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Dissertations / Theses on the topic 'Formability'
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1
Viswanathan, Karthik. "The OSU Formability Test to Assess the Formability of Sheet Metals." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1420730405.
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Kocak, Ozgur. "Analysis Of The Formability Of Metals." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1178714/index.pdf.
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Workpieces during cold forging fail basically due to ductile fracture. Ductile fracture can be predicted by damage models. In this study, various damage models such as Cockcroft &Latham, McClintock, Freudenthal, Rice &
Tracy, Oyane, Ayada, Brozzo are investigated for their applicability to three workpiece materials: bearing steel (100Cr6), stainless steel (X5CrNiMo1810) and brass (CuZn39). The damage material parameters have been obtained by various tests such as tensile, standard compression, ring compression, compression with flanges and conical compression tests. The characterization has been assisted by finite element simulation of the various tests. It has been shown that the available damage models can predict the location of failure satisfactorily but are no able to predict the onset of failure quantitatively. Keywords: Formability Limit, Failure Criteria, Cold Forming, Surface Cracks, Finite Element Analysis
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Mullan, H. B. "The formability of corus tubular blanks." Thesis, Swansea University, 2004. https://cronfa.swan.ac.uk/Record/cronfa42927.
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Tube hydroforming has already proved successful in sub frame and chassis applications. However, there has been limited uptake of this technology in the production of BIW structural components. Mainly due to the fact that standard tube making methods are restricted to production of tubes with a diameter to thickness ratio of 65:1 at best, where as typical BIW application would be more inline with a ratio of 100:1. The Corus Tubular Blank process enables a greater range of D/t ratio, and therefore a larger scope of manufacture for BIW parts. The major technical issue concerned with the manufacture of both Corus Tubular Blanks and Corus Tailor Welded Tubes (Corus Tubular Blanks made using LWTB’s sheets) is the effect of material elastic recovery after forming has taken place. It has been well documented in previously published literature that the magnitude of elastic recovery (springback) in a component is influenced by the material and forming properties. It is very difficult to have full control of the material properties. However, forming properties are controllable especially if the forming process is simple as in the case of the Corus Tubular Blank. Corus Tailor Welded Tubes introduce a complex combination of springback characteristics inherited from the constituent parent parts of the LWTB. This thesis provides a method of springback prediction, as well as indication of the important factors associated with springback. Highlighted is the ability of springback to be mitigation via means of increased forming force, in conjunction with the ability to predict the subsequent springback behaviour.
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Dehra, Mala Seth. "High velocity formability and factors affecting it." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1143214139.
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Cheng, Xiang-Ming. "TEXTURE, MICROSTRUCTURE AND FORMABILITY OF ALUMINUM ALLOYS." UKnowledge, 2001. http://uknowledge.uky.edu/gradschool_diss/392.
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Texture, microstructure and formability were studied in Direct Chill Cast (DC) and Strip Cast (SC) aluminum alloys with regard to crystallographic anisotropy, the Portevin-Le Chatelier effect and aging softening behavior. It was found that material properties change greatly with manufacturing processes (DC vs. SC) and chemical composition (3xxx vs. 5 xxx alloys). DC cast hot band materials are usually fully recrystallized and have strong softening textures while SC hot band materials have a rolling structure with strong deformation textures. Softening textures cause 90 earing while deformation textures result in 45 earing after deep drawing. During cold rolling, 90 earing in DC cast hot band materials decreases and eventually changes to 45 earing after certain degrees of cold reduction. Correspondingly, the intensity of the softening texture components in DC cast hot band materials decreases while the intensity of deformation texture components increases with increasing degrees of cold reduction. These two kinds of textures interact and attempt to balance each other during cold rolling which produces resultant earing. However, this is not true for SC hot band materials since it's hard to obtain strong softening textures and thus 90 earing in these materials. 5 xxx Al-Mg alloys are more difficult to work than 3 xxx aluminum alloys. Elevated temperature annealing which greatly reduces the strength (hardness) improves significantly the workability of Al-Mg alloys. On the other hand, the Portevin-Le Chatelier effect and aging softening behavior are stronger in Al-Mg alloys than in 3xxx aluminum alloys and both increase with increasing cold reduction and with increasing Mg content. An apparent tensile anisotropy exists in as received SC hot band materials. The tensile yield strength (YS) is smaller in the QD (45 to the rolling direction), and larger in the RD (rolling direction) and the TD (transverse direction). There is no obvious difference in YS between these RD and TD directions. The average stress drop of serrations in the PLC effect, D s , is strongest in the TD, smallest in the RD with QD in between but closer to TD. However, no tensile anisotropy was observed in a fully recrystallized DC hot band or in solution treated SC hot band materials. It was found that a rolling structure favors mechanical anisotropy while a recrystallized structure prevents it. The tensile anisotropy is due to anisotropic distributions of microstructures, i.e., dislocations, precipitates and solute atoms. A random microstructure is associated with material that shows little or no mechanical anisotropy. An elongated or preferably orientated microstructure is associated with material with high mechanical anisotropy. Recovery thermal treatments at sufficiently high temperatures so that dislocation annihilation and microstructure rearrangement occurs when applied to the final gauge material also lowers mechanical anisotropy because of the reduction in intensity of the elongated (preferably orientated) microstructure. In addition, plastically deforming the material in a more homogenous manner (such as cross rolling as compared to straight rolling) produces a more uniform microstructure with an accompanying lower mechanical anisotropy.
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Steel, David Thomas. "The formability of long fibre thermoplastic composites." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392679.
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Sokolowski, Todd Matthew. "Evaluation of tube formability and material characteristics." The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1283269233.
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Singhal, Hitansh. "Formability Evaluation of Tailor Welded Blanks (TWBs)." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1594916942734335.
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Uthaisangsuk, Vitoon. "Microstructure based formability modelling of multiphase steels." Aachen Shaker, 2009. http://d-nb.info/995433305/04.
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Gennari, Claudio. "Enhancement of alloys formability by electroplastic effect." Doctoral thesis, Università degli studi di Padova, 2020. http://hdl.handle.net/11577/3425792.
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This thesis summarizes the results obtained during the PhD research period in Industrial Engineering at the Industrial Engineering Doctorate School of University of Padua. The research project was mainly focused on the effect of the electrical current on the plastic deformation and on the microstructure of different metal alloys known as Electroplastic Effect (EPE).
The research project was conducted in collaboration with the Metallurgy, Mechanical and Electrical Engineering groups of the Industrial Engineering Department of University of Padua.
This thesis is organized in five different chapters. The first chapter deals with the state of the art of the Electroplastic Effect, starting from the first scientific papers and then focusing mainly on the various theories that try to explain the phenomenon. In the second chapter, already performed researches at University of Padua are reported. The third chapter focuses on the experimental apparatus used during the research period. Fourth chapter is focused on the experimental results obtained using continuous and pulsed direct current on four types of high technological interest metal alloys (pure aluminum, titanium grade five, an experimental TWIP steel and four grades of duplex stainless steels). The fifth chapter deals with electropulsed treatment on a super duplex stainless steel. It has been decided to include two appendixes that contributed to the scientific training of the candidate. Appendix A reports the results concerning the influence of small volume fraction and different morphologies of secondary phases on the ductile-to-brittle (DBT) transition of a UNS S32205 duplex stainless steels. Finally, appendix B describes the influence of cold rolling on the laser weldability of UNS S32750 duplex stainless steel.
Most of the research activities were carried out in the laboratories of the Metallurgy group, the Electrical Engineering group and the Mechanical Engineering group of the Industrial Engineering Department of University of Padua. Specifically, tensile tests were carried out at the Precision Manufacturing Laboratory under the supervision of Professor Stefania Bruschi and Professor Andrea Ghiotti, electrical measurements were performed at the Laboratory of Electroheating of Padova (LEP) under the supervision of Professor Michele Forzan and Professor Renato Gobbo, finally, the characterization of the samples were performed at the metallurgy laboratories supervised by Professor Irene Calliari and Professor Manuele Dabalà. Some activities were conducted outside the University of Padua in collaboration with other institutions. In particular laser welding and phase quantification by means of electromagnetic measurements were carried out thanks to Professor Istvan Mészáros of the Department of Materials Science and Engineering of the Budapest University of Technology and Economics and finally, impact toughness tests were conducted at the Quality Control Laboratories of Acciaierie Valbruna S.p.A. under the guidance of Engineer Enrico Piva.
This research work helped to improve the knowledge on the electroplasticity phenomenon, in particular for a specific class of steels in which two phases with different metallurgical characteristics are present.Il presente elaborato riassume i risultati ottenuti durante il periodo di ricerca necessario al conseguimento del titolo di Dottore di Ricerca in Ingegneria Industriale presso la Scuola di Dottorato dell’Università degli Studi di Padova. Il progetto di ricerca consiste nello studio dell’effetto della corrente elettrica sulla deformazione plastica e sulla stabilità microstrutturale di diverse leghe metalliche conosciuto come Effetto Elettroplastico (EPE). Il progetto di ricerca è nato all’interno del Dipartimento di Ingegneria Industriale dell’Università degli Studi di Padova in seguito ad una collaborazione tra il gruppo di Metallurgia, Ingegneria Meccanica e Ingegneria Elettrica. La tesi è suddivisa in cinque capitoli. Il primo capitolo tratta dello stato dell’arte del fenomeno dell’elettroplasticità, a partire dai primi articoli scientifici che ne hanno parlato per poi focalizzarsi principalmente sulle possibili spiegazioni del fenomeno. Nel secondo capitolo sono esposti i lavori già effettuati all’interno dell’Università di Padova prima dell’inizio del percorso di Dottorato. Il terzo capitolo riassume le apparecchiature utilizzate durante il periodo di ricerca. Il quarto capitolo espone i risultati ottenuti utilizzando corrente continua e pulsata su quattro categorie di leghe metalliche di elevato interesse tecnologico (alluminio commercialmente puro, lega di Titanio grado cinque, acciaio inossidabile TWIP e quattro acciai inossidabili bifasici). Nel quinto capitolo viene studiato l’effetto di trattamenti elettro-pulsati su un acciaio inossidabile bifasico. In appendice sono riportati due lavori che esulano dal progetto di ricerca ma che si sono ritenuti utili nella formazione scientifica del candidato. L’appendice A riporta uno studio sull’influenza della morfologia di una piccola frazione volumetrica di fasi secondarie sulla transizione duttile fragile di un acciaio inossidabile bifasico UNS S32205. L’appendice B tratta invece l’influenza della deformazione plastica a freddo sulla saldabilità tramite laser di un acciaio inossidabile bifasico UNS S32750. La maggior parte delle attività di ricerca sono state effettuate presso i laboratori del gruppo di Metallurgia, del gruppo di Ingegneria Elettrica e del gruppo di Tecnologia Meccanica del Dipartimento di Ingegneria Industriale (DII) dell’Università degli Studi di Padova. Nello specifico le prove di trazione sono state eseguite presso il laboratorio di Precision Manufacturing sotto la supervisione della Professoressa Stefania Bruschi e del Professor Andrea Ghiotti, le misure elettriche sono state eseguite presso il Laboratorio di Electroheating di Padova (LEP) sotto la guida del Professor Michele Forzan e del Professor Renato Gobbo, mentre la caratterizzazione è stata eseguita presso i laboratori di metallurgia supervisionati dalla Professoressa Irene Calliari e dal Professor Manuele Dabalà. Alcune attività sono state svolte in collaborazione con altre istituzioni, in particolare le saldature laser e la quantificazione delle fasi per mezzo di misure elettromagnetiche grazie al Professor Istvan Mészáros del Dipartimento di Scienza e Ingegneria dei Materiali della Budapest University of Technology and Economics e le prove di resilienza presso il laboratorio Controllo Qualità delle Acciaierie Valbruna S.p.A. di Vicenza sotto la guida dell’Ingegner Enrico Piva. Il presente lavoro di ricerca ha contribuito ad aumentare la conoscenza del fenomeno dell’elettroplasticità, in particolare per una determinata classe di acciai in cui sono presenti due fasi con diverse caratteristiche metallurgiche.
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Ah-Teck, Tommy C. T. "Formability of long glass-fibre reinforced polypropylene sheet." Thesis, Loughborough University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329863.
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Dhruv, Anand B. "Size effects on formability of very thin sheets." Thesis, IIT Delhi, 2015. http://localhost:8080/iit/handle/2074/6938.
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Ma, Lianzhong 1968. "Effect of pre-drawing on formability during cold heading." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=98993.
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One of the most common industrial cold forging processes is cold heading of steel wire or rod to produce screws, bolts, nuts and rivets. The process is limited by a complicated interplay of many factors. The cold work (pre-drawing) is one of them. Although several investigations into the effects of pre-drawing on the formability of metals during cold heading processes have been conducted, so far no attention has been given to the numerical simulations of this phenomenon. The current work aims at examining effects of pre-drawing on formability during cold heading through numerical simulations.Physical tests in the literature investigating the effects of pre-drawing on the formability of three metals are simulated using ABAQUS 6.4, with three successive FE models: the drawing model, the cutting model and the upsetting model. A new combined linear kinematic/nonlinear isotropic hardening constitutive model is proposed and derived to account for the Bauschinger effect existing in reverse plastic deformation. The new model is implemented into ABAQUS/Explicit v6.4 by a user subroutine VUMAT, which is verified by one-element numerical tests under tension, compression and reverse loading conditions. In addition, for the purpose of comparison, the Johnson-Cook isotropic hardening model is also applied for the materials. The Cockroft and Latham criterion is employed to predict surface fracture.
Although considerable discrepancies between the experimental and simulation results are observed, the proposed combined hardening model is more accurate in predicting material behavior in the reverse loading than the Johnson-Cook isotropic hardening model. In addition, the simulation results show that the proposed combined hardening material model has the potential to correctly predict the material behavior in the reverse loading process.
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Uthaisangsuk, Vitoon [Verfasser]. "Microstructure based formability modelling of multiphase steels / Vitoon Uthaisangsuk." Aachen : Shaker, 2009. http://d-nb.info/1156518733/34.
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Souter, Benjamin John. "Effects of fibre architecture on formability of textile preforms." Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275070.
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Scriven, Phillip John. "Formability and processing of welded blanks for automotive applications." Thesis, Cardiff University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439295.
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Boulton, Catherine Dorothy. "Control of texture and formability in ferritic stainless steels." Thesis, Sheffield Hallam University, 1986. http://shura.shu.ac.uk/19374/.
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The effects of processing variables on the microstructures, textures and press-formability of commercial 17 Cr, 0.05C (430) steel and low-interstitial Ti-stabilised 12 Cr (409) and 17 Cr (430 Ti) steels have been studied. The annealing textures have beencorrelated with tensile strain ratio measurements and from this correlation it has been possible to select combinations of cold rolling reduction and annealing treatments for texture control to improve deep drawability. Electron microscope examination has been used to identify possible nucleation mechanisms for the observed recrystallisation textures. Cold rolling texture development and tensile strain ratios have been discussed from theoretical considerations of slip in bcc metals. Pronounced differences in microstructural features between high interstitial 4-30 and low-interstitial Ti-stabilised steels are reflected in differences in texture development at all stages. Hot band condition is an important variable, affecting texture development during subsequent cold rolling and annealing. All three steels develop similar cold rolling textures, consisting mainly of ~{100} , ~{111} and ~{112} components. The ~{112} orientation is more prominent in 430 Ti steel than in 430 steel, and it is suggested that this difference may be due to irregular flow in high interstitial 430 steel. Other differences in cold rolling textures are attributed to texture inheritance from the hot band. Recrystallisation textures in 430 steel are mainly ~{114} , with ~{223} present after high reductions, and r-values are generally low. Recrystallisation textures in 409 and 430 Ti steels are mainly ~{110} after low cold rolling reductions, ~{554} after moderate or high reductions and -{223} after very high reductions. In most cases, ~{100} is only a minor component. Batch annealing of the hot rolled strip followed by cold rolling to 90% RA and rapid final annealing promotes maximum ~{554} intensity with low ~{100} intensity, and a correspondingly high r-value. The ~{223} and ~{114} orientations, attributed to grain boundary nucleation, have not been reported previously in 17 Cr ferritic stainless steels, although they have been reported occasionally in other low-carbon ferritic steels.
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Windholtz, Timothy Nolan. "Plane-Strain Formability of Sheet Metal at High Velocity." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1332509672.
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Hipps, Henry. "Developing a continuous emulsion PBD-Graft-SAN polymerization process: factors for morphology control." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/10973.
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Song, Xiao. "Identification of forming limits of sheet metals with an in-plane biaxial tensile test." Thesis, Rennes, INSA, 2018. http://www.theses.fr/2018ISAR0002/document.
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Les procédés de mise en forme des tôles minces sont largement utilisés dans l'industrie. L’utilisation optimale des alliages légers ou des aciers à haute résistance, propices à des économies d’énergie dans le domaine des transports, nécessite une connaissance approfondie de leurs limites de formabilité. Classiquement, la formabilité d’une tôle est caractérisée par l’apparition d’une striction localisée. Cependant, pour des chargements spécifiques (chemins de déformation complexes ...), la rupture caractérise la formabilité du matériau, la courbe limite de formage à rupture (CLFR) plutôt que celle à striction (CLFS) doit alors être considérée. Pour identifier la CLFS et la CLFR pour des chemins de déformation linéaires et non-linéaires, les méthodes conventionnelles requièrent différents dispositifs expérimentaux et différentes formes d'éprouvette pour atteindre une large gamme de chemins de déformation. L'essai de traction biaxiale, associé à une éprouvette cruciforme, est possible pour la réaliser. De plus, le changement de chemin est activé au cours de l’essai, sans déchargement. Le premier objectif de cette étude est de montrer que l'essai de traction biaxiale, associé à une forme unique d'éprouvette cruciforme, permet de tracer la CLFS et la CLFR pour plusieurs chemins de déformation, qu’ils soient linéaires ou non-linéaires. En premier lieu, des essais ont été réalisés sur des tôles d’alliage d’aluminium 5086 (épaisseur initiale de 4 mm) à partir d’une forme d’éprouvette déjà proposée au laboratoire. Une nouvelle forme d'éprouvette cruciforme a été proposée pour des tôles moins épaisses (2 mm), plus répandues. Cet éprouvette a été validée pour étudier la formabilité d’un acier dual phase DP600 pour plusieurs chemins de déformation. Le deuxième objectif est de discuter la validité de critères classiques de rupture ductile. Pour les deux matériaux, un critère a finalement été identifié pour prédire assez précisément les résultats expérimentauxSheet metal forming is very common in industry for producing various components. The optimal use of light alloys or high strength steels in transportation for energy economy, requires in-depth analysis of their formability. Usually, the formability of sheet metal is controlled by the onset of localized necking. However, under specific loadings (complex strain paths...), fracture characterizes the formability and the forming limit curve at fracture (FLCF) instead of the forming limit curve at necking (FLCN) should be considered. For identifying FLCN and FLCF under linear and non-linear strain paths, conventional methods require different experimental devices and geometrical specifications of specimen to cover a wide range of strain paths. However, using the in-plane biaxial tensile test with just one shape of cruciform is sufficient for that, even changes of strain path without unloading can be made during the test. The first objective of this study is to show that the in-plane biaxial tensile test with a single type of cruciform specimen permits to investigate the FLCN and FLCF of sheet metals under different linear and non-linear strain paths. Firstly, the forming limit strains at fracture of AA5086 sheet (t=4 mm) under linear and non-linear strain paths have been characterized, by testing an existed dedicated cruciform specimen. Thinner sheet metals are often used in industry, so a new shape of cruciform specimen with an original thickness of 2 mm was proposed. This specimen is successfully used to investigate the formability of DP600 sheet under linear and two types of non-linear strain paths. The second objective is to discuss the validity of commonly used ductile fracture criteria to predict the onset of fracture. Some ductile fracture criteria were used to produce numerical FLCFs for AA5086 and DP600 sheet. Finally, for the two tested materials, it is possible to find a criterion to predict the experimental FLCFs for either linear or non-linear strain paths
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Small, Neil. "A statistical method for determining and representing formability : innovation report." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/80224/.
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Formability, conventionally characterised by the Forming Limit Curve (FLC), is a critical measure used to define the working limit of sheet metal in a forming operation. The FLC defines the limit strain the material can undergo before failure occurs. The importance of this failure criterion means it is used at various stages in the development of automotive body panels: during material selection; during stamping simulations; and in the purchase of stamping tools before commencing serial production. To mitigate against the risk that the FLC is positioned incorrectly; that mechanical property variation between blanks causes reduced formability; and that conditions imposed by the stamping operation itself cause premature failure, a safety margin is introduced. The size of the safety margin is based on the industrial sponsor’s prior experience and attitude to risk, as opposed to an objective analysis of each of the risks posed to formability. Uncertainty around the position of an FLC arises from the dispersed limit strains that characterise the results of standardised formability tests. The aim of this research was to understand and characterise the uncertainty of the formability test, and develop a more accurate and precise method for determining and representing formability. Initial tests were carried out according to the standard ISO method, and a digital image correlation (DIC) technique was used to measure full-field strains on each specimen throughout the tests. Two observations were made. Firstly, the method of analysis advocated by the ISO standard requires subjective interpretation to define a limit strain. Secondly, the full-field strain measurements showed a “noisy” strain distribution overlaid over the expected strain field. This “noise” was significant compared to the uncertainty of the DIC instrument. A solution was developed by adopting a statistical attitude to model surface strain measurements. Strains from the beginning of deformation up to fracture were characterised by a fundamental analysis. The analysis showed that the forming limit of an individual test is statistical in nature, and that the strains’ statistical character exhibits recognisable trends that evolve from the start of the tests up to necking. A new 'time-dependent' method based on the innovative application of a Gaussian Mixture Model (GMM) was developed to characterise these trends, and quantify the forming limit. The GMM was used to objectively identify the locus of a localised neck; identify the onset of necking; and characterise the neck at the forming limit. Rather than selectively analysing strains in a pre-determined area of a specimen, and at a selected time of the test, the developed technique eliminates the subjectivity that is required by the current ISO-standard method. The new GMM technique describes formability as a probabilistic risk of failure. Strain measurements made on single specimens were turned into a complimentary statistical formability criterion using the logistic regression technique proposed by Strano & Colosimo (2006). Formability Maps (FMs) were constructed to show the probability of failure contours on the Forming Limit Diagram (FLD). FMs derived from the GMM provide the precise representation of formability that is missing from the FLC, and that is required to objectively interpret the risk of failure for an industrial panel. It was postulated that the presence of a surface roughness is responsible for surface strain variation because of the geometry of its asperities. Its evolution is controlled by underlying changes to the microstructure during the course of plastic deformation. A modified M-K model was used to predict the range of strains that arise from surface roughening at the forming limit. Formability predictions correspond well to FLCs drawn from ISO-standard limit strains, but less well to the FMs drawn from the GMM. It was concluded that surface roughening alone does not explain the heterogeneous strain behaviour measured in this research.
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Zhu, Bo. "Sheet forming of woven textile composite preforms : formability and wrinkling /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?MECH%202007%20ZHU.
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Lee, Yew-wing, and 李耀榮. "The effect of cold rolling on the formability of thermoplastics." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1987. http://hub.hku.hk/bib/B31207716.
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Mojarad, Farimani Saeed. "Experimental process development and aerospace alloy formability studies for hydroforming." Mémoire, École de technologie supérieure, 2013. http://espace.etsmtl.ca/1261/1/MOJARAD_FARIMANI_Saeed.pdf.
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Dans le procédé d’hydroformage, la pression d’un fluide est utilisée pour déformer plastiquement un tube paroi mince à l’intérieur d’une matrice fermée afin de remplir la cavité de la matrice. L’hydroformage des tubes possède de nombreux avantages qui rendent ce procédé très intéressant pour plusieurs industries telles que l’automobile et l’aérospatiale. Mais, à cause de différents facteurs tels que la formabilité des matériaux, l’ordre et les séquences du chargement (force de compression axiale et pression interne pendant le procédé), la géométrie de l’outil et la friction, c’est un procédé de mise en forme assez complexe. Ainsi, la simulation par éléments finis combinée à des méthodes d’optimisation peuvent réduire significativement le coût de l’approche “Essai – Erreur” utilisée dans les méthodes conventionnelles de mise en forme. Dans ce mémoire, pour étudier les effets de différent paramètres tels que les conditions de friction, l’épaisseur du tube et la compression axiale sur la pièce finale, des essais d’hydroformage de tube ont été menés en utilisant une matrice de forme ronde à carrée. Les expériences ont été effectuées sur des tubes d’acier inoxydable 321 de 50.8 mm (2 in) de diamètre et deux différentes épaisseurs ; 0.9 mm et 1.2 mm. L’historique du chargement a été enregistré avec le système d’acquisition de la presse. Un système de mesure de déformation automatique, Argus, a été utilisé pour mesurer les déformations sur les tubes hydroformés. Les données collectées à partir des essais initiaux ont été utilisées pour comparer avec les simulations. Le procédé a été simulé et optimisé à partir des logiciels Ls-Dyna et Ls-Opt, respectivement. Les variations de déformations et d’épaisseurs mesurées à partir des expériences ont été comparées aux résultats de la simulation par éléments finis dans les zones critiques. La comparaison des résultats de la simulation et des expériences sont en bon accord indiquant que l’approche peut être utilisée pour prédire la forme finale et les variations d’épaisseurs de pièces hydroformées pour des applications aérospatiales.
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Jiang, Jian. "Formability and fracture mechanisms of particle reinforced metal matrix composites." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360111.
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Keigler, Michael. "Enhancing the formability of aluminium components via temperature controlled hydroforming." Thesis, Glasgow Caledonian University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443242.
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Balanethiram, Venkata S. "Hyperlasticity: enhanced formability of sheet metals at high workpiece velocity." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1301933505.
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Balanethiram, Venkata S. "Hyperplasticity : enhanced formability of sheet metals at high workpiece velocity /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487935573771459.
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Lee, Yew-wing. "The effect of cold rolling on the formability of thermoplastics /." [Hong Kong] : University of Hong Kong, 1987. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12334364.
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Nolan, Ross Andrew. "Microstructure formability relationships in new generation high strength aluminium automotive alloys." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/microstructure-formability-relationships-in-new-generation-high-strength-aluminium-automotive-alloys(726d2c33-f190-44b1-8ab8-854e69dc5ec4).html.
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The desire to reduce weight in automotive products is driven by a need to improve efficiency. As such, to allow further weight reduction, higher performance aluminium alloys are in demand for sheet metal body structures. Due to their high strength to weight ratio 7xxx alloys are seen as an ideal candidate for this, however their use to date has been limited by poor formability. Previous work indicated that by moving to high temperatures (>350°C) or by using a soft temper (W), good formability could be achieved but the samples required further heat treatment post-forming. This work explored the warm forming temperature range to improve formability whilst developing the required properties during processing. The performance of a 7xxx candidate alloy, 7021, has been assessed in stretching and drawing operations, both at room temperature and over the elevated temperature range of 150-250°C. The microstructure and other properties of the alloy were investigated in W, T4 and T6 tempers, before and after testing, through a range of techniques, including DSC, DMTA, SEM, EBSD and TEM.In the T4 temper, UTS and proof stress increased with temperature up to 190°C, due to dynamic precipitation. Increasing temperature only provided a modest increase in strain to failure for both the T4 and T6 temper. Cup height was not significantly improved in the warm forming temperature range during Erichsen cup testing. By deep drawing at 250°C it was possible to fully draw a cup (with an LDR of 2.2) in both the T4 and T6 temper of 7021, with both tempers having comparable post-forming hardness. This indicates that at 250°C the starting condition has no impact on drawability. Although full drawability is achieved at 250°C the final product would require further heat treatment if it were to replace 6016. However, by deep drawing 7021-T4 at 190°C, a fully formed cup was produced with a hardness between that of the T4 and T6 temper. The microstructure of the formed cup showed no grain boundary precipitation and a fine distribution of the strengthening phase η', suggesting there is a dynamic effect on the precipitation during deep drawing at this temperature. In conclusion, the work has shown that warm forming does not significantly improve stretching behaviour of 7021, but by using warm forming temperatures deep drawing is improved.
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Srinivasan, Shekhar. "A Simulation Perspective on Dimensional Control and Formability in Impact Forming." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275004865.
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Davis, Trevor. "Formability and strength of sheet metals subjected to complex strain paths." Thesis, Aston University, 1985. http://publications.aston.ac.uk/11872/.
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Lai, Qingquan. "Optimisation de la microstructure d'aciers ferrito-martensitiques à 3.5 % pds Mn : des transformations de phases à la micro-mécanique." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI086/document.
Full textAbstract:
Les aciers Dual-Phase sont largement utilisés dans le secteur de l’automobile enraison de leurs propriétés mécaniques remarquables et du bon compromis résistanceductilité qui lui donne d’intéressante potentialités comme absorbeur d’énergiemécanique. Cependant, la recherche de bons compromis entre les propriétésmécaniques en traction et celles de formabilité nécessite une optimisation desparamètres microstructuraux. Ce travail de thèse s’inscrit dans cet optique. Dans unepremière partie, l’étude bibliographique proposée permet de mieux cerner lesparamètres influençant la formation des microstructures ainsi que les propriétés desaciers DP. Dans une seconde partie, nous proposons un travail expérimental originalpermettant de mieux comprendre la formation des microstructures des aciers DP etde découpler l’effet de certains paramètres microstructuraux sur les propriétés deces aciers. Enfin, la modélisation micromécanique proposée permet de compléter etd’interpréter les données expérimentales acquises. Ce travail ouvre des voiesintéressantes de « design » des microstructures des aciers DP en vue de développerdes aciers de nouvelles générations possédant des propriétés optimiséesFerrite-martensite dual-phase (DP) steels have been widely used in automotiveindustry due to their excellent mechanical properties, such as high work-hardeningrate and a good compromise between strength and ductility allowing high energyabsorbing performance. In order to fully exploit the potential of DP steels and extendthe application, the dual-phase microstructure has to be optimized for bettercombination of strength and formability that is characterized by uniform strainand/or fracture strain. As a starting point, detailed literature review is made on themicrostructure development and mechanical properties of DP steels, and the keyfactors controlling microstructural features and determining mechanical propertiesare identified. Through experimental investigation, microstructures are developed inorder to decouple the effects of various microstructural features, and themicrostructure—mechanical properties relationship is systematically studied.Micromechanical modeling is used to further understand the experimental resultswithin a quantitative framework, and to provide a support for microstructurerefinement of DP steels by parametric study. Strategies of designing DP steels tofulfill specific forming operation have been proposed, and the concept of DP steelswith graded martensite islands has been discussed with FEM analysis as a possibilityof improving strength—formability trade-off
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Dry, D. J. "The processing and formability of laser welded tailored blanks for automotive applications." Thesis, Swansea University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636740.
Full textAbstract:
To meet with stringent European and U.S. environmental legislation, the automotive industry has been actively researching methods of improving the fuel economy of their vehicles, in order to reduce harmful pollutant emissions. One of the most logical ways to achieve this is by reducing vehicle kerbside weight. This is increasingly difficult since customers are demanding more comfort and safety features in their vehicles, which add weight. Despite the customers' demands, significant advances in technology, e.g. state-of-the-art materials and component manufacturing techniques, have meant that vehicle weight can be reduced considerably. One significant area of lightweight technology, which has been researched in this Engineering Doctorate thesis, is that of laser welded tailored blanks (LWTB). A LWTB is produced by laser butt welding two or more materials together to form a single composite blank. The materials studied in this thesis were high strength steels, including newly developed ultra high strength steels, for application in structural body-in-white components. Although a wealth of LWTB research has been conducted since 1985, only now are their production and formability becoming fully understood. This thesis begins with an in-depth practical and FEA simulation study of simple small scale axi-symmetric tests, which were carried out on unwelded and laser welded blanks. The results from these tests were used to create LWTB design guidelines which culminated in the successful pressforming of a larger scale complex component utilising LWTBs comprising various steel combinations (dissimilar thicknesses and/or strengths). The huge potential of tailored welded blanks as a significant lightweighting technology is unquestionable. With rapidly increasing demand, and with many automotive manufacturers preferring to outsource their LWTB requirements, it is vital that welded blank producers should gain comprehensive knowledge of the processing and formability of LWTBs. This thesis provides design guidelines that can assist welded blank producers.
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Shuaib, Nasr AbdelRahman. "AN INVESTIGATION OF SIZE EFFECTS ON THIN SHEET FORMABILITY FOR MICROFORMING APPLICATIONS." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/680.
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The increasing demand for powerful miniaturized products for all industrial applications has prompted the industry to develop new and innovative manufacturing processes to fabricate miniature parts. One of the major challenges facing the industry is the dynamic market which requires continuous improvements in design and fabrication techniques. This means providing products with complex features while sustaining high functionality. As a result, microfabrication has gained a wide interest as the technology of the future, where tabletop machine systems exist. Microforming processes have the capability of achieving mass production while minimizing material waste. Microforming techniques can produce net-shape products with intricacy in fewer steps than most conventional microfabrication processes. Despite the potential advantages, the industrial utilization of microforming technology is limited. The deformation and failure modes of materials during microforming is not yet well understood and varies significantly from the behavior of materials in conventional forming operations. In order to advance the microforming technology and enable the effective fabrication of microparts, more studies on the deformation and failure of materials during microforming are needed.
In this research work, an effort to advance the current status of microforming processes for technologies of modern day essentials, is presented. The main contribution from this research is the development of a novel method for characterizing thin sheet formability by introducing a micro-mechanical bulge-forming setup. Various aspects of analyzing microscale formability, in the form of limiting strains and applied forces, along with addressing the well known size effects on miniaturization, were considered through the newly developed method. A high temperature testing method of microformed thin sheets was also developed. The aim of high temperature microforming is to study the material behavior of microformed thin sheets at elevated temperatures and to explore the capability of the known enhancement in formability at the macroscale level. The focus of this work was to develop a better understanding of tool-sheet metal interactions in microforming applications. This new knowledge would provide a predictive capability that will eliminate the current time-consuming and empirical techniques that, and this in turn would be expected to significantly lower the overall manufacturing cost and improve product quality.
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Sibanda, Mandla. "Evaluation of the formability properties of nitrogen alloyed metastable austenitic stainless steels." Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/18216.
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Bibliography: pages 92-95.This study examines the formability of an AISI 301 based metastable austenitic stainless steel, in which nitrogen partially substitutes nickel. In order to understand the formability of the experimental alloys, the tensile behaviour of the alloys is characterised. The tensile properties of metastable austenitic stainless steels are governed by austenite stability which is related to alloy composition and test temperature. At certain alloy compositions, transformation induced plasticity (TRIP) occurs. TRIP depends on the manner in which deformation induced martensite forms in the steels. Incipient necking is resisted if the martensite forms gradually and selectively, preventing propagation of micronecks and microcracks. Tensile tests performed from -5 to 100°C were used to study the effect of TRIP on the ductility of these alloys and optimum tensile properties were obtained at room temperature. In addition, the effect of copper on TRIP and subsequently formability were ascertained using copper alloyed stainless steels. Important stretch formability parameters were obtained from the tensile test which is an intrinsic formability test. TRIP results in improved formability of metastable austenitic stainless steels, and a simulative Engelhardt test was performed to ascertain the effect of TRIP on drawability of the test alloys. It was found that alloys with TRIP characteristics exhibited good drawability and in all cases the test alloys had better limiting drawing ratios than AISI 304 stainless steel. Delayed cracking occurred in alloys with more than 0.2 percent nitrogen content and a low austenite stability, probably as a result of embrittlement of the deformation induced martensite by nitrogen. A study of the cavitation erosion of the test alloys was initiated because it is known that TRIP enhances cavitation erosion resistance in stainless steels. Results indicate that the metastable test alloys demonstrate superior erosion resistance when compared with the stable experimental alloys. Cavitation induced martensite was found in metastable alloys using x-ray diffraction.
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Pilkey, A. Keith (Andrew Keith) Carleton University Dissertation Engineering Mechanical and Aerospace. "Effect of second-phase particle clustering on aluminium-silicon alloy sheet formability." Ottawa, 1997.
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Xie, Yun. "Development of Al-Mg-Si aluminium alloys for automobile applications." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366371.
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Linardon, Camille. "Etirage de tubes de précision pour applications biomédicales : contribution à l'analyse et l'amélioration du procédé par expérimentation, modélisation et simulation numérique." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00956588.
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Les tubes métalliques de précision sont largement utilisés pour des applications biomédicales. De tels tubes sont fabriqués par étirage à froid car ce procédé garanti le meilleur aspect de surface, le plus grand contrôle des dimensions du tube et le contrôle des propriétés mécaniques. L'objet de cette étude est de modéliser le procédé d'étirage de tube sur mandrin afin d'en améliorer la compréhension et de construire un outil permettant l'optimisation du procédé et de prédire la rupture des tubes en étirage. La construction du modèle élément finis s'appuie sur la réalisation d'essais expérimentaux afin de caractériser les propriétés mécaniques des matériaux et le frottement entre le tube et les outils d'étirage (mandrin, filière). Le comportement mécanique des alliages est caractérisé par des essais de traction sur tube, des essais de traction sur des éprouvettes découpées dans différentes orientations dans un tube déplié et des essais de gonflement de tube. Pour ces derniers, une machine et un outillage de gonflement de tubes ont été développés spécifiquement. Par le biais de ces essais différents aspects ont été étudiés : la viscoplasticité, l'anisotropie plastique, l'hétérogénéité des propriétés dans l'épaisseur du tube, la thermomécanique. Les coefficients de frottements ont été identifiés par analyse inverse sur des essais d'étirage instrumentés par des cellules d'effort. Des essais d'étirage ont été spécifiquement conçus en modifiant la géométrie du mandrin afin de conduire à la rupture des tubes lors de l'étirage. L'objectif de tels essais étant d'identifier la limite de formabilité des tubes. L'approche choisie pour prédire de la rupture a été d'utiliser des critères de ruptures qui pouvaient être calibrés sur des essais de traction uniquement. Les critères ont été calculés au cours de la simulation numérique de l'étirage sur mandrin et ils ont été évalués par rapport à leur capacité à prédire les réductions de section et d'épaisseur maximales. Enfin, des méthodes analytiques de calcul d'effort d'étirage ont été développées et comparées à la modélisation éléments finis.
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Sparks, Christopher Nigel. "Hot formability and microstructural development of spray-deposited Al-Li alloy and composite." Thesis, University of Sheffield, 1994. http://etheses.whiterose.ac.uk/1805/.
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The deformational and microstructural behaviour of the commercial Al-Li alloy 8090 and an 8090 based composite containing silicon carbide particulate has been investigated. The materials were deformed at elevated temperature by the test methods of plane strain compression (PSC) and torsion to provide stress-strain data for the formulation of constitutive relationships. Torsion testing also provided high temperature ductility data. Isothermal annealing of rolled samples was carried out at the solution temperature of 530°C to investigate the recrystallisation kinetics and microstructures produced, with particular emphasis on the effect of the inclusion of reinforcement particles on the behaviour of the matrix alloy. Hyperbolic sine forms of constitutive equation have been produced and are found to provide good agreement with the experimental data. High values of the activation energy are calculated for the deformation of both the alloy and composite from the PSC test data. The equations obtained from the two different test methods are found to be comparable for the composite material, but a discrepancy is found for the monolithic alloy, where apparently less hardening results from torsion testing. A distinct transition in microstructure from recrystallised equiaxed grains when deformed at low temperature to an elongated, sometimes partially recrystallised, structure for material rolled at high temperature is present in the monolithic material. This is attributed to the balance of recrystallisation driving force and the Zener pinning force exerted by the 13' (A1 3Zr) phase. The composite material exhibited greatly enhanced recrystallisation kinetics in agreement with the theory of particle stimulated nucleation (PSN) of recrystallisation.
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DeMania, Deborah Ann. "The influence of martensitic transformation on the formability of 304L stainless steel sheet." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11488.
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Clark, Darren. "Formability of Polycarbonate." Thesis, 2008. http://hdl.handle.net/10012/4176.
Full textAbstract:
Current thermoplastic processing techniques involve high capital costs for moulds and
significant use of energy to melt or soften the materials. Single-step process cold
forming techniques, such as stretch forming, could be cost effective methods for
manufacturing large parts with shallow cross-sections from plastic sheet. The present
work is a preliminary investigation of a cold forming technique for polycarbonate.
The objective of this work is to characterize the bulk deformation behaviour of
polycarbonate using tensile tests and dome stretch forming tests. Two different
molecular weight polycarbonate sheets with 1.6 mm thickness were studied: (i) one with
Mw = 42,000 g/mol and (ii) the other with Mw = 52,000 g/mol. For the latter, 3.2 mm
sheets were also studied.
Tensile tests conducted at three different cross-head speeds, i.e., 2, 20 and 200 mm/min
showed very similar elastic and plastic deformation properties for the two molecular
weights. Correspondingly, the activation volumes at yield were almost identical. There
was also negligible difference in the thermophysical properties between the two materials
as found by differential scanning calorimetry.
Dome stretch forming tests were conducted on a metal forming machine. Specimens of
varying width were tested to give different strain states ranging from deep drawing to biaxial. The limiting dome height or the maximum level of stretch forming
iv
increases with specimen width. This is due to biaxial deformation which increases the
maximum strain. Forming limit diagrams (FLDs) were also constructed from the local
strains measured from printed fine circle grid patterns on the polycarbonate sheet
surfaces. The FLDs showed common general characteristics with metals except for a few
key differences. An area of very few data points was found to lie between the “safe
zone” and the “necked zone”. This void was referred to as the “unstable neck formation
zone”. It exists because of the large local increases in strain associated with the unstable
nature of polymer neck formation.
Much more study is required before polycarbonate can be cold formed at strains below
the unstable neck deformation. However, the materials and techniques used in this work
have demonstrated that the process can be viable for forming shallow large parts from
relatively thin thermoplastic sheet a as long as the local biaxial strains are less than 20%.
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Liao, Chih-Chieh, and 廖志杰. "Formability of LZ Magnesium Alloy Sheets." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/41302535272845671964.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
94
Due to its lightweight and high specific strength, magnesium alloys have been widely used for structural components. However, because of the hexagonal closed-packed (HCP) crystal structures, magnesium alloys show low ductility at room temperature, and require thermal activation to increase their formability. It is well known that ductility of magnesium alloys can be improved with addition of lithium which develops the formation of body centered-cubic (BCC) crystal structures. The BCC crystal structure gives rise to high formability at room temperature. The formability of different magnesium-lithium alloy sheets, such as LZ61、LZ91 and LZ101, was investigated by conducting various experiments in the present study. Tensile tests and forming limit tests were first conducted to investigate the mechanical behavior and formability of magnesium-lithium alloys with various lithium content. CCV tests and cup drawing tests were also performed to examine the stamping formability at room temperature. The experimental results reveal that the formability is much improved with higher Li content. Since the friction coefficient is one of important parameters in a stamping process, friction tests were preformed with the use of different lubricants and without lubrication. The friction coefficients obtained from the friction tests suggest appropriate lubricants to be used in the stamping of magnesium-lithium alloy sheets. In addition, V-bend tests were performed to examine the springback property and minimum bending radius of magnesium-lithium alloy sheets at room temperature. Except for structural components, magnesium-lithium alloys can also be used for loudspeaker diaphragms because of its higher internal damping loss. Damping tests were performed to examine the damping coefficient of magnesium-lithium alloy sheets and the results were compared with those obtained for aluminum alloys. The experimental results obtained in the present study provide the fundamentals for the stamping die design of forming magnesium-lithium alloy sheets.
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Hung, Chen Hsin, and 陳信宏. "Formability of Stamping Magnesium Alloy Sheets." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/02912204542625110373.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
90
Due to its lightweight and high specific strength, magnesium alloy has been widely used for structural components. Although the principle manufacturing process has been die casting, the press forming has considerable potential because of its competitive productivity and performance. However, because of the hexagonal closed-packed crystal structures, magnesium alloys show low ductility at room temperature, and require thermal activation to increase their ductility and formability. The formability of magnesium alloy sheets which are AZ31、AZ61 and AM60 at elevated temperatures was investigated by conducting various experiments. Tensile tests and forming limit tests were first conducted to investigate the mechanical behavior and formability of magnesium alloys at various temperatures. In addition, the CCV tests performed in the present study reveals that an optimum forming temperature, which is below 400oC, exists, and a lower forming temperature should be applied to the actual forming process. The experimental results obtained in the present study provide the fundamentals for the stamping die design of forming AZ31 sheets. V-bend tests were performed to examine the springback property of magnesium alloy sheets at room temperature and elevated temperatures. Cup Drawing Tests were performed to examine the stamping formability of magnesium alloy sheets at room temperature and elevated temperatures. Furthermore, the experimental dies, stimulated by computer using finite element analysis, are applied at the Cup drawing experiment to test the accuracy and dependability.
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Korkolis, Ioannis. "Formability and hydroforming of anisotropic aluminum tubes." 2009. http://hdl.handle.net/2152/6557.
Full textAbstract:
The automotive industry is required to meet improved fuel efficiency standards
and stricter emission controls. Aluminum tube hydroforming is particularly well suited in
meeting the goals of lighter, more fuel-efficient and less polluting cars. Its wider use in
industry is hindered however by the reduced ductility and more complex constitutive
behavior of aluminum in comparison to the steels that it is meant to replace. This study
aims to address these issues by improving the understanding of the limitations of the
process as applied to aluminum alloys.
A series of hydroforming experiments were conducted in a custom testing facility,
designed and constructed for the purposes of this project. At the same time, several levels
of modeling of the process, of increasing complexity, were developed. A comparison of
these models to the experiments revealed a serious deficiency in predicting burst, which
was found experimentally to be one of the main limiting factors of the process. This
discrepancy between theory and experiment was linked to the adoption of the von Mises
yield function for the material at hand. This prompted a separate study, combining experiments and analysis, to calibrate alternative, non-quadratic anisotropic yield
functions and assess their performance in predicting burst. The experiments involved
testing tubes under combined internal pressure and axial load to failure using various
proportional and non-proportional loading paths (free inflation). A number of state of the
art yield functions were then implemented in numerical models of these experiments and
calibrated to reproduce the induced strain paths and failure strains.
The constitutive models were subsequently employed in the finite element models
of the hydroforming experiments. The results demonstrate that localized wall thinning in
the presence of contact, as it occurs in hydroforming as well as other sheet metal forming
problems, is a fully 3D process requiring appropriate modeling with solid elements. This
success also required the use of non-quadratic yield functions in the constitutive
modeling, although the anisotropy present did not play as profound a role as it did in the
simulation of the free inflation experiments. In addition, corresponding shell element
calculations were deficient in capturing this type of localization that precipitates failure,
irrespective of the sophistication of the constitutive model adopted. This finding
contradicts current practice in modeling of sheet metal forming, where the thin-walled
assumption is customarily adopted.text
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Lin, Yu-kai, and 林義凱. "Formability analysis of tube hydraulic bulge forming." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/47213857269783692369.
Full textAbstract:
博士國立中山大學
機械與機電工程學系研究所
93
Tube hydroforming process is a relatively new technology compared to conventional manufacturing via stamping and welding. However there is not much knowledge available for the product or process designers. The objective of this study will determine the flow stress and forming limit diagram of tubular materials to discuss the formability of tubes. Firstly, a mathematical model is proposed to examine the plastic deformation behavior of a thin-walled tube at different process parameters during the bulge hydroforming process without axial feeding. In the formulation of this mathematical model, an ellipsoidal surface and non-uniform thinning in the free bulged region and sticking friction between the tube and die are assumed. In the sticking friction mode, the elements after contact with the die do not move or slide. The effects of various forming parameters, such as the die entry radius, the bulge length, anisotropy, the initial thickness of the tube, etc., upon the forming pressures are discussed systematically. Secondly, an analytical model combined with hydraulic bulge tests is proposed to evaluate the properties of tubular materials considering anisotropy effect. Annealed AA6011 aluminum tubes and SUS409 stainless steel tubes are used for the bulge test. The tube thickness and radius at the pole and the internal forming pressure are measured simultaneously during the bulge test. The anisotropic values are obtained from tensile tests. From above experimental data, the effective stress - effective strain relations can be derived by this analytical model. The finite element method is used to conduct the simulations of hydraulic bulge forming with the flow stresses obtained by the above-mentioned model. The analytical forming pressures versus bulge heights are compared with the experimental results to validate the approach proposed in this study. Finally, this study also establishes the Forming Limit Diagram (FLD) of aluminum tubular material. An experimental system of tube hydroforming in which axial feed is applied to carry out the hydraulic bulge-forming test of the annealed aluminum alloy tubes. Furthermore, Hill’s new yield criterion is also used to predict the Forming Limit Curves of sheets. The predicted forming limit diagrams are compared with the experimental data. The results of this study can provide useful knowledge for process design. In addition, the process parameters of flow stress and forming limit diagram obtained can improve the accuracy of the simulation results in industrial and academic fields.
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Lin, Chien-Wei, and 林建維. "Formability Study for Stamping Aluminum Alloy Sheets." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/11730822911162970716.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
99
In recent year, customers had raising demands for the coziness of spaces and multi-functions, which makes the sizes and weights of vehicles increased. However, when facing the energy crisis and the deteriorating living environment, it is essential to decrease the emission of greenhouse gases. To produce light-weighted parts then becomes the goal of most sheet metal factories. In European and American countries, some factories have even launched aluminum alloy automotives and aluminum alloy yachts one after another. The weight of aluminum alloy is approximately one-third of steel; as a result, aluminum alloy has gradually substituted for steel. Aluminum alloy bears its own advantages of light-weight and better corrosion resistance, but its formability is inferior to that of steel. In the stamping process, except that aluminum alloy would crack easily, the low elastic modulus makes the aluminum alloy easier to produce a significant springback defect, which would lead to variation of accuracy hard to grapple with. As a result, the design concept of stamping conventional steel sheets cannot be completely applied to the die design of aluminum alloy, which causes the tooling maker to spend more time and money to develop a set of stamping dies. And thus, the computer-aided engineering (CAE)technology becomes even more necessary in helping the die design. It is well known that the material model including the yield criterion and the hardening rule plays an important role in the CAE analysis for predicting the springback. In the present study, the tension-compression reversal tests were conducted to obtain the stress-strain relations and the Bauschinger effect exhibited in the A5083-O and A6181-T4 sheets. The test results were fitted into different yield criteria and work hardening rules used in different finite element software. The finite element simulations were then preformed for V-bending and U-hat drawing of A5083-O and A6181-T4 sheets, and the results of springback and side-wall curl were compared with those obtained from experiments. It can be concluded from the comparison that the material model which includes the Bauschinger effect renders a more consistent results with the experimental data. The formability of stamping an engine hood with A6181-T4 was also examined in the present study. The aging phenomenon of A6181-T4 was first observed from aging tests and the test results were included in the subsequent finite element simulations. In order to investigate the difference of forming characteristics between conventional steel and A6181-T4 in the stamping process of an engine hood, the effects of material properties, such as n-value, r-value and yield stress, on the different forming modes were systematically analyzed by the finite element simulations. In addition, the stamping process of the outer panels of a yacht with A5083-O sheets was developed in the present study to replace the current welding process. Due to the V-shaped deep drawing, the defects of wrinkling and fracture are apt to occurring in the stamping process. In order to avoid the presence of these defects, the deformation mechanism in the stamping process of the yacht outer panels were characterized by the finite element simulations. An optimum die face shape with a proper addendum design was then developed according to the finite element analysis, and an actual stamping die set is scheduled to be manufactured following the suggested die design.
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hao-Chung, Chia, and 鍾嘉豪. "Formability Analysis of Automotive Aluminum Fender Panel." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/aha67q.
Full textAbstract:
碩士國立虎尾科技大學
機械與電腦輔助工程系碩士班在職專班
104
In recent years, the global automotive industry has faced two important issues. One is how to save energy and the others is how to reduce the emissions to protect the global environment. Therefore, vehicle weight reduction has become a major issue to decrease fuel consumption and emissions To use lightweight materials instead of traditional galvanized steel becomes a common concern. Aluminum alloy is the best material for lightweighting automobiles due to its light weight, high strength and corrosion resistance properties. However, the formability of aluminum alloy has great difference from galvanized steel. Finding out the most suitable technology to design the stamping die for aluminum alloy become a priority issue. To design a suitable forming method for aluminum fenders is the main target in this research. We can reach the technology design through A simulation and experimental method were used to analysis the formability of aluminum fenders.. Moreover, the theory calculation, experimental testing and sampling comparsion were adopted to verify the design. Finally, a stamping die particularly for the mass production of the aluminum fenders will be developed. The main research method are summarized below: （1）To analyze the material properties of 6016-T4P aluminum alloy and galvanized steel JAC-270D. Study how each parameters influence the formability and infer the comparative advantages of the two materials. （2）Apply the traditional methods- S-shaped pattern and trapezoidal pattern in finite Element simulations of galvanized steel and aluminum alloy plate. Make sure the applicability of their mold design. （3）Synchronously develop mold entity to get reverse verification, and with practical experience and computer software, we can find out the design pattern which meets the input production. Result demonstrates that the S-shaped cutting line used on galvanized steel is unsuitable for aluminum alloy. Also trapezoidal cutting line design for the forming of aluminum alloy fender showed unstable. Therefore,the save gluten feed was set up and debugging draw bead geometric approach was designed on the surface.Finally, experimental samples were made to verify the most suitable die designfor forming aluminum alloy fender.
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Bagheriasl, Reza. "Formability of Aluminum Alloy Sheet at Elevated Temperature." Thesis, 2012. http://hdl.handle.net/10012/7018.
Full textAbstract:
An experimental and numerical study of the isothermal and non-isothermal warm formability of an AA3003 aluminum alloy brazing sheet is presented. Forming limit diagrams were determined using warm limiting dome height (LDH) experiments with in situ strain measurement based on digital image correlation (DIC) techniques. Forming limit curves (FLCs) were developed at several temperature levels (room temperature, 100ºC, 200ºC, 250ºC, and 300ºC) and strain-rates (0.003, 0.018, and 0.1s-1). The formability experiments demonstrated that temperature has a significant effect on formability, whereas forming speed has a mild effect within the studied range. Elevating the temperature to 250C improved the formability more than 200% compared to room temperature forming, while forming at lower speeds increased the limiting strains by 10% and 17% at room temperature and 250ºC, respectively.
Non-isothermal deep draw experiments were developed considering an automotive heat exchanger plate. A parametric study of the effects of die temperature, punch speed, and blank holder force on the formability of the part was conducted. The introduction of non-isothermal conditions in which the punch is cooled and the flange region is heated to 250C resulted in a 61% increase in draw depth relative to room temperature forming.
In order to develop effective numerical models of warm forming processes, a constitutive model is proposed for aluminum alloy sheet to account for temperature and strain rate dependency, as well as plastic anisotropy. The model combines the Barlat YLD2000 yield criterion (Barlat et al., 2003) to capture sheet anisotropy and the Bergstrom (1982) hardening rule to account for temperature and strain rate dependency. Stress-strain curves for AA3003 aluminum alloy brazing sheet tested at elevated temperatures and a range of strain rates were used to fit the Bergstrom parameters, while measured R-values were used to fit the yield function parameters. The combined constitutive model was implemented within a user defined material subroutine that was linked to the LS-DYNA finite element code. Finite element models were developed based on the proposed material model and the results were compared with experimental data. Isothermal uniaxial tensile tests were simulated and the predicted responses were compared with measured data. The tensile test simulations accurately predicted material behaviour.
The user material subroutine and forming limit criteria were then applied to simulate the isothermal warm LDH tests, as well as isothermal and non-isothermal warm deep drawing experiments. Two deep draw geometries were considered, the heat exchanger plate experiments developed as part of this research and the 100 mm cylindrical cup draw experiments performed by McKinley et al. (2010). The strain distributions, punch forces and failure location predicted for all three forming operations were in good agreement with the experimental results. Using the warm forming limit curves, the models were able to accurately predict the punch depths to failure as well as the location of failure initiation for both the isothermal and non-isothermal deep draw operations.
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Hsu, Chang-chuan, and 徐章銓. "Formability and Characteristics of High Ductile Magnesium Alloys." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/15977292417914368674.
Full textAbstract:
博士國立中央大學
機械工程研究所
97
The magnesium is a very light metal(specific weight 1.74) that can be used for structural application. However, it is commonly recognized that magnesium possessed poor formability because of its hexagonal closed packed structure. Therefore, it is tempting to obtain the refining grain structure of Mg-Zn-Zr alloys plate passing through thermo-mechanical treatment processes and heat treatment, in order to get high strain rate superplasticity of Mg-Zn-Zr alloys for industry application. In this thesis, microstructures and mechanical properties of the Mg-Zn-Zr alloy in as-extruded, as-annealed and subsequent rolled states are studied. The effects of deformation amount, possible precipitates on mechanical properties are examined. The result of grain size is reduced to the of 3μm after 80% rolled and at 265℃x16hrs annealed specimens. High temperature tensile tests indicated that the fine-grained rolling structure exhibited superplasticity，the elongation can reach 240% and 429% at strain rate of 10-2S-1 and 10-3S-1 respectively. I also study two phase(α+β) Mg-Li series alloys，which have better mechanical properties and low density and high formability at room temperature. But Mg-Li series alloys normally have low strength and poor precipitation hardening effect. All those confine its application field. As-extruded of Mg-Li series alloys passed different processes such as extruded/natural aging, extruded/cold rolled, extruded/solid solution treatment, extruded/solid solution treatment/natural aging, and extruded/solid solution treatment/cold rolled . one effective process of improving the mechanical properties is that cold rolled 90% after solution treatment, which tensile strength from as-extruded at 166MPa get up to 276MPa.