scholarly journals Overall mechanical behavior of nanocrystalline materials accompanied by damage evolution on grain boundaries

2013 ◽  
Vol 23 (1) ◽  
pp. 25-42 ◽  
Author(s):  
Li Chen ◽  
Yueguang Wei
Keyword(s):  
Mechanical Behavior ◽  
Grain Boundaries ◽  
Nanocrystalline Materials ◽  
Damage Evolution

Deformation Twins Formed in Nanocrystalline Materials

2006 ◽  
Vol 503-504 ◽  
pp. 125-132 ◽  
Author(s):  
Yuntian T. Zhu
Keyword(s):  
Grain Boundaries ◽  
Nanocrystalline Materials ◽  
Partial Dislocation ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Nucleation And Growth ◽  
Analytical Models ◽  
Partial Dislocations ◽  
Deformation Twins ◽  
Low Strain Rate

Deformation twins have been oberved in nanocrystalline (NC) Al synthsized by cryogenic ball-milling and in NC Cu processed by high-pressure torsion under room temperature and at a very low strain rate. They were found formed by partial dislocations emitted from grain boundaries. This paper first reviews experimental evidences on deformation twinning and partial dislocation emissions from grain boundaries, and then discusses recent analytical models on the nucleation and growth of deformation twins. These models are compared with experimental results to establish their validity and limitations.

Two-Way Coupled Multiscale Model for Predicting Mechanical Behavior of Bone Subjected to Viscoelastic Deformation and Fracture Damage

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Taesun You ◽  
Yong-Rak Kim ◽  
Taehyo Park
Keyword(s):  
Mechanical Behavior ◽  
Material Properties ◽  
Damage Evolution ◽  
Multiscale Model ◽  
Local Scale ◽  
Viscoelastic Deformation ◽  
Rate Dependent ◽  
Deformation And Fracture ◽  
Evolution Characteristics ◽  
Fracture Damage

This paper presents a two-way linked computational multiscale model and its application to predict the mechanical behavior of bone subjected to viscoelastic deformation and fracture damage. The model is based on continuum thermos-mechanics and is implemented through the finite element method (FEM). Two physical length scales (the global scale of bone and local scale of compact bone) were two-way coupled in the framework by linking a homogenized global object to heterogeneous local-scale representative volume elements (RVEs). Multiscaling accounts for microstructure heterogeneity, viscoelastic deformation, and rate-dependent fracture damage at the local scale in order to predict the overall behavior of bone by using a viscoelastic cohesive zone model incorporated with a rate-dependent damage evolution law. In particular, age-related changes in material properties and geometries in bone were considered to investigate the effect of aging, loading rate, and damage evolution characteristics on the mechanical behavior of bone. The model successfully demonstrated its capability to predict the viscoelastic response and fracture damage due to different levels of aging, loading conditions (such as rates), and microscale damage evolution characteristics with only material properties of each constituent in the RVEs.

Grain Size Distribution Effect on Mechanical Behavior of Nanocrystalline Materials

2004 ◽  
Vol 821 ◽  
Author(s):  
A.V. Sergueeva ◽  
N.A. Mara ◽  
A.K. Mukherjee
Keyword(s):  
Grain Size ◽  
Mechanical Behavior ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Nanocrystalline Materials ◽  
Tensile Deformation ◽  
Size Structure ◽  
Niti Alloy ◽  
Distribution Effect ◽  
The Matrix

AbstractGrain size distribution effect on the mechanical behavior of NiTi and Vitroperm alloys were investigated. Yielding at significantly lower stresses than found in equiaxed counterparts, along with well defined strain hardening was observed in these nanocrystalline materials with large grains embedded in the matrix during tensile deformation at temperatures of 0.4Tm. At higher temperature the effect of grain size distribution on yield stress was not revealed while plasticity was increased in 50% in NiTi alloy with bimodal grain size structure.

What is Behind the Inverse Hall-Petch Behavior in Nanocrystalline Materials?

2006 ◽  
Vol 976 ◽  
Author(s):  
Christopher Carlton ◽  
P. J. Ferreira
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Strain Rate ◽  
Grain Boundaries ◽  
Nanocrystalline Materials ◽  
Critical Value ◽  
Petch Relationship ◽  
And Diffusion ◽  
Critical Grain Size

AbstractAn inverse Hall-Petch effect has been observed for nanocrystalline materials by a large number of researchers. This result implies that nanocrystalline materials get softer as grain size is reduced below a critical value. Postulated explanations for this behavior include dislocation based mechanisms and diffusion based mechanisms. In this paper, we report an explanation for the inverse Hall-Petch effect based on the statistical absorption of dislocations by grain boundaries, showing that the yield strength is both dependent on strain rate and temperature, and that it deviates from the Hall-Petch relationship at a critical grain size.

Computational Approach of the Cortical Bone Mechanical Behavior Based on an Elastic Viscoplastic Damageable Constitutive Model

2020 ◽  
Vol 12 (07) ◽  
pp. 2050081
Author(s):  
Tesnim Kraiem ◽  
Abdelwahed Barkaoui ◽  
Tarek Merzouki ◽  
Moez Chafra
Keyword(s):  
Mechanical Behavior ◽  
Bone Quality ◽  
Damage Evolution ◽  
Sensitivity Study ◽  
Computational Approach ◽  
Material Behavior ◽  
The Finite Element Method ◽  
Non Invasive ◽  
Applied Loading ◽  
Good Agreement

Bone mechanical behavior varies according to the mechanical loading to which it is subjected, and its response effectiveness mainly depends on its quality. Thus, measuring the indicators controlling the bone quality is required to assess its strength. Indeed, the Finite Element Method (FEM) provides a non-invasive tool to interpret bone quality. Therefore, this work coupled the FEM with a micromechanical law, aiming to provide an exhaustive description of the human bone mechanical behavior. Anisotropy, viscoplasticity and damage were introduced in the material behavior law and the damage evolution was plotted based on the applied loading. Then a sensitivity study was conducted to evaluate the effects of viscoplasticity and damage parameters on bone behavior. The obtained numerical results were in a good agreement with the previously reported experimental data and allowed to distinguish key parameters from non-significant ones. This new computational model provided a better understanding of the main parameters affecting bone behavior.

Further Advances on Concrete Coating Impact on Pipeline Strength

2017 ◽  
Author(s):  
Alberto Battistini ◽  
Luca Catena ◽  
Adelina Mancini ◽  
Lorenzo Marchionni ◽  
Antonio Parrella ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Damage Evolution ◽  
Bending Stiffness ◽  
The State ◽  
Fe Model ◽  
Deformation Capacity ◽  
Strain Concentration ◽  
Concrete Damage ◽  
Strength And Deformation ◽  
Concrete Coating

Concrete Weight Coating is used in offshore industry to provide for pipeline vertical and lateral stability against waves and currents and to guarantee protection against fishing activities. Reinforced concrete coating of adequate strength, especially in case of thick coatings for stringent in-place stability requirements, entails additional bending stiffness and consequently strain concentration at field joints, thus significantly affecting the state of stress and strain on the pipe steel during laying firstly, and then during operations. Attention of the offshore pipeline industry has been focused in the development of experimental and theoretical activities in a more scientific way, which aimed to satisfy the need of a better knowledge in this field. Both analytical and FEM solutions are available in the free literature and relevant standards to predict the contribution of concrete coating layer on global pipeline strength and deformation capacity and simplified threshold values for the concrete damage are provided, as well. Generally, for installation analysis purpose, a pipeline with equivalent mechanical behavior (bending moment-curvature relationship) and physical (weight) properties is used in installation and operation analyses. No assumptions are typically made on concrete damage evolution to evaluate the decay of pipe capacity beyond the elastic range. In this paper new advances in modelling the mechanical behavior of concrete coated joints are discussed. In particular an advanced ABAQUS finite element model is proposed to take into account the effect of concrete coating damage on the overall capacity. The following effects have been accounted: • Non-linear stress-strain relationship of the steel at large usage factors/curvatures on the strain concentration at the field joint. • Concrete coating damage evolution on global pipeline bending stiffness. In this paper: • The state-of-the-art about published materials, numerical studies and design approaches on concrete material modelling and concrete coated pipes is briefly presented; • A FEM based analysis methodology is drawn and proposed for the strength and deformation capacity assessment of a concrete coated pipe; • The FEM model is calibrated on available full scale tests; • The results of a project case study performed with ABAQUS FE Model are given.

Self-Diffusion Parameters of Grain Boundaries and Triple Junctions in Nanocrystalline Materials

2011 ◽  
Vol 309-310 ◽  
pp. 45-50 ◽  
Author(s):  
Aleksey Lipnitskii ◽  
I.V. Nelasov ◽  
Yurii Kolobov
Keyword(s):  
Grain Boundaries ◽  
Nanocrystalline Materials ◽  
Boundary Diffusion ◽  
Coarse Grained ◽  
Triple Junctions ◽  
Dynamic Simulations ◽  
Self Diffusion ◽  
Diffusion Parameters ◽  
Diffusion Characteristics ◽  
First Time

Suggested methods describe the process of self-diffusion along grain boundaries and triple junctions in polycrystals without using geometric models of the grain boundaries structure. The calculation method introduced diffusion characteristics along grain boundaries derived from the results of molecular dynamic simulations of nanocrystalline materials. The diffusion experiments were imposed to establish relationship between introduced diffusion characteristics and the diffusion parameters along grain boundaries and triple junctions of the Fisher’s grain boundary diffusion model. By the example of copper for the first time the characteristics of self-diffusion along grain boundaries of nanocrystalline materials and coarse grained analog defined in the same temperature range was compared for the first time. It was found that values of the self-diffusion characteristics along grain boundaries in high purity nanocrystalline and polycrystalline copper are equal at the same temperatures.

Sign in / Sign up

Export Citation Format

Share Document