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Artykuły w czasopismach na temat "Crack"
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Han, Zhichao, Caifu Qian i Huifang Li. "Investigation of the Enhancement Interactions between Double Parallel Cracks on Fatigue Growth Behaviors". Materials 13, nr 13 (1.07.2020): 2952. http://dx.doi.org/10.3390/ma13132952.
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In this paper, interactions of double parallel cracks were studied by performing experiments and numerical simulations. Fatigue crack propagation tests were carried out to measure crack growth rates in the specimens with double parallel cracks or a single crack. Finite element method was adopted to calculate stress intensity factors at the crack tips. Results show that the double parallel cracks at different positions present a shielding effect or enhancement effect on crack growth rates and stress intensity factors. When the double parallel cracks are offset, crack interactions mostly behave as enhancement effects. Empirical formulas were obtained to calculate the stress intensity factor at the “dangerous” crack tip of the double parallel cracks. By modifying the material parameters in Paris equation of the single crack, the double parallel cracks are simplified into a single crack with the same crack growth rates.
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Wang, Chaolin, Yu Zhao, Yanlin Zhao i Wen Wan. "Study on the Interaction of Collinear Cracks and Wing Cracks and Cracking Behavior of Rock under Uniaxial Compression". Advances in Civil Engineering 2018 (2018): 1–10. http://dx.doi.org/10.1155/2018/5459307.
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This paper investigates the crack interaction, initiation, and propagation rules of rock-like materials containing two collinear cracks. Based on the Kachanov method, the formulations for stress intensity factors (SIFs) of two collinear cracks and two winged cracks are derived, respectively. The influences of bridge ligament and crack length on the crack interaction are analyzed theoretically. The results show that the propagation of a long crack is independent of crack interaction when d≥a2 and the same rule applies for a short crack when d≥a1. With the growth of wing cracks, the SIF of wings first remarkably decreases and then it tends toward a steady value. Subsequently, the propagation of collinear cracks and cracking processes under uniaxial compression are analyzed experimentally and numerically. Both the experimental results and simulation results demonstrate that shear cracks tend to initiate and propagate at higher inclination angle. The crack coalescence is affected by the inclination angle of bridge ligament. For increasing the inclination angle, the crack coalescence varies from wing crack failure to shear crack coalescence. As bridge ligament increases, the crack coalescence varies from shear crack coalescence to shear-wing crack coalescence and then to wing crack failure.
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Xu, Yan Hai. "Study on Crack Retardation with the Consideration of Crack Surface Roughness by FEM". Advanced Materials Research 97-101 (marzec 2010): 471–74. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.471.
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As one of the key factors to induce crack closure, crack surface roughness plays a dominated role in evaluating the characteristics of short fatigue cracks. The crack retardation induced by the crack surface roughness was investigated by numerical simulation in this paper. The influence of crack surface roughness on short fatigue cracks was directly applied into the numerical simulation procedure with the help of friction coefficients on the contacted crack surfaces. The driving forces of cracks represented by the two indicators such as crack tip displacement and plastic strain range were studied and used to characterize the retardation induced by crack surface roughness. It is shown that the evidence of crack surface roughness affecting on crack retardation is obvious and the influence of crack surface roughness on the characteristics of short fatigue cracks must account for in evaluating the performance of short fatigue cracks.
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Xu, Yonglin, B. Moran i T. Belytschko. "Self-Similar Crack Expansion Method for Three-Dimensional Crack Analysis". Journal of Applied Mechanics 64, nr 4 (1.12.1997): 729–37. http://dx.doi.org/10.1115/1.2788976.
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The self-similar crack expansion method is developed to calculate stress intensity factors for three-dimensional cracks in an infinite medium or semi-infinite medium by the boundary integral element technique. With this method, the stress intensity factors at crack tips are determined by calculating the crack-opening displacements over the crack surface, and the crack expansion rate, which is related to the crack energy release rate, is estimated by using a technique based on self-similar (virtual) crack extension. For elements on the crack surface, regular integrals and singular integrals are evaluated based on closed-form expressions, which improves the accuracy. Examples show that this method yields very accurate results for stress intensity factors of penny-shaped cracks and elliptical cracks in the full space, with errors of less than one percent as compared with exact solutions. The stress intensity factors of subsurface cracks are in good agreement with other numerical solutions.
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Yoda, M. "Subcritical Crack Growth Characteristics on Compact Type Specimens and Indentation Cracks in Glass". Journal of Engineering Materials and Technology 111, nr 4 (1.10.1989): 399–403. http://dx.doi.org/10.1115/1.3226486.
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For the purpose of comparing crack growth characteristics on small indentation cracks with those for long cracks, subcritical crack growth data on soda-lime glass were obtained using the compact type (CT) specimens with long cracks and the indentation cracks. It was found that there is apparently a small crack effect in the as-indented cracks which increases crack growth. However, the annealed indentation crack shows the same trend of crack growth as that for the CT specimens. A residual stress effect can be used to explain this anomalous growth behavior of the as-indented cracks.
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Jin, Huijin, Bing Cui i Ling Mao. "Fatigue Growth Behaviour of Two Interacting Cracks with Different Crack Offset". Materials 12, nr 21 (28.10.2019): 3526. http://dx.doi.org/10.3390/ma12213526.
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Under cyclic fatigue load, multiple cracks would significantly deteriorate the service life of the components with respect to the case of a single crack owing to the crack interaction. The present study aims to explore the effect of crack interaction on the fatigue growth behaviour of samples with different crack offset. In this study, fatigue crack growth tests were performed for samples containing a single crack and non-collinear cracks of different crack offset in an aluminum–lithium alloy. It was shown that the two facing non-collinear cracks changed their growth direction when the cracks were overlapped, resulting in load mode transfers from mode I to I + II mixed mode. Then, the interaction behaviour was studied by establishing the finite element models to calculate the stress intensity factor K of samples with different crack offset. The results indicated that the K decreased, largely owing to the shielding effect as the two cracks overlapped, leading to retardation of crack growth in the position of overlap, especially for the specimens with a small crack offset. It was also shown that the interaction effect could change from positive to negative during the process of the multiple cracks’ growth, thus leading to the acceleration or deceleration of crack growth rates, suggesting that the influence of interaction on cracks’ growth behaviour could vary with the different stages of crack growth.
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Kamaya, Masayuki. "Evaluation of Fatigue Crack Growth of Interacting Surface Cracks". Advanced Materials Research 33-37 (marzec 2008): 187–98. http://dx.doi.org/10.4028/www.scientific.net/amr.33-37.187.
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Since mechanical interaction between multiple cracks affects the rate of crack growth due to fatigue and stress corrosion cracking, it is important to consider its influence when predicting growth. In this study, a procedure predicting the growth of interacting surface cracks was developed. First, using the results of fatigue crack growth tests performed in a previous study, the transient growth behavior during coalescence and growth under interaction was evaluated based on area of crack face. It was shown that the area is a representative parameter of the growth of interacting surface cracks as well as independent cracks. The growth in area showed good correlation with the crack driving force defined using size of area. Then, in order to investigate the relationship between growth of interacting cracks and their relative spacing, crack growth simulations were carried out. The body force method was used to evaluate the change in stress intensity factors (SIF) during crack growth under interaction, and the simulation could reproduce the crack configurations obtained in the fatigue crack growth test. SIF of an interacting crack tip converges to that of a coalesced crack as the distance between cracks decreases. It was concluded that when the distance between cracks is small enough, the cracks can be replaced with a semi-elliptical crack of the same area of crack face for a growth evaluation. The threshold offset distance for the replacement was suggested to be less than 0.1Rx, where Rx is the span length of two cracks on the surface.
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Luo, Xiaoyan, Guoyan Zhao, Peng Xiao i Wengang Zhao. "Fracture Process and Failure Mode of Brazilian Discs with Cracks of Different Angles: A Numerical Study". Mathematics 10, nr 24 (17.12.2022): 4808. http://dx.doi.org/10.3390/math10244808.
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In order to determine the effect of internal cracks on the tensile failure of materials, a hybrid finite–discrete element method was used to analyze the Brazilian disc test with cracks of different angles. When the pre-crack angle is between 0° and 60°, the wing crack is initiated from the pre-crack end. When the pre-crack is 90°, the crack initiated from the pre-crack center. When the pre-crack angle is between 0° and 60°, the maximum principal stress and plastic strain are concentrated at the pre-crack end. When the pre-crack angle is 90°, the maximum principal stress and plastic strain are concentrated in the pre-crack center. As the crack angle increased from 0° to 90°, the failure mode of Brazilian discs with cracks transits from splitting into two parts to splitting into four parts. The influence of crack length is further studied. When the crack length is less than 5 mm, the crack angle has little influence on the disc failure mode; Brazilian discs with cracks of different angles undergoes splitting failure along the loading axis. When the crack length is larger than 5 mm, the crack angle has a great effect on the disc failure mode.
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Han, Zhichao, Caifu Qian i Huifang Li. "Study of the Shielding Interactions between Double Cracks on Crack Growth Behaviors under Fatigue Loading". Metals 10, nr 2 (31.01.2020): 202. http://dx.doi.org/10.3390/met10020202.
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In this paper, the interactions between double cracks with a co-bisector-line were investigated theoretically and experimentally. Fatigue crack growth tests of specimens with a single crack or double cracks were carried out to measure the crack growth rates, and finite element calculations were performed to obtain the stress intensity factors at crack tips. It was found that when the double cracks are in co-bisector-line, they present shielding interactions which reduce the stress intensity factors at crack tips as well as the crack growth rates. By modifying the stress intensity factors and the Paris equation considering the shielding interactions, a new simplification method was proposed to simplify the double cracks into a single crack with the same crack growth rates.
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Kim, D. S., i K. H. Lo. "Crack Interaction Criteria in Pressure Vessels and Pipe". Journal of Offshore Mechanics and Arctic Engineering 117, nr 4 (1.11.1995): 260–64. http://dx.doi.org/10.1115/1.2827232.
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An attempt was made to define a new crack interaction criterion for pressurized cylinders with two co-planar surface cracks. Elastic-plastic finite element method with line spring concept (line spring element method) was used to verify the validity of the new interaction criterion and to establish the relative conservatism built into various codes/standards. The crack interaction criteria of two co-planar surface cracks as defined by ASME Section XI and BS PD6493 were studied and a new interaction criterion which accounts for crack shape and load factor was introduced. The basic idea behind the crack interaction criteria for co-planar surface cracks was the plastic zone and stress interaction near crack tips. To verify the new crack interaction criterion, comparisons of J-integral values were made for various crack sizes with different distances between cracks and loading conditions. Based upon these comparisons, the new crack interaction criteria, comparing a physical distance, s, to a characteristic distance d=(σ/σy)2(c1Q1 + c2Q2), proved to be a reasonable parameter for indication of the crack driving force interaction for co-planar cracks. The characteristic distance also represents a rigorous measure of an equivalent crack driving force for interacting cracks.
Rozprawy doktorskie na temat "Crack"
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Lee, Woong. "Crack deflection and interface cracks in layered composites". Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627252.
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McFadyen, Neil B. (Neil Barry) Carleton University Dissertation Engineering Mechanical. "Fatigue crack growth in semi-elliptical surface cracks". Ottawa, 1987.
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Hejman, Ulf. "On initiation of chemically assisted crack growth and crack propagation paths of branching cracks in polycarbonate". Licentiate thesis, Malmö högskola, Teknik och samhälle, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-7790.
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Stress corrosion, SC, in some cases gives rise to stress corrosion cracking, SCC, which differs from purely stress intensity driven cracks in many aspects. They initiate and grow under the influence of an aggressive environment in a stressed substrate. They grow at low load and may branch. The phenomenon of SCC is very complex, both the initiation phase and crack extension itself of SCC is seemingly associated with arbitrariness due to the many unknown factors controlling the process. Such factors could be concentration of species in the environment, stress, stress concentration, electrical conditions, mass transport, and so on.In the present thesis, chemically assisted crack initiation and growth is studied with special focus on the initiation and branching of cracks. Polycarbonate plates are used as substrates subjected to an acetone environment. Experimental procedures for examining initiation and branching in polycarbonate are presented. An optical microscope is employed to study the substrate.The attack at initiation is quantified from pits found on the surface, and pits that act as origin for cracks is identified and the distribution is analysed. A growth criterion for surface cracks is formulated from the observations, and it is used to numerically simulate crack growth. The cracks are seen to coalesce, and this phenomenon is studied in detail. Branching sites of cracks growing in the bulk of polycarbonate are inspected at the sample surface. It is found that the total width of the crack branches are approximately the same as the width of the original crack. Also, angles of the branches are studied. Further, for comparison the crack growth in the bulk is simulated using a moving boundary problem based algorithm and similar behaviour of crack branching is found.
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Patel, Surendra Kumar. "Experimental And Numerical Studies On Fatigue Crack Growth Of Single And Interacting Multiple Surface Cracks". Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/276.
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Design based on damage tolerance concepts has become mandatory in high technology structures. These concepts are also essential for evaluating life extension of aged structures which are in service beyond originally stipulated life. Fracture analysis of such structures in the presence of single or multiple three-dimensional flaws is essential for this approach. Surface cracks are the most commonly occurring flaws and development of accurate methods of analysis for such cracks is essential for structural integrity evaluation of newly designed or aged structures. The crack fronts of these surface flaws are usually approximated mathematically to be of either part-elliptical or part-circular in geometry. In this thesis, some of the issues related to fatigue crack growth of single and multiple surface cracks are studied in detail. Here emphasis is given to the development of simple and accurate post-processing techniques to estimate stress intensity factors for surface cracks, development and/or implementation of simple numerical methods to simulate three-dimensional single and multiple cracks in fatigue and their experimental verification.
Modified virtual crack closure integral (MVCCI) technique for estimation of strain energy release rates has been improved (chapter II) to deal with curved crack front and unequal elements across the crack front. The accuracy of this method is evaluated and presented in this chapter for certain benchmark surface flaw problems. The improved MVCCI is used in the investigation of interaction between multiple surface cracks in three-dimensional solids. The interaction effects are studied for both interacting and coalescing phases as observed to occur in the growth of multiple surface cracks. Extensive numerical work is performed to study the effects of various parameters such as aspect ratio, thickness ratio, interspacing on the interaction factors. These solutions are used in formulating empirical equations to estimate interaction factors. This facilitated the development of a simple semi-analytical method to study fatigue crack growth of multiple cracks.
The growth of surface cracks under fatigue loading in the finite width specimens of an aero-engine superalloy has been studied experimentally (presented in chapter III). Four configurations for single semi-elliptical cracks are considered. Fatigue crack growth is simulated by two models viz. two degrees of freedom and "multi degrees of freedom with ellipse fit'. These models are sometimes referred to as semi-analytical models as the crack growth is predicted by numerical integration combining Paris equation with an empirical form of stress intensity factor solution. In order to use two degrees of freedom model for fatigue crack growth prediction of semi-elliptical cracks, empirical solution for the Ml range of geometric parameters for stress intensity factor is required for the considered
configurations. The available Newman-Raju solution is useful for this purpose within a limited range of surface crack length to width (c/W) of the specimen. Based on the present finite element results, the empirical equations are developed for extended values of c/W. It is well understood that the fatigue prediction for two-dimensional crack can be improved by inclusion of crack closure effects. Usually, in semi-analytical models for growth of surface cracks under fatigue loading, the crack closure is included as a ratio of crack closure factor at surface and depth locations of semi-elliptical crack. In the present work, this ratio for the considered material of specimens is obtained by an experimental study. The difference in characteristics of preferred propagation path between semi-elliptical crack in a finite width plate and a wide plate is clearly brought out.
Current crack growth predictions for most of the structures are based on the presence of only a single crack. However, in structures several cracks may initiate simultaneously within a stress critical zone and may interact depending upon their geometry, spatial location, structure geometry and mode of loading. In this work various configurations of twin semi-elliptical cracks have been studied by experiments. The beachmarks created on the specimens during experiments are used in the investigation of crack shape progression during fatigue. A three degrees of freedom crack growth model for interacting and coalescing cracks has been proposed. The experimentally determined crack shape and lives have been compared with the corresponding values from numerical simulation.
The correlation of experimental results with numerical predictions was carried out through improved MVCCI for eight-noded brick elements. This has worked well in the configurations analysed. However, it is known in literature that there are benefits of using 20-noded singular elements. There could be special situations where the regular elements could fail, and singular elements could be essential. For this purpose, further development of MVCCI were carried out using 20-noded quarter-point elements (presented in chapter IV). Also a novel technique of decomposed crack closure integral (DCCI) was developed (presented in chapter V) for both regular and singular elements to represent the variation of MVCCI more accurately along the crack front.
It is well known that quarter-point elements at crack front produce the required singularity at the crack tip and give accurate stress distribution with fewer degrees of freedom than conventional elements. Thus to develop more efficient post-processing tools, the MVCCI expressions are formulated for 20-noded singular quarter-point element for various assumptions regarding stress and displacement distributions in the elements across the crack front. A comprehensive study is presented (chapter IV) on MVCCI for 20-noded singular brick element including various simplified expressions for three-dimensional part-through cracks in pure and mixed-mode state of deformation of fracture. The developed MVCCI expressions are also valid for 15-noded quarter-point Penta elements. The reduction in model size can further be obtained if 12-noded three-dimensional singular element is employed at the crack front and eight-noded elements are used away from the crack front. The MVCCI expressions are also developed for 12-noded singular element and their accuracy is evaluated by numerical solutions.
Presently, MVCCI, estimates the average stress intensity factor at the center of each element along the crack front. In this thesis, a Decomposed Crack Closure Integral (DCCI) is formulated to represent an assumed variation of stress intensity factor along the crack front in each element. The DCCI is formulated for 8-noded brick, 20-noded conventional brick and 20-noded singular brick elements. The numerical examples presented here deal with three-dimensional problems of patch repair technology and part-through cracks. The technique showed a major advantage for the patch repair problems where SIF variations along the crack front are of significance and large mesh sizes are computationally expensive. This along with MVCCI for 12-noded and 20-noded singular elements formed a part of the work on development of accurate and effective post-processing tools.
It is expected that the present work will be helpful in damage tolerance design and assessment of aerospace structures and the experimental work performed as a part of this thesis will enhance confidence in the damage tolerance analysis.
The thesis is concluded in chapter VI presenting the contributions of this thesis and projecting future lines of work possible in this area.
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CORBANI, SILVIA. "CRACK GROWTH WITH PARTIAL BENDING-INDUCED CRACK CLOSURE". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2012. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=23847@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Neste trabalho são investigadas experimentalmente e numericamente as mudanças de geometria em trincas inicialmente passantes submetidas a carregamento remoto de flexão pura induzindo fechamento parcial das faces da trinca. Esse crescimento de trinca pode ocorrer numa variedade de estruturas com defeitos pré-existentes, tais como fuselagens de aviões, cascos de navios, vasos de pressões e pontes metálicas. O carregamento de flexão pura ocasiona regiões de tração e compressão na frente da trinca. É inquestionável que parte das faces da trinca sob compressão fecha independentemente de qualquer mecanismo de fechamento; e outra parte das faces da trinca, por outro lado, sob tração cresce mudando gradualmente de geometria. Após realizar ensaios em corpos-de-prova de aço ASTM A-36, foi observado que tais carregamentos geram uma quina na frente da trinca, que é a transição de uma geometria parcialmente passante e um trecho remanescente da geometria inicial. Para entender a distribuição do fator de intensidade de tensão em tais frentes de trinca, suas geometrias foram reproduzidas em um modelador tridimensional de mecânica da fratura linear elástica, o FRANC3D, acoplado a um programa de análise de elementos finitos (ABAQUS). Com este sistema acoplado, foram executadas análises considerando efeitos não lineares causados pelo contato das faces da trinca sob compressão. Verificou-se a necessidade de propor metodologias para tratamento dos resultados numéricos na quina, obtendo-se predições eficientes das mudanças na geometria da trinca. Contudo, a estimativa de vida, quando se compara taxas de crescimento da trinca obtidas em um corpo-de-prova sob tração cíclica e as taxas em um corpo-de-prova sob flexão com fechamento parcial da trinca, foi melhor reproduzida usando um fator de correção de fechamento da trinca. Adicionalmente, uma série de expressões empíricas normalizadas para geometrias da trinca e fatores de intensidade de tensão são propostas.
This work investigates experimentally and numerically how the front of initially through edge cracks in plate changes after they pass to be remotely fatigue loaded under pure bending to induce partial closure of the crack faces. This type of crack growth problem can occur in a variety of structures with preexisting defects, such as aircraft fuselages, ship hulls, pressure vessels components, and steel bridges. The bending loads induce tension and compression regions along the crack front, with the part of the crack faces that work under compression undoubtedly closed by the load, independently of any other closure mechanism. The part of the crack faces that work under tension; on the other hand, crack grows by fatigue gradually changing its shape. After performing tests on ASTM A36 steel specimens, it was observed that the bending load induces a kink on the crack front, in the transition between the part through crack created on the tension side and initial crack geometry. To understand the distribution of the stress intensity factor along such crack fronts, the measured crack shapes were reproduced in a three-dimensional fracture mechanics modeler (FRANC3D) coupled to a finite element analysis program (ABAQUS). With this coupled system, linear elastic stress analysis simulations were performed considering the nonlinear effects caused by the crack face contact in the compressed region. In particular, methods had to be proposed to treat numerical noise around the kink. The proposed methodology efficiently predicts the observed crack front shape changes; although the observed fatigue lives were better reproduced using a crackclosure correction factor when compared to crack growth data obtained from standard compact tension specimens. In addition, a series of normalized empiric expressions for both crack front shapes and stress intensity factors are proposed.
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Milonopoulos, Alexis. "Máquina crack". Pontifícia Universidade Católica de São Paulo, 2014. http://tede2.pucsp.br/handle/handle/2487.
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Previous issue date: 2014-09-15Conselho Nacional de Desenvolvimento Científico e Tecnológico
Based on a cartographic writing, Crack Machine shows the games of power and the struggling forces within the cracolandia field, pointing out not only the battles, the gears and specific arrangements placed on networks of strategic places, but also dislocations, sinuosity, transversals, tracks, ruts and thresholds that cross the whole cracolandia issue and question our politics. By showing the profusion of useless actions in that area this dissertation treats this matter reaching beyond the discussions about hygienization process and the real estate speculation, pointing out another dimension of the State and the politics and demonstrating a machine that lives off exclusion, speculation, immolation, safety and potentializing more and more lucrative businesses that go from wars against drugs to humanitarianism. In another movement, it exposes the matter of irrecoverable population management, extrapolating the cracolandia space and the discussion about crack cocaine and the control of the undesirable population through technologies that provide administration and risk management. It also shows how these ungovernable populations have been, also with the formation of a new drug market, the main effect of the austerity politics that have taken the globe, questioning our model of society and our political rationality related to the way power has struggled to manage populations since the appearance of the biopower. Taking a step forward from a strictly biopolitical analysis, rewriting the to make die and to let die in the mark of power technologies, pointing out how death became a normal governmental mechanism, inserted in a military-political project of war on drugs and being a privileged strategy that allows the creation of a tension between to make live, to make die and to let die
A partir de uma escritura cartográfica, Máquina Crack mostra jogos de poder e forças em luta no campo da cracolândia, evidenciando não só batalhas, engrenagens e arranjos específicos situados em redes de lugares estratégicos, mas também deslocamentos, sinuosidades, transversais, rastros, sulcos e limiares que atravessam todo a questão da cracolândia e que colocam a nossa política em questão. Ao mostrar a profusão de ações inócuas na área, trata esta questão indo além das discussões acerca de processos de higienização e do fenômeno da especulação imobiliária, evidenciando uma outra dimensão do Estado e da política e demonstrando toda uma máquina que vive da exclusão, da especulação, da imolação e da segurança e que cada vez mais potencializa lucrativos negócios que vão da guerra às drogas ao humanitarismo. Em um outro movimento, expõe a problemática da gestão de populações irrecuperáveis, extrapolando o espaço da cracolândia e a discussão em torno do crack e problematizando a questão da gestão estratégica de populações, mais precisamente da contenção e do controle de populações indesejáveis por meio de tecnologias que propiciam a administração e a gestão de riscos. Mostra também como estas populações ingovernáveis têm sido, juntamente com a formação de um novo mercado de drogas, o principal efeito das políticas de austeridade que tem tomado o globo, colocando em xeque nosso modelo de sociedade e nossa racionalidade política, relacionada ao modo com que o poder esforçou-se para gerir populações desde o aparecimento do biopoder. Dando um passo para além de uma análise estritamente biopolítica, reinscreve o fazer morrer e o deixar morrer no marco das tecnologias de poder, evidenciando como a morte tornou-se um mecanismo normal de governo, inserido-se em um projeto político-militar de guerra às drogas e sendo uma estratégia privilegiada que permite a criação de uma tensão singular entre fazer viver, fazer morrer e deixar morrer
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Mohammad, Noor. "Desiccation Cracking Behaviour in Thin Bentonite Layers". Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/22231.
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This thesis investigates the behaviour of desiccation cracks in thin bentonite layers under different conditions (initial water content, layer thickness, temperature and mixtures with kaolinite). For this, a comprehensive series of experiment was conducted as well as some theoretical models were developed. The theoretical model was developed based on the critical cracking thickness following the principles of linear elastic fracture mechanics (Chapter 4). This model was then used in the following chapters and validated with the experimental investigations. Also, hydraulic properties of the cracked soil mass were modelled and the effects of cracks on hydraulic conductivity and water retention properties were shown. In the experimental investigations, firstly, the combined effects of initial water content and layer thickness were studied in a phase diagram to observe the behaviour of desiccation cracks (Chapter 5). It was found that critical cracking thickness could be an important factor in distinguishing cracked and non-cracked samples in the phase diagram. Characteristics of cracks (crack density, total crack length, average crack length and crack width) increase with increasing layer thicknesses as well as initial water contents. The effects of temperature (Chapter 6) and mixtures of bentonite-kaolinite (Chapter 7) on desiccation cracking were investigated in the phase diagram developed in Chapter 5. At higher temperatures, the critical thickness of a clay layer ould be decreased. Results of bentonite-kaolinite mixture demonstrated that the phase boundary shifted to increase the critical thickness of the clay layers of mixtures containing less bentonite (i.e. more kaolinite). Crack morphology was also affected by the change in temperatures and properties of the mixtures. In summary, this study shows some understanding of desiccation cracking behaviour and could provide insights for better design of clay liners, which often at risk of desiccation problem.
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Lanfranchi, Noe͏̈l. "Toxicologie du crack". Paris 5, 1992. http://www.theses.fr/1992PA05P152.
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Zanotto, Daniele Farina. "Usuários de crack". reponame:Repositório Institucional da UFSC, 2016. https://repositorio.ufsc.br/xmlui/handle/123456789/172180.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Programa de Pós-Graduação em Saúde Coletiva, Florianópolis, 2016.Made available in DSpace on 2017-01-03T03:15:53Z (GMT). No. of bitstreams: 1 343122.pdf: 1296653 bytes, checksum: fb56bd92cf8165b2e622c174b163e35a (MD5) Previous issue date: 2016
O consumo e os conceitos do uso de drogas passaram por modificações em seu significado no desenrolar da história. Hoje é o crack que detém a atenção e é veiculado constantemente pelos meios de comunicação. Seus primeiros registros no Brasil datam do final dos anos 1980, mas somente a partir de 2010 sua visibilidade ganhou mais espaço nas pesquisas, na atenção e assistência a saúde, no Plano de Enfrentamento do Governo Federal, mas principalmente na mídia, escrita, falada e televisionada. Diante desse cenário esta tese parte do pressuposto que o conhecimento transmitido por reportagens forma opiniões sobre o tema, e essa forma de apresentar o usuário de crack vem na contramão da Reforma Psiquiátrica Brasileira. A Lei nº 10.216/2001, que dispõe sobre a proteção e os direitos das pessoas portadoras de transtornos mentais e redireciona o modelo assistencial em saúde mental, não foi suficiente para atingir estas lacunas e são reproduzidas, por esta via de informação, formas biomédicas e medicalizadas do cuidado a estes indivíduos. Dessa forma desenvolvemos uma pesquisa documental com abordagem qualitativa, que buscou compreender como os usuários desta droga são descritos nas reportagens de um jornal e duas revistas de circulação nacional nos últimos 5 anos. O material encontrado foi submetido à análise textual discursiva. A base teórica para acessar o objeto de estudo contou com os autores Michel Foucault, Erwin Goffman, Howard Becker e John Thompson. Buscamos, por meio do percurso metodológico e marco teórico, desnaturalizar as maneiras como os discursos sobre os usuários de crack são veiculados pela mídia. Nosso corpus de pesquisa mostrou que as propostas de cuidado, presentes na maioria das reportagens, continuam mantendo seu caráter disciplinar e normalizador, muito mais do que terapêutico em relação aos usuários de crack. Bem como na história da loucura na Idade Clássica de Foucault, estas pessoas continuam sendo excluídas com o intuito de deixar a população livre dos perigos de seu convívio. Os textos analisados também permitiram afirmar que o discurso veiculado pela mídia constrói no senso comum um perfil negativo sobre o usuário de crack, permeado por preconceito e estigma. É transmitido de forma sensacionalista e em alguns casos higienista, dando ênfase ao enfrentamento aos usuários e não somente à droga em si. Por fim, a forma como os usuários de crack são apresentados pela mídia é capaz de materializar as representações da classe dominante e de refletir na forma em que a sociedade convive com eles. Entende-se como classe dominante aquela representada pelo modelo biomédico de cuidado em saúde mental.
Abstract : The consume and the ideas of drugs use have been changed in the course of time. Nowadays, the crack cocaine got so visibility in the media. Althought your history on Brazil began in the eights end, the studies, the healthcares, the Federal Combat Plan and the media (writennpress, oralpress, tvpress) have been show it from the penultimate year of first decade of 21 century. In view of this, this thesis pressuppose that the reports make ideias about the crack cocaine users. This description, however, affront the brasilian Psychiatric Reform. The reports reveal that the Law 10.216/2001 doesn´t implanted inside de the brasilian society. The biomedics healthcares are still strongs, same more than ten years after that. This law intend protect and guarantee the citizens mental disorders rights as well as reorganize the mental heath politics. The reseach is a documental qualitative study. The aim is comprehend the descriptions about the crack cocaine users in a national newspaper and in two national magazines between january 2009 and july 2015. The reports was submitted to discourse textual analysis. Michel Foucault, Erwin Goffman, Howard Becker and John Thompson compose the theoretical base. We seek denaturalize the media discourses about the crack cocaine users. According with our reseach corpus, the heathcares still keep a normalizing and disciplining line much more than a real therapy. As in Foucault´s madness history, the crack cocaine users currently are censure to exclusion. The idea is repel them to avoid your problems. The reports created a negative portrait of crack cocaine users. This portraits are prejudice and full of stigmas. The discourse is sensacionalist and sometimes hygienist, emphasizing the confront with the crack cocaine users. At last, the crack cocaine users portraits are still controled by the biomedic model of mental health.
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Yandow, Chantelle. "Crack mothers, crack babies, and black male dope dealers productions of deviance during america's crack cocaine panic in the 1980s". Honors in the Major Thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/529.
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A moral panic erupted during the 1980s among the American public when stories about crack cocaine saturated the media. In this thesis I analyze how discursive productions of deviancy operated in the CBS news documentary: 48 Hours on Crack Street (1986) and other print news sources at that time. Three salient characters that appear in news media discourse during the panic are "crack mothers," "crack babies," and "Black male dope dealers." The news media frightened the public with such representations (among others) and the public urged politicians to get tough on drug crime to control the so-called crack cocaine plague. Politicians responded with omnibus drug reforms that established mandatory minimum sentences and the controversial 100:1 sentencing disparity between crack and powder cocaine. The enforcement of the draconian drug laws that were passed in response to the crack cocaine panic continues to be a contributing factor to America's current prison crisis. Moreover, the laws are enforced in ways that disproportionately punish the poor and African-Americans. I conclude that the criminal disenfranchisement of millions of people since the 1980s relates to the media's representation of the crack cocaine "epidemic" and the legislation that was passed to control illicit drugs such as crack cocaine.B.A.
Bachelors
Arts and Humanities
Religious Studies
Książki na temat "Crack"
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Hodge, Merle. Crick Crack, Monkey. Oxford: Heinemann, 2000.
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Revill, G. W. An automatic crack measuring system using the direct-current potential-difference method. Melbourne: Aeronautical Research Laboratories, 1985.
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Nancy, Levitin, red. Crack. New York: F. Watts, 1994.
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Clancy, Leo. Crack. London: Secker & Warburg, 1986.
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Cleary, Brendan. Crack. Newcastle upon Tyne: Echo Room Press, 1990.
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Olive, M. Foster. Crack. Redaktor Triggle D. J. New York: Chelsea House, 2008.
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Crack. New York: Rosen Pub. Group, 1991.
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Peck, Rodney G. Crack. New York: Rosen Pub. Group, 2000.
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Hudak, S. J. A comparison of single-cycle versus multiple-cycle proof testing strategies. Huntsville, Ala: George C. Marshall Space Flight Center, 1990.
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M, Fisher Douglas, Holka Donna i Lewis Research Center, red. Variables controlling fatigue crack growth of short cracks. [Cleveland, Ohio: National Aeronautics and Space Administration, Lewis Research Center, 1986.
Znajdź pełny tekst źródłaCzęści książek na temat "Crack"
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Sun, Zhaoyun, Lili Pei, Bo Yuan, Yaohui Du, Wei Li i Yuxi Han. "Pavement Crack Detection and Quantification Based on Scanning Grid and Projection Method". W Lecture Notes in Civil Engineering, 273–81. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-1260-3_24.
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AbstractPavement cracks are difficult to monitor and quantify due to their complex texture and easy to be disturbed by noise and illumination. To solve this problem, a road crack monitoring and quantification method based on vehicle video is proposed. First, a method for extracting morphological features of dynamic road cracks is proposed. Combine automated vehicle-mounted equipment with GPS signals to obtain crack images with location information. Then, a calculation algorithm of crack parameters based on the combination of UK scanning grid and projection method is proposed, which uses the reverse engineering principle of perspective transformation to correct the image and divides the entire image into grid blocks. Finally, based on the analysis of different crack grades, the crack distress evaluation method is improved. The experimental results show that the proposed method has strong reliability and adaptability and achieves high-frequency and wide-range road detection.
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Bährle-Rapp, Marina. "crack". W Springer Lexikon Kosmetik und Körperpflege, 132. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-71095-0_2496.
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Gooch, Jan W. "Crack". W Encyclopedic Dictionary of Polymers, 176. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_3030.
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Hoyer, Daniel, Eric P. Zorrilla, Pietro Cottone, Sarah Parylak, Micaela Morelli, Nicola Simola, Nicola Simola i in. "Crack". W Encyclopedia of Psychopharmacology, 361. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-540-68706-1_1559.
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Arndt, T. "Crack". W Springer Reference Medizin, 630. Berlin, Heidelberg: Springer Berlin Heidelberg, 2019. http://dx.doi.org/10.1007/978-3-662-48986-4_789.
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Arndt, T. "Crack". W Lexikon der Medizinischen Laboratoriumsdiagnostik, 1. Berlin, Heidelberg: Springer Berlin Heidelberg, 2017. http://dx.doi.org/10.1007/978-3-662-49054-9_789-1.
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Pandey, Pratima. "Crack". W Encyclopedia of Earth Sciences Series, 163. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-90-481-2642-2_77.
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Clutterbuck, Richard. "Crack". W Drugs, Crime and Corruption, 70–77. London: Palgrave Macmillan UK, 1995. http://dx.doi.org/10.1057/9780230376472_9.
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Koyama, Motomichi, Hiroshi Noguchi i Kaneaki Tsuzaki. "Microstructural Crack Tip Plasticity Controlling Small Fatigue Crack Growth". W The Plaston Concept, 213–34. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-7715-1_10.
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AbstractIn this chapter, we present a metallurgical–mechanical mechanism-based strategy for the design of fatigue-resistant metals. Specifically, we elucidate the importance of the metallurgical microstructure in a mechanical singular field (crack tip). The fatigue crack growth resistance is controlled through the crack tip “plasticity”, and the effect of the associated microstructure becomes significant when the crack is “small (or short)”. More importantly, the resistance to small crack growth determines a major portion of fatigue life and strength. Therefore, the microstructural crack tip plasticity is a key breakthrough to the development of fatigue-resistant metals. As successful examples of this concept, we introduce the effects of grain refinement, martensitic transformation, strain aging, dislocation planarity enhancement, and microstructure heterogeneity on small fatigue crack growths.
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Li, Feng, Jinyan Feng, Youxin Li i Siqi Zhou. "Crack Filling and Crack Seal Band". W Springer Tracts on Transportation and Traffic, 55–71. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-6206-8_3.
Pełny tekst źródłaStreszczenia konferencji na temat "Crack"
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"FEATHERING CRACKS FORMATION AT SINGLE WING CRACK EVOLUTION". W Engineering Mechanics 2019. Institute of Thermomechanics of the Czech Academy of Sciences, Prague, 2019. http://dx.doi.org/10.21495/71-0-157.
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Biner, S. B. "Crack Tip Stress Fields and Creep Crack Growth of Interface Cracks in Functionally Graded/Layered Materials". W ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0650.
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Abstract In this study, the growth behavior of interface cracks in bimaterials and in graded/layered materials resulting from the creep cavitation was studied. The growth model includes the effects of material deposition resulting from the growth of creep cavities on the crack tip stress fields. The results indicate that in graded/layered materials under identical applied loading, the location of the interface crack strongly influence the amplitude of the stress field (C*) at steady-state. Due to large variation in the distribution of the stresses ahead of the interface cracks at creep regime, depending upon the crack location, the creep crack growth rates will be significantly different from each other under identical loading for a given graded/layered material.
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Li, Chuangmin, Heming Zhou, Zhiyong Wu i Zhiyong Wang. "Alleviating Crack Properties of Crack Alleviating Mixture". W Second International Conference on Transportation Engineering. Reston, VA: American Society of Civil Engineers, 2009. http://dx.doi.org/10.1061/41039(345)290.
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Patel, S. K., B. Dattaguru i K. Ramachandra. "Crack Shape Development of Two Interacting Surface Elliptical Cracks". W ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-1909.
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The issue of assessing residual life of an aged structure based on damage tolerance concepts attained significance in high technology fields such as aerospace, piping and pressure vessels and nuclear engineering. Computational fracture analysis of these structures in the presence of single or multi-site surface flaws is essential for life estimation and life extension. In this paper development of accurate post-processing technique (Modified Virtual Crack Closure Integral) to estimate strain energy release rates, and simple numerical method to simulate crack shape development in single and multiple interacting cracks (till they merge into single dominant crack) is presented. Crack shape development in single surface elliptical cracks was carried out earlier in literature using 2 degree of freedom model wherein fatigue crack growth is estimated along the major and minor axis of the ellipse and new crack shape was derived by fitting an ellipse to these points. A special three-degree of freedom model is proposed and presented in this paper for interacting and coalescing cracks. The crack shape development was checked with experimental work on coupons with multi-site surface cracks tested under fatigue loading. In safety critical aerospace and thick piping structures this work is significant in predicting the remaining life of aged components with multi-site damage.
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Varney, Philip, i Itzhak Green. "Rotordynamic Crack Diagnosis: Distinguishing Crack Depth and Location". W ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-94615.
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The goal of this work is to establish a condition monitoring regimen capable of diagnosing the depth and location of a transverse fatigue crack in a rotordynamic system. The success of an on-line crack diagnosis regimen hinges on the accuracy of the crack model used. The model should account for the depth of the crack and the localization of the crack along the shaft. Negating the influence of crack location on system response ignores a crucial component of real cracks. Two gaping crack models are presented; the first simulates a finite-width manufactured notch, while the second models an open fatigue crack. An overhung rotordynamic system is modeled, imitating an available rotordynamic test rig. Four degree-of-freedom equations of motion for both crack models are presented and discussed, along with corresponding transfer matrix techniques. Free and forced response analyses are performed, with emphasis placed on results applicable to condition monitoring. It is demonstrated that two identifiers are necessary to diagnose the crack parameters: the 2X resonance frequency and the magnitude of the 2X component of the rotor angular response at resonance. First, a contour plot of the 2X resonant shaft speed versus crack depth and location is generated. The magnitude of the 2X component of the rotor’s angular response along the desired contour is obtained, narrowing the possible pairs of crack location/depth to either one or two possibilities. Practical aspects of the diagnosis procedure are then discussed.
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Anand, Sukhad, Saksham Gupta, Vaibhav Darbari i Shivam Kohli. "Crack-pot: Autonomous Road Crack and Pothole Detection". W 2018 Digital Image Computing: Techniques and Applications (DICTA). IEEE, 2018. http://dx.doi.org/10.1109/dicta.2018.8615819.
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Yoon, Yeo-San, Seongdeok Bang, Francis Baek i Hyoungkwan Kim. "Pavement Crack Mosaicking Based on Crack Detection Quality". W 36th International Symposium on Automation and Robotics in Construction. International Association for Automation and Robotics in Construction (IAARC), 2019. http://dx.doi.org/10.22260/isarc2019/0160.
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Kim, Nak Hyun, Yun Jae Kim, Catrin M. Davies, Ali Mehmanparast i Kamran M. Nikbin. "The Effect of Discontinuous Crack in Creep Crack Growth Tests". W ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-98142.
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Discontinuous cracks ahead of the leading crack tip may be present in observedcertain creep crack growth tests as well as in components. In this work, a single crack of different dimensions and distance from the leading crack has been numerically modeled in a compact tension specimen using elastic, elastic-plastic and elastic-plastic-creep loading. In order to examine their effects on fracture mechanics parameters a sensitivity analysis was performed to determine the effects of size and distance of the secondary crack with respect to the main crack. t The elastic analysis shows that the compliance is insensitive small cracks ahead of the main crack. Limit load analyses, assuming an elastic-perfectly plastic material, show that the limit load decreases due to the presence of discontinuous cracks ahead of the main crack. Theload versus plastic load-line displacement response of the specimen was significantly influenced by discontinuous cracking. The J contour parameter and C*-integral have been evaluated at the three crack tips and the average of all of them derived for the appropriate contours were compared with the valuesobtained from on ASTM E1820(1) and E1457(2). Whilst the average values of the contour integral are similar to the ASTM J and C* values there is significant differences in J and C* for the individual crack tip values. This need to be further evaluated in future work.
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Slaughter, Mark, Kevin Spencer, Jane Dawson i Petra Senf. "Comparison of Multiple Crack Detection In-Line Inspection Data to Assess Crack Growth". W 2010 8th International Pipeline Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ipc2010-31255.
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Ultrasonic inline inspection (ILI) tools have been used in the oil and gas pipeline industry for the last 14 years to detect and measure cracks. The detection capabilities of these tools have been verified through many field investigations. ILI ultrasonic crack detection has good correlation with the crack layout on the pipe and estimating the maximum crack depth for the crack or colony. Recent analytical developments have improved the ability to locate individual cracks within a colony and to define the crack depth profile. As with the management of corroding pipelines, the ability to accurately discriminate active from non-active cracks and to determine the rate of crack growth is an essential input into a number of key integrity management decisions. For example, in order to identify the need for and timing of field investigations and/or repairs and to optimize re-inspection intervals crack growth rates are a key input. With increasing numbers of cracks and crack colonies being found in pipelines there is a real need for reliable crack growth information to use in prioritizing remediation activities and planning re-inspection intervals. So as more and more pipelines containing cracks are now being inspected for a second time (or even third time in some cases), the industry is starting to look for quantitative crack growth information from the comparison of repeat ultrasonic crack detection ILI runs. This paper describes the processes used to analyze repeat ultrasonic crack detection ILI data and crack growth information that can be obtained. Discussions on how technical improvements made to crack sizing accuracy and how field verification information can benefit integrity plans are also included.
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Nakanishi, Shin, Fuminori Iwamatsu, Masaki Shiratori i Hisao Matsushita. "Estimation of Fatigue Crack Propagation of Subsurface Cracks by “SCAN”". W ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93248.
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The authors have proposed an influence function method to calculate stress intensity factor, K, of the surface cracks. This method makes the calculating task easier for arbitrarily distributed surface stresses. They have developed the database of influence coefficients, Kij, for various types of surface cracks through a series of finite element analyses.[1] They also have developed a software system “SCAN” (Surface Crack Analysis), from the database. The K values of surface cracks can be evaluated immediately, and further, fatigue crack propagation can be simulated easily with a personal computer. A fatigue crack often initiates from a defect located at the subsurface of a structural member. In this case, it is important to account for the fatigue life from the initiation of a subsurface crack to its propagation into a surface crack. However, since it is difficult to simulate this process precisely, the authors have proposed a simple model about the transition from a subsurface crack into a surface crack based upon ASME CODE SECTION XI [2] and WES 2805 STANDARD. [3] They have developed a SCAN system – Subsurface Crack Version-. They calculated the fatigue life for some models of subsurface cracks and compared the quantitative differences between two standards.
Raporty organizacyjne na temat "Crack"
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Pitas, A. Crack Parameters. Office of Scientific and Technical Information (OSTI), październik 1985. http://dx.doi.org/10.2172/1030022.
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Wendelberger, James G. Pit and Crack Detection Summary Report Crack Detection. Office of Scientific and Technical Information (OSTI), marzec 2019. http://dx.doi.org/10.2172/1504667.
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Post, Roger A. Crack Growth Testing. Fort Belvoir, VA: Defense Technical Information Center, marzec 1994. http://dx.doi.org/10.21236/ada361403.
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Oster, C. A., i M. J. Danielson. Model of crack electrochemistry. Office of Scientific and Technical Information (OSTI), marzec 1986. http://dx.doi.org/10.2172/5973736.
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Welch, DE. Nonlinear Crack Growth Monitoring. Office of Scientific and Technical Information (OSTI), marzec 2001. http://dx.doi.org/10.2172/814371.
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Welch, D. E. Nonlinear Crack Growth Monitoring. Office of Scientific and Technical Information (OSTI), styczeń 2000. http://dx.doi.org/10.2172/816619.
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Gavenda, D. J., P. R. Luebbers i O. K. Chopra. Crack initiation and crack growth behavior of carbon and low-alloy steels. Office of Scientific and Technical Information (OSTI), styczeń 1997. http://dx.doi.org/10.2172/505296.
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Biner, S. B. An analysis of creep crack growth of interface cracks in layered/graded materials. Office of Scientific and Technical Information (OSTI), lipiec 1997. http://dx.doi.org/10.2172/505289.
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Smith, C. W., D. M. Constantinescu i C. T. Liu. Stress Intensity Factors and Crack Paths for Cracks in Photoelastic Motor Grain Models. Fort Belvoir, VA: Defense Technical Information Center, maj 2002. http://dx.doi.org/10.21236/ada410794.
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Keeney-Walker, J., B. R. Bass i J. D. Landes. An investigation of crack-tip stress field criteria of predicting cleavage-crack initiation. Office of Scientific and Technical Information (OSTI), wrzesień 1991. http://dx.doi.org/10.2172/5205137.
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