Bibliografías temáticas / Void growth and coalescence

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Literatura académica sobre el tema "Void growth and coalescence"

Autor: Grafiati

Publicado: 4 de junio de 2021

Última modificación: 3 de febrero de 2022

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Artículos de revistas sobre el tema "Void growth and coalescence"

Klassen, R. J., G. C. Weatherly y B. Ramaswami. "Void growth and coalescence". Metallurgical Transactions A 23, S1 (diciembre de 1992): 3273–80. http://dx.doi.org/10.1007/bf03024534.

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Ma, Dong Fang, Gao Tao Deng, Da Nian Chen, Shan Xing Wu y Huan Ran Wang. "A Visualized Investigation of Void Growth and Coalescence in Pure Copper Sheets under Impact Tension". Advanced Materials Research 317-319 (agosto de 2011): 1717–24. http://dx.doi.org/10.4028/www.scientific.net/amr.317-319.1717.

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The multi-tension loading in the optimized tensile split Hopkinson bar tests for pure copper sheets was used to investigating growth and coalescence of drilled voids in pure copper sheets, recorded by a high-speed camera. The results of scanning electron microscopical investigation of the microvoid evolution in recovered pure copper sheets showed void coalescence mechanisms which are similar to that of visualized drilled voids. The semi-empirical relation [8] for void shape evolution under quasi-static tension was compared with our computed results revealing the dynamic and clustering effects on void growth. The possibility of application of Thomason model[9] and Considere’s condition[10] for void coalescence to thermoviscoplatic constitutive model was explored under impact tension. The main effects affecting dynamic growth and coalescence of voids were presented including the geometry (void size, shape, orientation, spacing), the material properties (dynamic constitutive model) and the stress state (impact tension condition).

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Rao, U. S. y R. C. Chaturvedi. "Sheet Metal Forming Limits Under Complex Strain Paths Using Void Growth and Coalescence Model". Journal of Engineering Materials and Technology 108, n.º 3 (1 de julio de 1986): 240–44. http://dx.doi.org/10.1115/1.3225875.

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It is well established that ductile fracture occurs by nucleation, growth and coalescence of voids. Several models have been developed to predict limits under constant strain ratio paths considering void inhomogeneity and void growth. In this paper the void growth and coalescence model developed by Rao and Chaturvedi for predicting forming limits under constant strain ratio paths, has been extended for predicting forming limits under two stage strain paths. The predicted results have been compared with experimental results of Ishigaki and analyzed.

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Tsuji, Tomoaki. "The Void Growth Simulations in the Hyper-Elastic Material with Multiple Seeds". Materials Science Forum 502 (diciembre de 2005): 45–50. http://dx.doi.org/10.4028/www.scientific.net/msf.502.45.

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The behaviors of a material are nonlinear in the large deformed region. The hyper elastic models can describe such non linear materials. If the hyper elastic material is applied to the hydrostatic tensile load, the void begins to grow when the load exceed the critical value. It is important to study the coalescence of the void growth in order to consider the destruction of the material. In this paper, the void growth simulations in the hyper-elastic material with multiple seeds are studied. The unit rectangular cell with small voids is subjected to the hydrostatic tensile load. This problem can be analyzed by FEM. However, the simulation with the larger number of the voids is not possible. Thus, the CA (Cellular Automaton) is used to describe the behaviors of the void coalescence and the possibility of CA is discussed.

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WONG, W. H., T. F. GUO y L. CHENG. "VOID GROWTH AND INTERACTION IN A SOFT MATERIAL". International Journal of Modern Physics B 24, n.º 01n02 (20 de enero de 2010): 295–304. http://dx.doi.org/10.1142/s021797921006423x.

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Void growth and interaction in a soft material is explored numerically in this work in a three-dimensional context. Discrete initially spherical voids are explicitly modeled ahead of a crack front under small-scale yielding. While a multiple void interaction mechanism can be identified in our study, computations show a qualitatively similar void growth exhibited for the initial void volume fractions considered, f0 = 0.1% and 1%. Extensive void growth in the damage process zone are observed upon application of load, with the resultant deformed voids taking on a prolated void shape. A micromechanical analysis of void growth is also carried out and the numerical results suggest a failure mechanism in the soft material not attributed to void coalescence but by a mechanism analogous to tearing.

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Jones, M. K., M. F. Horstemeyer y A. D. Belvin. "A Multiscale Analysis of Void Coalescence in Nickel". Journal of Engineering Materials and Technology 129, n.º 1 (9 de junio de 2006): 94–104. http://dx.doi.org/10.1115/1.2400265.

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An internal state variable void coalescence equation developed by Horstemeyer, Lathrop, Gokhale, and Dighe (2000, Theor. Appl. Fract. Mech., 33(1), pp. 31–47) that comprises void impingement and void sheet mechanisms is updated based on three-dimensional micromechanical simulations and novel experiments. This macroscale coalescence equation, developed originally from two-dimensional finite element simulations, was formulated to enhance void growth. In this study, three-dimensional micromechanical finite element simulations were employed using cylindrical and spherical void geometries in nickel that were validated by experiments. The number of voids, void orientation, and void spacing were all varied and tested and simulated under uniaxial loading conditions. The micromechanical results showed excellent agreement with experiments in terms of void volume fractions versus strain and local void geometry images. Perhaps more importantly, the macroscale internal state variable void coalescence equation did not require a functional form change but just a coefficient value modification.

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Chen, Jie, Darby J. Luscher y Saryu J. Fensin. "The Modified Void Nucleation and Growth Model (MNAG) for Damage Evolution in BCC Ta". Applied Sciences 11, n.º 8 (9 de abril de 2021): 3378. http://dx.doi.org/10.3390/app11083378.

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A void coalescence term was proposed as an addition to the original void nucleation and growth (NAG) model to accurately describe void evolution under dynamic loading. The new model, termed as modified void nucleation and growth model (MNAG model), incorporated analytic equations to explicitly account for the evolution of the void number density and the void volume fraction (damage) during void nucleation, growth, as well as the coalescence stage. The parameters in the MNAG model were fitted to molecular dynamics (MD) shock data for single-crystal and nanocrystalline Ta, and the corresponding nucleation, growth, and coalescence rates were extracted. The results suggested that void nucleation, growth, and coalescence rates were dependent on the orientation as well as grain size. Compared to other models, such as NAG, Cocks–Ashby, Tepla, and Tonks, which were only able to reproduce early or later stage damage evolution, the MNAG model was able to reproduce all stages associated with nucleation, growth, and coalescence. The MNAG model could provide the basis for hydrodynamic simulations to improve the fidelity of the damage nucleation and evolution in 3-D microstructures.

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Tekoğlu, C., J. W. Hutchinson y T. Pardoen. "On localization and void coalescence as a precursor to ductile fracture". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, n.º 2038 (28 de marzo de 2015): 20140121. http://dx.doi.org/10.1098/rsta.2014.0121.

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Two modes of plastic flow localization commonly occur in the ductile fracture of structural metals undergoing damage and failure by the mechanism involving void nucleation, growth and coalescence. The first mode consists of a macroscopic localization, usually linked to the softening effect of void nucleation and growth, in either a normal band or a shear band where the thickness of the band is comparable to void spacing. The second mode is coalescence with plastic strain localizing to the ligaments between voids by an internal necking process. The ductility of a material is tied to the strain at macroscopic localization, as this marks the limit of uniform straining at the macroscopic scale. The question addressed is whether macroscopic localization occurs prior to void coalescence or whether the two occur simultaneously. The relation between these two modes of localization is studied quantitatively in this paper using a three-dimensional elastic–plastic computational model representing a doubly periodic array of voids within a band confined between two semi-infinite outer blocks of the same material but without voids. At sufficiently high stress triaxiality, a clear separation exists between the two modes of localization. At lower stress triaxialities, the model predicts that the onset of macroscopic localization and coalescence occur simultaneously.

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Banabic, Dorel y Abdolvahed Kami. "Applications of the Gurson’s model in sheet metal forming". MATEC Web of Conferences 190 (2018): 01002. http://dx.doi.org/10.1051/matecconf/201819001002.

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Recent advances in the modelling of metals encompass modelling of metals structural inhomogeneity, damage, porosity, twinning/untwining and non-local and second order effects. This presentation is focused on modelling the void growth in ductile fractures. The growth and coalescence of microscopic voids are the main mechanisms in ductile fracture of bulk metallic parts. In sheet metals, ductile fracture is preceded by necking during which existing voids do not have significant growth. However, necking is highly sensitive to plastic flow direction which in turn is sensitive to the presence of voids. Also, under biaxial strain loading, the final fracture in the necking region is still controlled by void growth; hence an accurate fracture prediction is crucial for crash simulations. Finally, in super-plastic sheet forming, void growth and coalescence may precede or accompany necking. Therefore, there is as increasing interest in modelling of voids in the sheet metals. As an application, we show how the predictions of some forming limit curves (FLCs) can be affected by accurate simulation of voids growth.

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Wang, Yong Gang, Hong Liang He, Li Li Wang y Fu Qian Jing. "Percolation-Relaxation Model with Critical Damage for Describing the Dynamic Tensile Spall of Ductile Metals". Key Engineering Materials 324-325 (noviembre de 2006): 121–24. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.121.

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In the framework of percolation theory, a simple void-coalescence model combined with the constitutive relations for describing the stress relaxation and material softening during the void-coalescence process, name as the percolation-relaxation (P-R) model, is proposed to describe the dynamic tensile spallation of ductile metals. A critical damage is introduced and coupled into the model to identify the onset of the void coalescence. Mesoscopically, the critical damage corresponds to the critical intervoid ligament distance (ILD), indicating the start of transition from the void-growth to the void-coalescence.

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Tesis sobre el tema "Void growth and coalescence"

Thomson, Ronald D. "Ductile fracture by void nucleation, growth and coalescence". Thesis, University of Glasgow, 1985. http://theses.gla.ac.uk/6487/.

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Plastic deformation in ductile metals is limited by a mechanism in which voids, nucleated at second phase particles, grow and coalesce to form a crack. The results of a finite element solution for spherical elastic inclusions in a plastically deforming matrix are discussed. These results have been used in conjunction with experimental work using notched tensile specimens to generate multiaxial states of stress from which the local conditions leading to decohesion of the inclusion/matrix interface were determined. An important feature of these results is the statistical distribution of the interfacial strength. This distribution is bimodal, showing the presence of both weakly and strongly bonded particles. The latter have a modal strength of about 7 times the initial yield stress and the weakly bonded particles are assumed to be pre-existent. Experiments in plane and axisymmetric states of strain indicate that while the stress state is of relevance, the remote strain state is not. The absence of a macroscopic strain state effect is explained in terms of the statistical distribution of the voids nucleated from the population of randomly distributed inclusions. The stress and strain concentrations possible in local patches of high porosity have been investigated by a finite element approach based on the mechanics of a dilating continuum to determine void growth in the porous aggregate and the local conditions at failure. This investigation recognises the importance of the local hardening rate of the aggregate material and leads naturally to the idea of a size scale for failure, in the light of which the concept of a crack-like defect is re-examined.

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Azhar, Mishaal. "2D Effects of Anisotropy on the Ductile Fracture of Titanium". Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/26280.

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Titanium is a widely used metal in industrial and commercial applications. It retains anisotropic mechanical properties at room temperature due to its HCP crystal structure. The effects of crystal orientation have been studied theoretically and through modeling though there is a lack of empirical data available on the topic. The work presented here uses laser-machined voids along with EBSD analysis to study the ductility of grains in different orientations to better understand the microscale fracture process in α-titanium. Experimental results show that hard grains with their c-axis parallel to the tensile direction behave in a less ductile manner than grains with their c-axis oriented away from the tensile direction. This is due to the basal slip systems activating in the former case and prismatic slip systems in the latter. Models utilized include the McClintock model for void growth, Brown-Embury model for void coalescence and FEM crystal plasticity simulations

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Alinaghian, Yaser. "The Effect of Pre-strain and Strain Path Changes on Ductile Fracture". Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/23917.

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Industrial metal forming operations generally require several deformation steps in order to create the final product. The mechanical behavior of materials undergoing strain path changes can be very different from those deformed in a given direction to fracture. The work presented here employed laser drilled model materials to better understand the effect of pre-strains and strain path changes on void growth and linkage leading to fracture is studied. The experimental results show that increasing pre-strain results in faster void growth which was justified in terms work hardening rate in the sample. Scanning electron microscope images revealed that the ductility of the sample decreased with increasing pre-strain but only slightly compared to the large decrease in far field strain at failure. This suggests that pre-strain affects strain localization significantly and to a lesser extent the ductility. Finally a finite element model has been built to predict the linkage between voids.

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Barsoum, Imad. "The effect of stress state in ductile failure". Doctoral thesis, Stockholm : Hållfasthetslära, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4667.

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Landron, Caroline. "Ductile damage characterization in Dual-Phase steels using X-ray tomography". Phd thesis, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00738820.

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Dans le cadre du développement de nuances d'aciers toujours plus performantes en termes de résistance à l'effort et à l'endommagement, les aciers Dual-Phase (DP) présentent un bon compromis résistance/ductilité. Cependant, il est nécessaire de disposer de meilleures connaissances concernant les mécanismes menant à la rupture de tels aciers. Les mécanismes d'endommagement ont ainsi été étudiés dans cette thèse à l'aide de la tomographie aux rayons X. Des essais de traction in-situ ont été réalisés sur plusieurs nuances d'aciers DP, un acier ferritique et un acier martensitique afin de caractériser chaque étape de l'endommagement ductile. Des observations qualitatives et des données quantitatives concernant la germination de l'endommagement, la croissance des cavités et la coalescence ont été recueillies lors de ces essais. Ces données quantitatives ont ensuite été utilisées pour le développement et/ou la validation de modèles d'endommagement. Une prédiction de la cinétique de germination a ainsi été proposée et la version du modèle de croissance de cavités de Rice et Tracey corrigée par Huang et prenant mieux en compte l'effet de la triaxialité a été validée expérimentalement. L'étape de coalescence des cavités menant à la rupture des matériaux a pour la première fois été caractérisée de façon quantitative dans un matériau industriel et des critères de coalescence ont été appliqués localement sur les couples de cavités présentes dans le matériau. L'utilisation de ces modèles analytiques a permis une meilleure compréhension des propriétés agissant sur les phénomènes mis en jeu. L'effet de la part cinématique de l'écrouissage sur la germination et la croissance de l'endommagement a notamment été souligné et validé par des essais de chargements complexes.

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Jones, Matthew Kenneth. "Multiscale Analysis of Void Coalescence in Ductile Metals". MSSTATE, 2004. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11112004-165827/.

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A mulitscale approach is used to model the coalescence of voids. At the microscale, cylindrical and spherical voids in nickel and the magnesium alloy AM60 are simulated through finite element analyses. The nickel cylindrical void simulations are compared to a set of experiments to validate this micromechanical finite element approach used to study void coalescence. At the macroscale, the coalescence portion of a microstructure-property material model is modified to reflect the behavior of three-dimensional spherical voids using results from the micromechanical simulations. An analysis of an automotive component illustrates the influence of void coalescence at the structural scale.

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Griffin, Joel Sterling. "A Numerical and Experimental Investigation of Void Coalescence Causing Ductile Fracture". Thesis, Fredericton: University of New Brunswick, 2012. http://hdl.handle.net/1882/36784.

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A series of experiments and finite-element simulations were performed in order to assess existing void coalescence criteria and propose a new model for the coalescence of cylindrical holes in a pure metal matrix during uniaxial stretching. The finite-element simulations were performed so that various plastic limit-load models could be evaluated at each strain increment during deformation, rendering predictions concerning the farfield strains required for coalescence. The experiments were performed in order to identify the actual far-field strain at the moment of incipient coalescence for the specimen geometries considered. The cylindrical-void models of Thomason (1990) and McClintock (1966) outperformed all of the other considered models in their original states. A modified form of the Ragab (2004) plastic limit-load model is proposed in the present work and is shown to have good agreement with the experimental results. The present model accounts for ligament work-hardening and ligament orientation.

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Galvin, Kevin Patrick. "Growth and coalescence in condensation". Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46310.

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Zhang, Hong Carleton University Dissertation Engineering Mechanical. "Fatigue crack growth and coalescence study". Ottawa, 1993.

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Camposagrado, Gabriel Rene. "Investigation of the cause and effect of air void coalescence in air-entrianed concrete mixes". Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-07082004-150638.

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Libros sobre el tema "Void growth and coalescence"

Chandra, Abhijit. Void nucleation and growth during plane strain extrusion. [S.l.]: The Danish Center for Applied Mathematics and Mechanics, The Technical University of Denmark, 1992.

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Bennasar, A. Modelling of void nucleation and growth in particle filled polymer film processing. Manchester: UMIST, 1994.

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Modeling void growth and movement with phase change in thermal energy storage canisters. [Washington, DC]: National Aeronautics and Space Administration, 1993.

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Crandall, Amy. Growth Hurts: A True Journey of Breaking the Chain and Filling the Void. AuthorHouse, 2007.

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Crandall, Amy. Growth Hurts: A True Journey of Breaking the Chain and Filling the Void. AuthorHouse, 2007.

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Modeling void growth and movement with phase change in thermal energy storage canisters. [Washington, DC]: National Aeronautics and Space Administration, 1993.

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Development and Implementation of a Shell Element With Pressure Variation Through the thickness and Void Growth and Nucleation Effects. Storming Media, 1999.

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Hendricks, Wanda A. A Distinctive Generation. University of Illinois Press, 2017. http://dx.doi.org/10.5406/illinois/9780252038112.003.0006.

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This chapter examines the unprecedented growth in activity and the coalescence of women's local and regional clubs in the early 1890s, a period that also saw Fannie Barrier Williams increase her reform activities in the black community and with the black women who had come to her aid. It begins with a discussion of Barrier Williams' involvement in the women's equality movement, citing in particular her membership in the Colored Women's League in Chicago that ushered in what she later referred to as the beginnings of “a reformatory movement” created entirely by women. It then considers how the push for political equality linked club women in Chicago to black club women across the country, along with Barrier Williams' belief in the ballot as a means of maintaining and improving black women's constitutional rights as well as her belief in black women's role in guiding the progress of the race in the new century. The chapter shows how Barrier Williams emerged as a leading representative and promoter of reforms and women's activism in the West/Midwest.

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Jorda, Vanesa y Jose M. Alonso. What works to mitigate and reduce relative (and absolute) inequality? A systematic review. UNU-WIDER, 2020. http://dx.doi.org/10.35188/unu-wider/2020/909-9.

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Over the past two decades, research on the impacts of a diverse range of public policies and income inequality has seen rapid growth. Despite the large number of publications to date, there remain important lacunae in our understanding of how policy interventions might help to reduce income inequality. This paper aims to fill this void by providing a systematic literature review of 270 publications that examine four key policy areas: (1) tax policy, (2) social benefits, (3) labour market interventions, and (4) education policy. We describe patterns of empirical findings and implications drawn from the reviewed publications. The strengths and weaknesses of the existing literature are also discussed, along with potential future research avenues.

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Venturelli, Shalini. Global Knowledge Society and Information Technology. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190846626.013.204.

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The Global Knowledge Society is a broad interdisciplinary effort that emerged in the last decade of the twentieth century to probe the socioeconomic, technological, and geopolitical dimensions of knowledge production, growth, diffusion, and exploitation, in terms of impact on the development of societies worldwide. As a field of inquiry, the Global Knowledge Society encompasses all areas of social science including international relations, international communication, information technology, international development, and economics, as well as across the physical sciences and humanities. It also aims to fill a historical void in traditional social science—from economics and political science to international affairs and development studies—for explaining structural and environmental differences in societal rates of knowledge generation, application and adoption. A number of models on knowledge development have been explored in the literature, including the “Distributed Information Networks” approach, the “Technological Diffusion” approach, the “Genius Theory of Invention” approach, the “Creative and Proprietary Incentives” approach, and the “Cultural Legacy” approach. Models outside the social sciences and humanities also offer some rich possibilities, such as those under the label of “Idea Evolution.” Several of the models suggest the need for rethinking the mystery of persistent societal differences in knowledge growth within and between countries. Future research on knowledge society should consider bringing together researchers and policymakers from many disciplines across the natural and social sciences to review the substance of the field’s comparative methods and findings using interdisciplinary frameworks and complex factors.

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Capítulos de libros sobre el tema "Void growth and coalescence"

Jin, Helena, Wei-Yang Lu, Alejandro Mota, Jay Foulk y George Johnson. "Void Growth and Coalescence in Aluminum Alloy". En Conference Proceedings of the Society for Experimental Mechanics Series, 199–202. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4614-4235-6_27.

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Chen, Zengtao y Cliff Butcher. "Void Growth to Coalescence: Unit Cell and Analytical Modelling". En Micromechanics Modelling of Ductile Fracture, 101–32. Dordrecht: Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-94-007-6098-1_4.

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Chen, Zengtao y Cliff Butcher. "Modelling Void Growth to Coalescence in a 3-D Particle Field". En Micromechanics Modelling of Ductile Fracture, 245–74. Dordrecht: Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-94-007-6098-1_10.

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Vu, Cong Hoa, Do Won Seo y Jae Kyoo Lim. "Analysis of Spherical Void Growth and Coalescence in Metal Plastic Straining Process". En Key Engineering Materials, 2837–42. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-978-4.2837.

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Litster, Jim y Bryan Ennis. "Consolidation, Coalescence and Growth". En Particle Technology Series, 75–120. Dordrecht: Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-94-017-0546-2_4.

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Kardos, J. L. "Void Growth and Dissolution". En Processing of Composites, 182–207. München: Carl Hanser Verlag GmbH & Co. KG, 2000. http://dx.doi.org/10.3139/9783446401778.006.

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Needleman, A., V. Tvergaard y J. W. Hutchinson. "Void Growth in Plastic Solids". En Topics in Fracture and Fatigue, 145–78. New York, NY: Springer New York, 1992. http://dx.doi.org/10.1007/978-1-4612-2934-6_4.

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Carroll, M. M. "Micromodeling of Void Growth and Collapse". En Homogenization and Effective Moduli of Materials and Media, 78–96. New York, NY: Springer New York, 1986. http://dx.doi.org/10.1007/978-1-4613-8646-9_4.

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Abdelkader, A. y Ch A. R. Saleh. "Coupling Void Coalescence Criteria in Finite Element Models: Application to Tensile Test". En TMS 2018 147th Annual Meeting & Exhibition Supplemental Proceedings, 369–76. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-72526-0_35.

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Roychowdhury, S., J. W. Gillespie y S. G. Advani. "Void Formation and Growth in Thermoplastic Processing". En Computer Aided Design in Composite Material Technology III, 89–107. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2874-2_7.

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Actas de conferencias sobre el tema "Void growth and coalescence"

Zheng, Yao-Ting, Zaoxiao Zhang, Guang-xu Cheng, Fu-Zhen Xuan y Zhengdong Wang. "Molecular Dynamics Simulation of Hydrogen-Activated Coalescence and Growth of Nano-Voids". En ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65577.

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The understanding of hydrogen embrittlement (HE) is of significant importance and fundamental interest owing to its negative effects on industrial metallic materials. The effect of solute H on the void coalescence and growth needs to be clarified. Using molecular dynamics simulation, the evolution of preexisting nano voids is studied in the presence of H atoms. As the per unit area concentration of trapped H atom on void surface reaches 0.45 /Å2, the movement of void is observed. It proceeds along with the interdiffusion of H and Fe atoms around the voids. Strain-mediated diffusion of H atoms from void surface to the zone between nearest voids occurs at first. Then the Fe atoms are affected by migrated H and diffuse in the opposite direction following the principle of energy minimization. Such mechanism can help us understand the formation of high pressure bubble at nano scale. Based on this useful information, some methods could be obtained to prevent the growth of voids further, such as strengthening the stability of metal lattice around voids by dopant etc.

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Tsuji, Tomoaki. "Multiple Void Growth Simulations in the Hyper-Elastic Material". En ASME/JSME 2004 Pressure Vessels and Piping Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/pvp2004-2741.

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If the hydrostatic tensile load is applied to a hyper-elastic material, the void initiates when the load exceeds the critical value. On the other hand, it is important to study multiple void growth phenomena, in order to consider the fracture by coalescence of voids. In this paper, we study the growth of multiple voids in the hyper-elastic material. The material is characterized by the energy function as the compressive material. Some experiments for the rubber, as a hyper-elastic material, are proceeded, in order to obtain these mechanical properties in the energy function. A square cell with some small voids is constructed and applied with tensile deformation by moving outer surface. The large deformation and the non-linear simulations are proceeded by using FEM. If there is only one seed, one void grows from the seed. However, when there are some seeds, we observed the void growing and the void vanishing by the influence from the other voids. The influence of the initial voids scale to the void growth is studied.

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Butcher, Cliff y Zengtao Chen. "A Coupled-Constitutive Model for Ductile Fracture: Void Nucleation to Coalescence". En ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39229.

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A novel framework and integration scheme has been developed to implement a secant-based homogenization theory for particle-reinforced plasticity into an existing damage-based constitutive model, the well known Gurson-Tvergaard (GT) model. In this approach, the material is treated as a three-phase composite composed of voids and particles embedded in a ductile matrix. Two successive homogenization theories (damage- and particle-based) are then applied to determine the macro-mechanical response of the material as well as the average stress state within the constituents as a function of the particle shape, composition, and volume fraction. By identifying the stress state within the particles and the matrix, void nucleation can be accurately represented and the void growth and coalescence models are improved through knowledge of the stress state within the matrix. The performance of the coupled model is evaluated using a model aluminum alloy. A parametric study is performed to elucidate the influence of the second-phase particles and their shape on damage evolution and ductile fracture.

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Cao, Q., K. C. Ee, O. W. Dillon y I. S. Jawahir. "A Finite Element Analysis of Void Evolution in 2-D Machining". En ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-39187.

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The objective of this paper is to study void evolution and its effects on material failure during the machining process. The influence of cutting conditions on void nucleation, growth and coalescence is studied. The ultimate goal of this approach, as applied to machining, is to predict chip breakage and surface conditions via damage mechanics. A damage mechanics model proposed by Komori [1] is chosen to study the evolution of the void volume fraction in the chip and workpiece being machined with a grooved tool. A Thomason [2] type criterion as modified by Dhar et al. [3], that uses the variables calculated by FEM analysis, is used to predict void coalescence (failure). The distribution of the variables, such as effective strain-rate, nondimensional hydrostatic stress, and effective strain are obtained using the FEM methodology described by Zhang [4]. It is found that void coalescence always occurs in the newly machined surface below the flank face of the tool and in the chip flowing around the chip-groove region near the upper end of the face land. On the other hand, whether void coalescence occurs inside the chip or not, depends on the complex interactions between the machining parameters and chip geometry.

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Hammi, Youssef, Mark F. Horstemeyer y Doug J. Bammann. "An Anisotropic Damage Model for Ductile Metals". En ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32887.

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An anisotropic ductile damage description is motivated from fracture mechanisms and physical observations in Al-Si-Mg aluminum alloys with second phases. Ductile damage is induced by the classical process of nucleation of voids at inclusions, followed by their growth and coalescence. These mechanisms are related to different microstructural and length scale parameters like the fracture toughness, the void size, the intervoid ligament distance, etc. The classical thermodynamic constraints of irreversible processes with material state variables are used to model the tensorial damage evolution coupled to the Bammann-Chiesa-Johnson (BCJ) rate-dependent plasticity. The damage-plasticity coupling is based on the effective stress concept, assuming the total energy equivalence, and written through a deviatoric damage effect tensor on the deviatoric part and through the trace of the second rank damage tensor on the hydrostatic part. The damage rate tensor is additively decomposed into a nucleation rate tensor, a void growth rate scalar, and a coalescence rate tensor. The induced damage anisotropy is mainly driven by the nucleation, which evolves as a function of the absolute value of the plastic strain rate tensor. Finally, some experimental data of cast A356 aluminum alloy are correlated with predictive void-crack evolution to illustrate the applicability of the anisotropic damage model.

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Daly, Michael, Andrew H. Sherry y John K. Sharples. "Advanced Assessment of the Integrity of Ductile Components". En ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78774.

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Nuclear Reactor Pressure Vessels (RPV) are manufactured from medium strength low alloy ferritic steel, specifically selected for its high toughness and good weldability. The ability of the pressure vessel to resist crack growth is crucial given that it is one of the fundamental containment safety systems of the reactor. For most of their lifetime, the pressure vessel operates at sufficiently elevated temperatures to ensure the material is ductile. However, the development of ductile damage, in the form of voids, and the ability to predict the ductile crack growth in RPV materials requires further work. The Gurson-Tvergaard-Needleman (GTN) model of void nucleation, growth and coalescence provides one tool for predicting ductile damage development. The model is normally calibrated against fracture toughness test data. However, recent work [1] has demonstrated the benefit of refining calibrations against measured void volume fractions generated from notched and pre-cracked specimen tests. This paper described the measurement of void distributions below the fracture surface of a range of notched and pre-cracked specimens. The void distribution below the fracture surface is shown to be dependent upon the local stress triaxiality and plastic strain distribution. As a result, pre-cracked specimens show a greater concentration of voids close to the fracture surface, whilst notched tensile specimens show a lower volume fraction of voids close to the crack surface. In both specimen types, voids are observed to extend between 2.5 and 3.5 mm below the fracture surface.

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Daly, Michael, Fabien Leonard, John K. Sharples y Andrew H. Sherry. "Advanced Assessment of the Ductile Fracture Mechanism in A508 Class 3 Reactor Pressure Vessel Steel Using Laboratory X-Ray Tomography". En ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97924.

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Ductile damage is characterised by the nucleation, growth and coalescence of voids at initiating particles within the volume of high triaxial stresses and plastic strain ahead of a crack-tip or stress concentrator. To establish a more detailed understanding of the mechanism of ductile fracture in the A508 Class 3 ferritic RPV steels and to improve fracture models, the ductile damage was quantified below the fracture surface of tested compact test specimens using laboratory X-ray tomography imaging with sufficient resolution to image voids of approximately 10μm in diameter. The average distribution of void volume fraction as a function of distance below the fracture surface was quantified, and the initiating and coalescence mechanisms were characterised. The highest void volume fraction was observed at the fracture surface and this tends to decrease as a function of distance below the fracture surface. This decrease is periodically perturbed by large voids associated with inclusions which are distributed throughout the microstructure and act as further nucleating sites at low strains. This distribution of voids was correlated with the local variations in stress triaxiality and plastic strain derived from finite element analyses to provide a relationship between experimental observations and the Rice and Tracey model. These correlations aim to provide new data and understanding with which to calibrate mechanistically based models such as the Gurson-Tvergaard-Needleman (GTN) model.

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Jin, Zhaoyu y Xin Wang. "The Effects of Non-Proportional Biaxial Loading Paths on Ductile Fracture Initiation: A Void Growth Analysis". En ASME 2019 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/pvp2019-93312.

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Abstract The effects of non-proportional biaxial loading paths on ductile fracture initiation toughness are studied in this paper. To this end, the growth of a cylindrical void (hole) located in front of a mode I plane strain crack has been studied using large deformation finite element analysis (FEA). A specific microstructural feature of a steel alloy was thoroughly studied by having a single void positioned at a fixed distance from the crack tip and void that was equal to 10 times the diameter of the void. In particular, the non-proportional biaxial loading path effects on the crack tip blunting, void-growth, ligament reduction and near-tip stress fields are investigated computationally. Under small-scale yielding conditions, one proportional loading and two non-proportional loading paths are applied to the modified boundary layer (MBL) model. It is observed that the non-proportional load paths have a marked effect on the void growth, crack tip blunting and their interaction. By applying the criteria for the coalescence of the crack tip and void, the ductile fracture initiation toughness is estimated. It is shown that the ductile fracture toughness is dependent on loading paths, and the T-stress ratios. Results from this study are of relevance to ductile fracture assessment of components or pressure vessels that operate under non-proportional biaxial loading conditions.

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Kikuchi, Masanori, Kazuhiro Suga y Shota Kawasaki. "Simulation of Ductile Fracture for Multiple Flaws". En ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-25453.

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Interaction effect of multiple flaws on ductile fracture is studied numerically by using Gurson’s constitutive equation. Based on experiments, 2 parallel cracks problems and 3 parallel cracks problems are simulated. In some problems, crack coalescence does not occur, and it occurs in other cases. In all cases, ductile fracture processes are obtained, and results are compared with experimental ones. Fracture pattern and load-displacement curves agree well with experiments. It is shown that void growth term is dominant for the coalescence of cracks. Slanted crack problem and non-uniform length crack problem are simulated and evaluation method of multiple cracks problem is discussed.

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Daly, Michael, Fabien Leonard y Andrew H. Sherry. "Application of 3D X-Ray Tomography to Enhance the Calibration of Ductile Fracture Models". En ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28318.

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Reactor Pressure Vessels (RPV) are manufactured from medium strength low allow ferritic steel specifically selected for its high toughness and weldability. The normal operating temperature of RPV steels is sufficiently high to ensure that the material remains ductile throughout its service life with an extremely low probability of cleavage under normal and off-normal loading conditions. Understanding and having the ability to predict ductile fracture behaviour is consequently important. The ductile fracture mechanism is characterised by the nucleation, growth and coalescence of voids at initiating particles within the volume of high triaxial stress and plastic strain ahead of a crack-tip or stress concentrator. The fracture properties of the steels are conventionally determined using standard pre-cracked compact test specimens. Mechanistically based models of fracture can be calibrated against those data. This paper describes the use of 3D laboratory X-ray tomography to characterise the void distribution associated with the ductile fracture in test specimens and use the data to calibrate the Gurson-Tvergaard-Needleman ductile fracture model. The tomography successfully captures voids ≥ 6um in diameter and has been used to define the average distribution of void volume fraction as a function of distance below the fracture surface. The tomography results also allow an estimate of the critical and final void volume fractions to be made as well as capture secondary void peaks well below the fracture surface. This distribution of voids was used to calibrate the Gurson-Tvergaard-Needleman model in order to correlate experimental observations with the finite element models. The models have been able to replicate the observed trends of the void volume fraction distributions away from the fracture surface including the secondary peaks observed by tomography and to reproduce similar J-R curve behaviour as that observed in the test specimens.

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Informes sobre el tema "Void growth and coalescence"

Reding, Derek J., Pavol Stofko, Robert J. Dorgan y Michael E. Nixon. Void Growth and Coalescence Simulations. Fort Belvoir, VA: Defense Technical Information Center, agosto de 2013. http://dx.doi.org/10.21236/ada593137.

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de Almeida, Valmor F., Sophie Blondel, David E. Bernholdt y Brian D. Wirth. Cluster Dynamics Modeling with Bubble Nucleation, Growth and Coalescence. Office of Scientific and Technical Information (OSTI), junio de 2017. http://dx.doi.org/10.2172/1376497.

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Yang, Chih-Chung. Optimization of GaN Nanorod Growth Conditions for Coalescence Overgrowth. Fort Belvoir, VA: Defense Technical Information Center, febrero de 2016. http://dx.doi.org/10.21236/ada635078.

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Fausett, Diego Manuel. Tracking Void Growth in Material Undergoing Tensile Loading. Office of Scientific and Technical Information (OSTI), julio de 2018. http://dx.doi.org/10.2172/1463467.

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Kostka, Timothy D. Clustered void growth in ductile metals : final LDRD report. Office of Scientific and Technical Information (OSTI), septiembre de 2012. http://dx.doi.org/10.2172/1055872.

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Ilinskii, Yurii A., Preston S. Wilson y Mark F. Hamilton. Advanced Mathematical Modeling of Sonar-Induced Bubble Growth and Coalescence in Humans and Marine Mammals. Fort Belvoir, VA: Defense Technical Information Center, septiembre de 2008. http://dx.doi.org/10.21236/ada486650.

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Bentz, Dale P. y Claus-Jochen Haecker. X-ray microtomography studies of air-void instability and growth during drying of tile adhesive mortars. Gaithersburg, MD: National Institute of Standards and Technology, 2008. http://dx.doi.org/10.6028/nist.ir.7532.

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STUDY ON MICROMECHANICAL FRACTURE MODELS OF STRUCTURAL STEEL AND ITS WELDS. The Hong Kong Institute of Steel Construction, junio de 2021. http://dx.doi.org/10.18057/ijasc.2021.17.2.2.

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Steel structures have been widely used in constructions due to their advantages of lightweight, high strength, short construction time and high recycling and reuse potential. Fracture failure in steel structures should be prevented to avoid collapse of the whole structures. Micromechanical fracture models can capture the fracture initiation mechanisms and therefore can be used to predict ductile fractures in steel. Twelve smooth round bars were carried out to obtain the material properties and 36 notched round bars were tested to calibrate the parameters of stress modified critical strain (SMCS) model and the void growth model (VGM) for structural steels (Q235B and Q345B) and the corresponding welds. Specimens were extracted from the base metal, the weld metal and the heat affected zone (HAZ) to investigate fracture behaviour in different parts of the welded joint. Scanning electron microscope (SEM) measurements were taken and finite element models were developed to calibrate the models. The test results and calibrated parameters are reported. Moreover, the calibrated models are applied to analyses the fracture behaviour of welded joints and their accuracy are validated. The calibrated and validated models can be used for further numerical fracture analysis in welded steel structures.

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