Papers by Keyword: Multiscale Modelling

Abstract: The superplastic performance of the dual-phase Ti-6242S titanium alloy makes it a good material for aerospace application to produce structural components using the advanced superplastic forming (SPF) process. The need to optimize the SPF process demands the understanding and quantifications of the influence of the different phase constituents - α and β on the global superplastic behavior. Numerical modelling has been useful to predict mechanical behavior for both one-level and multiscale approach. Multiscale approach: bottom-up (microscale to macroscale) has enabled to understand how the different microstructural parameters influence global material/structural mechanical response; which by large means the modelling approach depends on the material local properties. The identification of these local properties is non-trivial in polycrystal materials, particularly at superplastic (elevated) temperatures. We have developed a methodology that permit us to quantify the microstructural parameters of each of the constitutive phases of a polycrystal at a superplastic temperature using genetic algorithm optimization method on the data from in-situ high energy X-ray diffraction (synchrotron radiation), coupled with SEM (scanning electron microscope) and EBSD (electron backscattered diffraction). These identified local microstructural parameters were directly used in the finite strain crystal plasticity model to simulate the material global response. This approach enabled the quantification of the phase influences on global behavior with much accuracy. It was found that α phase planes have high critical resolved shearing stress (CRSS) at 730°C which is similar to its behaviours at room temperatures, while β phase slip planes have low CRSS that encourage slip shearing at low stress. However, more applied load is partitioned in β phase than in α phase, despite that β phase fraction is about 15% at 730°C. Keyword: Multiscale modelling, CPFE, optimization, HEXRD, dual-phase titanium alloy, superplasticity

Abstract: This paper presents homogenization of twill woven composites. It includes presenting formulated geometrical unit cell models, establishing meshfree micromechanical and CDM models for twill woven composites. The results cover meshfree nodal distributions, meshfree yarn geometries, predicted mechanical properties, effectiveness of yarn waviness, non-linear stress-strain relation of unit cell, stress distributions inside unit cell volume, and necessary comparisons with existing literatures.

Abstract: In this paper, an effective approach to couple finite elements (FEs) with discrete elements (DEs) is presented. The proposed approach conforms to displacement compatibility condition at the interface between FEs and DEs, and this constraint is enforced by the Lagrange multiplier method. The coupling system is solved by the Gauss-Seidel iteration strategy and the incompatibility of degrees of freedom between FEs and DEs can be effectively addressed. Two numerical examples are employed for validation and the effectiveness of the proposed approach is also demonstrated via comparison with other numerical methods.

Abstract: This paper presents a three-dimensional multiscale computational model, which is proposed to combine the simplicity of FEM model and the atomistic interactions between two solids. A significant advantage of the model is that atoms are populated in the contact regions, which saves significant computation time compared to fully MD simulations. The model is used in the case of asperity contact. The normal displacement, contact radius and pressure distribution are compared with those from Hertz’s solution and atomistic simulations in the literature. Some important features of nanoscale contacts obtained by MD simulations can be caught by the model with acceptable accuracy and low computational cost.

Abstract: The multiscale modelling of the behaviour of metal alloys during processing is often limited by the computing power required to run them. The Agile Multiscale Methodology was conceived to enhance the designing and controlling of complex multiscale models through an automatic run-time adaptation of its constitutive sub-models. This methodology is used to simulate the behaviour of an 6082 aluminium alloy during its thermomechanical treatment. The macroscopic deformation, the work-hardening and the state of precipitation are computed in different modules, allowing the coupling of several software solutions (DEFORM^TM2D and © MatCalc) through an external storage of the relevant data.