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Plastic Zone (plastic + zone)
Selected AbstractsAdvanced Analysis of Steel Frames Using Parallel Processing and VectorizationCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2001C. M. Foley Advanced methods of analysis have shown promise in providing economical building structures through accurate evaluation of inelastic structural response. One method of advanced analysis is the plastic zone (distributed plasticity) method. Plastic zone analysis often has been deemed impractical due to computational expense. The purpose of this article is to illustrate applications of plastic zone analysis on large steel frames using advanced computational methods. To this end, a plastic zone analysis algorithm capable of using parallel processing and vector computation is discussed. Applicable measures for evaluating program speedup and efficiency on a Cray Y-MP C90 multiprocessor supercomputer are described. Program performance (speedup and efficiency) for parallel and vector processing is evaluated. Nonlinear response including postcritical branches of three large-scale fully restrained and partially restrained steel frameworks is computed using the proposed method. The results of the study indicate that advanced analysis of practical steel frames can be accomplished using plastic zone analysis methods and alternate computational strategies. [source] Analysis of temperature distribution near the crack tip under constant amplitude loadingFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2008K. N. PANDEY ABSTRACT An analytical/numerical method has been developed to find the temperature rise near the crack tip under fatigue loading. The cyclic plastic zone ahead of the crack tip is assumed to be the shape of the source of heat generation and some fraction of plastic work done in cyclic plastic zone as heat generation. Plastic work during fatigue load was found by obtaining stress and strain distribution within the plastic zone by Hutchinson, Rice and Rosengren (HRR) crack tip singularity fields applied to small scale yielding on the cyclic stress strain curve. A two-dimensional conduction heat transfer equation, in moving co-ordinates, was used to obtain temperature distribution around the crack tip. Temperature rise was found to be a function of frequency of loading, applied stress intensity factor and thermal properties of the material. A power,law relation was found between the rise in temperature at a fixed point near the crack tip and range of stress intensity factor. [source] Crack initiation in the brittle fracture of ferritic steelsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 9-10 2006M. COATES ABSTRACT Fracture in many steels is thought to initiate from fractured carbides. It is often supposed that in pre-cracked specimens, many carbides fracture in the plastic zone of the pre-crack, and that eventually fracture propagates from one of these to cause fracture of the whole specimen. Sources of fracture initiation in steels were investigated using a modified A533B steel as a model material. Specimens were annealed to produce a distribution of micron-sized carbides in a ferrite matrix. Four-point bend tests were carried out in the temperature range 77,373K to determine the material's ductile brittle transition. Pre-cracked samples were loaded up to 90% of the fracture strength at temperatures on the lower shelf (163K) and at the mid point of the transition region (243K). The samples were then sectioned and polished to produce SEM and TEM samples containing the crack tip. Other samples were made of areas some distance from the crack tip and out of the plastic zone. An extensive search for fracture initiation sites found no evidence for fracture initiation originating from fractured carbides. [source] Prediction of crack growth direction under plane stress for mixed-mode I and II loadingFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2000Wasiluk The estimation of the plastic zone geometry ahead of a crack is fundamental to the evaluation of crack growth. Presented here is an analytical investigation for predicting crack growth direction for mixed-mode I and II loading under plane stress conditions. It is proposed that under complex loading the crack will extend in the direction where the radius of the plastic zone attains a minimum value. There is good agreement between the predicted results which are computed on the basis of this criterion and experimental data published in the literature. [source] The analysis of thermoelastic isopachic data from crack tip stress fieldsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 4 2000Dulieu-Barton A computer program,FACTUS (fracture analysis of crack tips using SPATE),has been developed for the efficient analysis of thermoelastic data obtained from around a crack tip. The program is based on earlier work for the determination of stress intensity factors (SIFs), and also includes a novel solution procedure for the derivation of the non-singular stress term ,0x,. The program has been used in the analysis of a series of large plate specimens with central or edge slots/cracks. The derived SIFs are compared with independent values. Issues, e.g. crack closure and the extent and effect of the plastic zone, are discussed. [source] Fracture behavior of polyetherimide (PEI) and interlaminar fracture of CF/PEI laminates at elevated temperaturesPOLYMER COMPOSITES, Issue 1 2005Ki-Young Kim To investigate the effects of environmental temperature on fracture behavior of a polyetherimide (PEI) thermoplastic polymer and its carbon fiber (CF/PEI) composite, experimental and numerical studies were performed on compact tension (CT) and double cantilever beam (DCB) specimens under mode-I loading. The numerical analyses were based on 2-D large deformation finite element analyses (FEA). Elevated temperatures greatly released the crack tip triaxiality (constraint) and promoted matrix deformation due to low yield strength and enhanced ductility of the PEI matrix, which resulted in the greater plane-strain fracture toughness of the bulk PEI polymer and the interlaminar fracture toughness of its composite during delamination propagation with increasing temperature. Furthermore, the high triaxiality was developed around the delamination front tip in the DCB specimen, which accounted for the poor translation of matrix toughness to the interlaminar fracture toughness by suppressing the matrix deformation and reducing the plastic energy dissipated in the plastic zone. Especially, at delamination initiation, the weakened fiber/matrix adhesion at elevated temperatures led to premature failure of fiber/matrix interface, suppressing matrix deformation and preventing the full utilization of matrix toughness. Consequently, low interlaminar fracture toughness was obtained at elevated temperatures. POLYM. COMPOS., 26:20,28, 2005. © 2004 Society of Plastics Engineers. [source] Measuring the Plastic Zone Size by Orientation Gradient Mapping (OGM) and Electron Channeling Contrast Imaging (ECCI)ADVANCED ENGINEERING MATERIALS, Issue 1-2 2007T. Welsch Abstract For the local investigation of plastic deformation mechanisms non-destructive methods are needed to image the distribution of dislocations and to measure dislocation densities. Additionally these methods should be usable in situ. Therefore the well known methods EBSD and ECCI are improved by an appropriate processing of the measured data. The resulting two new techniques OGM and ECCI-plus are validated in detail for two complex sets of experiments. Both techniques are used to image plastic deformation zones and to measure the size of plastic zones on a macro scale (hardness indents) as well as on a micro scale (crack tips) as demonstrated in this paper. Additionally OGM gives even quantitative data of the degree of deformation. The capability of both methods is discussed in detail and it is shown that they are independent from the topography which is critically surveyed. [source] Molecular dynamics simulation of crack tip blunting in opposing directions along a symmetrical tilt grain boundary of copper bicrystalFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 11 2007A. LUQUE ABSTRACT Mode I crack growth along some grain boundaries of copper embrittled by solute segregation shows strong anisotropy. For instance, growth along the direction on the symmetrical tilt boundary has been reported to occur by intergranular brittle fracture, whereas growth along the opposite sense occurs in a ductile manner. In this paper, we simulate such crack configurations using molecular dynamics (embedded atom method [EAM]) in 3-dimensional perfect bicrystalline samples of pure copper of the aforementioned orientation at room temperature. In both cases the response is ductile, crack opening taking place by dislocation emission from the crack tip. The critical stress intensity factors (SIFs) for dislocation emission have been calculated by matching the displacement fields of the atoms in the tip neighbourhood with the continuum elastic fields. They are of the same order of magnitude for both growth senses despite the different morphology of their respective blunted crack tips and of the patterns of dislocations constituting their plastic zones. Thus, it seems that, in agreement with published results of continuum crystalline plasticity for the same problem, the plastic anisotropy associated with the different orientation of the slip systems with respect to the crack cannot in this case explain the experimental behaviour observed with solute embrittled bicrystals. [source] Slope stability analysis based on elasto-plastic finite element methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 14 2005H. Zheng Abstract The paper deals with two essential and related closely processes involved in the finite element slope stability analysis in two-dimensional problems, i.e. computation of the factors of safety (FOS) and location of the critical slide surfaces. A so-called ,,v inequality, sin ,,1 , 2v is proved for any elasto-plastic material satisfying Mohr,Coulomb's yield criterion. In order to obtain an FOS of high precision with less calculation and a proper distribution of plastic zones in the critical equilibrium state, it is stated that the Poisson's ratio v should be adjusted according to the principle that the ,,v inequality always holds as reducing the strength parameters c and ,. While locating the critical slide surface represented by the critical slide line (CSL) under the plane strain condition, an initial value problem of a system of ordinary differential equations defining the CSL is formulated. A robust numerical solution for the initial value problem based on the predictor,corrector method is given in conjunction with the necessary and sufficient condition ensuring the convergence of solution. A simple example, the kinematic solution of which is available, and a challenging example from a hydraulic project in construction are analysed to demonstrate the effectiveness of the proposed procedures. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||