The Experts below are selected from a list of 18045 Experts worldwide ranked by ideXlab platform

Veronique Favier - One of the best experts on this subject based on the ideXlab platform.

  • Micromechanical Modelling of twinning-induced plasticity steels
    Scripta Materialia, 2012
    Co-Authors: Veronique Favier, D Barbier
    Abstract:

    The paper discusses a number of issues related to the development of a Micromechanical polycrystalline model for twinning-induced plasticity steels: twinning features that have to be incorporated, identification procedure, description of the work hardening, role of the texture and the role of the interaction law between grains. Monotonous and reverse strain paths are investigated.

  • Micromechanical Modelling of the elastic viscoplastic response of metallic alloys under rapid compression in the semi solid state
    Acta Materialia, 2011
    Co-Authors: Veronique Favier, Helen V Atkinson
    Abstract:

    Semi-solid processing is used commercially to produce a variety of components and it is therefore important to be able to model the die fill. Micromechanical Modelling is one approach to this. Here we compare the Micromechanical predictions for the load vs. displacement, in tests where a cylindrical billet is rapidly compressed, with previous experimental findings for an A356 aluminium alloy. Purely viscoplastic Modelling is shown to be inadequate. We propose a new model that clearly associates the elastic-type response with the saturated solid skeleton. This gives much more accurate prediction of the initial peak and of the form of the curve as the skeleton breaks down under load. In agreement with experiment, the model predicts the time for the solid skeleton breakdown and that the peak load increases with increasing ram speed and with decreasing fraction liquid.

  • transient and non isothermal semi solid behaviour 3d Micromechanical Modelling
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2009
    Co-Authors: Veronique Favier, Pierre Cezard, Regis Bigot
    Abstract:

    Abstract Simulating semi-solid metal forming requires Modelling of semi-solid behaviour. However, such Modelling is difficult because semi-solid behaviour is thixotropic and depends on the liquid–solid spatial distribution within the material. In order to better understand and model the relationships between the microstructure and the behaviour, this paper presents a model based on Micromechanical approaches and homogenisation techniques. Shear rate jump tests for solid fraction lower than 0.5 and compression tests for solid fraction higher than 0.5 were simulated. Predicted transient responses for both types of tests are in qualitative agreement with experimental results. The gradual stress decrease in step-change up in shear rate is associated with the disagglomeration of isolated solid aggregates while the sharp fall in load observed in the load–displacement curves originates from a 3D continuous solid skeleton, which suddenly breaks down under load. These microstructural changes are related to the shear rate field distribution.

Thomas K. Bader - One of the best experts on this subject based on the ideXlab platform.

  • structure function relationships in hardwood insight from Micromechanical Modelling
    Journal of Theoretical Biology, 2014
    Co-Authors: Karin De Borst, Thomas K. Bader
    Abstract:

    A Micromechanical model is presented that predicts the stiffness of wood tissues in their three principal anatomical directions, across various hardwood species. The wood polymers cellulose, hemicellulose, and lignin, common to all wood tissues, serve as the starting point. In seven homogenisation steps, the stiffnesses of these polymers are linked to the macroscopic stiffness. The good agreement of model predictions and corresponding experimental data for ten different European and tropical species confirms the functionality and accuracy of the model. The model enables investigating the influence of individual microstructural features on the overall stiffness. This is exploited to elucidate the mechanical effects of vessels and ray cells. Vessels are shown to reduce the stiffness of wood at constant overall density. This supports that a trade-off exists between the hydraulic efficiency and the mechanical support in relation to the anatomical design of wood. Ray cells are shown to act as reinforcing elements in the radial direction.

  • Structure-function relationships in hardwood--insight from Micromechanical Modelling.
    Journal of Theoretical Biology, 2013
    Co-Authors: Karin De Borst, Thomas K. Bader
    Abstract:

    Abstract A Micromechanical model is presented that predicts the stiffness of wood tissues in their three principal anatomical directions, across various hardwood species. The wood polymers cellulos ...

M H Aliabadi - One of the best experts on this subject based on the ideXlab platform.

  • meshfree based Micromechanical Modelling of twill woven composites
    Composites Part B-engineering, 2020
    Co-Authors: Y H Chen, M H Aliabadi
    Abstract:

    Abstract This paper presents a novel, meshfree-based Micromechanical model for homogenising the elastic properties and analysing the deformation and microscopic strains/stresses of twill woven composites. The proposed model was based on a minimum unit cell (mUC) whose internal features such as the cross-sectional shape and waviness of yarns were described by using sophisticated functions. The boundary conditions imposed on the mUC were derived by applying an equivalence approach, which converts the standard form of periodic boundary conditions into a generic set of fixed and relative displacement constraints. Theoretical formulations were developed to implement the Micromechanical model within the framework of the moving kriging (MK)-based element-free Galerkin (EFG) method. An in-house computer program implementing the proposed model was developed for analysing a typical twill woven composite. Good agreements were found between the meshfree-based predictions and the reference results, highlighting the proposed model capable of homogenising twill woven composites and meanwhile avoiding the commonly required pre-processing tasks such as building an explicit geometry model and generating identical meshes on the mapping surfaces to enforce boundary conditions. Three case studies were also performed to identify the sensitivities of the predicted results to three numerical parameters, i.e. the total number of field nodes, the total number of background cells, and the support domain scaling factor. The results of these studies suggest that the numbers of field nodes and background cells used must be sufficiently large, while the support domain scaling factor in an appropriate range (e.g. 2.0−3.25) to achieve convergent results.

  • Micromechanical Modelling of the overall response of plain woven polymer matrix composites
    International Journal of Engineering Science, 2019
    Co-Authors: Y H Chen, M H Aliabadi
    Abstract:

    Abstract This paper presents a novel approach to Micromechanical Modelling of plain woven polymer matrix composites and predicting the overall response including the nonlinear and rate-dependent behaviour. The nonlinearity and rate-dependence of plain woven composites is evaluated by describing the behaviour of the polyer matrix using a viscoplastic model. The damage evolution of the yarn material and deformation of the woven fabric are investigated by considering Weibull distribution based formulations and a shear-modulus discount approach, respectively. The explicit meshfree method with time-dependent periodic boundary conditions for unit cell (UC) models that describe the internal architecture of plain woven composites is presented for the first time. For validation, numerical examples are performed to simulate the EP121-C15-53 plain woven composite subjected to in-plane normal/off-axis tensile loading conditions and at three different strain rates, i.e. 10−1 s−1, 10−3 s−1 and 10−5 s−1. Good agrements are found between the numerical and experimental results, with both the quasi-linear, rate-insensitive behaviour in the normal direction and the nonlinear, rate-dependent response in the off-axis direction successfully predicted.

  • Micromechanical Modelling of cohesive thermoelastic cracking in orthotropic polycrystalline materials
    Computer Methods in Applied Mechanics and Engineering, 2018
    Co-Authors: G Geraci, M H Aliabadi
    Abstract:

    Abstract In this paper a new Micromechanical formulation is proposed for Modelling thermoelastic intergranular and transgranular damage and microcracking evolution in brittle polycrystalline materials. Polycrystalline microstructures are created through a Voronoi tessellation algorithm. Each crystal has an elastic orthotropic behaviour. Damage evolution along (inter- or trans-granular) interfaces is modelled using thermo-mechanical cohesive laws and, upon failure, non-linear frictional contact analysis is introduced to model separation, stick or slip. Numerical simulations are presented either to demonstrate the validity and study the physical implications of the proposed thermoelastic formulation, in comparison with other numerical methods as well as experimental observations and literature results.

Ziaei S Rad - One of the best experts on this subject based on the ideXlab platform.

  • Micromechanical Modelling of damage behaviour of ti 6al 4v
    Materials & Design, 2013
    Co-Authors: S Katani, F Madadi, M Atapour, Ziaei S Rad
    Abstract:

    Abstract The effort of this study is to develop a simulation method to predict the effect of microstructural morphology in mechanical properties and failure mechanism of Ti–6Al–4V with 55% α and 45% β. Finite element models were then created based on a clarification of a damage mechanism to control the ductile cracking with focusing on the heterogeneity in strength of microstructure. By the way, Simulation for the dimple failure of the material, using the Gurson–Tvergaard–Needleman (GTN) model, will be presented. The large number of micro-voids nucleation at lower strength side near two phase boundary associated with the localisation of stress/strain is found to control ductile cracking. Numerical simulations, which were carried out using the scanning electron micrograph, are able to predict the void initiation in the material. During fractography of the material, some evidence is observable which can validate the results obtained by the simulation. The good correlation between the numerical and experimental observations from fractographic and tensile test results shows the efficiency of the proposed models in predicting the failure mechanism of Ti–6Al–4V.

Athanasios Skarpas - One of the best experts on this subject based on the ideXlab platform.

  • Micromechanical Modelling of complex shear modulus of crumb rubber modified bitumen
    Materials & Design, 2020
    Co-Authors: Haopeng Wang, Xueyan Liu, Hong Zhang, P. Apostolidis, Sandra Erkens, Athanasios Skarpas
    Abstract:

    Abstract Crumb rubber modified bitumen (CRMB) can be considered as a binary composite system where rubber particles are embedded in the bitumen matrix. The bitumen-rubber interaction process (mainly swelling) significantly changes the mechanical properties of both bitumen and rubber phases. This study aims to predict the complex moduli of CRMB binders with more representative constituent parameters using Micromechanical models. To achieve this goal, frequency sweep tests using a dynamic shear rheometer were performed on the liquid phase of CRMB and swollen rubber samples to represent the essential properties of bitumen matrix and rubber inclusion. In addition, the numerical swelling model was developed to estimate the effective volume concentration of rubber after swelling. Results show that the liquid phases of CRMB are stiffer and more elastic than the neat bitumen while the swollen rubber is softer and more viscous than the dry rubber. The effective volume concentration of rubber can increase to 2.126 times as the blend percentage based on the finite element analysis. Using the liquid phase of CRMB binder and swollen rubber properties as the Micromechanical model inputs yield more accurate predictions. The used four Micromechanical models predict well at higher frequencies while underestimating the complex modulus at lower frequencies.