Lingfei Gao¹, Xiaoping Zheng^1,2, Zhenhan Yao¹

CMC-Computers, Materials & Continua, Vol.3, No.1, pp. 25-36, 2006, DOI:10.3970/cmc.2007.003.025

Abstract A general numerical approach is developed to model the elastic behaviours and failure processes of heterogeneous materials. The heterogeneous material body is assumed composed of a large number of convex polygon lattices with different phases. These phases are locally isotropic and elastic-brittle with the different lattices displaying variable material parameters and a Weibull-type statistical distribution. When the effective strain exceeds a local fracture criterion, the full lattice exhibits failure uniformly, and this is modelled by assuming a very small Young modulus value. An auto-select loading method is employed to model the failure process. The proposed More >

Luming Shen¹, Zhen Chen²

CMES-Computer Modeling in Engineering & Sciences, Vol.7, No.3, pp. 305-320, 2005, DOI:10.3970/cmes.2005.007.305

Abstract To simulate the dynamic responses involving different material phases in a finite computational domain without discretizing the whole problem domain, a silent boundary scheme is proposed within the framework of the material point method (MPM) that is an extension from Computational Fluid Dynamics to Computational Solid Dynamics. Because the MPM does not employ fixed mesh connectivity, a robust spatial discretization procedure in the moving domain of influence could be designed by applying viscous damping forces along the computational boundary. To establish a simple interface between the discretization procedures with and without fixed mesh connectivity, a More >

Hiroshi Kadowaki¹, Wing Kam Liu²

CMES-Computer Modeling in Engineering & Sciences, Vol.7, No.3, pp. 269-282, 2005, DOI:10.3970/cmes.2005.007.269

Abstract A method to derive governing equations and elastic-plastic constitutive relations for the micropolar continuum model is proposed. Averaging procedures are operated over a surrounding sub-domain for each material point to bridge a discrete microstructure to a macro continuum model. Material parameters are determined by these procedures. The size of the sub-domain represents the material intrinsic length scale, and it is passed into the macroscopic governing equation so that the numerical solution can be regularized for analyses of failure phenomena. An application to a simple granular material model is presented. More >

John T. Parissis, Stamatis Adamopoulos¹, Koula Venetsanou, George Kostakis, Antonios Rigas, Spilios M. Karas, Dimitrios Kremastinos¹

European Cytokine Network, Vol.15, No.2, pp. 139-144, 2004

Abstract No in vivo data exist about the relationship of circulating granulocyte-macrophage colony stimulating factor (GM-CSF) and soluble adhesion molecules ICAM-1 and VCAM-1 (sICAM-1 and sVCAM-1) to the severity of acute myocardial infarction (AMI) and the pathophysiological events of post-infarction left ventricular dysfunction. We investigated the kinetics of these inflammatory mediators in the plasma of patients with AMI, and correlated the findings with the clinical severity of the disease during the first week of hospitalization as well as the degree of left ventricular dysfunction one month after the AMI.
Plasma levels of inflammatory markers were determined in… More >

Dimitrios Tziakas¹, Georgios Chalikias¹, John T. Parissis², Helen Hatzinikolaou¹, Dimitrios Stakos¹, Evropi Papadopoulou³, Alexandros Kortsaris³, Dimitrios Hatseras¹

European Cytokine Network, Vol.15, No.3, pp. 231-239, 2004

Abstract Introduction. Recent clinical and experimental studies indicate that upregulation of the TNF system can contribute to the progression of cardiac remodeling and heart failure decompensation, by promoting alterations in cardiomyocyte biology and extracellular matrix metabolism. Extracellular matrix turnover is regulated by the matrix metalloproteinases (MMPs), which are endogenous enzymes responsible for extracellular collagen degradation. The present study investigates the fluctuation of serum levels of TNF-α, soluble TNF receptor-1 (sTNFR1) and -2 (sTNFR2), in patients with chronic heart failure both during acute decompensation and the stable state of the syndrome. The second goal of this study… More >

Amy E. Krambeck, Kent C. Krejci, David E. Patterson, Andrew J. LeRoy, Joseph W. Segura

Canadian Journal of Urology, Vol.11, No.5, pp. 2383-2389, 2004

Abstract Objective: Shock wave lithotripsy (SWL) is an attractive initial treatment for nephrolithiasis. Unfortunately, a significant number of stones are resistant to SWL therapy and require subsequent percutaneous ultrasonic lithotripsy (PUL) for definitive treatment. Our objective was to determine if previous SWL had adverse effects on PUL success and if there were differences between the patients undergoing primary PUL and those undergoing PUL after SWL failure.
Materials and methods: In 2001, 108 PULs were performed at our institution, of which 40 (37%) were performed after SWL failure. Stone location, anesthesia time, stone composition and size, and complication rates… More >

E. Ferretti ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.5, pp. 453-476, 2004, DOI:10.3970/cmes.2004.006.453

Abstract The Cell Method (CM) code with automatic remeshing for crack propagation analysis [Ferretti (2003)] is here used for modeling the pullout test. Particular emphasis is given to the analysis in the Mohr-Coulomb plane, since previous numerical models were not decisive in describing failure mechanism in pullout tests. The interpretations of experimental and analytical studies vary widely, and none of the existing explanations offer a complete description of the progressive failure of the concrete medium [Yener (1994)]. Nor do most existing interpretations appear to be totally compatible with the experimental evidence. Analysis of the failure mechanism… More >

Ch,ra S. Yerramalli¹, Anthony M. Waas²

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.1, pp. 1-16, 2004, DOI:10.3970/cmes.2004.006.001

Abstract Results from a 3D finite element based study of the compression response of unidirectional fiber reinforced polymer matrix composites (FRPC) are presented in this paper. The micromechanics based study was used to simulate the compressive response of glass and carbon fiber reinforced polymer matrix composites, with a view to understanding the effect of fiber diameter on compression strength. Results from the modeling and simulation indicate the presence of a complex three dimensional stress state in the matrix of the FRPC. Results from the simulation highlight the role of fiber diameter on the compressive response of More >

H.J. Bohm¨ ¹, W. Han^1,2, A. Eckschlager^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.1, pp. 5-20, 2004, DOI:10.3970/cmes.2004.005.005

Abstract Three-dimensional periodic micromechanical models are used for studying the mechanical behavior of discontinuously reinforced ductile matrix composites. The models are based on unit cells that contain a number of randomly positioned and, where applicable, randomly oriented spherical, spheroidal or cylindrical reinforcements. The Finite Element method is used to resolve the microscale stress and strain fields and to predict the homogenized responses under overall uniaxial tensile loading in the elastic and elastoplastic regimes. Periodicity boundary conditions are employed in the analyses.\\ The main emphasis of the contribution is put on studying the microscale stresses in the More >

Kunigal Shivakumar¹, Anil Bhargava²

CMC-Computers, Materials & Continua, Vol.1, No.2, pp. 173-190, 2004, DOI:10.3970/cmc.2004.001.173

Abstract The fiber optic sensor (FOS) embedded perpendicular to reinforcing fibers causes an `Eye' shaped defect. The length is about 16 times fiber optic radius (R_Fos) and height is about 2R_Fos. The eye contains fiber optics in the center surrounded by an elongated resin pocket. Embedding FOS causes geometric distortion of the reinforcing fiber over a height equal to 6 to 8 R_Fos. This defect causes severe stress concentration at the root of the resin pocket, the interface (in the composite) between the optical fiber and the composite, and at 90° to load direction in the composite. The… More >