Jeng-Tzong Chen^1,2, Jia-Nan Ke¹, Huan-Zhen Liao¹

CMC-Computers, Materials & Continua, Vol.9, No.2, pp. 93-110, 2009, DOI:10.3970/cmc.2009.009.093

Abstract A null-field approach is employed to derive the Green's function for boundary value problems stated for the Laplace equation with circular boundaries. The kernel function and boundary density are expanded by using the degenerate kernel and Fourier series, respectively. Series-form Green's function for interior and exterior problems of circular boundary are derived and plotted in a good agreement with the closed-form solution. The Poisson integral formula is extended to an annular case from a circle. Not only an eccentric ring but also a half-plane problem with an aperture are demonstrated to see the validity of More >

E.V. González¹, P. Maimí¹, A. Turon¹, P.P. Camanho², J. Renart¹

CMC-Computers, Materials & Continua, Vol.9, No.1, pp. 51-92, 2009, DOI:10.3970/cmc.2009.009.051

Abstract This paper presents the formulation of a tri-dimensional cohesive element implemented in a user-written material subroutine for explicit finite element analysis. The cohesive element simulates the onset and propagation of the delamination in advanced composite materials. The delamination model is formulated by using a rigorous thermodynamic framework which takes into account the changes of mixed-mode loading conditions. The model is validated by comparing the finite element predictions with experimental data obtained in interlaminar fracture tests under quasi-static loading conditions. More >

Praveen Ch.¹, Shishir Sinha^1,2

CMC-Computers, Materials & Continua, Vol.9, No.1, pp. 41-50, 2009, DOI:10.3970/cmc.2009.009.041

Abstract Fluid catalytic cracking (FCC) unit plays most important role in the economy of a modern refinery that it is use for value addition to the refinery products. Because of the importance of FCC unit in refining, considerable effort has been done by scientists till now on the modelling of this unit for better understanding and improved productivity. To model a FCC unit we have to know the unknown kinetic parameters of the governing equations.
The basic aim of this paper is to prove that MATLAB^TM can be used as a tool to find unknown kinetic parameters More >

D.T. Fullwood¹, S.R. Kalidindi², B.L. Adams¹, S. Ahmadi¹

CMC-Computers, Materials & Continua, Vol.9, No.1, pp. 25-40, 2009, DOI:10.3970/cmc.2009.009.025

Abstract Localization relations arise naturally in the formulation of multi-scale models. They facilitate statistical analysis of local phenomena that may contribute to failure related properties. The computational burden of dealing with such relations is high and recent work has focused on spectral methods to provide more efficient models. Issues with the inherent integrations in the framework have led to a tendency towards calibration-based approaches. In this paper a discrete Fourier transform framework is introduced, leading to an extremely efficient basis for the localization relations. Previous issues with the Green's function integrals are resolved, and the method More >

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 >

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 >

C.M. Hefferan¹, S.F. Li¹, J. Lind¹, U. Lienert², A.D. Rollett³, P. Wynblatt³, R.M. Suter^1,3

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 >

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 >

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 >

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 >