Статті в журналах: "Gas shrinkage porosity"

1

Dybowski, Bartłomiej, Łukasz Poloczek, and Andrzej Kiełbus. "The Porosity Description in Hypoeutectic Al-Si Alloys." Key Engineering Materials 682 (February 2016): 83–90. http://dx.doi.org/10.4028/www.scientific.net/kem.682.83.

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Al-Si alloys are the most important group among aluminum casting alloys. They are widely used in automotive and aerospace industries. Chemical modification of the Al-Si alloys leads to formation of fine, fibrous Al-Si eutectic mixture ensuring high mechanical properties. The modification is however known to increase the alloy porosity, which may, in turn, result in decrease of its properties. The following paper presents results of the research on quantitative description of the Al-Si cast alloys porosity and influence of Na modification on the porosity of AlSi9Mg alloy. Porosity in the hypoeutectic Al-Si alloys occurs in four types: shrinkage cavities, shrinkage porosity, isolated gas pores and gas pores surrounded by shrinkage porosity. Na modification leads to increase of shrinkage pores volume fraction.

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2

Kim, Sung Bin, Young Hoon Yim, Joong Mook Yoon, and Doru Michael Ştefănescu. "Prediction of Shrinkage Defects in Iron Castings Using a Microporosity Model." Materials Science Forum 925 (June 2018): 411–18. http://dx.doi.org/10.4028/www.scientific.net/msf.925.411.

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A numerical model for prediction of shrinkage defects in iron castings has been developed. The model is based on gas pores evolution during solidification. It describes the evolution of gas concentration using mass conservation, and the change in melt pressure due to solidification contraction using Darcy’s equation, with mixture continuity assumption in the liquid and the mushy zone. Gas pores nucleation has been calculated using the partial pressure of gas obtained from Sievert’s law. The growth of porosity has been estimated using an equation based upon the total melt pressure on the pore, concentration and temperature of the gas. The porosity model was calibrated against literature data for microporosity, and then applied to the prediction of shrinkage defects in a ductile iron casting. Comparison between the model predictions and experimental measurements indicated that the porosity model can be applied not only to the prediction of micro-shrinkage but also to that of macro-shrinkage. Existing shrinkage prediction models based upon thermal models, such as Niyama criterion and the modulus of retained melt in mushy regions cannot predict correctly both micro- and macro-shrinkage.

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3

Roskosz, Stanisław. "Quantitative Characterization of Shrinkage and Gas Pores in Turbine Blades Made of MAR M247 and IN 713C Superalloys." Solid State Phenomena 197 (February 2013): 64–69. http://dx.doi.org/10.4028/www.scientific.net/ssp.197.64.

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The subject matter of the paper is the quantitative evaluation of gaseous and shrinkage porosity in construction elements of a low-pressure aircraft engine turbine using quantitative metallography methods. The research material comprised blades and blade segments with a polycrystalline structure made of IN 713C and MAR M247 superalloys. One of the major problems that occur in the precision castings is their porosity: gaseous, which is the result of emission of dissolved gases from the superalloy during solidification, and shrinkage, being the result of shrinkage of the superalloy and of insufficient feeding of the interdendritic space. The developed practical procedure of selective measurement of gaseous and shrinkage porosity enabling the examination of precision castings made of high-temperature creep resisting nickel superalloys is presented.

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4

Thanabumrungkul, S., W. Jumpol, Rungsinee Canyook, N. Meemongkol, and Jessada Wannasin. "Characterization of Microstructure and Shrinkage Porosity of a Semi-Solid Metal Slurry in Gravity Die Casting." Solid State Phenomena 285 (January 2019): 161–66. http://dx.doi.org/10.4028/www.scientific.net/ssp.285.161.

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Current aluminum automotive parts such as wheels, engine and transmission components are produced by tilted gravity die casting for control gas porosity. But, there are still problems resulting in inefficient production: shrinkage porosity, microstructure size and uniformity. Shrinkage porosity is one of the major issues which affects mechanical properties such as strength and elongation in tilted pour permanent mold. Recent work using slurry casting technique has shown potential in gravity sand casting. Results show that the casting parts have complete filling at low solid fractions and the casting yield is also higher than conventional gravity sand casting. This paper extends important work for potential industrial applications in gravity die casting: microstructure size, uniformity, solid fraction control for micro shrinkage level.

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5

Rashid, Abira. "Optimization of Shrinkage Porosity in Grinding Media Balls by Casting Design Modification and Simulation Technique." International Journal for Research in Applied Science and Engineering Technology 9, no. VIII (August 15, 2021): 344–53. http://dx.doi.org/10.22214/ijraset.2021.37352.

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Shrinkage porosity or cavity are associated with the solidification of the metal either due to gas/air entrapment or when the shrinkage occurring during solidification is not entirely compensated by the riser. Shrinkage cavities occurring in the casting reduces its strength which leads to unfulfillment of the desired serviceability. In this paper, casting design has been modified using the DISA manual to achieve directional solidification which directly relates to improvement of casting quality. The running of metal from pouring basin into casting along with solidification has been analysed through PROCAST which is a casting simulation software based on Finite Element Method and CAFE (Cellular Automata Finite Element) Model. The feeding system of the casting has been modified in terms of shape and volume to minimize air aspiration effect and promote directional solidification. The model used is of grinding media balls casting of high chromium cast iron. The feeding pattern, feeding velocity and solidification with respect to pouring temperature, pouring rate, ambient temperature and film coefficient has been analysed. The final optimum range of all parameters with corresponding minimum shrinkage porosity in casting was obtained. Main aim was to minimize shrinkage porosity in the main casting, ignoring gating and feeding system. The actual minimization of shrinkage porosity comes out around 56 %.

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6

Wannasin, Jessada, Marc Fuchs, Ji Yong Lee, Cheol Ung Lee, T. V. L. Narasimha Rao, and Merton C. Flemings. "GISS Technology: Principle and Applications in Die Casting." Solid State Phenomena 285 (January 2019): 470–75. http://dx.doi.org/10.4028/www.scientific.net/ssp.285.470.

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In the past, there have been a lot of effort to solve gas and shrinkage porosity defects in die casting. The common solutions are vacuum technology, jet cooling technology, and application of squeeze pins. However, these solutions often increase the die casting production costs. A new solution that has recently been introduced worldwide is GISS Technology. This technology applies the superheated slurry casting process. Gas and shrinkage porosity defects can be reduced. Furthermore, the production costs are lowered due to die life extension, cycle time reduction, melting energy reduction, and lubrication usage reduction. This paper describes the principle of GISS Technology, and selected applications and case studies are also be presented.

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7

Ignaszak, Z., and J. Hajkowski. "Contribution to the Identification of Porosity Type in AlSiCu High-Pressure-Die-Castings by Experimental and Virtual Way." Archives of Foundry Engineering 15, no. 1 (March 1, 2015): 143–51. http://dx.doi.org/10.1515/afe-2015-0026.

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Abstract The paper concerns the problem of discontinuity in high pressure die castings (HPDC). The compactness of their structure is not perfect, as it is sometimes believed. The discontinuities present in these castings are the porosity as follow: shrinkage and gas (hydrogen and gas-air occlusions) origin. The mixed gas and shrinkage nature of porosity makes it difficult to identify and indicate the dominant source. The selected parameters of metallurgical quality of AlSi9Cu3 alloy before and after refining and the gravity castings samples (as DI - density index method), were tested and evaluated. This alloy was served to cast the test casting by HPDC method. The penetrating testing (PT) and metallographic study of both kinds of castings were realized. The application of the NF&S simulation system allowed virtually to indicate the porosity zones at risk of a particular type in gravity and high-pressure-die-castings. The comparing of these results with the experiment allowed to conclude about NF&S models validation. The validity of hypotheses concerning the mechanisms of formation and development of porosity in HPDC casting were also analyzed.

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8

Bhagavath, Shishira, Zhixuan Gong, Tim Wigger, Saurabh Shah, Bita Ghaffari, Mei Li, Shashidhara Marathe, Shyamprasad Karagadde, and Peter D. Lee. "Mechanisms of gas and shrinkage porosity formation in solidifying shear bands." Journal of Materials Processing Technology 299 (January 2022): 117338. http://dx.doi.org/10.1016/j.jmatprotec.2021.117338.

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9

Zhou, Fengde, Guangqing Yao, Zhonghua Tang, and Oyinkepreye D. Orodu. "Influence and Sensitivity Study of Matrix Shrinkage and Swelling on Enhanced Coalbed Methane Production and CO2 Sequestration with Mixed Gas Injection." Energy Exploration & Exploitation 29, no. 6 (December 2011): 759–75. http://dx.doi.org/10.1260/0144-5987.29.6.759.

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Matrix compressibility, shrinkage and swelling can cause profound changes in porosity and permeability of coalbed during gas sorption and desorption. These factors affect the distribution of pressure, methane production and CO2 sequestration. This paper compares the effects of cleat compression and matrix shrinkage and swelling models with the injection of different compositional gas mixtures (CO2 and N2). It shows that well performance, pressure distribution and properties of the seam are strongly affected by matrix shrinkage and swelling. Matrix shrinkage and swelling also affects net present value of the enhanced coalbed methane recovery scheme. In order to select the best enhanced coalbed methane recovery schemes, economic evaluation and sensitivity studies are necessary.

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10

Rattanadakul, Sureebhorn, Jessada Wannasin, Somjai Janudom, Thawatchai Plookphol, and Sirikul Wisutmethangoon. "Effects of Solid Fractions in a Slurry Casting Process on Shrinkage and Microstructure of 7075 Aluminum Alloy." Advanced Materials Research 968 (June 2014): 125–28. http://dx.doi.org/10.4028/www.scientific.net/amr.968.125.

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Effects of Gas Induce Semi Solid (GISS) on shrinkage porosity of 7075 aluminum alloy were investigated. Initial solid fractions were controlled by rheocasting time at 5, 10 and 15 seconds and 4 and 6 bar of gas pressure. The results showed that the initial solid fractions were increased by increasing rheocasting time and gas pressure. As for the shrinkage, values of the GISS process samples were lower than those of the conventional process samples. In addition, the shrinkage areas of semi solid samples were decreased by increasing the initial solid fractions. The microstructure of semi solid samples was shown to be uniform globular grains along the samples.

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11

Tang, An-Ching, and John S. Boyer. "Leaf shrinkage decreases porosity at low water potentials in sunflower." Functional Plant Biology 34, no. 1 (2007): 24. http://dx.doi.org/10.1071/fp06222.

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Leaves often shrink significantly when soil water is limited. For gas exchange measurmements, the shrinkage can require correction for changing amounts of tissue in the apparatus. In sunflower plants (Helianthus annuus L.), a comparison was made between mathematically-corrected transpiration and clamping leaves at their original turgid size without mathematical correction. These methods should give the same result, but transpiration was substantially greater in the clamped leaves than in the shrunken and mathematically-corrected ones. Because the clamped leaves remained at their original turgid area, wounding was not a factor. If shrunken leaves were stretched to their original area, transpiration increased immediately and was traced to increased leaf conductance to water vapor and greater porosity for bulk air movement through the leaf, implicating the stomata. Releasing the leaf caused each of these properties to return to the tightened condition. When all the leaves were held at their original size during a soil water deficit, whole-plant water use was greater than when the leaves shrank naturally. It was concluded that shrinkage decreases the porosity of sunflower leaves. This natural tightening can be disrupted by stretching leaves during gas exchange measurements. However, stretching provides a useful means of changing leaf porosity for experimental purposes.

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12

Kim, Young Chan, Se Weon Choi, and Chang Seog Kang. "Effect of Controlling Process Parameters on Shrinkage Porosity in Aluminum Die-Casting Rotor." Advanced Materials Research 813 (September 2013): 136–43. http://dx.doi.org/10.4028/www.scientific.net/amr.813.136.

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Aluminum rotor prone to have many casting defects especially large amount of gas and shrinkage porosity, which caused eccentricity, loss and noise during motor operation. Many attempts have been made to develop methods of shrinkage porosity control, but still there are some problems to solve. In this research, the process of vacuum squeeze die casting is proposed for limitation of defects. The 6 pin point gated dies which were in capable of local squeeze at the end ring were used. Influences of filling patterns on HPDC were evaluated and the important process control parameters were high injection speed, squeeze length, venting and process conditions. By using local squeeze and vacuum during filling and solidification, air and shrinkage porosity were significantly reduced and the feeding efficiency at the upper end ring was improved 10%. As a result of controlling the defects, the dynamometer test showed improved motor efficiency by more than 4%.

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13

Ignaszak, Zenon, and Jakub Hajkowski. "Gas- and Shrinkage Porosities in Al-Si High-Pressure Die-Castings - Virtualization and Experimental Validation." Defect and Diffusion Forum 364 (June 2015): 80–91. http://dx.doi.org/10.4028/www.scientific.net/ddf.364.80.

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The porosity (void caused by technological reasons) in engineering materials always decrease their mechanical characteristics and usually affects the deterioration of the functional mechanical characteristics of the finished products. In the castings the porosity resulting from the specific casting processes phenomena occurs inevitably in the matrix structure. The paper shows this problem in relation to the High-Pressure-Die-Casting (HPDC) technology of Al-Si alloy. The analysis of the experimental results and the results from virtualization of HPDC process allowed to assess the effectiveness of this mixed scenario and improve the quality predictions probability for HPDC, with particular consideration of shrinkage and gas porosities. The problem of the tolerance (admissibility) of porosity occurrence in castings and the castings made of liquid Al-Si alloy to which the gas (hydrogen) was introduced intentionally are signalized.

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14

Kucharčík, L., M. Brůna, and A. Sládek. "Influence of Chemical Composition on Porosity in Aluminium Alloys." Archives of Foundry Engineering 14, no. 2 (June 1, 2014): 5–8. http://dx.doi.org/10.2478/afe-2014-0026.

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Abstract Porosity is one of the major defects in aluminum castings, which results is a decrease of a mechanical properties. Porosity in aluminum alloys is caused by solidification shrinkage and gas segregation. The final amount of porosity in aluminium castings is mostly influenced by several factors, as amount of hydrogen in molten aluminium alloy, cooling rate, melt temperature, mold material, or solidification interval. This article deals with effect of chemical composition on porosity in Al-Si aluminum alloys. For experiment was used Pure aluminum and four alloys: AlSi6Cu4, AlSi7Mg0, 3, AlSi9Cu1, AlSi10MgCu1.

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15

Boroń, Kinga. "Evaluation of porosity of AlZn5Mg castings made by squeeze casting technology." Acta Innovations, no. 32 (July 1, 2019): 12–19. http://dx.doi.org/10.32933/actainnovations.32.2.

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The paper shows the results of research aimed to assess the impact of high squeeze pressure on the porosity of AlZn5Mg alloy castings, including its distribution in slab-type castings with dimensions of 25 x 100 x 200 mm. The research was carried out on castings made by two methods: squeeze casting and gravity casting. The pressing was conducted at a pressure of 100 MPa at an initial mould temperature of 200°C. The research identified the middle and outer parts of the casting. Experimental research was preceded by numerical simulation of the casting solidification, then a porosity assessment was carried out using the hydrostatic weighing method, which was supplemented by structural observations. The results of the research showed a two-fold decrease in the porosity in the middle part of the casting which is most exposed to the occurrence of shrinkage voids formed in the final clotting phase. Structural tests revealed the occurrence of dispersed porosity in castings, mainly of shrinkage and / or shrinkage-gas origin. The impact of pressure of 100 MPa during solidification caused fragmentation of the primary structure of castings, which resulted in a higher grain density.

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16

Prasad, Mahesh R. G., Siwen Gao, Napat Vajragupta, and Alexander Hartmaier. "Influence of Trapped Gas on Pore Healing under Hot Isostatic Pressing in Nickel-Base Superalloys." Crystals 10, no. 12 (December 17, 2020): 1147. http://dx.doi.org/10.3390/cryst10121147.

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Under the typical hot isostatic pressing (HIP) processing conditions, plastic deformation by dislocation slip is considered the primary mechanism for pore shrinkage, according to experimental observations and deformation mechanism maps. In the present work, a crystal plasticity model has been used to investigate the influence of applied pressure and holding time on porosity reduction in a nickel-base single crystal superalloy. The influence of trapped gas on pore shrinkage is modeled by coupling mechanical deformation with pore–gas interaction. In qualitative agreement with experimental investigations, we observe that increasing the applied pressure or the holding time can effectively reduce porosity. Furthermore, the effect of pore shape on the shrinkage is observed to depend on a combination of elastic anisotropy and the complex distribution of stresses around the pore. Simulation results also reveal that, for pores of the same shape, smaller pores (radius < 0.1 μm) have a higher shrinkage rate in comparison to larger pores (radius ≥ 0.1 μm), which is attributed to the increasing pore surface energies with decreasing pore sizes. It is also found that, for smaller initial gas-filled pores (radius < 0.1 μm), HIP can result in very high gas pressures (on the order of GPa). Such high pressures either act as a driving force for argon to diffuse into the surrounding metal during HIP itself, or it can result in pore re-opening during subsequent annealing or mechanical loading. These results demonstrate that the micromechanical model can quantitatively evaluate the individual influences of HIP processing conditions and pore characteristics on pore annihilation, which can help optimize the HIP process parameters in the future.

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17

Lee, Soon Gi, and Arun M. Gokhale. "Formation of gas induced shrinkage porosity in Mg-alloy high-pressure die-castings." Scripta Materialia 55, no. 4 (August 2006): 387–90. http://dx.doi.org/10.1016/j.scriptamat.2006.04.040.

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18

Khalajzadeh, Vahid, Kent D. Carlson, Daniel G. Backman, and Christoph Beckermann. "A Pore-Centric Model for Combined Shrinkage and Gas Porosity in Alloy Solidification." Metallurgical and Materials Transactions A 48, no. 4 (January 17, 2017): 1797–816. http://dx.doi.org/10.1007/s11661-016-3940-6.

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19

Selivyorstov, Vadim, Tatjana Selivyorstova, and Anton Guda. "SYSTEM ANALYSIS OF POROSITY FORMATION PROCESSES IN STEEL CASTINGS AND THEIR MATHEMATICAL MODELS." System technologies 6, no. 125 (December 27, 2019): 89–104. http://dx.doi.org/10.34185/1562-9945-6-125-2019-09.

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The analysis of scientific and technical information about the hardening features of steel castings, which lead to the formation of shrinkage defects is presented. The mechanisms of the relationship of the casting properties of alloys are shown. The analysis of factors that determine fluidity is carried out. The technological parameters of casting are determined, which lead to the formation of pores in steel castings. The mechanisms of porosity formation of endogenous and exogenous nature are considered. Siverts law is given, that describes the dependence of gas concentration on pressure. Graphs of changes in the concentration of nitrogen and hydrogen in the pressure range 1 - 4 atm are given for medium alloyed steel, open-hearth steel, cast iron. The mechanism of the influence of temperature and gas pressure on the process of gas evolution in the melt is analyzed. Technological methods for influencing the solubility of gases during the solidification of the casting are described. The microporosity model of Advanced Porosity Module, the Niyama criterion are analyzed. The need for further studies to develop a general model for the formation of shrinkage defects, which will take into account, inter alia, the dependence of the concentration of gases dissolved in the metal on pressure temperature, is noted.

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20

Cabrera-Covarrubias, Francisca, José Gómez-Soberón, Carlos Rosas-Casarez, Jorge Almaral-Sánchez, and Jesús Bernal-Camacho. "Recycled Mortars with Ceramic Aggregates. Pore Network Transmutation and Its Relationship with Physical and Mechanical Properties." Materials 14, no. 6 (March 21, 2021): 1543. http://dx.doi.org/10.3390/ma14061543.

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The porosity of mortars with recycled ceramic aggregates (10, 20, 30, 50, and 100% as a replacement of natural aggregate) was evaluated and analyzed using three different techniques. The results of gas adsorption (N2), Scanning Electron Microscopy (SEM) image analysis and open porosity allowed establishing the relationship between the recycled aggregate content and the porosity of these mortars, as well as the relationship between porosity and the physical and mechanical properties of the mortars: absorption, density, compressive strength, modulus of elasticity, and drying shrinkage. Using the R2 coefficient and the equation typology as criteria, additional data such as Brunauer, Emmett, and Teller (BET) surface area (N2 adsorption) established significant correlations with the mentioned properties; with SEM image analysis, no explanatory relationships could be established; and with open porosity, revealing relationships were established (R2 > 0.9). With the three techniques, it was confirmed that the increase in porosity is related to the increase in the amount of ceramic aggregate; in particular with gas adsorption (N2) and open porosity. It was concluded that the open porosity technique can explain the behavior of these recycled mortars with more reliable data, in a simple and direct way, linked to its establishment with a more representative sample of the mortar matrix.

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21

Raza, M., M. Irwin, and B. Fagerström. "The Effect of Shell Thickness, Insulation and Casting Temperature on Defects Formation During Investment Casting of Ni-base Turbine Blades." Archives of Foundry Engineering 15, no. 4 (December 1, 2015): 115–23. http://dx.doi.org/10.1515/afe-2015-0090.

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Abstract Turbine blades have complex geometries with free form surface. Blades have different thickness at the trailing and leading edges as well as sharp bends at the chord-tip shroud junction and sharp fins at the tip shroud. In investment casting of blades, shrinkage at the tip-shroud and cord junction is a common casting problem. Because of high temperature applications, grain structure is also critical in these castings in order to avoid creep. The aim of this work is to evaluate the effect of different process parameters, such as, shell thickness, insulation and casting temperature on shrinkage porosity and grain size. The test geometry used in this study was a thin-walled air-foil structure which is representative of a typical hot-gas-path rotating turbine component. It was observed that, in thin sections, increased shell thickness helps to increase the feeding distance and thus avoid interdendritic shrinkage. It was also observed that grain size is not significantly affected by shell thickness in thin sections. Slower cooling rate due to the added insulation and steeper thermal gradient at metal mold interface induced by the thicker shell not only helps to avoid shrinkage porosity but also increases fill-ability in thinner sections.

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22

Ignaszak, Z., J. Hajkowski, and P. Popielarski. "Examples of New Models Applied in Selected Simulation Systems with Respect to Database." Archives of Foundry Engineering 13, no. 1 (March 1, 2013): 45–50. http://dx.doi.org/10.2478/afe-2013-0009.

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Abstract The tolerance of damage rule progressively meets the approval in the design casting parts procedures. Therefore, there were appeared the new challenges and expectations for permanent development of process virtualization in the mechanical engineering industry. Virtualization is increasingly developed on the stage of product design and materials technologies optimization. Increasing expectations of design and process engineers regarding the practical effectiveness of applied simulation systems with new proposed up-grades modules is observed. The purpose is to obtain simulation tools allowing the most possible realistic prognosis of the casting structure, including indication, with the highest possible probability, places in the casting that are endangered with the possibility of shrinkage- and gas porosity formation. This 3D map of discontinuities and structure transformed in local mechanical characteristics are used to calculate the local stresses and safety factors. The needs of tolerance of damage and new approach to evaluate the quality of such prognosis must be defined. These problems of validation of new models/modules used to predict the shrinkage- and gas porosity including the chosen structure parameters in the example of AlSi7 alloy are discussed in the paper.

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23

STROTSKIY, Valeriy, Aleksey KROKHIN, and Vladimir SAVIN. "ACCOUNTING FOR THE INFLUENCE OF HUMIDITY PROPERTIES OF AUTOCLAVE- CURED CELLULAR CONCRETE IN THE DESIGN AND CONSTRUCTION OF ENCLOSING STRUCTURES." Bulletin of Science and Research Center “Stroitelstvo”, no. 3 (30) (August 31, 2021): 88–99. http://dx.doi.org/10.37538/2224-9494-2021-3(30)-88-99.

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The results of studies of porosity, water absorption, moisture shrinkage and frost resistance of cellular concrete, which are some of the main factors determining the durability of cellular concrete enclosing structures manufactured using autoclave hardening technology, are considered. Methods for determining water absorption, moisture shrinkage and frost resistance are presented. The relationship between the moisture shrinkage and the capillary forces (the sum of the surface tension forces on the micromeniscs of liquid in the capillaries of cellular concrete), as well as the dependence of the shrinkage on the size (radius) of the capillary and gas pores of cellular concreteand on the water-solid ratio (W/S-factor) of cellular concrete, is established. In the field of frost resistance of cellular concrete, the relationship between the structure of the pore space of concrete and its deformation characteristics under the action of negative temperatures is studied. The effect of the presence of gas pores in cellular concrete on the reduction of frost expansion deformations is described.

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24

WEI, ZHIJIE, and DONGXIAO ZHANG. "COUPLED FLUID FLOW AND GEOMECHANICS IN COALBED METHANE RECOVERY STUDY." Modern Physics Letters B 24, no. 13 (May 30, 2010): 1291–94. http://dx.doi.org/10.1142/s0217984910023451.

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In this paper, we present a coupled fluid flow and geomechanics model for simulating coalbed methane recovery. In the model, the fluid flow process is simulated with a triple porosity/dual permeability representation, and the coupling effects of effective stress and matrix swelling/shrinkage approach are simulated with a coupled fluid flow, geomechanics and gas adsorption/desorption model. The mathematical model is implemented with a fully implicit finite volume method and simulation is conducted to evaluate the effect of coupled fluid flow, geomechanics, and gas adsorption/desorption.

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25

Gu, Cheng, Colin D. Ridgeway, Emre Cinkilic, Yan Lu, and Alan A. Luo. "Predicting gas and shrinkage porosity in solidification microstructure: A coupled three-dimensional cellular automaton model." Journal of Materials Science & Technology 49 (July 2020): 91–105. http://dx.doi.org/10.1016/j.jmst.2020.02.028.

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26

Yin, Yi Bin, Yon Gan Zhang, Bai Qing Xiong, Feng Wang, Hong Wei Liu, Zhi Hui Li, and Xi Wu Li. "Morphologies and Formation Mechanism of Interconnected Pores in a Spray Formed 7XXX Aluminum Alloy." Materials Science Forum 788 (April 2014): 193–200. http://dx.doi.org/10.4028/www.scientific.net/msf.788.193.

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In this paper, Al-Zn-Mg-Cu alloys were produced through spray forming technique. Microstructures of interconnected porosity defects in spray-deposited preforms were characterized by means of field emission scanning electron microscopy (FESEM). The formation mechanisms of different types of interconnected pores were investigated. The densification of deposited alloy preforms with interconnected pores was also analyzed. Interconnected pores in deposited alloys may be classified into four types, interconnected pores between interstices, between gas pores, between interstices and gas pores, and interconnected pores associated with solidification shrinkage, according to morphology and formation mechanism.

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27

Li, Lei, Guanglong Sheng, and Yuliang Su. "Water-Gas Two-Phase Flow Behavior of Multi-Fractured Horizontal Wells in Shale Gas Reservoirs." Processes 7, no. 10 (September 27, 2019): 664. http://dx.doi.org/10.3390/pr7100664.

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Hydraulic fracturing is a necessary method to develop shale gas reservoirs effectively and economically. However, the flow behavior in multi-porosity fractured reservoirs is difficult to characterize by conventional methods. In this paper, combined with apparent porosity/permeability model of organic matter, inorganic matter and induced fractures, considering the water film in unstimulated reservoir volume (USRV) region water and bulk water in effectively stimulated reservoir volume (ESRV) region, a multi-media water-gas two-phase flow model was established. The finite difference is used to solve the model and the water-gas two-phase flow behavior of multi-fractured horizontal wells is obtained. Mass transfer between different-scale media, the effects of pore pressure on reservoirs and fluid properties at different production stages were considered in this model. The influence of the dynamic reservoir physical parameters on flow behavior and gas production in multi-fractured horizontal wells is studied. The results show that the properties of the total organic content (TOC) and the inherent porosity of the organic matter affect gas production after 40 days. With the gradual increase of production time, the gas production rate decreases rapidly compared with the water production rate, and the gas saturation in the inorganic matter of the ESRV region gradually decreases. The ignorance of stress sensitivity would cause the gas production increase, and the ignorance of organic matter shrinkage decrease the gas production gradually. The water film mainly affects gas production after 100 days, while the bulk water has a greater impact on gas production throughout the whole period. The research provides a new method to accurately describe the two-phase fluid flow behavior in different scale media of fractured shale gas reservoirs.

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28

Anjos, Vitor, Carlos A. Silva Ribeiro, Fátima Dias, Wolfgang Baumgart, and João Cunha. "Literature Survey on Porosity and Microporosity in Cast Irons Related to Expansion and Gas Entrapment Phenomena." Key Engineering Materials 457 (December 2010): 410–15. http://dx.doi.org/10.4028/www.scientific.net/kem.457.410.

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Macro and microporosity in castings are a problem that persists at many foundries, despite the use of advance simulation software’s. This fact indicates that other parameters rather then the casting shape/design or the “standard” metallurgical characteristics are not properly controlled, considered or modelled in the solidification simulation. In this paper we present the Phase I of a research project, which consists on a bibliographic review of the previous attempts to evaluate the relationship between solidification sequence and the measurement of expansion of molten metal during eutectic solidification and is relation to porosity and shrinkage defects.

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29

Jarfors, Anders E. W., Qing Zhang, and Stefan Jonsson. "Feeding and Pore Formation in Semisolid Metal Casting." Metals 10, no. 11 (November 23, 2020): 1560. http://dx.doi.org/10.3390/met10111560.

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Semisolid casting can provide excellent castings, but the nature of the pore-forming mechanisms has not been properly clarified. In the current communication, it was suggested that hydrogen precipitated during slurry making might have a decisive role in the formation of both gas and shrinkage porosity. Intensive stirring at the end of the slurry making process may act as a degassing step. Without the intense shearing, structures of primary slurry particles form around the hydrogen pores, strongly affecting pore formation and feeding during the intensification stage.

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30

Ogawa, Kazuhiro, and Takahiro Niki. "Repairing of Degraded Hot Section Parts of Gas Turbines by Cold Spraying." Key Engineering Materials 417-418 (October 2009): 545–48. http://dx.doi.org/10.4028/www.scientific.net/kem.417-418.545.

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Hot section parts of combined cycle gas turbines are susceptible to degradation due to high temperature creep, crack formation by thermal stress, and high temperature oxidation, etc. Thus, regularly repairing or replacing the hot section parts such as gas turbine blades is inevitable. For this purpose, revolutionary and advanced repair technologies for gas turbines have been developed to enhance reliability of the repaired parts and reduce the maintenance cost of the gas turbines. The cold spraying process, which has been studied as not only a new coating technology but also as a process for obtaining a thick deposition layer, is proposed as a potential repairing solution. The process results in little or no oxidation of the spray materials, so the surfaces stay clean, which in turn enables superior bonding. Since the operating temperature is relatively low, the particles do not melt and the shrinkage on cooling is very low. In this study, the cold spraying conditions were optimized by taking into account the particle kinetic energy and the rebound energy for application in repairing gas turbine blades. A high quality cold-sprayed layer is that which has lowest porosity; thus the spraying parameters were optimized to achieve low-porosity layer, which was verified by scanning electron microscopy (SEM).

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31

Ignaszak, Zenon, Paweł Popielarski, Jakub Hajkowski, and J. B. Prunier. "Problem of Acceptability of Internal Porosity in Semi-Finished Cast Product as New Trend "Tolerance of Damage" Present in Modern Design Office." Defect and Diffusion Forum 326-328 (April 2012): 612–19. http://dx.doi.org/10.4028/www.scientific.net/ddf.326-328.612.

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Discontinuities in cast products, obtained from a liquid state of an alloy, are the result of phenomena occurring during multiphase system crystallization. On the one hand, compacted defects as a shrinkage pipe are relatively easy to eliminate. On the other hand, it is known that presence of fine shrinkage and gas porosity is unavoidable. Detectability of these dispersed discontinuities depends on type of inspection method applied. Structure, including intensity and location of porosity zones, is dependent on the type of the alloy, casting configuration and conception of technological solution, related with control of velocity of the heat extraction to the mould. Thus, mechanical properties in the volume of a casting are not homogenous and are strongly reduced only in the zones of porosity. However, in strength calculations of cast products, this obvious fact is not taken into consideration. The rule of material homogeneity is applied instead, along with drastic increase of factor of safety. The paper indicates benefits of precise determination of limits of porosity zones located in the casting, using the NTD methods (for example, Phased Array ultrasonic tomography). Coordinates of porosity zones in 3D, introduced into CAD geometry and assigned with different properties allow to estimate the actual state of stress and strain of real object using FEM methods (systems like Ansys, Comsol). Load justified by operating conditions and application of tolerance of damage rule, with simultaneous reference to the limited state of stress according to LOV (Loss of Volume) and LEFM (Linear Elastic Fracture Mechanics) methods should find their place in design procedures of cast products, which will allow for better use of material and reduction of weight of the casting. This approach, named Tolerance of damage concerning the castings is the motto of this paper.

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32

Hehsan, H., and Roslee Ahmad. "The Effect of Vortex well Thickness on Microstructure and Mechanical Properties of Aluminium LM6." Applied Mechanics and Materials 465-466 (December 2013): 1219–23. http://dx.doi.org/10.4028/www.scientific.net/amm.465-466.1219.

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Gating system in a casting mold consists of a series of channels and reservoirs designed to feed molten metal to all parts of the mold cavity. The design of the system is the principle means by which the mold designer can control the rate of the metal flow and promote the desirable temperature distribution of cooling that will take place within the filled cavity. This research was conducted to determine the effects of vortex well thickness on the microstructure and mechanical properties of Aluminium LM6 in sand casting process. The experimental results show that increasing the vortex well thickness leads to a significance improvement on the flexural strength of the cast material. In addition, casting defects such as shrinkage porosity and gas porosity would be minimized as the thickness of the vortex well increases.

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33

Prihtiantoro, Dedhy, Agus Dwi Anggono, and Waluyo Adi Siswanto. "Defect Investigation of Sand Casted Aluminum Cooling Fan." Materials Science Forum 991 (May 2020): 30–36. http://dx.doi.org/10.4028/www.scientific.net/msf.991.30.

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Sand casting is one of manufacturing process that still exist today. Numerous products are produced to serve industrial and domestic use. Defect could lead to product performance, and unfortunately inevitable in a casting process. This paper aim to investigate typical defect resulted from sand casting process. An aluminum cooling fan was selected as the model since it has complicated shape with different thicknesses. The casted fan was investigated under photo micro for defect analysis. Porosity, gas inclusion, pinhole, and shrinkage were found as the common defects occured at different part of the fan.

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34

Wang, Guangxin, Jinqing Wang, Jie Wang, Zuohe Chi, Guangxue Zhang, Zhiyi Zhou, Zhi Feng, and Yunhao Xiong. "A Sinter Visualization Device for Observing the Relationship Between Fillers and Porosity of Precursor-Derived Ceramic Coatings." Coatings 10, no. 6 (June 9, 2020): 552. http://dx.doi.org/10.3390/coatings10060552.

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Adding fillers to polysilazane (PSZ)-derived ceramic coating is one of the main methods used to reduce PSZ porosity. In this study, we designed a sinter visualization device for understanding the effect of fillers on coating porosity and observed pore evolution within the coating sintering process using different filler ratios. When there was no filler in the coating, gas evolution occurred at the initial sintering stage due to a PSZ pyrolysis reaction. In the final stage, numerous cracks appeared because of volume shrinkage. It was determined that such coatings cannot provide good protection. Although the cracks disappeared after adding glass powder, many bubbles appeared. After adding ZrO2, the bubbles in the coating significantly reduced. When the volume ratio of PSZ/glass powder/ZrO2 was 1:2:1, the coating porosity after sintering was the lowest. Based on our visualization experimental results, we concluded that the glass powder’s healing effect and the ZrO2 skeleton effect were the main reasons for the reduced coating porosity. In addition, the sinter visualization device can be used to observe the surface morphology of other similar coatings during the sintering processes.

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35

Choudhari, C. M., K. J. Padalkar, K. K. Dhumal, B. E. Narkhede, and S. K. Mahajan. "Defect Free Casting by Using Simulation Software." Applied Mechanics and Materials 313-314 (March 2013): 1130–34. http://dx.doi.org/10.4028/www.scientific.net/amm.313-314.1130.

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The use of Aluminum castings parts in the automotive industry has increased dramatically over the past few decades. The driving force for this increased use is vehicle weight reduction for improved performance. In many cases the mechanical properties of the cast aluminum parts are superior to those of the cast iron or wrought steel parts being used.This paper proposes the computer simulation of the sand casting of Aluminum Plate. It aims to study the behavior of fluid flow during mould filling and solidification and to optimize the process parameters, which help to predict and control casting defects such as gas porosity and shrinkage porosity. Here an attempt is being made to model and simulate the casting process using the AutoCAST software. The technological as well as practical aspects of using casting software are illustrated with an industrial case study.

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36

Otsuka, Yukio. "Experimental Verification and Accuracy Improvement of Gas Entrapment and Shrinkage Porosity Simulation in High Pressure Die Casting Process." MATERIALS TRANSACTIONS 55, no. 1 (2014): 154–60. http://dx.doi.org/10.2320/matertrans.f-m2013835.

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37

Zhou, Rui, Jian Fei Sun, and Ying Jun Yang. "Microstructure and Mechanical Properties of Spray Deposited W9Mo3Cr4V High Speed Steel." Advanced Materials Research 391-392 (December 2011): 714–18. http://dx.doi.org/10.4028/www.scientific.net/amr.391-392.714.

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Microstructure and mechanical properties of W9Mo3Cr4V high speed steel fabricated by spray deposition have been studied. Spray deposited W9Mo3Cr4V high speed steel has a typical equiaxed structure which is finer and more homogeneous with a grain size of 20-30 micrometer compared with conventional casted counterparts. There are pores in the matrix of the deposited steel, which involve gas porosity, filling porosity and solidification shrinkage. As-deposited high speed steel is mainly composed of martensite, austenite and carbides which comprise MC carbide and M6C carbide. Mechanical properties show that the hardness and bending strength of the as-deposited steel are higher than that of the conventionally casted ones. However, impact toughness of the high speed steel is lower than that of the conventionally casted steel, which can be attributed to the existence of porosities and M6C carbides which reduce the impact toughness of high speed steels.

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38

Ichard, J. C., R. Pailler, and Jacques Lamon. "Ceramic Matrix Composite with Increased Thermal Conductivity." Advances in Science and Technology 45 (October 2006): 1405–10. http://dx.doi.org/10.4028/www.scientific.net/ast.45.1405.

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The purpose of the study was to increase the thermal conductivity of multilayered and self-sealing ceramic matrix composites via the silicon melt infiltration process. The first step of the process consisted in filling porosity using various organic xerogels by the sol-gel route. Carbon xerogels obtained by subsequent pyrolysis may reduce and homogenize the porous network within the composite. Cracking of the xerogels due to volumic shrinkage occurring during air drying may be decreased by controlling the initial parameters as concerns the gel solution and/or by operating a second impregnation/pyrolysis step. Filling of such composites by liquid silicon revealed that a specific route and particular conditions are necessary to eliminate porosity by controlling gas production species from pore surface at high temperature. This may be achieved through a directional flow and using highly viscous silicon (thanks to a localized wick), and by keeping the sides of the materials permeable to gas. This led to composite materials with a thermal conductivity which was four times as high as that of those materials densified via CVI. An increase in mechanical properties was also observed.

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39

Hajkowski, M., Ł. Bernat, and J. Hajkowski. "Mechanical Properties of Al-Si-Mg Alloy Castings as a Function of Structure Refinement and Porosity Fraction." Archives of Foundry Engineering 12, no. 4 (December 1, 2012): 57–64. http://dx.doi.org/10.2478/v10266-012-0107-9.

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Abstract During design of the casting products technology, an important issue is a possibility of prediction of mechanical properties resulting from the course of the casting solidification process. Frequently there is a need for relations describing mechanical properties of silumin alloys as a function of phase refinement in a structure and a porosity fraction, and relations describing phase refinement in the structure and the porosity fraction as a function of solidification conditions. The study was conducted on castings of a 22 mm thick plate, made of EN AC-AlSi7Mg0,3 alloy in moulds: of quartz sand, of quartz sand with chill and in permanent moulds. On the basis of cooling curves, values of cooling rate in various casting parts were calculated. The paper also presents results of examination of distance between arms in dendrites of a solid solution α (DASL), precipitations length of silicon in an eutectic (DlSi) and gas-shrinkage porosity (Por) as a function of cooling rate. Statistical relations of DASL, DlSi, Por as a function of cooling rate and statistical multiparameter dependencies describing mechanical properties (tensile strength, yield strength, elongation) of alloy as a function of DASL, DlSi and Por are also presented in the paper.

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40

Gorucu, Fatma Burcu, Sinisha A. Jikich, Grant S. Bromhal, W. Neal Sams, Turgay Ertekin, and Duane H. Smith. "Effects of Matrix Shrinkage and Swelling on the Economics of Enhanced-Coalbed-Methane Production and CO2 Sequestration in Coal." SPE Reservoir Evaluation & Engineering 10, no. 04 (August 1, 2007): 382–92. http://dx.doi.org/10.2118/97963-pa.

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Summary Increases in carbon dioxide (CO2) levels in the atmosphere and their contributions to global climate change are a major concern. CO2 sequestration in unmineable coals may be a very attractive option, for economic as well as environmental reasons, if a combination of enhanced-coalbed-methane (ECBM) production and tax incentives becomes sufficiently favorable compared to the costs of capture, transport, and injection of CO2. Darcy flow through cleats is an important transport mechanism in coal. Cleat compression and permeability changes caused by gas sorption/desorption, changes of effective stress, and matrix swelling and shrinkage introduce a high level of complexity into the feasibility of a coal sequestration project. The economic effects of CO2-induced swelling on permeabilities and injectivities has received little (if any) detailed attention. CO2 and methane (CH4) have different swelling effects on coal. In this work, the Palmer-Mansoori model for coal shrinkage and permeability increases during primary methane production was rewritten to also account for coal swelling caused by CO2 sorption. The generalized model was added to a compositional, dual-porosity coalbed-methane reservoir simulator for primary (CBM) and ECBM production. A standard five-spot of vertical wells and representative coal properties for Appalachian coals was used (Rogers 1994). Simulations and sensitivity analyses were performed with the modified simulator for nine different parameters, including coal seam and operational parameters and economic criteria. The coal properties and operating parameters that were varied included Young's modulus, Poisson's ratio, cleat porosity, and injection pressure. The economic variables included CH4 price, CO2 cost, CO2 credit, water disposal cost, and interest rate. Net-present-value (NPV) analyses of the simulation results included profits resulting from CH4 production and potential incentives for sequestered CO2. This work shows that for some coal seams, the combination of compressibility, cleat porosity, and shrinkage/swelling of the coal may have a significant impact on project economics. Introduction In recent years, primary production of natural gas from coal seams has become an important source of energy in the United States. Proven CBM reserves have been estimated at 18.5 Tscf, representing 10% of the total natural-gas reserves in the United States. CBM production started in the early 1980s as a small, high-cost operation but reached 1.6 Tscf in 2002. This was more than 8% of the total US natural-gas production that year (Kuuskraa 2003). The production of CBM reservoirs begins with the pumping of significant volumes of water to lower reservoir pressure and to allow CH4desorption and flow (Stevens et al. 1998). The fraction of the original gas in place typically produced by primary depletion seems to be somewhat controversial. However, according to recent publications, recoveries are often between 20 and 60% of the original gas in place, so that considerable amounts of gas are left behind (Gale and Freund 2001; Stevens et al. 1999; Van Bergen et al. 2001).Because of this, and because of concerns about global warming caused by accumulations of CO2 in the atmosphere (National Energy Technology Laboratory 2003, 2004), new technologies for ECBM production based on the injection of carbon are being investigated in the US, Europe, China, and Japan (Coal-Seq Forum 2004, 2006). In the CO2-ECBM/sequestration process, injected CO2 flows through the cleats in the coal by Darcy flow, diffuses into the coal matrix, and is sorbed by it; CH4 diffuses from the matrix into the cleats, through which it flows to production wells (Sams et al. 2005). The injection of CO2 into coalbeds has many potential advantages: It sequesters CO2, it reduces the production time for CBM, and it increases reserves by improving the recovery of CBM. However, the improved CH4 recovery is accompanied by an increase in costs for CO2 supply, additional drilling, and well and surface equipment. Thus, CO2-ECBM and sequestration are accompanied not only by promised benefits but also by new technical challenges and financial risks.

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41

Szalva, Péter, and Imre Norbert Orbulov. "Influence of Vacuum Support on the Fatigue Life of AlSi9Cu3(Fe) Aluminum Alloy Die Castings." Journal of Materials Engineering and Performance 29, no. 9 (August 27, 2020): 5685–95. http://dx.doi.org/10.1007/s11665-020-05050-y.

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Abstract High-pressure die casting (HPDC) is a near-net-shape process that produces high quality castings with narrow dimensional tolerances. The HPDC castings are being increasingly used due to good flexibility and high productivity, especially for the automotive industry. Depending on the location of the cast components, there are ever more complex geometries and increasing strength requirements that can be achieved by the application of vacuum-assisted die casting (VPDC). The most specific features of the HPDC process are the rapid mold filling, high cooling rate and intensification pressure. As a consequence of these highlighted features, the process generally leads to the formation of casting defects, such as gas porosity, shrinkage, and entrapped oxide films. However, the VPDC casting process is capable to significantly reduce the amount of these casting defects. The aim of this work is to compare the HPDC and VPDC castings’ high-cycle fatigue behavior and to describe how the casting defects affect the fatigue failure. Before the fatigue tests, the samples were investigated with non-destructive (NDT) materials testing methods such as hydrostatic weighing, x-ray, and computer tomography (CT) to characterize the gas pore and shrinkage pore populations of the material. The AlSi9Cu3(Fe) aluminum alloy castings have been subjected to constant amplitude load by uniaxial fatigue tests in the high-cycle fatigue region with a stress asymmetry ratios of R = −1 and R = 0.1. The resulting fracture surfaces are analyzed through light optical microscopy (LOM) and scanning electron microscopy (SEM). VPDC increased the number of cycles to fracture and decreased the scatter at the given load levels compared to conventional HPDC casting. Moreover, VPDC significantly decreased the porosity size and volume, and the occurrence of oxide flakes is also decreased, resulting in the improvement in the number of cycle to failure.

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42

Chen, Rui Feng, Yong Huang, and Chang An Wang. "Characterization Methods of Pores in Ceramics and Their Analysis." Key Engineering Materials 280-283 (February 2007): 1819–22. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.1819.

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Pores in ceramics have their peculiarity different from common porous materials, so the existing characterization methods should be re-recognized. In the present work, thermal shrinkage curves adequately characterize the dynamic process of porosity evolution in ceramics, and the results are checked by Archimedes method. In order to detect pore-size distribution quantitatively, gas adsorption (BET method), mercury penetration and a new Scanning Acoustic Microscope (SAM) technique are used on Alumina ceramics with large and median pores. The results acquired by these three methods are discussed in detail and unified by the introduction of effective pore-size coefficient t. It shows that a complete characterization system adapt to pores in ceramics should be established.

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43

Santos, Jorge, Anders E. W. Jarfors, and Arne K. Dahle. "Filling, Feeding and Defect Formation of Thick-Walled AlSi7Mg0.3 Semi-Solid Castings." Solid State Phenomena 256 (September 2016): 222–27. http://dx.doi.org/10.4028/www.scientific.net/ssp.256.222.

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Aluminium semi-solid castings have gained increased attention due to their superior mechanical properties, lower porosity compared to conventional high pressure die cast material. These characteristics suggests that semi-solid casting should be suitable to produce thick-walled structural components, yet most successful applications of semisolid casting have been for thin-walled components. There is a lack of understanding on filling and feeding related defect formation for semi-solid castings with thick-walled cross-sections. In the current study an AlSi7Mg0.3 aluminium alloy was used to produce semi-solid castings with a wall thickness of 10mm using a Vertical High Pressure Die Casting machine. The RheoMetalTM process was used for slurry preparation. The primary solid α-Al fraction in the slurry was varied together with die temperature. The evaluation of the filling related events was made through interrupted shots, stopping the plunger at different positions. Microscopy of full castings and interrupted test samples were performed identifying the presence of surface segregation layer, shear bands, gas entrapment, shrinkage porosity as well as burst feeding.

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44

Bobkov, Vladimir I., and Elvira V. Morgunova. "Analysis of the Granulometric Composition of the Feedstock Influence on Mechanical Properties of Iron Ore Pellets." Materials Science Forum 1052 (February 3, 2022): 272–83. http://dx.doi.org/10.4028/p-2r8x9q.

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The paper investigates the effect of high-temperature roasting and cooling modes of roasted iron ore pellets on their strength and porosity. These characteristics depend on the initial iron ore raw materials properties, the parameters of the raw pellets, the firing temperature, the holding time at this temperature, the heating and cooling rate, and take into account the change in these indicators in connection with the chemical and mineralogical compositions of the pellets. It has been established that the strength of iron ore pellets obtained at the optimum firing temperature depends on the characteristics of the initial finely dispersed iron ore raw material. The relationship between the content of draw rock and the strength of calcined pellets has been revealed. A significant influence of the raw pellets porosity on the strength of the calcined pellets was found. It is shown that the crushing strength of pellets cooled in air is higher than the strength of pellets cooled with water, and a decrease in the final cooling temperature leads to an increase in the strength of the pellets. It is substantiated that the heating rate should not exceed the rate of gas diffusion, and with a decrease in the size of finely dispersed iron ore raw materials, the shrinkage of the pellet layer increases during heating. It is shown that shrinkage appears at temperatures lower than the optimal calcining temperature and insignificantly affects the strength of the pellets. The results obtained can be used to substantiate resource-and-energy efficient operating modes of horizontal-grate machines in ferrous metallurgy.

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45

Garbacz-Klempka, Aldona, Edward Czekaj, Janusz Kozana, Małgorzata Perek-Nowak, and Marcin Piękoś. "Influence of Al and Fe Additions on Structure and Properties of Cu-Sn Alloys." Key Engineering Materials 682 (February 2016): 226–35. http://dx.doi.org/10.4028/www.scientific.net/kem.682.226.

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The studies regard analysis of variable Al and Fe additions on the chosen group of CuSn alloys. The group of tin bronzes known and applied for thousands of years has still found its application in many branches of industry, however it was observed that small amounts of aluminum and iron may affect the original properties strongly. The changes of mechanical properties and microstructure is discussed in detail. Aside of many advantageous properties of these bronzes, it is noted that the mentioned alloying additions have beneficial effect on the gas-induced shrinkage porosity. Simultaneously, the effect of the aluminum addition on the characteristic phase transformation points was determined basing on the analysis of calorimetric curves. The results are correlated with microstructure observations.

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46

Suprapto, Wahyono, Bambang Suharno, Johny Wahyuadi Soedarsono, and Dedi Priadi. "Analytical and Experimental Models of Porosity Formation of Duralumin Cast in Vacuum Casting System." Advanced Materials Research 277 (July 2011): 76–83. http://dx.doi.org/10.4028/www.scientific.net/amr.277.76.

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Porosity in cast metals often leads to cracking of components due to stress concentration and leakage, and as the result, the castings need be repaired or rejected. Disharmony in casting process was resulting in porosity. Prediction of porosity in the casting is necessary as a step to avoid the waste products and reduce costs. But to ensure whether these predictions are accurate and precise, it is still necessary to validate the test trials and testing. This paper aims to provide early information when, where, and how large a defect occurs in particular foundry casting porosity on duralumin. The analytical study of porosity formation based analytic equilibrium wt% of element, the behavior of the thermodynamic, hydrodynamic, and rules of metallurgical on vacuum casting of duralumin. Experiments as a validation study are conducted by duralumin remelting on stainless-steel bowl in a vacuum casting furnace. Analytical simulation and experiments of the casting that has been vacuumed by melting 10 cmHg pressures higher than the pressure solidification, and duralumin melt is poured automatically into permanent mold carbon steel. In the study cast duralumin created five different thicknesses. Both these studies assume the addition of copper (2.5%, 3.0%, 3.5 %, 4.0%, and 4.5% Cu) and vacuum pressure (76, 50, 40, cmHg), as independent variables, while dependent variable in the studies is porosity characteristics, which includes morphology, number and dimensions of the porosity. Optical emission spectrometry test, Reynold's and Niyama numbers, Sievert's law, Archimedes' principle (Pycnometry and Straube-Pfeiffer tests), and Eichenauer equation are instruments which are used to determine the characterization of duralumin casting porosity. Duralumin ingots remelting process was performed by the control pressure (p1) and temperature (T1). Vacuuming process performed after the smelting room temperature reaches 600 °C. Once melted, it followed by duralumin into a permanent mold (p2, T2). As a control parameter is the height of pouring (7 cm), pour temperature and mold temperature respectively at 750 °C and 300 °C. The porosity characteristics studies of two models produce two types of porosity (gas and shrinkage), the quantity dimension and porosity, and distribution of porosity in the cast duralumin.

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47

Xu, Yu Lei, Kui Zhang, Li Han, and Ming Feng Li. "Analyses of P-S-N Curve and Fracture Morphology of Die-Casting Magnesium Alloy AZ91D Containing Mischmetal." Applied Mechanics and Materials 467 (December 2013): 103–7. http://dx.doi.org/10.4028/www.scientific.net/amm.467.103.

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The p-S-N curve (p = 50%) of die casting magnesium alloy AZ91D with 1% mischmetal was determined and the fatigue strength corresponding to 3.8 × 105 cycles with 50% probability was 70 MPa. The fatigue fracture surfaces were observed using scanning electron microscopy. The fatigue factures varied with the applied stress and their own defects. The fracture surfaces of some samples loaded lower stress exhibited rubbing mark. The fatigue fracture surface of samples with minor defect possessed the mixed characteristics of quasi-cleavage, tearing ridge, dimple and fatigue striation. Fatigue cracks initiated at gas pores and shrinkage porosity clusters. It were found there was an minor defect size as the site of damage incubation on fracture surface of die casting testing bars which fatigue life was near to the upper bound of fatigue lives.

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48

Wanjara, Priti, and Xin Jin Cao. "Hybrid Laser-Arc Welding of AA6061-T6 Butt Joints." Materials Science Forum 783-786 (May 2014): 2833–38. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.2833.

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Hybrid laser-arc welding (HLAW) of butt joints in 3.18 mm thick aluminum alloy (AA) 6061-T6 sheets was investigated in the present study. Under optimized process conditions, high integrity welds with approximately 2% shrinkage and gas porosity were obtained. The weld bead geometry was determined to conform to the crown and root reinforcement specifications for welded aluminum construction - CSA W 59.2 M1191. Softening in the heat-affected zone (HAZ) and fusion zone (FZ) of the welds was observed, the former due to grain coarsening and the latter due to the dissolution of the hardening precipitates as well as the dilution from the application of the ER 5356 filler wire. Under optimized process conditions, the gap tolerance was determined to be 0.5 mm, beyond which the performance of the joints during bend testing was compromised.

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Liu, Jiang-Feng, Frédéric Skoczylas, and Jean Talandier. "Gas permeability of a compacted bentonite–sand mixture: coupled effects of water content, dry density, and confining pressure." Canadian Geotechnical Journal 52, no. 8 (August 2015): 1159–67. http://dx.doi.org/10.1139/cgj-2014-0371.

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The gas-tightness of compacted bentonite–sand mixtures is important to the total sealing efficiency of geological repositories. The initial aim of this work was to determine whether the combination of a high confining pressure (Pc) and incomplete saturation could cause a bentonite–sand mixture to become gas-tight. The results show that the physical characteristics of the materials (degree of saturation, Sr; porosity, [Formula: see text]; and dry density, ρd) are very sensitive to changes in the applied confining pressures and their own swelling deformation (or shrinkage). The combination of these changes affects the sample’s effective gas permeability (Keff). For materials prepared at a relative humidity (RH) of 98%, Keff decreased from 10−16 to 10−20 m2 when Pc increased from 1 to 7 MPa. This means that gas-tightness can be obtained for a compacted bentonite–sand mixture when the materials experience a series of changes (e.g., w, Sr, [Formula: see text], and ρd). In addition, larger irreversible deformation (or hysteresis) was observed during the loading–unloading cycle for the sample with higher water content. This phenomenon may be attributed to larger interactions between the macrostructural and microstructural deformations and the decrease of preconsolidation pressure during hydration.

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Faramazyan, A. M., S. S. Remchukov, and I. V. Demidyuk. "Application of the vacuum casting technology in the production of small-size gas turbine engine blade machines." VESTNIK of Samara University. Aerospace and Mechanical Engineering 20, no. 3 (December 1, 2021): 152–59. http://dx.doi.org/10.18287/2541-7533-2021-20-3-152-159.

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The application of casting technologies in the production of parts and assemblies of small-size gas turbine engines is justified in the paper. The technology of vacuum casting in gypsum molds was tested during the production of an experimental centrifugal compressor of a small-size gas turbine engine. On the basis of a 3D model of the designed centrifugal compressor, computational studies of vacuum casting were carried out and rational parameters of the technological process were determined. Prototypes of the developed centrifugal compressor of a small-size gas turbine engine were made. The results of calculations and the performed technological experiment confirmed the fill rate of the gating form and the absence of short pour. The distribution of shrinkage porosity and cavities corresponds to the design values and is concentrated in the central part of the casting that is subjected to subsequent machining. The area of the blades, disc and sleeve is formed without defects. The use of casting technologies in the production of parts and assemblies of small-size gas turbine engines assures the required quality with a comparatively low price of the finished product, making it possible to achieve the balance between the cost of the technology and the quality of the product made according to this technology.

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