C. Becker¹, S. Jox², G. Meschke³

CMES-Computer Modeling in Engineering & Sciences, Vol.57, No.3, pp. 245-278, 2010, DOI:10.3970/cmes.2010.057.245

Abstract A three-dimensional numerical model based on the Extended Finite Element Method (X-FEM) is presented for the simulation of cohesive cracks in cementitious materials, such as concrete, in a hygro-mechanical framework. Enhancement functions for the small scale resolution of the displacement jump across cracks in the context of the X-FEM is used in conjunction with a higher order family of hierarchical shape functions for the representation of the large scale displacement field of the investigated structure. Besides the theoretical and computational formulation in a multiphase context, aspects of the implementation, such as integration and crack tracking More >

Jun Xu^1,2, Yibing Li¹, Xi Chen^2,3, Yuan Yan^2,3, Dongyun Ge^4,1, Bohan Liu¹

CMC-Computers, Materials & Continua, Vol.18, No.2, pp. 183-212, 2010, DOI:10.3970/cmc.2010.018.183

Abstract The crack pattern in a PVB laminated windshield upon head impact is of considerable interest because it contains important information on energy mitigation, pedestrian protection, and accident reconstruction. We carry out a systematic numerical study based on the extended finite element method (XFEM), to investigate the effects of various material and system variables, including the impact speed, effective head mass, PVB interlayer material thickness and property, windshield curvature, aspect ratio and size, boundary constraint, impact angle and off-center impact, on the parameters characterizing the resulting crack pattern, i.e. the crack length, crack angle and circumferential More >

M.A. Arafin, J.A. Szpunar

The International Conference on Computational & Experimental Engineering and Sciences, Vol.13, No.3, pp. 59-60, 2009, DOI:10.3970/icces.2009.013.059

Abstract This paper introduce a novel approach for face image segmentation base on Voronoi Diagram (VD) technique. We used intensity value and region pixels value for enhance preprocessing step on gray-scale image. The method for locating and extraction face/head boundary are applied feature point of the original image which are useful dual tessellation of the VD is know as Delaunay Triangulation (DT). A target of experiment is reported face image segmentation that uses still face image from BioID database. The result of this method clearly demonstrates the segmentation which performs in comparison with another method in More >

Sudib K. Mishra¹, J. K. Paik², S. N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.1, pp. 67-96, 2009, DOI:10.3970/cmes.2009.050.067

Abstract We present a simulation based study, by combining several models involving multiple time scales and physical processes, which govern the interfacial stress corrosion cracking (SCC) in grain boundaries, layered composites or bi-materials, and the mechanisms of inhibition using `smart' agents. The inhibiting agents described herein, automatically sense the initiation of damage, migrate to the sites and delay the corrosion kinetics involved in the process. The phenomenon of SCC is simulated using the lattice spring model (for the mechanical stresses), coupled with a finite difference model of diffusing species, causing the dissolution of the interfacial bonds.… 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 >

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 >

J. Toribio¹, V. Kharin²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.7, No.3, pp. 135-140, 2008, DOI:10.3970/icces.2008.007.135

Abstract This paper deals with the meaning and significance of the fracture mechanics approach to hydrogen assisted cracking, analyzing the question of K-dominance not only over the purely mechanical aspects, but also over the environmental (physicochemical) events. Two key factors able to violate the uniqueness of the crack growth kinetics curve v = v(K) are discussed: the role of far field (the stress-strain field which is not K-dominated) and the effect of the history of hydrogenation and crack growth. The far field is shown to have a minor effect on near-tip hydrogen diffusion, and thus it can only… More >

Shishir Sinha¹, Praveen Ch.

CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.2, pp. 85-102, 2008, DOI:10.3970/cmes.2008.032.085

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 on the modeling of this unit for better understanding and improved productivity. The process is characterized by complex interactions among feed quality, catalyst properties, unit hardware parameters and process conditions. \newline The traditional and global approach of cracking kinetics is lumping. In the present paper, five lump kinetic scheme is considered, where gas oil… More >

E. Ferretti¹, A. Di Leo¹

CMC-Computers, Materials & Continua, Vol.7, No.2, pp. 59-80, 2008, DOI:10.3970/cmc.2008.007.059

Abstract The main assumption on the basis of the identifying model of the effective law, developed by the Author, is the impossibility of considering the specimen as a continuum, when an identifying procedure from load-displacement to stress-strain in uniaxial compression is attempted. Actually, a failure mechanism with propagation of a macro-crack was found to activate from the very beginning of the uniaxial compression test forth. This leads to considering the acquired displacements as composed by two quotes: one constitutive, due to the material strain, and one of crack opening. Since the ratio between these two quotes… More >

J. Toribio ¹

Structural Durability & Health Monitoring, Vol.2, No.4, pp. 239-248, 2006, DOI:10.3970/sdhm.2006.002.239

Abstract This paper reviews the fracture performance in air and aggressive environment (stress corrosion cracking) of eutectoid prestressing steel wires with different levels of cold drawing. In air environment, a micromechanical model of fracture is proposed to rationalize the results on the basis of the microstructure of the steels after drawing and the model of Miller & Smith of fracture of pearlitic microstructure by shear cracking of the cementite lamellae. In hydrogen assisted cracking (HAC), a microstructure-based model is proposed on the basis of the Miller & Smith model and the mechanism of hydrogen enhanced decohesion or, more More >