Frontiers in Materials Science and Technology

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Authors: W.L. Wang, Yuan Tong Gu, Liang Chi Zhang
Abstract: Meshless method has advantages in analyzing the deformation around a crack. However, the effectiveness of such method is influenced by the treatment of local support domain which is a base for an appropriate selection of field nodes in the construction of shape functions. In the current practice, the methods to determine support domain have some drawbacks. It is therefore beneficial to develop a more flexible technique for determining the support domain in crack simulation. This paper presents such a technique which could be used in both regularly and irregularly distributed nodes. Numerical examples show that the technique produces accurate results in these two situations. Moreover, the new technique can be integrated with different types of meshless methods to provide an effective way in handling arbitrary nodal distribution to meet the needs of solutions to problems with complex geometric boundaries.
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Authors: Sam Yang, Scott Furman, Andrew Tulloh
Abstract: A mathematical model has been developed for predicting material compositional microstructures using measured data as constraints. Examples of measured data include 3-D sets of tomography data, 2-D sets of compositional data on surfaces and sections, and material absorption and interaction properties. The model has been partially implemented as a MS-Windows application. Reasonable agreement has been obtained between the numerical predictions from the software and the simulated data. The predicted microstructures could be used to study various material properties such as porosity distribution, diffusion and corrosion.
267
Authors: H. Wang, Q. Li
Abstract: A model based on the cellular automaton (CA) technique for the simulation of solidification microstructure has been developed. An improved solid fraction calculating method is used, in which the solid fraction of the interface unit is calculated by temperature compensation method combined with local equilibrium phase diagram. And then, a quadratic equation of solid fraction can be calculated according to the local temperature, solute concentration and curvature. The method avoids the assumption of the position and shape of solid/liquid interface. By using this model on A356 aluminium alloy, a dendrite growth process is simulated. The model can predict the final microstructure both grain size and grain morphology. It also predicts the Si concentration distribution in both solid and liquid phases.
271
Authors: Luis F. Herrera, Duong D. Do, Greg R. Birkett
Abstract: The determination of the properties of porous solids remains an integral element to the understanding of adsorption, transport and reaction processes in new and novel materials. The advent of molecular simulation has led to an improved understanding and prediction of adsorption processes using molecular models. These molecular models have removed the constraints of traditional adsorption theories, which require rigid assumptions about the structure of a material. However, even if we possess a full molecular model of a solid, it is still desirable to define the properties of this solid in a standard manner with quantities such as the accessible volume, surface area and pore size distribution. This talk will present Monte Carlo integration methods for calculating these quantities in a physically meaningful and unambiguous way. The proposed methods for calculating the surface area and pore size distribution were tested on an array of idealised solid configurations including cylindrical and cubic pores. The method presented is adequate for all configurations tested giving confidence to its applicability to disordered solids. The method is further tested by using several different noble gas probe molecules. Finally, the results of this technique are compared against those obtained by applying the BET equation for a range of novel materials.
275
Authors: Sachin Patil, Shi Wei Zhou, Qing Li
Abstract: Despite significant success in developing various periodic composites, the challenge remains how to more efficiently design the base cell so that one or more physical properties can be attained. In this paper, the material design problem is formulated in a form of the least square of the difference between the targeted and designed values. By minimizing the objective subject to volume constraints and periodic boundary conditions, an optimal material distribution in base cell can be generated. Different from existing methods, this paper shows how to use the Evolutionary Structural Optimization (ESO) method to design composite material attaining to thermal conductivity defined by the Hashin-Strikman (H-S) bounds. The effectiveness of this method is demonstrated through several 2D examples, agreeing well with commonly known benchmarking microstructures.
279
Authors: S.A. Asgari, Peter D. Hodgson, Vincent Lemiale, C. Yang, Bernard F. Rolfe
Abstract: Advanced High Strength Steels (AHSS) offer outstanding characteristics for efficient and economic use of steel. The unique features of AHSS are direct result of careful heat treatment that creates martensite in the steel microstructure. Martensite and carbon content in the microstructure greatly affects the mechanical properties of AHSS, underlining more importance on microstructural discontinuities and their multiphase characteristics. In this paper, we present the Multiscale Particle-In-Cell (MPIC) method for microstructural modelling of AHSS. A specific particle method [1] usually used in fluid mechanics is adapted and implemented in a parallel multiscale framework. This multiscale method is based on homogenisation theories; with Particle-In-Cell (PIC) method in both micro and macroscale, and offers several advantages in comparison to finite element (FE) based formulation. Application of this method to a benchmark uniaxial tension test is presented and compared with conventional FE solutions.
285
Authors: Ye Lu, Lin Ye, Dong Wang, Guang Meng
Abstract: A piezoelectric active sensor network is configured to collect the wave scattering from a throughthickness hole on an aluminium rectangular tube. It is found that guided waves are capable of propagating across the tube edges, while keeping the sensitivity to the damage even not on surfaces where the actuator and sensor are located. Signal correlation between the intact and damaged structure is evaluated and the probability distribution of damage is thus achieved on the unfolded tube surface.
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