tearing of the cladding panel). Therefore I would like to use Abaqus/Explicit. The problem is that I cannot use *visco step together with Explicit. Is there any way to solve it?

Teng Li's picture

EML Webinar on 11 November 2020 on Mechanobiology: A Tale of Stressed Life by Sulin Zhang

EML Webinar on 11 November 2020 will be given by Sulin Zhang, Penn State University. Discussion leader: Teng Li, University of Maryland

Title: Mechanobiology: A Tale of Stressed Life

Emilio Martínez Pañeda's picture

Phase field modelling of fracture and fatigue in Shape Memory Alloys

Dear iMechanicians. I hope that the following paper is of interest to you. We develop the first phase field formulation for fracture (and fatigue) in Shape Memory Alloys. Its potential is demonstrated by solving a variety of paradigmatic 2D and 3D boundary value problems, from R-curves to fatigue cracking of a NiTi biomedical stent.

M. Simoes, E. Martínez-Pañeda. Phase field modelling of fracture and fatigue in Shape Memory Alloys. Computer Methods in Applied Mechanics and Engineering 373 (2021) 113504

Teng Li's picture

EML Webinar on 4 November 2020 on Topological adhesion, wet and elastic by Zhigang Suo

EML Webinar on 4 November 2020 will be given by  Zhigang Suo, Harvard University. Discussion leader: Jimmy Hsia, Nanyang Technological University

Title: Topological adhesion, wet and elastic


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