Dissertations / Theses on the topic 'Die castings'
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Hosking, Timothy Donald, and mikewood@deakin edu au. "Casting yield improvement in graphitic iron castings." Deakin University. School of Engineering and Technology, 2001. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20051017.122220.
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A well designed runner and feeding system should produce castings with minimal defects and low pour weight. This thesis investigates how the filling regime and solidification of the mould influences defects in the castings produced from that mould. Design guidelines to reduce such defects are proposed and tested.
An existing shrinkage fault in a Grey Iron disc brake casting is simulated using a commercial finite-difference computer program. Three criteria are used to predict the defect and the effect of changes to the feeder geometry. Critical Fraction Solidification analysis is used to determine whether the feeder remains in liquid contact with the casting during solidification and this approach is shown to correctly predict the presence or absence of porosity* The feeder block is extended below the ingate of the casting to improve liquid contact between the casting and feeder without significantly increasing the feeder mass. Plant trials confirm the change to the feeder eliminates the porosity defect.
The runner system and mould venting for a thin walled Ductile Iron casting are investigated. Trials show that by setting the total mould vent area to be greater than the net ingate area of the castings, the cold-shut frequency is halved. A method for runner system design based on peak linear flow velocity in the runner during mould filling is proposed. A new pressurised runner system produces castings with significantly fewer defects and reduced pour weight when runner areas are designed to maintain peak velocity below 1 m/s. Peak velocity and magnesium levels are demonstrated to be critical factors in the elimination of cold-shut defects. A pressurised runner system is also shown to isolate inclusion defects from castings more effectively than an unpressurised system.
From this work, a technique is proposed which allows the yield of an existing runner and feeder system for iron castings to be improved with confidence in the results.
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Ziolkowski, Joseph Edmund. "Modeling of an aerospace sand casting process." Link to electronic thesis, 2002. http://www.wpi.edu/Pubs/ETD/Available/etd-1223102-102625.
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Low, Chun Yu Danny. "Prediction of the dimensional accuracy of small extra-coronal titanium castings." University of Sydney, 1998. http://hdl.handle.net/2123/4655.
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Master of Science in DentistryThis work was digitised and made available on open access by the University of Sydney, Faculty of Dentistry and Sydney eScholarship . It may only be used for the purposes of research and study. Where possible, the Faculty will try to notify the author of this work. If you have any inquiries or issues regarding this work being made available please contact the Sydney eScholarship Repository Coordinator - ses@library.usyd.edu.au
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Deez, Brent Steven. "An investigation on the suitability of layer manufacturing methods for rapid tooling development in investment casting of light metal alloys." Thesis, Cape Peninsula University of Technology, 2010. http://hdl.handle.net/20.500.11838/2228.
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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2010.The research presented in this report focuses on Investment Casting capabilities for light metal alloys in South Africa and forms part of the Advanced Manufacturing Technology Strategy's (AMTS): Light Weight Metals flagship programme. The research is centred on the suitability of rapid prototyping (RP)/Iayer manufacturing (LM) methods to produce patterns for the investment casting of aluminium (AI), magnesium (Mg) and titanium (Ti) alloys, together known as Rapid Investment Casting. Three core RP technologies are investigated namely: Three Dimensional Printing - Drop-on-Bed from Z-corporation, Three Dimensional Printing - Drop-on- Drop from ThermoJet - 3D Systems and Selective Laser Sintering from EOS. Various RP/LM processes are discussed in detail and highlight the technologies selected in this study. A standard benchmark part, adapted from the European project framework FP6, designed and utilised in similar studies is used as the basis for the research. The Investment Casting process is discussed fully and compared to the Rapid Investment Casting, listing both the advantages and disadvantages of the above mentioned methods. In addition a special study has been conducted on investment casting of large components using layer manufactured patterns. This study not only helped to establish and validate the shrinkage value calculated for the aluminium castings but also showed substantial capability lacks in SA foundries to handle this type of components, which are by definition most often of high added value.
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Dewhirst, Brian A. "Castability Control in Metal Casting via Fluidity Measures: Application of Error Analysis to Variations in Fluidity Testing." Worcester, Mass. : Worcester Polytechnic Institute, 2008. http://www.wpi.edu/Pubs/ETD/Available/etd-121608-125755/.
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Thesis (Ph. D.)--Worcester Polytechnic Institute.Keywords: castability; metal casting; error analysis; casting fluidity; a356; solidification processing; fluidity. Includes bibliographical references (leaves 85-90).
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Spataro, Mark Paul. "Comparison of mechanical performance between magnesium alloy sand castings and high pressure die castings /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18378.pdf.
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Morey, Erica Frances. "The effect of casting ring liners on the dimensional accuracy of full crown castings." Thesis, The University of Sydney, 1986. http://hdl.handle.net/2123/4770.
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Whateley, Philip N. "Defects in steel investment castings." Thesis, Aston University, 1991. http://publications.aston.ac.uk/11879/.
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A general investigation was performed, in an industrial environment, of the major types of defect specific to investment castings in steel. As a result of this work three types of metallurgical defect were selected for further study. In the first of these, defects in austenitic stainless steel castings were found to result from deoxidation by-products. As a result of metallographic investigation and the statistical analysis of experimental data, evidence was found to support the hypothesis that the other two classes of defects - in martensite stainless and low alloy steels -both resulted from internal or grain boundary oxidation of the chromium alloy constituent This was often found to be followed by reaction between the metal oxides and the ceramic mould material. On the basis of this study, proposals are made for a more fundamental investigation of the mechanisms involved and interim suggestions are given for methods of ameliorating the effect in an industrial situation.
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Palanisamy, Suresh. "Ultrasonic inspection of gas porosity defects in aluminium die castings." Australasian Digital Thesis Program, 2006. http://adt.lib.swin.edu.au/public/adt-VSWT20060828.103450.
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Thesis (PhD) - Swinburne University of Technology, Industrial Research Institute Swinburne - 2006.A thesis submitted to the Industrial Research Institute Swinburne, Swinburne University of Technology in fulfilment of the requirements to the degree of Doctor of Philosophy, 2006. Typescript. Includes bibliographical references (p. 199-211).
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Umaru, Darma Katsina. "Task and need analysis of metal work casting in Katsina State of Nigeria." Online version, 2009. http://www.uwstout.edu/lib/thesis/2009/2009darmak.pdf.
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Chintalapati, Pavan. "Solidification under pressure of aluminum castings." Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2010r/chintalapati.pdf.
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Thesis (Ph. D)--University of Alabama at Birmingham, 2009.Title from PDF t.p. (viewed June 30, 2010). Additional advisors: Viola L. Acoff, Krishan K. Chawla, Raymond J. Donahue, Gregg M. Janowski, Harry E. Littleton (ad hoc). Includes bibliographical references (p. 143-138).
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Lora, Ruben, and Jayesh Namjoshi. "Simulation of Residual Stresses in Castings." Thesis, Jönköping University, JTH, Mechanical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-1587.
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This work presents a study and implementation of the simulation of residual stresses in castings. The objects of study are a cast iron truck Hub part (provided by the company Volvo 3P) and an optimized version of the Hub resulting from the application of a topology optimization process. The models are solved through an uncoupled thermo-mechanical solidification analysis, performed both in the FE commercial software Abaqus and the FD commercial software Magmasoft and the results are compared. First, a thermal analysis is carried out where the casting is cooled down from a super-heated temperature to room temperature. The thermal history obtained, is then used as an external force to calculate the residual stresses by means of a quasi-static mechanical analysis, using a J2-plasticity model. The simulation procedures are explained through a simplified model of the Hub and then applied to the geometries of interest. A results comparison between the original Hub and its optimized version is also presented. The theoretical base is given in this work as well as detailed implementation procedures. The results shows that the part subjected to the topology optimization process develop less residual stresses than its original version.
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Kålås, Øystein Heden. "Patternless direct moulding of sand castings." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-12957.
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Divandari, Mehdi. "Mechanisms of bubble damage in castings." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.699801.
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Hugo, Philip. "Suitability of layer manufacturing technologies for rapid tooling development in investment casting." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/847.
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Tantipaibulvut, Chairath. "An evaluation of the production of magnesium base alloy castings by the expendable pattern casting process." Thesis, Loughborough University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250959.
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Charmeux, Jean-Francois. "Capabilities of the Investment Casting process for producing meso/micro metal castings using Rapid Prototyping manufacturing routes." Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/54701/.
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This thesis examines the capabilities of different Rapid Prototyping (RP) manufacturing processes for producing sound metallic parts incorporating features in the micrometre range using the Investment Casting (IC) process. RP has been growing in the past twenty years and is nowadays widely employed in the area of precision investment casting since the technology offers the possibility of manufacturing wax patterns which can be directly implemented into investment casting. Owing to the steady improvements of the technology, some of the recently developed RP building machines offer the possibility of manufacturing small parts incorporating micro-features. In this work, a detailed description of the accuracy and capabilities of the IC process regarding its potential for producing sound meso/micro components is given using two types of conventional RP machines. The results of this analysis are then compared through a benchmarking study with a recently developed RP process suitable for the direct manufacture of ceramic moulds. The different technological chains are compared regarding their overall accuracy, surface finish, the amount of structural defects present in the castings and their relative production costs and lead-time. Finally, the potential of the investment casting process for manufacturing sound micro-castings with high aspect ratio is approached from a structural point of view. Through a metallographic analysis study, the research investigates the size-scale effect of cast micro-components upon their microstructure and the subsequent changes in their mechanical properties.
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Gustafsson, Erik. "Optimization of Castings by using Surrogate Models." Licentiate thesis, Linköping University, Department of Management and Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-10192.
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In this thesis structural optimization of castings and thermomechanical analysis of castings are studied.
In paper I an optimization algorithm is created by using Matlab. The algorithm is linked to the commercial FE solver Abaqus by using Python script. The optimization algorithm uses the successive response surfaces methodology (SRSM) to create global response surfaces. It is shown that including residual stresses in structural optimization of castings yields an optimal shape that differs significantly from the one obtained when residual stresses are excluded.
In paper II the optimization algorithm is expanded to using neural networks. It is tested on some typical bench mark problems and shows very promising results. Combining paper I and II the response surfaces can be either analytical functions, both linear and non-linear, or neural networks. The optimization is then performed by using sequential linear programming or by using a zero-order method called Complex. This is all gathered in a package called StuG-OPT.
In paper III and IV focus is on the thermomechanical problem when residual stresses are calculated. In paper III a literature review is performed and some numerical simulations are performed to see where numerical simulations can be used in the industry today. In paper IV simulations are compared to real tests. Several stress lattices are casted and the residual stresses are measured. Simulations are performed by using Magmasoft and Abaqus. In Magmasoft a J2-plasticity model is used and in Abaqus two simulations are performed using either J2-plasticity or the ”Cast Iron Plasticity” available in Abaqus that takes into account the different behavior in tension and compression for grey cast iron.
Report code: LIU-TEK-LIC-2007:34.
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Escobar, de Obaldia Enrique R. "SIMULATION OF MICROPOROSITY IN ALUMINUM PLATE CASTINGS." MSSTATE, 2007. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04082007-152803/.
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Porosity is known to be one of the primary factors controlling fatigue life and total elongation in cast aluminum components. The thrust of this study is to examine pore nucleation and growth effects for predicting gas microporosity in A356 plates. In this work, a solidification model is used to quantify and evaluate the discrepancy between experimental data and porosity calculated with different approaches. The first approach considers hydrogen supersaturation based on the transport of dissolved hydrogen and Sievert?s law. The second approach uses the hydrogen supersaturation calculated in the first approach combined with a local solidification time. The third approach considers a new hydrogen technique based on the transport of inclusions through the liquid metal and mushy zone. Computer simulations were performed modeling aluminum plate castings.
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Abdul, Karem Waleed. "Vibration assisted filling of thin section castings." Thesis, University of Birmingham, 2009. http://etheses.bham.ac.uk//id/eprint/951/.
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Understanding of the mechanism of the vibration needed to fill thin section or one with sharp edges in profile shapes and clarifying the dominant control parameters of the vibration in thin wall investment casting is key to producing sound casting (one free of misrun defects). It's also a central issue for study in this thesis. The filling capability in thin wall investment casting method was assessed in relation to metal head. It was found that the effect of the vibration on the metal head is markedly dependent on acceleration. Generally, it was observed that the metal head required to force the metal in thin sections in the casting vibrated at (1g) acceleration is approximately half that used in castings made without vibration. Two potential mechanisms were observed from the experimental result during the filling process in thin wall casting i] discontinuous propagation flow in vibration conditions; and ii] continuous propagation flow without vibration. These mechanisms may be acting to modify the contact angles between liquid metal and a wall of the mould. Experiments also showed that two features of the transition can be observed from the front of the morphology; i] a coherent liquid metal front - this occurs in thin wall investment casting when the acceleration due to vibration is less than (1g); and ii] jetting at the free surface - this occurs in thin wall investment casting when the acceleration due to vibration exceeds 1g. This is present in terms of a unifying concept, using a frequency and amplitude ( f - a ) map. The time of the vibration operation has a moderate effect on the relative filling area when the acceleration is less than 1g. However, it is more effective when the acceleration of the vibration is greater than 1g. The mathematical models comprised one-dimensional heat transfer with phase change and had an established flow field for molten A356 alloys flow in the thin section ceramic channel mould. The work was concerned with the fluidity of A356 alloys in thin wall investment casting with and without vibration in two type of filling (flowability and fillability filling types), combining heat and metal flow in addition to the simultaneous solidification stage. The results of the mathematical model, produced agreement with the experimental test carried out in the foundry and also agreed with other published data. The results on fluidity indicated that the fluidity of the molten metal was affected by mould temperature, pouring temperature, the velocity of the molten metal flow relative to the surface tension and the channel thickness. The data used in the mathematical model of the fluidity in thin section under vibration condition were deduced experimentally; namely, velocity of the molten metal and the heat transfer coefficient between the liquid metal and the chilled surface of the mould. This model was used to estimate the fluidity characteristics in thin wall investment casting with and without vibration. Real-time X-ray observation and computer modelling of the metal head-driven mould filling sequences reveal that no surface turbulence occurred when the liquid metal flowed into the thin section and the advance metal front continued to flow under surface tension control. X-ray was also used to measure the flow time and the velocity of the metal inside the thin channel and confirm the modification on Bernoullis Equation (kinetic energy+ potential energy = constant) to estimate the velocity relative to surface tension in the fluidity mathematical model. Flow-3D software was used to calculate the velocity of the liquid metal in the flowability filling type and the fluidity characteristics. Weibull analysis identifies the acceleration vibration as practical criterion to judge the reliability of casting. A vibration mould with vertical direction in the thin wall investment casting after filling can make the liquid metal flow into the thin section under surface tension control. This technique is used to achieve mould filling free from misrun defects and surface turbulence and this makes vibration casting a promising technique for producing high quality castings. On the basis of these findings, an operation window for the production of reliable castings has for the first time been developed in this research.
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Lawrence, James Andrew. "The prediction of bubble defects in castings." Thesis, University of Greenwich, 2004. http://gala.gre.ac.uk/6219/.
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Objective of this research was to develop models that capture the entrainment, breakup and transport of gas bubbles in solidifying TiAl castings. The candidate has reviewed the literature, programmed in FORTRAN code, and validated a number of competing techniques for two phase flow relevant to the filling of moulds. He has developed a hybrid (Donor-acceptor/ Level Set) method, which captures the characteristics of gas bubbles based on the surface tension —fluid inertia balance on the free surface. He has demonstrated the ability of this method to reproduce observed phenomena. The candidate also conducted an experimental campaign in Birmingham University under the supervision of Dr R.A. Harding to provide real casting data for his simulations. KAP Edited extract from RD3 MPhil/PhD form: "This research was carried out at the University of Greenwich in conjunction with the University of Birmingham as part of a larger EPSRC- funded project concerned with the development of a casting process route for the production of gamma-TiAl components. Focus of the research was the development of a model of entrained bubbles in the metal casting process. This model comprises the combination of several physical phenomena coupled within the PHYSICA multi-physics framework. The key areas the research has touched on are, surface tension modelling and free-surface modelling using the finite volume technique. A model has been developed that simulates bubble formation during the filling of castings due to surface entrainment and subsequent motion. Once entrained these bubbles tend to solidify in the casting where the rate of solidification is too fast for escape by buoyancy. This problem is particularly acute in thin blade sections of TiAl, where sufficient superheat cannot be maintained during the casting process. Mould filling techniques have to be modified accordingly to improve the mechanical integrity of components. Two phase systems with a sharp, well-defined interface governed by surface tension are required to be modelled. The Level Set Method (LSM) is such a method, used to maintain the position of the interface as it moves through a fixed computational grid. The interface is moved or distorted by the advection equation. In this case two numerical methods are used in differencing: Van-Leer and Donor Acceptor. The Donor Acceptor method is of use when modelling highly dynamic surfaces, such as those encountered during the metal pouring phase in castings, or when fuel sloshes in a fuel tank. This method is best for capturing the entrapment of large bubbles of gas by surface folding. A process directly related to the moving surface. However, the LSM, which allows many surface properties to be calculated, cannot be used in conjunction with the Donor Acceptor method which uses heuristics to sharpen the interface in each compu6tational cell. Once bubbles are formed, their existence and motion are governed by the action of surface tension, therefore the mathematically more rigorous Van-Leer differencing scheme is used in conjunction with the LSM. Bubbles are then tracked using the freesurface method. The tracking limit is determined by the fineness of the mesh used. Sub grid bubbles or bubbles that only occupy a small number of cells can no longer be tracked in a continuum Eulerian simulation. Lagrangian particle tracking is then necessary. The original work in this research can be described as the coupling of the formation of bubbles using the Donor Acceptor method, with the LSM / Van-Leer technique for their subsequent motion and behaviour. This involves: • Modelling the initial free-surface dynamics with the Donor Acceptor technique. • Modelling bubble formation using the Donor Acceptor technique. • Using Results from bubble formation database to "re-start" the simulation with the inclusion of surface tension. • Tracking bubbles as a free-surface, computing their subsequent break up or coalescence • Once the bubbles reach a minimum size for a given mesh, continue tracking using the Lagrangian particle tracking technique. The model was applied to: • Simple validation experiments to test the correctness of the coding • Sloshing/collapsing column experiments to evaluate bubble formation • Simple geometry situations where the combined model is used with Bubble Formation/Tracking Surface Tension • Model the filling of the flat plate experimental setup Future work (not completed ...) • Develop criteria for switching between the Eulerian (free surface) and Lagrangian (particle tracking) scheme • Compare with Experimental Data obtained at the University of Birmingham • Run 3D Cases representing real geometries with HT and solidification • Model the counter-gravity filling process"
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Raffaelli, Giovanni. "ADVANCED ALUMINUM ALLOYS FOR HIGH PERFORMANCE CASTINGS." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423780.
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In order to produce aluminum high performance castings, two main factors are essential: alloy and process. High performance castings are the result of the ideal equation of combination of these two factors. For this reason this PhD research project consisted in two main parts:
1. the first part has been developed together with Rheinfelden Alloys GmbH & Co. KG and consisted in an in deep analysis of aluminum alloys and their reinforcements mechanisms.
2. the second part has been developed in collaboration with TMB SpA and focused on the process and on process-related aspects affecting the quality of castings.
A new way to introduce nanoparticles to reinforce aluminum-silicon alloys was found and an in deep analysis of the very high mechanical properties obtained has been carried out. This way, in comparison to the processes to produce Al-alloy based nanocomposites already present in literature, is very cheap and could be scaled-up to industrial scale.
Nevertheless there are still some critical aspects in the use in industrial scale of these highly innovative nanocomposites and for this reason in the second part of the project has been studied how to produce high performance castings with already available alloys by optimizing the other factor of the equation: the process.
Based on the defect classification made by Gariboldi, Bonollo and Parona in the “Handbook of defects in high pressure die castings” (2010) [1], several aspects regarding the process were taken in account and relevant results were obtained in order to get always high performance castings.Al fine di produrre getti altoprestazionali in alluminio sono essenziali due fattori: la lega e il processo. Fusioni altoprestazionali sono il risultato dell’ideale equazione di combinazione di questi due fattori. Per questo motivo questo progetto di ricerca di dottorato consiste in due parti principali: 1. la prima parte è stata sviluppata in collaborazione con Rheinfelden Alloys GmbH & Co. KG e consiste in un’analisi approfondita delle leghe di alluminio e dei meccanismi del loro rafforzamento. 2. la seconda paste è stata sviluppata in collaborazione con TMB SpA ed è stata focalizzata sul processo e sugli aspetti del processo che possono influenzare la qualità dei getti. E’ stato sviluppato un nuovo metodo per l’introduzione di nanoparticelle al fine di rafforzare le leghe Alluminio-Silicio ed è stata svolta un’analisi approfondita delle notevoli proprietà meccaniche ottenute. Questo metodo, in confronto con gli altri processi per produrre nanocompositi a matrice lega di Alluminio presenti in letteratura, è molto economico e potrebbe essere sviluppato su scala industriale. Persistono tuttavia alcuni aspetti critici nell’utilizzo industriale di questi nanocompositi altamente innovativi e per questo motivo nella seconda parte del progetto è stato studiato come produrre getti altoprestazionali con leghe già disponibili ottimizzando l’altro fattore dell’equazione: il processo. Basandosi sulla classificazione dei difetti sviluppata da Gariboldi, Bonollo e Parona nel “Manuale di difettologia dei getti pressocolati” (2010) [1], sono stati presi in considerazione numerosi aspetti riguardanti il processo e sono stati ottenuti risultati rilevanti al fine di ottenere sempre getti altoprestazionali.
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Collins, Stephanie Karen. "Study of the effect of the casting skin on the tensile properties of light weight ductile iron castings." The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406710017.
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Diem, Matthew M. "Development of a combined hot isostatic pressing and solution heat-treat process for the cost effective densification of critical aluminum castings." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0107103-162146.
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Ho, Kwok-hung Eric. "Dimensional calibration of castings in phosphate bonded investment." Click to view the E-thesis via HKUTO, 1994. http://sunzi.lib.hku.hk/HKUTO/record/B3862798X.
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Walker, Justin Daniel. "An innovative new pouring design for steel castings." [Ames, Iowa : Iowa State University], 2008.
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Moosavi, Khoonsari Elmira. "Reinforced aluminum structure castings for powertrain automotive applications." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66990.
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The reinforcement of an Al casting with ferrous inserts (hybrid systems) through a joining technique to utilize both Al alloys (lightness) and Fe-based alloys (stiffness) is of interest, especially in the transportation sector. This work focuses on different technological aspects of cast joining of cast iron to an Al alloy using an intermediate material (or coating). The experimental set up consisted of preparing the insert surface followed by coating the insert, and then, immersing it into an Al melt, and allowing the system to cool down to room temperature. The effects of flux treatment, decarburization, and the coating application, as well as the immersion time in the Al melt on the Al-Fe joint quality were investigated. The microstructure evolution of the reaction layer forming at the insert-coating interface was determined as a function of the coating time and the coating composition, and their effects on the joint properties were evaluated. The relationship between the microstructure and microhardness of the joint zone was established. Decarburization, flux treatment, suitable coating, and optimizing the process parameters improved the joint properties. Combination of "McGill 2" coating alloy and 1 min immersion time (in the Al melt) resulted in the formation of an Al-Fe joint with optimized characteristics. The results showed that the cast joining could be used to strengthen the Al castings and improve their performance.Le renfort des pièces coulées en aluminium par l'assemblage d'insertions ferreuses (systèmes hybrides) permet de combiner la légèreté de l'aluminium avec la rigidité des alliages à base de fer. Cette technique présente donc un grand intérêt pour plusieurs applications, spécialement dans le secteur des transports. Ce projet porte sur les différents aspects technologiques de la coulée de pièces avec joint aluminium-fonte auquel est ajouté une couche intermédiaire (ou revêtement). La procédure expérimentale a consisté à préparer la surface des insertions, à appliquer le revêtement, puis immerger la pièce dans un bain d'aluminium liquide, pour finalement refroidir le système jusqu'à la température de la pièce. Les effets du traitement par flux, de la décarburisation, et des paramètres de revêtement ainsi que la durée d'immersion dans l'aluminium liquide sur la qualité du joint aluminium-fonte ont été étudiés. L'évolution de la microstructure par la formation d'une zone de réaction à l'interface de l'insertion de réaction et zone du revêtement a été déterminée en fonction de la composition du revêtement er du temps d'immersion dans le revêtement liquide, et leurs effets sur les propriétés du joint été évalués. La corrélation entre la microstructure et la microdureté du joint ont a été établie. La décarburisation, le traitement par flux, l'utilisation d'un revêtement approprié et l'optimisation des paramètres du procédé améliorent significativement les propriétés du joint. L'utilisation du revêtement "McGill 2" avec un temps d'immersion dans le bain d'aluminium d'une minute permet la formation d'un joint Al-Fe avec des caractéristiques morphologiques, d'épaisseur, de microdureté et de composition optimisées. Les résultats montrent que l'insertion de pièces formant un joint peut être utilisée pour renforcer les pièces d'aluminium et
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Abdullah, S. "Finite element simulation of filling thin section castings." Thesis, Swansea University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635834.
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The finite element simulation of filling thin section cavities has been studied in the present research, with an emphasis on the casting application. This thesis describes the development of appropriate governing equations for filling thin section cavities and finite element analysing software used to simulate some selected filling examples as case studies. As the transverse velocity profile across a thin section can be approximated between the parabolic and plain distributions, the flow throughout the cavity can be represented by in-plane velocity components and simulated using a quasi three-dimensional formulation. By applying an appropriate velocity profile and accounting for any thickness variation, the governing filling formulation was derived using the conservation laws of mass, momentum and free surface, which produced the thickness-integrated continuity, Navier-Stokes and pseudo-concentration equations, respectively. Appropriate transformations were incorporated into the thickness-integrated Navier-Stokes equations to accommodate the three-dimensional form of the cavity. Since surface tension also affects the flow in thinner sections, a study on the inclusion of this topic was also included. The finite element flow formulation was constructed by discretising the governing equations spatially and temporally using the conventional Galerkin method and the implicit backward difference method, respectively, and was solved via a mixed formulation. This was found to be the best approach for the cavity having thickness changes. For free surface tracking, the explicit Taylor-Galerkin method was used to discretise the pseudo-concentration equation since it gave more accurate results. This filling simulation model was applied to three case studies, where the numerical results were compared with the experimental data for the benchmark gravity sand casting as gathered by other researchers, a cylindrical shaped cavity in the laboratory and a high pressure die casting in the foundry. Good agreement was obtained in each case.
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Ho, Kwok-hung Eric, and 何國雄. "Dimensional calibration of castings in phosphate bonded investment." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1994. http://hub.hku.hk/bib/B3862798X.
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Hsu, Fu-Yuan. "Further developments of running system for aluminium castings." Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289752.
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The purpose of this research is the development of guiding principles and rules for the design of running systems for aluminium castings, employing both the "virtual" experiment, a computational modelling package, and the "physical" experiment, the real-time X-ray radiography study. "Diverging-Bend" geometry has an essential feature in which the flow rate of the system could achieve the maximum and the velocity of advancing flow could reduce without developing surface turbulence. In liquid aluminium, the surface tension becomes more significant compared to water during the flow transformation from supercritical to subcritical velocities. To describe the phenomenon of hydraulic jump for liquid aluminium it is necessary to include the surface tension, giving the relation pV 2 = (pxgxH) + (4T/H) where p: density, V: average velocity, g: gravitational acceleration, H: the height of the hydraulic jump, and T: surface tension. Guidelines for the designing of L-junctions are developed. Five geometries of L-junctions can be applied and assembled in the design of runners and multiple-gate system. Progressive filling along the L-junction geometry can be achieved by reducing the area of the "dead zone". In a multiple-gate system uniform distribution of flow rate through each gate into the mould cavity is achieved. Quantification of a running system is established by the measurement of coefficient of discharge Cd. The loss coefficient K for individual component of runners is also estimated.
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Gorsky, Daniel A. "Niyama Based Taper Optimizations in Steel Alloy Castings." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1316191746.
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Matys, Paul. "Fluid flow and heat transfer in continuous casting processes." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28504.
Full textAbstract:
A three-dimensional finite difference code was developed to simulate fluid flow and heat transfer phenomena in continuous casting processes.
The mathematical model describes steady state transport phenomena in a three dimensional solution domain that involves: turbulent fluid flow, natural and forced convection, conduction, release of latent heat at the solidus surface, and tracing of unknown location of liquid/solid interface.
The governing differential equations are discretized using a finite volume method and a hybrid central, upwind differencing scheme. A fully three-dimensional ADI-like iterative procedure is used to solve the discretized algebraic equations for each dependent variable. The whole system of interlinked equations is solved by the SIMPLE algorithm.
The developed computer code was used for parametric studies of continuous casting of aluminum. The results were compared against available experimental data. This numerical simulation enhances understanding of the fluid flow and heat transfer phenomena in continuous casting processes and can be used as a tool to optimize technologies for continuous casting of metals.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Lee, Peter D. "The formation of hydrogen porosity during the solidification of aluminium alloys." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318700.
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Grandfield, John F. "Hot tear defect formation during horizontal direct chill casting of magnesium /." St. Lucia, Qld, 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16285.pdf.
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Singh, Kaushlendra. "Numerical simulation of solidification and porosity formation in castings." Ohio : Ohio University, 1988. http://www.ohiolink.edu/etd/view.cgi?ohiou1182870813.
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Zhang, Chunhui. "Controlled cooling of permanent mold castings of aluminum alloys." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19619.
Full textAbstract:
The permanent mold casting process is a relatively popular and effective casting technology that can produce near-net-shape aluminum components with integrity, particularly for the automotive and aerospace industries. It is well recognized by the casting industry that it is essential to control the cooling of permanent mold castings in order to improve the quality of the castings, so there is a considerable incentive to develop a more effective method of mold cooling to control the temperature distribution of the mold and the casting. The current technologies for controlled cooling are air or water cooling passages and chill inserts. Each of these cooling methods presents certain disadvantages, and none offer optimum cooling control. Based on these considerations, a novel, effective and controllable water-based heat pipe has been successfully developed to be used as a new method of permanent mold cooling where high heat fluxes are normally encountered. Heat pipes featuring this design have been incorporated in an experimental permanent mold made of HI3 tool steel that contains three symmetric steps. Computer modeling for the permanent mold casting process has been accomplished to predict the effect and potential of heat pipe cooling for permanent mold casting. Castings of A3 56 alloy have been produced by this permanent mold. The effects of heat pipe cooling on permanent mold castings have been evaluated by analyzing the temperature distribution of the mold and the casting, as well as by measuring the dendrite arm spacing and shrinkage distribution of the castings. The effect of heat pipe cooling on the mold solidification time of castings of A356 alloy with different coating types was also studied. Industrial trials have been carried out to evaluate this new cooling technology on an industrial scale casting machine. Because the space around the mold installed on a low pressure die casting machine is very limited, it is often very difficult to install the heat pipe in the specific desired location in the mold. A new version flexible heat pipe cooling system has been developed for the industrial casting process. Preliminary and industrial tests of the heat pipe cooling system have been performed. The effects of heat pipe cooling, as well as the effects of using traditional water and air cooling on the low pressure die casting were studied. Data on the cooling rates obtained by heat pipes, as well as some microstructures and measurements of the dendrite arm spacing are presented in this thesis. Modeling and experimental results have shown that the water based heat pipe can provide high cooling rates in casting processes. The dendrite arm spacing (DAS) of A356 alloy is refined considerably by the heat pipes, and changes in the shrinkage pattern are provided by the dramatic changes in the heat flow patterns.
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Te, Alino. "Improvement in Toughness of Castings through Chemical Surface Modification." Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/1271.
Full textAbstract:
Alloys with good toughness and elevated temperature properties like A201 are expensive and can be more difficult to process. This results in the use of heavier but less expensive alternatives in many applications where toughness is of concern, such as steels. Common alloys such as A356 and E357 are relatively cheap and easy to work with. However, these alloys have considerably lower toughness than premium alloys. This research aims to investigate surface modification treatments that could yield better toughness at a low cost in a common aluminum alloy. The process must show significant improvement in said properties, be cost effective, and easily adaptable in a common foundry. Diffusion of coating material into the substrate was investigated with a variety of coating metals. The diffusion process was facilitated in the solutionizing step for the given substrate aluminum in order to strengthen the sub-surface region of the parts. This research aims to provide a platform for further research into the practical effects of the coating and tempering on impact and toughness properties. These samples were characterized by optical and scanning electron microscopy, EDS, impact testing, and tensile testing.
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Unal, Ogun. "Characterization of Tensile Deformation in AZ91 Mg Alloy Castings." UNF Digital Commons, 2016. http://digitalcommons.unf.edu/etd/632.
Full textAbstract:
Tensile deformation characteristics of cast aluminum alloys have been investigated extensively. Cast Mg alloys have remained mostly neglected by researchers, despite their potential for weight savings. This present study is motivated by this gap in the literature and consists of two stages; in Stage 1, analysis of tensile data gathered from literature were reanalyzed, and in Stage 2, data generated from tensile testing of 60 specimens of AZ91 Mg alloy castings in both T4 and T6 conditions were analyzed to characterize work hardening behavior.
In Stage 1, more than 1600 data were collected from the literature for various Mg alloy families. After plotting these data in yield strength-elongation charts, highest points were identified and interpreted as the maximum ductility, i.e., ductility potential (eFmax). The trend in maximum points indicated a linear relationship with yield strength (σY), expressed as;
eF(max) = 41.8 - 0.106σY (1)
This ductility potential equation can be used as a metric to compare elongation obtained from tensile specimens to measure the structural quality of Mg alloy castings. Moreover, results indicated that ductility potential was not affected by heat treatment, grain size (within 30-120 μm), casting geometry, size, the type of casting process nor chemical composition.
In Phase 2, AZ91 cast Mg alloy specimens in T4 and T6 conditions were tested in tension to obtain stress-strain data for each specimen. Fits of four constitutive equations, namely, the Hollomon, Voce, Ludwik and Swift, to true stress-true plastic strain data in the elastoplastic region were characterized for the specimens with highest elongation values for T4 and T6 specimens. The coefficient of determination, R2, values for all equations were in excess of 0.99, suggesting that all four equations provide excellent fits to tensile data in both conditions.
The change in work hardening rate with true stress was investigated for all specimens by using Kocks-Mecking (KM) plots. It was determined that work hardening behavior of Mg alloy castings in T4 and T6 is distinctly different. In T4 specimens, there is a plateau in work hardening rate at approximately E/25 which was observed in all specimens. The presence of this plateau is consistent with results given in the literature for pure Mg. However, this plateau was not observed in any of the T6 specimens. The reasons for the absence of the plateau in T6 specimens are unknown at this time. In both T4 and T6 specimens, the KM work hardening model in which work hardening rate changes linearly with true stress was found to be applicable. This is the first time that KM model was found to be valid for Mg alloys. Moreover in all specimens, there was a sudden drop in work hardening rate just prior to final fracture. This drop was first hypothesized to be due to structural defects in specimens, which was subsequently validated via fractography. Structural defects were found in all specimens whose fracture surfaces were investigated, indicating low to medium levels of quality.
The quality index method, originally developed for cast aluminum alloys as the ratio of elongation to ductility potential, was found not to be applicable to Mg alloys, at least in its original form. This is due to the fact that work hardening behavior of cast aluminum alloys follows the KM model and there is no plateau where work hardening rate is constant. Hence the work hardening behavior of cast aluminum alloys and AZ91 specimens in T6 condition was similar. However the plateau of constant work hardening rate had a strong effect on elongation in T4 specimens. Therefore quality index analysis, which is supposed to be independent of alloy condition, did show that T4 and T6 specimens had different quality index levels. This finding contradicted the result from Stage 1 that aging has no effect on ductility potential. However because of the presence of structural defects in all specimens, quality index levels were low (0.30-0.45). Therefore it is unclear at this point whether the work hardening behavior of T4 and T6 specimens would still be different if elongation values were in the proximity of the ductility potential line. More research is needed to characterize work hardening behavior of cast Mg alloys in the absence of major structural defects and also address other questions raised in this study.
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Saha, Deepak. "Novel Processing Methods and Mechanisms to Control the Cast Microstructure in Al Based Alloys - 390 and Wrought Alloys." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-041405-150300/.
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Schaub, Henning. "Comparison of different aluminium casting processes from an environmental perspective : Case study on plaster mould castings produced in Mid Sweden." Thesis, Mittuniversitetet, Avdelningen för ekoteknik och hållbart byggande, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-35659.
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While Aluminium has lots of unique properties and is seen as a material of the future, its production and manufacturing has significant environmental impacts. For complex and dimensional shapes casting remains the main manufacturing method and in this study the environmental pressure of different casting techniques is compared. A screening LCA is conducted to determine the environmental impacts of plaster mould castings in a case study at the Ventana Hackås AB foundry in Mid Sweden. The findings are compared to models of sand, pressure die and lost wax castings, based on literature datasets. The most relevant factors for the environmental performance are identified as the production of the aluminium alloy and the amount and source of energy. For plaster mould castings additionally the plaster consumption is significant, while lost wax castings are dominated by the mould production and general processes. Under similar circumstances a relatively similar performance was found for all casting techniques except the lost wax process, which is at least 3 times more emission intensive. Of the remaining techniques pressure die castings performed the best and plaster mould castings the worst, but different sources of uncertainties have been identified in this comparison. In addition a carbon footprint interface is created based on these findings, to enable specific comparisons of different casting method setups. Customizable variables allow the adaptation of three scenarios to real world conditions. As the main influencing factors the aluminium alloy, source of electricity and casting technique have been identified.2018-10-10
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Lim, Chu-Sing. "The production and evaluation of fibre preform-infiltrated metal matrix composite castings produced by a developed pressure-assisted investment casting process." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/28175.
Full textAbstract:
The squeeze casting process is well known for its ability to produce castings with good integrity due to the high direct pressure application on the liquid metal during solidification. This concept has been used to squeeze infiltrate fibre preforms with liquid metal for metal-matrix composite (MMC) production. Squeeze casting employs fast cycle times to produce high integrity castings. The squeeze casting process is, however, limited in terms of shape complexity and flexibility (e.g. thin sections). One-offs or small production runs become very expensive to produce because of the complex nature and high cost of the die steel tooling.
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Palanisamy, Suresh, and n/a. "Ultrasonic inspection of gas porosity defects in aluminium die castings." Swinburne University of Technology. Industrial Research Institute Swinburne, 2006. http://adt.lib.swin.edu.au./public/adt-VSWT20060828.103450.
Full textAbstract:
This thesis documents a PhD research program undertaken at Swinburne
University of Technology between the years 2000 and 2004. The research was
funded by the Cooperative Research Centre for Cast Metals Manufacturing and was
undertaken in collaboration with Nissan Casting Plant Australia Pty Ltd and the Ford
Motor Company Australia Limited. This thesis reports on the investigation of the
possibility of using an ultrasonic sensing-based, non-destructive testing system to
detect gas porosity defects in aluminium die casting parts with rough surfaces. The
initial intention was to develop a procedure to obtain ultrasonic signals with the
maximum possible amplitude from defects within the rough surface areas of the
castings. A further intention was to identify defects with the application of a suitable
signal processing technique to the raw ultrasonic signal. The literature review has
indicated that ultrasonic techniques have the potential to be used to detect subsurface
defects in castings. The possibility of classifying very weak ultrasonic signals
obtained from rough surface sections of castings through a neural network approach
was also mentioned in the literature. An extensive search of the literature has
indicated that ultrasonic sensing techniques have not been successfully used to detect
sub-surface defects in aluminium die castings with rough surfaces.
Ultrasonic inspection of castings is difficult due to the influence of
microstructural variations, surface roughness and the complex shape of castings. The
design of the experimental set-up used is also critical in developing a proper
inspection procedure. The experimental set-up of an A-scan ultrasonic inspection rig
used in the research is described in this thesis. Calibration of the apparatus used in
the inspection rig was carried out to ensure the reliability and repeatability of the
results. This thesis describes the procedure used to determine a suitable frequency
range for the inspection of CA313 aluminium alloy castings and detecting porosity
defects while accommodating material variations within the part. The results
obtained from ultrasonic immersion testing indicated that focused probes operating at
frequencies between 5 MHz and 10 MHz are best suited for the inspection of
castings with surface roughness Ra values varying between 50 [micro milli] and 100 [micro milli]. For
the purpose of validating the proposed inspection methodology, gas porosity defects
were simulated through side-drilled holes in the in-gate section of selected sample
castings. Castings with actual porosity defects were also used in this research.
One of the conclusions of this research was that it was extremely difficult to
detect defects in castings with surface roughness above 125 [micro milli]. Once the ultrasonic
signal data was obtained from the sample aluminium die castings with different
surface roughness values ranging from 5 [micro milli] to 150 [micro milli] signal analysis was carried
out. Signal feature extraction was achieved using Fast Fourier Transforms (FFT),
Principal Component Analysis (PCA) and Wavelet Transforms (WT) prior to passing
the ultrasonic signals into a neural network for defect classification. MATLAB tools
were used for neural network and signal pre-processing analysis. The results
indicated that poor classification (less than 75%) was achieved with the WT, PCA
and combination of FFT/PCA and WT/PCA pre-processing techniques for rough
surface signals. However, the classification of the signals pre-processed with the
combination of WT/FFT, FFT/WT and FFT/WT/PCA classifiers provided much
better classification of more than 90% for smooth surface signals and 78% to 84%
for rough surface signals. The results obtained from ultrasonic testing of castings
with both real and simulated defects were validated with X-ray analysis of the
sample castings. The results obtained from this research encourage deeper
investigation of the detection and characterisation of sub-surface defects in castings
at the as-cast stage. Implications for the industrial application of these findings are
discussed and directions for further research presented in this thesis.
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Shirani, Mehdi. "Probabilistic and defect tolerant fatigue assessment of wind turbine castings." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-15558.
Full textAbstract:
The present thesis deals with probabilistic and defect tolerant fatigue assessment of wind turbine castings. To this end, two types of EN-GJS-400-18-LT ductile cast iron were investigated in this research, clean baseline material in the shape of casting blocks with different thicknesses and also defective material from a rejected wind turbine hub. To establish the required P–S–N diagrams for safe-life design of wind turbine castings, fatigue specimens with different dimensions machined from baseline casting blocks with different thicknesses. Constant amplitude axial fatigue tests were performed on these specimens at room temperature at R = 0 and R = −1. Geometrical size effect, wall-thickness effect (technological size effect) and mean stress effect on fatigue strength of baseline EN-GJS-400-18-LT material were evaluated and analyzed. Statistical analysis of fatigue data was done by means of the Weibull distribution, and P–S–N diagrams were established. The established P–S–N diagrams showed that the Weibull distribution is well fit to the scatter of the experimentally obtained fatigue life data. Weibull’s weakest-link method was used to evaluate the size effect. It made a satisfactory prediction of the fatigue strength for specimens with different dimensions. To study damage tolerant design of wind turbine castings, a rejected wind turbine hub was flame cut to several blanks and several defective fatigue specimens were machined from these blanks. Constant amplitude axial fatigue tests were performed on these specimens at room temperature at R = 0 and R = −1. Fatigue strength of baseline EN-GJS-400-18-LT was compared with that of defective material from the rejected wind turbine hub. The effect of graphite nodules and defects type, shape, size and position on fatigue strength of defective material was evaluated. The hypothesis that the endurance observed in an S−N test can be predicted based on the analysis of crack growth from casting defects through defect-free ‘base’ material was tested for the analyzed defective material in this research. It was shown that fatigue life of the analyzed defective cast component is controlled by fatigue crack growth and the slope of S − N curve for baseline EN-GJS-400-18-LT is different than the slope of S − N curve for defective EN-GJS-400-18-LT. To perform random defect analysis of wind turbine castings, establish the scatter of fatigue life and obtain the probability of failure of these components, 3D X-ray computed tomography was use to detect defects in defective specimens and find the defect size distribution and density of defects (number of defects per unit volume). The obtained defect size distribution and density for the defective material was used in random defect analysis to establish the scatter of fatigue life for defective specimens. Finally both safe-life and damage-tolerant design philosophies were used to evaluate the fatigue life of an EN-GJS-400-18-LT ductile cast iron block, representative of heavy-section wind turbine castings. The estimated S−N curves for the analyzed component based on these two methods were compared. It was shown that fatigue design of heavy section wind turbine cast iron components based on safe-life design philosophy may result in non-conservative design of these components
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Gales, ShaRolyn. "Effects of Pressurization on Aluminum 319 and A356.2 Alloy Castings." MSSTATE, 2001. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04062001-163331/.
Full textAbstract:
Castings made of aluminum 319 and A356.2 alloy were examined to determine the effectiveness of using pressure application during solidification to reduce porosity levels. Pyknometry was the method chosen to measure porosity. It was determined that the porosity of castings poured in both alloys was reduced in some instances. During the study, the surfaces of these castings were also examined and some were found to have defects present. After the porosity was evaluated, specimens of castings poured in both alloys were tested to determine whether or not the surface intrusions affected the castings. The defects were found to reduce the strength of the castings poured in aluminum 319. The castings poured in A356.2 did not have surface intrusions or any significant decreases in strength. Therefore it was concluded that of the two alloys tested, A356.2 alloy is most suited for using pressurization as a method of reducing porosity.
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Aliravci, A. "Elimination of shrinkage microporosity in magnesium castings by strontium additions." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22409.
Full textAbstract:
In this study a technique--that almost completely eliminates shrinkage microporosity--has been developed which uses small additions of strontium together with risers and chills to produce porosity-free AZ91C (Mg/Al/Zn) magnesium casting alloy castings. With the optimum level of Sr addition (0.01% to 0.02% Sr), shrinkage microporosity was removed from the casting and concentrated in the riser. The castings were already grain-refined by carbon inoculation. The effect of strontium is explained by a further reduction in the grain size of the castings from 250$ mu$m to 120$ mu$m. This effect produces a much denser casting due to increased mass feeding. In addition, a slow grain growth rate, caused by Sr addition, may keep the liquid intergranular-channel radius large during the final stages of solidification, and results in improved intergranular feeding. Another effect of strontium addition may possibly be attributed to a decrease in the surface tension and viscosity of the liquid AZ91C alloy, which in turn increases capillary feeding of the liquid metal. (Abstract shortened by UMI.)
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Shang, Lihong. "Prediction of microporosity in aluminum silicon castings using criteria functions." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81564.
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Microporosity, a serious defect in Al-Si based castings, severely prevents their widespread applications in many critical conditions. The use of criteria functions to quantitatively predict microporosity level holds promise. To date, an ideal criteria function has yet to be obtained.In the present work, microporosity distribution in three prominently used hypoeutectic Al-Si alloys (319, 356, and 332) was investigated. The prediction effectiveness of single solidification parameter and existing criteria functions was evaluated by correlating thermal data from simulation studies to experimentally obtained microporosity values. Several new criteria functions are proposed based on experimental observation and multivariable regression analysis. The results indicate that the thermal parameters associated with the solidification process have a strong impact on the formation of the microporosity in Al-Si alloys. Thermal parameter-based criteria functions may be used to predict the microporosity in Al-Si castings but have their limitations. A general criteria function tf1.18 Vs1.13 (tf: local solidification time, Vs: solidification velocity) can be applied to predict microporosity for the family of hypoeutectic Al-Si casting alloys within 0.2 ~ 0.4 (%) error.
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Ford, David Alan. "The origin of secondary grains in single crystal superalloy castings." Thesis, University of Warwick, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397604.
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Byczynski, Glenn Edwin. "The strength and fatigue performance of 319 aluminum alloy castings." Thesis, University of Birmingham, 2002. http://etheses.bham.ac.uk//id/eprint/7030/.
Full textAbstract:
Analysis of fatigue samples sectioned from commercial 319 (Al-Si-Cu-Mg) alloy cylinder block castings showed that shrinkage pore networks and oxide films played an important role in fatigue failure. A reduced pressure technique was employed to study the relationship between porosity and oxide films. Links between oxide films and porosity were made and mechanisms for the inflation of films into porosity networks were established. Tensile tests performed on samples cast with and without filters showed that the ultimate tensile strengths of the filtered group had a Weibull modulus 2.4 times that of the unfiltered. Samples with abnormally low strengths were found to contain oxide film defects. These films had an approximately 5 times greater damaging effect on strength than that predicted by reduction in cross sectional area. The fracture strengths of these flawed samples were found to obey a linear elastic fracture mechanics model (LEFM). A LEFM crack growth model was particularly successful in predicting the life of fatigue samples that initiated at oxide films. Having crack-like geometry, and a minute crack tip radius, oxide films effectively acted as preformed cracks. Consequently there was an absence of crack nucleation time, explaining the correlation of predicted propagation life to fatigue life.
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Yang, Chao. "Solidification behaviour and hipping induced surface modification in Ti4522XD castings." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/7614/.
Full textAbstract:
The solidification behaviour of Ti45Al2Mn2Nb1B (at.%) has been studied together with its response to HIPing (Hot Isostatic Pressing) in order to understand the mechanism of grain refinement in castings and to understand the influence of surface changes occurring during HIPping on the properties of HIPped net shape cast turbine blades. Samples which had been rapidly cooled from near the melting point from a Bridgman furnace, where a thermal gradient was imposed, have been used to understand the grain refinement mechanism and the details of the solidification sequence. In addition the structure of powder samples, which have been gas-atomised and hence very rapidly cooled have also been used to further the understanding of solidification and of the role of borides. It has been shown that borides themselves play an important role in grain refinement. It has been shown that HIPping results in the formation of a surface which is caused by oxidation from the oxygen present in the argon used in the HIP. The details of the chemistry and microstructure of the surface layers have been shown to be influenced by oxygen partial pressure, by HIPping time and HIPping temperature. Conventional HIPping conditions lead to a surface which contains a γ-layer which does not appear to downgrade either the tensile properties or fatigue properties of the samples and may slightly improve the corrosion resistance. Further work is required to produce net shape castings, which have properties comparable with conventionally cast Ti4522XD, but the present work shows that these could then be HIPped without the γ-layer contained surface causing any downgrading in properties.
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Jahajeeah, N. "Application of numerical modelling in SSM automotive brake calliper castings." Journal for New Generation Sciences, Vol 4, Issue 1: Central University of Technology, Free State, Bloemfontein, 2006. http://hdl.handle.net/11462/491.
Full textAbstract:
Published ArticleNumerical modelling has successfully been used as an efficient tool to convert a gravity cast brake calliper to a thixocasting process. The thixo-module of Procast has been used for the modelling process to obtain optimum processing parameters. Results from interrupted shot castings show excellent correlation with the fluid dynamics and flow pattern of the model. The level and location of porosity revealed by non-destructive X-rays and microscopic analyses showed good correlation with the model prediction.