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  • Open Access

    ARTICLE

    A Chain Approach of Boundary Element Row-Subdomains for Simulating the Failure Processes in Heterogeneous Brittle Materials

    Zhenhan Yao1, Lingfei Gao1

    CMC-Computers, Materials & Continua, Vol.9, No.1, pp. 1-24, 2009, DOI:10.3970/cmc.2009.009.001

    Abstract To improve the effectiveness of the lattice model for simulating the failure processes of heterogeneous brittle materials, each lattice element is refined as a subdomain with homogenous material, and is modeled by the boundary element method in this paper. For simplicity, each subdomain is modeled with constant boundary elements. To enhance the efficiency, a row of sub-domains is formed, and then a chain structure of such row-subdomain is constructed. The row-equation systems are solved one by one, and then back substituted, to obtain the final solution. Such a chain subdomain approach of the boundary element… More >

  • Open Access

    ARTICLE

    An Analytical Method for Computing the One-Dimensional Backward Wave Problem

    Chein-ShanLiu1

    CMC-Computers, Materials & Continua, Vol.13, No.3, pp. 219-234, 2009, DOI:10.3970/cmc.2009.013.219

    Abstract The present paper reveals a new computational method for the illposed backward wave problem. The Fourier series is used to formulate a first-kind Fredholm integral equation for the unknown initial data of velocity. Then, we consider a direct regularization to obtain a second-kind Fredholm integral equation. The termwise separable property of kernel function allows us to obtain an analytical solution of regularization type. The sufficient condition of the data for the existence and uniqueness of solution is derived. The error estimate of the regularization solution is provided. Some numerical results illustrate the performance of the More >

  • Open Access

    ARTICLE

    Statistics of High Purity Nickel Microstructure From High Energy X-ray Diffraction Microscopy

    C.M. Hefferan1, S.F. Li1, J. Lind1, U. Lienert2, A.D. Rollett3, P. Wynblatt3, R.M. Suter1,3

    CMC-Computers, Materials & Continua, Vol.14, No.3, pp. 209-220, 2009, DOI:10.3970/cmc.2009.014.209

    Abstract We have measured and reconstructed via forward modeling a small volume of microstructure of high purity, well annealed nickel using high energy x-ray diffraction microscopy (HEDM). Statistical distributions characterizing grain orientations, intra-granular misorientations, and nearest neighbor grain misorientations are extracted. Results are consistent with recent electron backscatter diffraction measurements. Peaks in the grain neighbor misorientation angle distribution at 60 degrees (∑3) and 39 degrees (∑9) have resolution limited widths of ≈ 0.14 degree FWHM. The analysis demonstrates that HEDM can recover grain and grain boundary statistics comparable to OIM volume measurements; more extensive data sets More >

  • Open Access

    ARTICLE

    Measurements of the Curvature of Protrusions/Retrusions on Migrating Recrystallization Boundaries

    Y.B. Zhang1, A. Godfrey2, D. Juul Jensen1

    CMC-Computers, Materials & Continua, Vol.14, No.3, pp. 197-208, 2009, DOI:10.3970/cmc.2009.014.197

    Abstract Two methods to quantify protrusions/retrusions and to estimate local boundary curvature from sample plane sections are proposed. The methods are used to evaluate the driving force due to curvature of the protrusions/retrusions for partially recrystallized pure nickel cold rolled to 96% reduction in thickness. The results reveal that the values calculated by both these methods are reasonable when compared with the stored energy measured by differential scanning calorimetry. The relationship between protrusions and the average stored energy density in the deformed matrix is also investigated for partially recrystallized pure aluminum cold rolled to 50%. The More >

  • Open Access

    ARTICLE

    EBSD-Based Microscopy: Resolution of Dislocation Density

    Brent L. Adams, Joshua Kacher

    CMC-Computers, Materials & Continua, Vol.14, No.3, pp. 185-196, 2009, DOI:10.3970/cmc.2009.014.185

    Abstract Consideration is given to the resolution of dislocation density afforded by EBSD-based scanning electron microscopy. Comparison between the conventional Hough- and the emerging high-resolution cross-correlation-based approaches is made. It is illustrated that considerable care must be exercised in selecting a step size (Burger's circuit size) for experimental measurements. Important variables affecting this selection include the dislocation density and the physical size and density of dislocation dipole and multi-pole components of the structure. It is also illustrated that simulations can be useful to the interpretation of experimental recoveries. More >

  • Open Access

    ARTICLE

    Identification of Particle Stimulated Nucleation during Recrystallization of AA 7050

    D.P. Field1, L. Behrens2, J.M. Root1

    CMC-Computers, Materials & Continua, Vol.14, No.3, pp. 171-184, 2009, DOI:10.3970/cmc.2009.014.171

    Abstract Mechanical properties of polycrystalline metals are dependent upon the arrangement of microstructural features in the metal. Recrystallization is an important phenomenon that often occurs during thermo-mechanical processing of metals. This work focuses upon aluminum alloy 7050 and uses crystallographic texture and pair correlation functions of recrystallized grains to characterize the dominance of particle stimulated nucleation in the recrystallization process. The randomization of the recrystallization texture and similar pair correlation functions for the particle distribution and the recrystallization nuclei distribution indicate that particle stimulated nucleation controls the recrystallization behavior in this alloy. More >

  • Open Access

    ARTICLE

    An Eulerian-Based Formulation for Studying the Evolution of the Microstructure under Plastic Deformations

    S.Ahmadi1, B.L.Adams1 , D.T.Fullwood1

    CMC-Computers, Materials & Continua, Vol.14, No.2, pp. 141-170, 2009, DOI:10.3970/cmc.2009.014.141

    Abstract In this paper, a model is introduced to examine the evolution of the microstructure function under plastic deformations. This model is based upon a double continuity relationship that conserves both material particles in the mass space and orientations in the orientation space. An Eulerian description of the motion of material particles and orientations is considered, and continuity relations are derived for both spaces. To show how the proposed model works, two different case studies are provided. In the mass space, the continuity relation is used to examine the evolution of the microstructure function of a More >

  • Open Access

    ARTICLE

    Modeling Intergranular Crack Propagation in Polycrystalline Materials

    M.A.Arafin1, J.A.Szpunar2

    CMC-Computers, Materials & Continua, Vol.14, No.2, pp. 125-140, 2009, DOI:10.3970/cmc.2009.014.125

    Abstract A novel microstructure, texture and grain boundary character based model has been proposed to simulate the intergranular crack propagation behavior in textured polycrystalline materials. The model utilizes the Voronoi algorithm and Monte Carlo simulations to construct the microstructure with desired grain shape factor, takes the texture description of the materials to assign the orientations of the grains, evaluates the grain boundary character based on the misorientation angle - axis calculated from the orientations of the neighboring grains, and takes into account the inclination of grain boundaries with respect to the external stress direction. Markov Chain More >

  • Open Access

    ARTICLE

    Studies of Texture Gradients in the Localized Necking Band of AA5754 by EBSD and Microstructure-Based Finite Element Modeling

    Xiaohua Hu1, Gordana A. Cingara1, David S. Wilkinson1, Mukesh Jain2, PeidongWu2, Raja K. Mishra3

    CMC-Computers, Materials & Continua, Vol.14, No.2, pp. 99-124, 2009, DOI:10.3970/cmc.2009.014.099

    Abstract This work aims to understand the texture distribution in the localized necking band formed during uni-axial tension of AA5754 using an edge-constrained, plane strain post-necking FE model. The model domain is a long cross section of the band. Initial grain structure is mapped into the mesh from EBSD data using a modified Voroni-cell interpolation and considering pre-straining prior to localized necking. The material points in grains are assumed to exhibit isotropic elastoplastic behavior but have a relative strength in terms of Taylor factors which are updated by a Taylor-Bishop-Hill model. The predicted textures and gradients More >

  • Open Access

    ARTICLE

    Applications of the Phase-Coded Generalized Hough Transform to Feature Detection, Analysis, and Segmentation of Digital Microstructures

    Stephen R. Niezgoda1, Surya R. Kalidindi1,2

    CMC-Computers, Materials & Continua, Vol.14, No.2, pp. 79-98, 2009, DOI:10.3970/cmc.2009.014.079

    Abstract The generalized Hough transform is a common technique for feature detection in image processing. In this paper, we develop a size invariant Hough framework for the detection of arbitrary shapes in three dimensional digital microstructure datasets. The Hough transform is efficiently implemented via kernel convolution with complex Hough filters, where shape is captured in the magnitude of the filter and scale in the complex phase. In this paper, we further generalize the concept of a Hough filter by encoding other parameters of interest (e.g. orientation of plate or fiber constituents) in the complex phase, broadening More >

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