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Yue, T. M. "The microstructure and mechanical properties of squeeze cast aluminium alloy 7010." Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277565.
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Hepples, W. "Environment-sensitive cracking of 7000 series aluminium alloys." Thesis, University of Newcastle Upon Tyne, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375141.
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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/.
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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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Silva, José Wilson de Jesus [UNESP]. "Efeito dos oxi-ânions do grupo VIB sobre a corrosão aquosa das ligas Al(2024) e Al(7050) utilizadas na indústria aeronaútica." Universidade Estadual Paulista (UNESP), 2003. http://hdl.handle.net/11449/97122.
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Foram caracterizados os comportamentos eletroquímicos e avaliadas as resistências à corrosão das ligas aeronáuticas 2024-T351 e 7050-T7451 em soluções aquosas de cloreto contendo cromato, molibdato e tungstato. Foram realizados ensaios de corrosão não-eletroquímicos de imersão prolongada acompanhados de análise metalográfica de superfície por microscopia óptica e identificação dos produtos de corrosão por difratometria de raios-X. A análise quantitativa de superfícies das ligas após a imersão, indica que os pites formados têm áreas médias similares. Os pites são mais largos do que profundos e de geometria, predominantemente, cônica ou quase-cônica e irregular. Em todos os produtos de corrosão de cada liga foi encontrado hidróxido de alumínio, em suas diferentes formas cristalinas. Medidas de perda de dureza, como uma conseqüência da deterioração superficial, também foram determinadas. Além disso, ensaios eletroquímicos como medidas de potencial em circuito aberto, curvas de polarização e voltametria cíclica complementaram este estudo. Em meio aerado os resultados obtidos mediante medidas eletroquímicas são consistentes com aqueles obtidos nos ensaios de imersão, em particular o efeito do CrO42- e do MoO42-. O WO42- mostrou-se agressivo em períodos prolongados de imersão. Apesar dos ensaios revelarem uma redução parcial de MoO42- em ambas as ligas, o efeito desse oxi-ânion parece ser diferente sobre cada liga. Em meio desaerado as ligas apresentam passivação em todos os eletrólitos. A adição dos oxi-ânions não modificou significativamente o potencial de pite para a liga 7050, enquanto que para a liga 2024 ele foi deslocado levemente para valores mais positivos.
It has been characterized the electrochemical behavior and evaluated the 2024-T351 and 7050-T7451 aircraft alloys corrosion resistance in chloride aqueous solutions containing chromate, molybdate and tungstate. It has been carried out non-electrochemical long immersion corrosion testings accompanied by surface metalography analysis achieved by light microscopy and corrosion products identification by X-ray difratometry. Surfaces quantitative analysis upon the alloys after immersion, indicates that formed pits have similar average area. Pits are widther than deeper and own predominantly a conical or quasi-conical and irregular geometry. In all corrosion products of each alloy it has been found aluminum hydroxide in its different crystalline ways. Hardness loss measurements have also been determined. In addition, electrochemical testings such as open circuit potential measures, polarization curves and cyclical voltammetry have completed this study. In aerated means the obtained results before electrochemical mesurements are similar to those obtained in the immersion tests, in particular CrO42- and MoO42- effects. WO42- has been found to be aggressive in very long immersion period. Though tests display a MoO42- partial reduction in both alloys, this oxi-anion effect seems to be different upon each alloy. In de-aerated means alloys present passivation in all eletrolytes. Oxi-anion addition has not changed significantly pit potential for 7050 alloy, while for 2024 alloy it has been dislocated, slightly, for more positive values.
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Silva, José Wilson de Jesus. "Efeito dos oxi-ânions do grupo VIB sobre a corrosão aquosa das ligas Al(2024) e Al(7050) utilizadas na indústria aeronaútica /." Guaratinguetá : [s.n.], 2003. http://hdl.handle.net/11449/97122.
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Resumo: Foram caracterizados os comportamentos eletroquímicos e avaliadas as resistências à corrosão das ligas aeronáuticas 2024-T351 e 7050-T7451 em soluções aquosas de cloreto contendo cromato, molibdato e tungstato. Foram realizados ensaios de corrosão não-eletroquímicos de imersão prolongada acompanhados de análise metalográfica de superfície por microscopia óptica e identificação dos produtos de corrosão por difratometria de raios-X. A análise quantitativa de superfícies das ligas após a imersão, indica que os pites formados têm áreas médias similares. Os pites são mais largos do que profundos e de geometria, predominantemente, cônica ou quase-cônica e irregular. Em todos os produtos de corrosão de cada liga foi encontrado hidróxido de alumínio, em suas diferentes formas cristalinas. Medidas de perda de dureza, como uma conseqüência da deterioração superficial, também foram determinadas. Além disso, ensaios eletroquímicos como medidas de potencial em circuito aberto, curvas de polarização e voltametria cíclica complementaram este estudo. Em meio aerado os resultados obtidos mediante medidas eletroquímicas são consistentes com aqueles obtidos nos ensaios de imersão, em particular o efeito do CrO42- e do MoO42-. O WO42- mostrou-se agressivo em períodos prolongados de imersão. Apesar dos ensaios revelarem uma redução parcial de MoO42- em ambas as ligas, o efeito desse oxi-ânion parece ser diferente sobre cada liga. Em meio desaerado as ligas apresentam passivação em todos os eletrólitos. A adição dos oxi-ânions não modificou significativamente o potencial de pite para a liga 7050, enquanto que para a liga 2024 ele foi deslocado levemente para valores mais positivos.Abstract: It has been characterized the electrochemical behavior and evaluated the 2024-T351 and 7050-T7451 aircraft alloys corrosion resistance in chloride aqueous solutions containing chromate, molybdate and tungstate. It has been carried out non-electrochemical long immersion corrosion testings accompanied by surface metalography analysis achieved by light microscopy and corrosion products identification by X-ray difratometry. Surfaces quantitative analysis upon the alloys after immersion, indicates that formed pits have similar average area. Pits are widther than deeper and own predominantly a conical or quasi-conical and irregular geometry. In all corrosion products of each alloy it has been found aluminum hydroxide in its different crystalline ways. Hardness loss measurements have also been determined. In addition, electrochemical testings such as open circuit potential measures, polarization curves and cyclical voltammetry have completed this study. In aerated means the obtained results before electrochemical mesurements are similar to those obtained in the immersion tests, in particular CrO42- and MoO42- effects. WO42- has been found to be aggressive in very long immersion period. Though tests display a MoO42- partial reduction in both alloys, this oxi-anion effect seems to be different upon each alloy. In de-aerated means alloys present passivation in all eletrolytes. Oxi-anion addition has not changed significantly pit potential for 7050 alloy, while for 2024 alloy it has been dislocated, slightly, for more positive values.
Orientador: Eduardo Norberto Codaro
Coorientador: Roberto Zenhei Nakazato
Banca: Luis Rogerio de Oliveira Hein
Banca: Gilberto Luis Jardim Pinto da Silva
Mestre
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Lemke, Kevin L. "A comparison of the fatigue properties of aluminum lithium 8090 forgings and 7050 aluminum plate in low strength orientations." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/19971.
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Reed, Jordan Derek. "Ultrasonic Processing of Aluminum 2139 and 7050." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1248496/.
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Acoustics is the study of all sound waves, with ultrasound classified as those frequencies above 20,000 Hz. Currently, ultrasound is being used in many industries for a variety of purposes such as ultrasonic imaging, ultrasonic assisted friction stir welding, and ultrasonic spot welding. Despite these uses, the effects of ultrasound on phase stability and resultant mechanical properties has been minimally analyzed. Here we study the impact waves play in ultrasonic welding and design an apparatus to maximize waves entering aluminum alloy samples. Aluminum 2139 and 7050 are used because they are precipitation strengthened by metastable phases so temperature change, and the corresponding phase stability, can greatly impact their strength. Results suggest that the ultrasonic welder primarily imposes a localized temperature spike due to friction, averaging over 200°C in a few seconds, which generally lowers the Vickers hardness due to coarsening or even dissolution of strengthening precipitates. Conversely, the new design increases the Vickers hardness by up to 30% over the initial hardness of approximately 63HV for aluminum 2139 and 83HV for aluminum 7050, respectively, while only increasing the temperature by an average of approximately 10°C. This new design was unable to achieve peak hardness, but the strengthening it achieved in two minutes was equivalent to one month of natural aging. If this system was able to be fine-tuned, it could serve as a quick strengthening process for recently weakened aluminum alloys, such as after friction stir welding.
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Slouka, Marek. "Mechanické vlastnosti hliníkové slitiny EN AW 7020 za zvýšených teplot." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229460.
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The master’s thesis deals with high strength aluminium alloys AlZn4Mg (EN AW 7020). This alloy is used for high strength, low density, a good corrosion resistant and a good weldability in protective atmospheres. At first this thesis is described to aluminium alloys, ways of manufacturing and history. Next this thesis mainly deals with wrought aluminium alloys, heat treatment this alloys and alloys Al-Zn-Mg. Tensile tests were made of alloys EN AW 7020 at room temperature and increased temperature. Next this alloy was made of fatigue test and metallographic analysis. The model was construct. This model describe to behaviour alloy at increased temperature and this model was compared with measure values. This thesis describe to behaviour of study alloy at room temperature and increased temperature.
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Deshpande, Nishkamraj U. "Characterization of fracture path and its relationship with microstructure and fracture toughness of aluminum alloy 7050." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/20210.
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Nowill, Courtney Ann. "Investigation of the quench and heating rate sensitivities of selected 7000 series aluminum alloys." Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-081307-103919/.
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Clark, David A. "Durability of the residual stresses surrounding cold expanded fastener holes in 7050-T7451 aluminum." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17828.
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Goetz, John M. "Investigation of coating cracking and fatigue strength of 7050-T74 aluminum alloy with different anodize coating thicknesses." Connect to this title online, 2005. http://hdl.handle.net/1811/327.
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Thesis (Honors)--Ohio State University, 2005.Title from first page of PDF file. Document formattted into pages: contains v, 40 p.; also includes graphics. Includes bibliographical references (p. 39-40). Available online via Ohio State University's Knowledge Bank.
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Yurtoglu, Mine Ender. "Mode Ii Fatigue Crack Growth Behavior And Mode Ii Fracture Toughness Of 7050 Aluminum Alloy In Two Orientations." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615581/index.pdf.
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Fatigue crack growth behavior of AA7050 T7451 aluminum alloy under mode II loading condition in two orientations was investigated. Compact shear specimens were prepared in TL and LT directions. A loading frame for mode II type of loading was manufactured. Using the loading frame and the specimen, KIIC values and mode II fatigue crack growth rates were calculated.
Fractographic analysis of the fracture surfaces of both mode II fracture toughness test specimens and mode II fatigue crack growth test specimens were done to examine the effects of mode II load.
KIIC values were measured between 1.3 and 1.5 times the KIC values for this alloy. As for mode II fatigue crack growth rates, TL orientation shows the highest mode II fatigue crack growth resistance.
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Cevik, Gul. "Investigation Of The Effect Of Orientation And Heat Treatment On The Stress Corrosion Cracking Susceptibility Of 7050 Aluminum Alloy." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12605220/index.pdf.
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In the present work, the effect of variation in specimen orientation and heat treatment on the Stress Corrosion Cracking (SCC) susceptibility of 7050 aluminum alloy was investigated in 3,5% NaCl solution and under freely corroding conditions. For this purpose, Constant Extension Rate Tests (CERT) was performed on precracked Compact Tension (CT) specimens and the Direct Current Potential Drop technique was applied to measure the crack lengths. In addition to crack length versus time curves, the relationship between the crack growth rate and the stress intensity factor was determined. Fractographic analysis was utilized extensively to support the findings related with basic mechanisms of cracking.
The alloy was found to be in the most susceptible state in the SL orientation, in which the crack propagation direction is parallel to the rolling direction. The resistance to SCC is higher in the TS but at maximum in LT orientation where the loading direction is parallel to the rolling direction.
In the peak aging treatment, T651, alloy is susceptible to SCC in SL orientation. When the over aging treatment, T7651, is applied the resistance is increased and the two step over aging treatment, T73651, has resulted in an additional improvement in this orientation. On the other hand, the alloy showed higher resistance to SCC in TS and LT orientations in T651 condition compared to the T7651 and T73651 treatments. In these orientations, the alloy is less susceptible in T73651 condition than in T7651 treatment.
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Tardelli, Joffrey. "Etude du comportement électrochimique des phases intermétalliques des alliages d'aluminium 2214-T6 et 7050-T74 : approche multi-échelle de matériaux polyphasés." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0082/document.
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L'étude du comportement électrochimique des phases intermétalliques Al2Cu, Al2CuMg, Al7Cu2Fe, (Al,Cu)16Mn4Si3 et MgZn2, caractéristiques des alliages d'aluminium 2214-T6 et 7050-T74 et réalisée à partir d'échantillons massifs synthétisés, a montré que la formation de défauts majeurs dans la couche d'oxyde, obtenue par anodisation des alliages en milieu H2SO4 200 g/l, était directement due à la présence de ces particules au sein des alliages. L'important dégagement gazeux d'oxygène qui se produit à la surface de ces particules lors de l'étape d'anodisation explique la formation de trous et de fractures dans la couche d'oxyde. En milieu marin, ces défauts facilitent la migration des ions chlorures à la surface de l'alliage mise à nu localement et favorisent par conséquent le développement de la corrosion localisée. Les résultats obtenus en milieu NaCl 35g/l ont permis de mieux comprendre le mécanisme de corrosion des phases intermétalliques ainsi que leur rôle sur la propagation des piqûres. L'élimination des particules intermétalliques de la surface des alliages lors de l'étape de décapage (avant anodisation) permet de favoriser une croissance plus régulière de la couche d'oxyde lors de l'anodisation. Par conséquent, la résistance à la corrosion des alliages 2214 et 7050 augmente considérablement, permettant d'atteindre les objectifs fixés lors de ce projetThe electrochemical behaviour of the bulk intermetallic particles such as Al2Cu, Al2CuMg, Al7Cu2Fe, (Al,Cu)16(Mn,Fe)4Si3 and MgZn2 showed that the formation of wide defects in the oxide layer during the 2214-T6 and 7050-T74 alloys anodization was directly due to the presence of these kind of particles in the microstructure which are able to sustain both high dissolution rate and high water oxidation kinetics in acidic electrolyte. In marine environment, these defects facilitate the migration of aggressive ions like chloride on the locally bare alloys and are the onset of the pitting corrosion. The results obtained in 3.5 wt.% sodium chloride electrolyte permit to understand the corrosion mechanism of the intermetallic phases and their influence on the pits propagation. The optimization of the alloys pickling conditions in order to remove this kind of particles (prior to the anodization step) has been investigated in this work. Consequence of removing intermetallic particles, the aluminium enrichment of the surface facilitates the oxide growth and the formation of regular layer. The corrosion tests on treated aluminium alloys have clearly showed the influence of the pickling step on the resistance corrosion of 2214 and 7050 alloys, reaching the objectives fixed in this project
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Dighe, Manish Deepak. "Development of digital image processing based methodology to study, quantify and correlate the microstructure and three dimensional fracture surface morphology of aluminum alloy 7050." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/21013.
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Nizery, Erembert. "Amorçage et propagation des fissures de fatigue dans les alliages d'aluminium 2050-T8 et 7050-T7451." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0131/document.
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Les alliages d'aluminium utilisés dans les structures aéronautiques (fuselage, voilure) sont soumis à des chargements cycliques, faisant de la fatigue l'un des facteurs dimensionnant. Dans cette thèse, les mécanismes d'amorçage de ces fissures de fatigue – au niveau des particules intermétalliques – et de micropropagation sont étudiés expérimentalement et numériquement sur les alliages 2050-T8 et 7050-T7451. Les analyses des premiers chapitres portent sur la description des particules intermétalliques qui sont les plus susceptibles de donner lieu à une amorce de fissure dans la matrice d'aluminium. Les effets de la nature des particules et de leur taille sont quantifiés. La proximité entre les particules intermétalliques et les pores y est décrite. Cette analyse expérimentale fait intervenir des observations de surface en microscopie électronique à balayage (MEB), ainsi que des caractérisations tridimensionnelles (3D) réalisées à l'aide de la tomographie par rayonnement synchrotron. Dans les chapitres suivants, les analyses traitent de la prévision des chemins de fissuration à l'échelle d'un grain. Elles s'appuient sur des observations expérimentales de surface et des simulations de plasticité cristalline 3D pour comprendre les chemins de fissuration. Un modèle d'endommagement tenant compte de la cristallographie est alors proposé pour simuler la propagation de fissure par éléments finisAluminium alloys used for aerospace structures (wing, fuselage) are subjected to cyclic loading. Fatigue properties of such alloys are therefore taken into account for the design of such parts. In this thesis, initiation mechanisms of fatigue cracks – near intermetallic particles – and micropropagation are studied experimentally and numerically on alloys 2050-T8 and 7050-T7451. In the first chapters, the analysis focuses on intermetallic particles which are most prone to initiate a fatigue crack in the aluminium matrix. The effects of the nature of particles as well as their size are quantified. The proximity between intermetallic particles and pores is described. This experimental analysis use surface observations obtained with a scanning electron microscope (SEM), and three-dimensional (3D) characterizations using synchrotron tomography. In the last chapters, analysis are oriented towards the prediction of crack paths at the grain size. They rely on surface experimental observations and 3D crystal plasticity modelling in order to understand crack paths. A damage model taking into account crystallography is proposed to simulate crack propagation using the finite element method
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Assai, Natany Dayani de Souza. "ESTUDO DA RELAXAÇÃO DE TENSÕES RESIDUAIS EM CONDIÇÕES DE CARREGAMENTO CÍCLICO DA LIGA DE ALUMÍNIO 7050 – T7451." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2014. http://tede2.uepg.br/jspui/handle/prefix/1464.
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Previous issue date: 2014-08-27The residual stress may decrease and redistribute through a process called relaxation. The relaxation of the residual stress is an important phenomenon in relation to the estimated fatigue resistance of the material and can occur due to static mechanical loading, thermal, cyclical and extension fatigue effects. Residual stresses are usually harmful for overlapping the operating voltage, while the fatigue resistance of metals and alloys can be improved by compressive residual stresses present in the surface layer by means of shot peening surface. The fatigue life with the compressive residual stress field caused by shot peening or sophisticated models for modeling voltage field Compressive Residual (CTRC) usually does not take into account the possibility of this change during the cyclic loading, ie , place the relaxation process, which also changes the fatigue life. This study aimed to obtain the residual stress profile relaxation by cyclic loading on aluminum alloy samples 7050- T7541 with shot peening glass and ceramics subjected to axial fatigue test. The technique for determining the residual stress was the X-ray diffraction for measuring accurately the redistribution of residual stresses along the depth of fatigue produced by the process. The removal of layers of material was performed by electrolytic attack. Hereby, it was possible to establish the relationship between the maximum stress and number of cycles in relation to the greater or lesser relaxation test specimens in different regimes of cyclic peening conditions with spherical glass and ceramics in the longitudinal and transverse directions. The results showed that the samples with the longitudinal direction shot peening redistribution showed higher compressive residual stresses in the transverse direction along the depth. For the samples of shot peening ceramic was virtually no relaxation on the surface only in depth when compared to the original profile, samples of ceramic shot peening obtained relaxation in remote locations of the surface, due to the influence of roughness. The redistribution of stresses for samples of shot peening glass were higher than those with shot peening ceramic along the depth in all cyclic regimens studied in the L and T directions. The residual stress relaxation occurred in both directions did not compromise beneficial effect of shot peening increase the fatigue life thereof, in relation to the base material.
As tensões residuais podem diminuir e se redistribuir por meio de um processo chamado relaxação. A relaxação das tensões residuais é um fenômeno importante no que se refere à previsão da resistência à fadiga dos materiais e pode ocorrer devido a carga mecânica estática, térmica, cíclica como efeitos de extensão da fadiga. As tensões residuais geralmente são prejudiciais por se sobreporem às tensões de serviço, enquanto a resistência à fadiga dos metais e ligas pode ser melhorada por tensões residuais compressivas presentes nas camadas superficiais por meio do tratamento de superfície de shot peening. A vida em fadiga com o campo de tensão residual compressiva originada pelo shot peening ou modelos sofisticados para a modelagem do Campo de Tensão Residual Compressivo (CTRC), geralmente não leva em consideração, a possibilidade deste alterar-se durante o carregamento cíclico, ou seja, ocorrer o processo de relaxação, que também altera a vida em fadiga. Este trabalho teve como objetivo obter o perfil de tensão residual de relaxação por carregamento cíclico em amostras de liga de alumínio 7050- T7541 com shot peening de vidro e cerâmica submetidas a ensaio de fadiga axial. A técnica para determinação das tensões residuais foi a difração de raios X que permite medir com precisão a redistribuição de tensões residuais ao longo da profundidade produzidas pelo processo de fadiga. A remoção das camadas de material foi realizada por ataque eletrolítico. Por meio deste, foi possível constatar a relação entre a tensão máxima e quantidade de ciclos no que se refere à maior ou menor relaxação de corpos de prova em diferentes regimes cíclicos nas condições de shot peening com esfera de vidro e cerâmica nas direções longitudinal e transversal à laminação.Os resultados mostraram que as amostras com shot peening na direção longitudinal apresentaram redistribuição de tensões residuais compressivas maiores que no sentido transversal ao longo da profundidade. Para os corpos de prova de shot peening de cerâmica praticamente não houve relaxação na superfície apenas na profundidade quando comparado ao perfil original, as amostras de shot peening de cerâmica obtiveram a relaxação em posições mais afastadas da superfície, devido a influência da rugosidade. A redistribuição de tensões para as amostras de shot peening de vidro foram superiores em relação aquelas com shot peening de cerâmica ao longo da profundidade em todos os regimes cíclicos estudados nas direções L e T. A relaxação de tensão residual ocorrida em ambas direções não comprometeu o efeito benéfico do shot peening no aumento da vida em fadiga das mesmas em relação ao material base.
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Lee, Trevor J. "Investigation of ASTM E 238 Bearing Pin Properties for Various Aerospace Alloys." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1074.
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Aircraft are often designed with numbers determined by testing in a lab, rather than by repeatedly building prototypes. These lab tests conform to testing specifications so that the numbers can be compared between manufacturers, suppliers, and lab technicians. One such specification is ASTM specification E238 – 84(08), and it is used to determine important properties of a bearing pin joint like hinges, bolt holes, and rivet joints. The properties determined from this fastener-through-plate method are bearing strength, bearing yield strength, and bearing stiffness.
Adhering to the methods outlined in ASTM E238, a study was performed, looking at the effects that plate material, fastener used, fastener lubrication, and plate hole preparation method (whether drilled and reamed or just drilled) have on the three bearing joint properties. The plate materials used were Al 7050 – T7451, Ti – 6Al – 4V (mill annealed), and PH13 – 8Mo – H1000. The fasteners were Ti – 6Al – 4V screws, coated A286 screws, and high speed steel (HSS) pins used as a control. Lubrication was tested using a corrosion inhibitor, PR – 1776M B – 2 from PRC – DeSoto, on the fastener or leaving the fastener uncoated. The HSS pins were always tested in the uncoated condition. 54 runs were performed, as outlined by a D-optimal design of experiment.
It was discovered from the statistical analysis of the results via ANOVA that both the plate material used and the pin material, whether a screw or a pin, had a significant effect on the bearing strength, bearing yield strength, and bearing stiffness. The interaction between the two factors was also significant on all responses but the bearing stiffness. PH13 – 8Mo – H1000 plates seemed to perform best on average, followed by Ti – 6Al – 4V plates, then Al 7050 – T7451 plates. PH13 – 8Mo – H1000 and Ti – 6Al – 4V plates had similar bearing strength and bearing yield strength averages with the HSS control pins being used, which had the highest mean values for a given plate and fastener. The Ti – 6Al – 4V and A286 screws behaved and performed statistically similar in most cases, except when hole preparation method was take into account. The Ti – 6Al – 4V screws performed better when the hole was drilled and reamed, while the coated A286 screws performed better when the hole was drilled only. All screws had lower resulting bearing properties than the HSS control pins.
It was also found that ASTM specification E238 – 84(08) is a precise test method, since the method could be performed repeatably and reliably with no missing data points. Therefore, this ASTM testing method is reasonable for determining bearing properties, which can then be used to design aircraft.
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Hähnel, Veronika. "Elektrochemisch hergestellte Fe-Pd-Schichten und Nanodrähte - Morphologie, Struktur und magnetische Eigenschaften." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-166120.
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Mit Fe-Pd-Legierungen nahe der Zusammensetzung Fe70Pd30 kann man aufgrund des thermischen oder magnetischen Formgedächtniseffekts große Dehnungen erzeugen. Daher sind sie für Mikro- und Nanoaktoren sowie Sensoren von großem wissenschaftlichen und technologischen Interesse. Im Vergleich zu Massivmaterial und dünnen Schichten erwartet man für eindimensionale Geometrien wie Nanodrähte deutlich höhere Arbeitsfrequenzen und Dehnungen. Zur Herstellung von Nanodrähten eignet sich die elektrochemische Abscheidung in selbstordnende nanoporöse Membranen als effizienteste Methode gegenüber lithographischen oder physikalischen Methoden. Um den Formgedächtniseffekt auch in Fe-Pd-Nanodrähten mit ca. 30 at.% Pd zu nutzen, werden in dieser Arbeit entsprechende Herstellungsbedingungen wie Elektrolytsystem, Abscheideparameter und Nachbehandlung herausgearbeitet. Die Zusammenhänge zwischen Abscheidebedingungen und Morphologie, lokaler Mikrostruktur, Struktur sowie magnetischen Eigenschaften werden untersucht und bewertet. Es wird gezeigt, dass Fe-Pd-Nanodrähte trotz der Kombination aus edlem und unedlem Metall elektrochemisch hergestellt werden können. Ein komplexierter Fe-Pd-Elektrolyt in Kombination mit optimierten alternierenden Abscheidepotentialen führt reproduzierbar zu durchgehenden, nahezu defektfreien Nanodrähten nahe der Zusammensetzung Fe70Pd30. Mit einer nachträglichen Wärmebehandlung erreicht man eine vollständige Umwandlung der Fe-Pd-Legierung von der kubisch raumzentrierten zur kubisch flächenzentrierten Struktur. Die erfolgreiche Herstellung dieser Nanodrähte stellt eine Schlüsselposition auf dem Weg zu formgedächtnisbasierten Nanoaktoren dar. In dieser Arbeit konnten wichtige Ansatzpunkte zur Strukturkontrolle während der elektrochemischen Abscheidung und somit zur Aktivierung des Formgedächtniseffekts identifiziert werdenFe-Pd alloys at about 30 at.% Pd allow obtaining high length changes or strains in the percent range due to thermal or magnetic shape memory effect. They are especially promising candidates for smart and intelligent materials in micro- and nanoactuators as well as sensors. In comparison to bulk materials and thin films the utilization of nanowires promises higher actuation frequencies and strains, which further heighten the scientific and technological interest. Electrodeposition within self-organized nanoporous templates is a very time efficient method to prepare even large arrays of Fe-Pd nanowires of different length and diameter compared to lithographic or physical methods. The aim of this work is to exhibit the preparation conditions such as electrolyte system, deposition parameter and post treatment for shape memory active Fe-Pd nanowires at about 30 at.% Pd. Correlations between morphology, local microstructure, structure and magnetic properties are investigated and evaluated. Fe-Pd nanowires are successfully prepared by electrodeposition despite the combination of noble Pd and less noble Fe metals. The usage of an electrolyte with complexed Fe and Pd ions and an optimized alternating potential deposition regime leads to continuous and almost defect free nanowires close to the composition Fe70Pd30. The complete transition from the bcc to fcc structure of the Fe-Pd alloy is achieved by an additional heat treatment. However, the successful preparation of these nanowires represents a key element towards nanoactuators based on shape memory alloys. Fundamental knowledge about electrochemical preparation of Fe-Pd nanowires is gained. Important starting points towards structure control during deposition and activation of the shape memory effect are identified
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Ramesh, Aashish, and Gaurav Kalkur. "Fatigue life validation of aircraft materials." Thesis, Linköpings universitet, Mekanik och hållfasthetslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-170893.
Full textAbstract:
Fatigue is one of the critical design aspects with immense significance where thefatigue life of a material can be stated as the number of cycles that a componentcan withstand under a particular type of loading without failure. The design processhas to include fatigue analysis in order to predict failure due to fatigue. This helpsin maintenance and servicing of a component reducing the chance of failure duringoperation of the component. Increased efficiency of predictive maintenance improvesthe life of the component.This thesis aims to study the relationship between the experimental, analytical andnumerical solutions of two high strength aluminium alloys and one steel alloy fortheir life in aircraft applications covering the effects of geometrical irregularities. Italso aims to answer convergence between the numerical and the analytical methodwhen compared with each other. The simulations are carried out for three materialsamong many used in aircraft and industrial applications (Al 7050-T7451, Al 7075-T6 and AISI 4340 Steel) for a pre-defined set of geometries. The stress field andthe stress concentration factor variations are also studied to identify their effects onfatigue life.The results from this work forms a strong background for the future research alongside SAAB or any other industries using these materials for their structures to findout the failure or predicting it accurately. Also, integral structures can be analysedin detail using this thesis as a base.
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Yang, Hwe-Wen, and 楊慧文. "The Precipitates in 7050 Aluminum Alloy." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/97548303037200595606.
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Wen, Chi Horng, and 溫啟宏. "The Thermomechanical Treatment of 7050 Aluminum Alloy." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/57581105629751054905.
Full textAbstract:
碩士國立清華大學
材料科學(工程)研究所
83
7050 鋁合金是改進以往廣泛使用的 7075 鋁合金的缺點所設計的航空結 構材料。 本研究利用滾壓作為熱機處理的變形方式，並以 T76、T73、 RRA 等熱處理作為析出處理方法，來改變原有 7050 鋁合金的顯微結構 ， 希望能使 7050 鋁合金具有更優越的高強度及抗腐蝕能力。 原材料 以 350 ℃做製程退火的冷滾壓，得到的晶粒大小為 dS =25μ m、dT =180 μ m、dL =220 μ m；而以 220 ℃熱滾壓，其晶粒大小為 dS =10 μ m、dT =25 μ m、dL = 30 μ m。 再經過 T73、T76、RRA 熱處理的 材料皆較 T7451- 原材料有較高的強度和伸長率。 在 3.5 wt% NaCl 水 溶液的動態極化測試結果顯示， Initial Aging- 大晶粒的腐蝕電位為 -1180 mVSCE，抗腐蝕能力最差； 而 RRA- 小晶粒的腐蝕電位為 -1050 mVSCE， 抗腐蝕效果最好。 在剝蝕測試中，RRA及 T73 的小晶粒試片抗 剝蝕能力是最好的， Initial Aging- 大晶粒試片的剝蝕情形最為嚴重， 且所有的剝蝕都是沿晶腐蝕。 在 3.5 wt% NaCl 溶液中控制初始應變速 率在 1.8x10^-6 /sec 做拉伸測試，其結果顯示， 強度和伸長率皆較空 氣中為低且斷裂面有應力腐蝕的現象，從 SEM 觀察其斷裂面發現，所有 細晶粒的材料和 Initial Aging- 大晶粒的試片應力腐蝕是沿晶斷裂， 但對原材料和 RRA- 大晶粒的試片而言， 裂縫的成長則是穿晶斷裂，且 應力腐蝕的破裂面上有許多相互平行的裂口停止條紋， 此意味著裂縫成 長的機構並不是連續的，而是一步一步成長的過程。 7050 aluminum alloy is an airframe structure material used widely by AIDC and developed with the goal of improving the disadvantages of 7075 aluminum alloy. In this work, two rolling procedures and four types of heat treatments, namely Initial Aging, T76, T73, and RRA, are used as deforming method and precipitation treatments for 7050 aluminum alloy. The grain sizes of specimens cold rolled and process annealed at 350 ℃ are dS =25 μ m, dT =180 μ m, dL =220 μ m and those hot rolled at 220 ℃ are dS =10 μ m, dT =25 μ m, dL =30 μ m. For all the T73, T76 and RRA treatments used in this study, the material after thermomechanical treatments can have both higher strength and longer elongation than the as received material. From the result of the potentiodynamic polarization curves of 7050 Al alloys in 3.5% NaCl aqueous solution, the corrosion potential of the Initial Aging treated large grain specimen (-1180 mVSCE) is more negative than the RRA treated small grain specimen (-1050 mVSCE). It indicates that Initial Aging-large grain specimen has the worst corrosion resistance, while the RRA-small grain specimen is the best. It is consistent with the result of the exfoliation test. Intergranular corrosion was observed in the exfoliation test specimens. When tension tested in 3.5% NaCl solution at an initial strain rate of 1.8x10^-6/sec, both the strength and elongation of all materials were reduced. A region of stress corrosion cracking was observed on the fracture surfaces. The stress corrosion cracking were intergranular for all small grain materials and Initial Aging treated large grain material. For the as received material and RRA treated large grain material, the cracks were transgranular. The observation of parallel crack stop marks in the as received material and RRA treated large grain material tested in 3.5% NaCl solution implies a stepwise growth mechanism of the crack.
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Bagheriasl, Reza. "Formability of Aluminum Alloy Sheet at Elevated Temperature." Thesis, 2012. http://hdl.handle.net/10012/7018.
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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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Liu, Meng-Chung, and 劉孟崇. "Study on Heat Treatment of 7050 Aluminum Alloy." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/19548200533509611671.
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碩士逢甲大學
材料科學所
97
Abstract In this study, Taguchi statistical methods were used to determine the order of contributions of factors which may closely related to the fatigue test of 7050 aluminum alloy specimen. Four factors such as heat treatment solution temperature, quenching temperature, artificial aging temperature and time were chosen to perform L9 orthogonal array experiment. The effect of those factors on fatigue test life could be examined by metallography, dispersion of precipitates, hardness, yield strength, and electric conductivity. Observations by optical microscope (OM), scanning electron microscope (SEM), and measurements based on hardness (Rockwell hardness B scale, HRB), tensile test, and electric conduction (EC) for treated specimen were utilized to correlate the results of fatigue test. The expected optimal process parameters are: solution temperature at 475 C, quenching temperature at 20C, aging temperature at 160C and aging time for 12 hours. The fatigue test life of specimen under these conditions is 44,869 cycles which is acceptable and satisfactory. The Taguchi Experiment program provides a method to obtain the most useful information with the least number of experiments.
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Chiou, Yen Hao, and 邱彥豪. "The Precipitates and Stress Corrosion Cracking of 7050 Aluminum Alloy." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/61471674283807507876.
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CHIOU, YEN HAO, and 邱彥豪. "The Precipitates and Stress Corrosion Cracking of 7050 Aluminum Alloy." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/13313466113604380624.
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Qing-De, Jiang, and 江慶德. "The Shear Band Formation in Compression of 7050 Aluminum Alloy." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/44475087803708355101.
Full textAbstract:
碩士國立清華大學
材料科學工程學系
85
The microstructure and compressive deformation behavior of a 7050-T7451 aluminum alloy were studied. The shear bands formed during the process of compression are more visible on T plance than on L plane, and the tenency to form shear bands is higher in the center portion of the plate than in the outer portion. I was also found that when compressed in the short transverse direction, the strain in the longitudinal direction is at least 50% larger than that in the transverse direction. On T plane, two sets of slip bands which make an angle of about 70° with each other and having the longitudinal direction as their bisector were observed. On L plane, two sets of parallel slip traces which make an angle of about 40° with each other and having the transverse direction as their bisector were observed. Slip band formation is more evident when specimens were cold rolled in the longitudinal direction than in the transverse direction. The macroscopic shear bands are close related to the microscopic slip bands. All the phenomena described above are in association with textures. A duplex texture of two superimposed components, ｛1 －1 0｝〈0 0 1〉 Goss texture ＋｛1 1 0｝〈－1 1 2〉 Brass texture, were found in the 7050-T7451 aluminum alloy. Based on the effect of textures, an explanation of the phenomena described above is proposed in this study.
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Shao, Guan-Jhang, and 邵冠璋. "Influence of corrosion environment on fatigue behavior of aerospace 7050 aluminium alloy." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/98190936555308740286.
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碩士國立中央大學
機械工程研究所
92
A program of experimental and analytical tasks has been conducted to discuss the relationship between corrosion environment(immersion NaCl solution and open flow NaCl solution) and fatigue crack propagation（FCP）in an aluminum aerospace alloy 7050.We observe the influence of environmental change for the accelerating of crack growth rate,too. The experiment was investigated via different heat treatments, corrosion environments, frequency, stress intensity factor range, crack length of add corrosion solution condition and load ratio. The influence of fatigue crack propagation was characterized and analyzed by using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Instron Model 8800 Testing System. The basis of airframe structural application is the result of experiment combining with tensile properties and stress corrosion cracking effect. The result indicate that the alloys received homogenuzation-H470×24h have bigger plastic zone, more rough in crack surface and oxide debris then Step-homogenuzation (StepH) when load ratio (R) are 0.1 and 0.8. So homogenuzation-H470×24h have higher resistance to fatigue crack growth with the crack closure effect. And the accelerating of crack growth rate is changed by stress intensity factor range. Keyword：Aluminum alloy 7050, immersion NaCl solution, open flow NaCl solution, accelerating of crack growth rate, crack closure.
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Wang, Chong-An, and 王崇安. "The Shear Band formation in Plane Strain Compression of 7050 Aluminum Alloy." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/83692486280291125600.
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碩士國立清華大學
材料科學工程學系
87
The evolution of shear band and mechanical properties in plane strain compression of 7050- T7451 aluminum alloy were studied. The shear bands or slip lines formed on L plane with L direction constrained are more diffuse than those formed on T plane with T direction constrained. The constrained surface is rougher when it is L plane than T plane. The shear band formation is mainly in accord with the macroscopic mechanics approach. The flow strength of specimens with constraint in L direction is higher than that with constraint in T direction, except the final stage of true stress- engineering curve of specimen cut from surface and deformed with constrained in L direction. The specimens form trapezoid shape and decrease the true stress we measured. Compared with the tensile properties in previous study, shear bands formed at a strain near but a little bit larger than the uniform strain in tension. There is no obvious hardening phenomenon after formation of shear bands. The maximum and minimum points appeared in true stress- engineering strain curves of family II specimens are related to the formation of shear band. Regarding microstructure and texture in the alloy, when T direction was constrained, most slip bands fell into two sets which make an angle of 35°to the longitudinal direction on T plane of the specimen. On L plane of the specimens with constraint in L direction, most slip bands fell into two sets roughly follow the direction of the shear bands and make an angle about 90°. By X-ray diffraction, it is found that the texture in the alloy is mainly a mixture of Goss texture and Brass texture . Goss texture is the main texture to deform when constrained in T direction. Multiple slip occurs when the constraint is in L direction.
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Chou, Hung-Chi, and 周紘吉. "Study on Mechanical Properties of 7050 Aluminum alloy by Friction Stir Welding." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/44182920379479121479.
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碩士國立臺灣海洋大學
機械與機電工程學系
105
7000 series aluminum alloy have been widely utilized in aeronautic industry, bridge, highly stressed structures. Using traditional welding can’t obtain great jointed quality. 7050 aluminum alloy have high strength and high content of zinc but when alloy melts it will makes micro holes and poor jointed quality in welding bead. Friction Stir Welding don’t approach melting point, so there’s no micro hole and cracking of solidification, suitable for application of aluminum welding. The aims of this study is to apply Friction Stir Welding, comparing different welding parameters and mechanical properties. Utilize Taguchi method to attempt experimental parameters include feed rate, rotating speed, dimension of pushing down and holding time. The experimental results are shown most of cracking concentrated on the bottom of stirring area, but microstructure of Friction Stir Welding do not have macro holes in welding bead. Hardness of 7050 aluminum alloy elevate greatly because of plastic deformation and grain refining by FSW. Whether horizontal or vertical welding bead make hardness of 7050 aluminum alloy elevate, but elongation decrease significantly. Welding bead of 7050 aluminum alloy make hardness degrade by FSW. Friction Stir Welding is not suitable for 7050 aluminum alloy welding.
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Fu, Chien Hao, and 傅建豪. "The Formation of Shear Bands in 7050 Aluminum Alloy and Alminum Single crystal." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/82472822794529121989.
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碩士國立清華大學
材料科學工程學系
90
The formation of shear bands and the true stress - true strain curves were studied by plane strain compression of 7050 Al alloy and pure Al single crystal. Two types of plane strain compression specimens were studied. One is channel die specimens and the other is thin sheet specimens. The plane strain compression test was conducted at room temperature by compression in S direction to different amount of reduction in thickness with T or L direction constrained. Macroscopic shear band was observed in compression of 7050 Al alloy. Assuming that the formation of shear bands was determined by the plane of maximum shear stress in continuum mechanics, the fluctuation of true stress - true strain curves of channel die and thin sheet specimens can be simulated by the ideal σ/2τy vs. ε curve. Most of the angles of shear bands of channel die specimens are between 40˚ to 50˚. Most angles of shear bands of thin sheet specimens are between 45˚ to 57˚. This result can be explained by the shape of specimens and the characteristics of the dies. Pure Al single crystal specimen in Cubic {100}<001>, Goss {110}<001> and Brass{110}<1-12> orientation were plane strain compressed in a channel die. In contrast to 7050 Al alloys, no macroscopic shear bands were observed in Al single crystals specimens. For all single crystal specimens, the true flow strength increase monotonically with true strain. The Cubic and Brass oriented single crystals have nearly the same initial flow strength. They both show linear work hardening behavior but the work hardening rate of Cubic oriented crystal is higher than that of Brass oriented crystal. In contrast, the Goss oriented crystal shows a higher initial flow strength and a parabolic work hardening behavior with a decreasing work hardening rate. The flow strength of Cubic oriented crystal goes above that of Goss oriented crystal when the true strain is larger than 0.5. In the compression test, the initially cubic shaped Al single crystal in Brass orientation gradually turns into a parallelepiped. The acute angle of the parallelepiped as a function of compressive strain can be predicted by the slip of the active systems of Brass orientation.
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Lee, Jui-Hsien, and 李瑞賢. "The Study of Mechanical Properties after Thermal Cycling in 7050 T6 Aluminum Alloy." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/ym975w.
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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
This study investigated the mechanical properties and microstructures of 7050-T6 aluminum alloys (AA7050-T6) after heat cycling at 60°C, 85°C, and room temperature (25°C). The experimental methods were as follows: (a) For the mechanical properties, the Rockwell B scale was used to identify the hardness, the International Annealed Copper Standard was used to obtain the electrical conductivity, and a tensile test was conducted to measure the elongation; and (b) An optical microscope was used to observe changes in microstructures of the AA7050-T6 during thermal cycling. The results revealed that the hardness fluctuated irregularly yet no significantly after thermal cycling at 25°C and 60°C. The hardness also fluctuated after heat cycling at 85°C. During the 25th–55th cycles at 85°C, the overall hardness increased gradually. However, the hardness did not vary substantially after the 60th heat cycle, although the magnitude of change exceeded that observed during heat cycling at 65°C and 25°C.The experimental results also demonstrated that the conductivity was inversely proportional to the hardness. The tensile test results revealed similar elongation rates among the samples subjected to thermal cycling at the three temperatures. All fractures were therefore similar in type and were brittle fractures. Shorter fractures exhibited increasingly more substantial secondary cracks. Metallographic observation of the AA7050-T6 microstructure revealed that the smaller the crystal grains were, the greater the yield strength and hardness were.
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CHIANG, YUN-CHENG, and 江昀晟. "Effect of Aging Treatment on the Microstructure and Material Properties of the 7050 Aluminium Alloy." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/33qry8.
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碩士南臺科技大學
機械工程系
107
In this paper, the effects of differentheat treatment processes on the microstructures and mechanical properties of the AA 7050 aluminum alloy under different heat treatment condition were investigated by optical microscope, X-ray diffraction analyzer, scanning transmission electron microscope, Rockwell hardness tester, wear resistance tester and tensile test machine.The heat treatment process includes artificial aging and Retrogression and Reaging treatment, and avoid excessive grain growth , the artificial aging temperature is selected below the recrystallization temperature of the aluminum alloy. Then discuss the influence of microstructure and mechanical properties. According to the research results of this thesis, the samples subjected to aging, recovery and aging, and T6I6 aging treatment can effectively improve the hardness and tensile strength, and can be kept in the unheated sample regardless of the heat treatment process. A fairly close ductility, especially as a result of the heat treatment of T6I6, maintains the same ductility as the unheated test piece.The experimental data of this thesis shows that the AA7050 aluminum alloy is solution treated in an environment of 475 ° C for one hour, and then subjected to water quenching, and then preheated at 140 ° C for 3 hours, and then applied at 60 ° C for 24 hours. The low temperature aging of the hour, and finally the application of the sample held at 140 ° C for 3 hours can obtain the best mechanical properties. In the observation of the transmission electron microscope, fine and dense precipitates were evenly dispersed in the base of the sample treated with T6I6 heat treatment. According to the analysis results of EDS, the precipitates were common strengthening phases of general 7 series aluminum alloys. η' (MgZn2). It can be seen that the mechanical properties of the 7050 aluminum alloy can be effectively influenced according to the density and size of the precipitate.
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Yang, Sheng-Tseng, and 楊盛增. "The Corrosion Fatigue Properties of 7050 Aluminum alloys in different heat treatments." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/90667783589319037442.
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碩士國立中央大學
機械工程學系
85
Abstract This study investigated the corrosion fatigue properties of 7050 aluminum alloys in different heat treatments. In particular, the fatigue life and fatigue crack growth rate in air and 3.5 wt% NaCl solution for specimens in various tempers were compared. The effect of the fatigue and stress corrosion cracking mechanisms on the corrosion fatigue behavior was characterized. Fractograph and microstructure analyses with scanning electron microscoy (SEM) and optical microscoy (OM) were conducted to determine the corrosion fatigue crack initiation and propagation mode. Results showed that in all tempers both fatigue life and fatigue crack growth rate tended to be worse in corrosive environment than in air. The effect of NaCl solution facilitates the fatigue crack initiation at corrosion pits and enhances crack propagation by hydrogen embrittlement as compared to air alone. 7050 Aluminum alloy in T73 temper exhibited longer fatigue life in air but shorter fatigue life in 3.5 wt% NaCl as compared to that in T6 temper. This is attributed to the fact that fatigue crack initiation is easier from corrosion pits in T73 than in T6 under corrosive environment. Microstructural observations indicate that corrosion fatigue cracking is transgranular type and stress corrosion cracking is intergraular. Therefore, improvement of grain boundary characteristics by overaging treatment such as T73 to increase the stress corrosion cracking resistance did not guarantee the improvement of corrosion fatigue resistance. Fractography analyses indicate that corrosion fatigue cracks mostly initiated from corrosion pits followed by feathery river line features and striations as the cracks stably grew until final fracture. The striations observed in corrosive environment are brittle type in contrast to the ductile ones observed in air.
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Tehinse, Olayinka. "Response of 7075 and 7050 aluminium alloys to high temperature pre-precipitation heat treatment." 2014. http://hdl.handle.net/1993/23892.
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Al-Zn-Mg-Cu (7xxx series) aluminium alloys are widely used for aircraft structures. It is difficult to obtain a combination of optimal strength and stress corrosion cracking (SCC) resistance for these alloys. It appears that SCC resistance of these alloys is related to grain boundary precipitate morphology. One technique to control the grain boundary precipitate morphology is to introduce a controlled cooling procedure referred to as High Temperature Pre-precipitation (HTPP) treatment following the solution heat treatment. There is need for a detailed study of the effect of HTPP on the properties of commercial Al-Zn-Mg-Cu alloys using different intermediate temperatures. In this thesis research, the results of ten HTPP processes applied to 7075 and 7050 commercial 7xxx series alloys are presented in terms of hardness, electrical conductivity, corrosion resistance, TEM analysis of grain boundary precipitate morphology and EDS analysis of solute concentration profile at the grain boundary. Results indicate that subsequent to HTPP processing, the 7050 alloy can be precipitation aged to a higher hardness compared to 7075; this result is associated with the modification of 7050 alloy by zirconium versus chromium in 7075 alloy. HTPP heat treatment achieves better SCC resistance compared to standard T6 temper. However, it does not appear that HTPP can achieve a combination of hardness, electrical conductivity and corrosion resistance superior to standard T6 and T7X tempers.October 2014
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Liu, Chih-Yao, and 劉至曜. "Effects of Soldering Temperatures on the Mechanical Properties and Corrosion Resistance of 7050 Aluminum Alloy." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/88436920589785652367.
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碩士國立雲林科技大學
機械工程系碩士班
101
The grain size, tensile strength, elongation, and corrosion properties of the 7050 aluminum alloy have been investigated after 48 hours of heat treatment at various soldering temperatures 150℃, 180℃, 210℃ and 240℃. After the heat treatment the micro hardness testing and tensile testing were used to measure the surface hardness and tensile strength, respectively. The tensile fracture morphology was observed by scanning electron microscope (SEM) with energy dispersive spectrometer (EDS). The corrosion potential and corrosion current density were measured by electrochemical testing to determine the corrosion resistance of 7050 aluminum alloy after heat treatment and soldering temperatures. The results showed the grain structure was mixed of cell-like and the island-like grain. The average grain size was about 30-40μm for non soldering temperature treatment. After heat treatment at 210℃to 240℃, the average grain size was about 50-60μm . Therefore, increasing with the soldering temperature increased the grain size. After 48 hours heat treatment at 150℃, 180℃, 210℃ and 240℃, the tensile strengths of 7050 aluminum alloy were 612, 536, 480, 365MPa, and the micro hardness were 175, 127, 107, 99HV, respectively. The results showed increasing with the temperature decreased the tensile strength and hardness. The results of the electrochemical tests showed the corrosion potential (Ecorr) were -0.78, -0.86, -0.96 and -1.11V, and the corrosion current (Icorr) were 1.02×10-8, 7.36×10-7, 2.65×10-7 and 2.46×10-6 A/cm2 in 3.5 wt.% NaCl solution after 48 hours heat treatment at 150℃, 180℃, 210℃ and 240℃, respectively. The main corrosion products were alumina.
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Lin, Yuan-Yuan, and 林淵源. "The Development of Shear Bands in Plane Strain Compression of 7050 Aluminum Alloys." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/59854813254898381600.
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Yu-TingLi and 黎寓庭. "Effects of Annealing and Solution Treatment on Microstructure and Tensile Properties of 7001 Aluminum Alloy Tube." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/46nce3.
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碩士國立成功大學
材料科學及工程學系
103
7001 aluminum alloy tube has higher strength but lower ductility in Al-Zn-Mg-Cu alloy system. Heat treatments are conducted to improve formability before plastic process. Annealing―415℃/2h→260℃/2h→RT(by furnace cooling) and solution treatment―490℃→RT(by water quenching) were used in this study. Microstructure observation by OM and SEM, phase analysis by XRD and DSC, and tensile tests were done. Properties of parallel and vertical to extrusion direction were investigated respectively. As the results showed, microstructure (alignment of particles and texture) affected the tensile properties, but no obvious difference of tensile properties between two directions. After annealing, Al matrix became soft and second phases particles remained, which caused low strength and high ductility. The major fracture mode was ductile fracture, and dimple distributed throughout the fracture surface. After solution treatment, most second phases dissolved into matrix, leading to supersaturated state of material. During deformation, it showed high work hardening rate and exhibited larger uniform elongation than annealing treated one, and it ruptured in shear fracture mode. As a whole, solution treatment had a bigger benefit of improving formability before plastic process.
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Tzeng, Kuang-Hui, and 曾光輝. "The Study of Microstructures and Mechanical Properties after Natural Aging in 7050 Aluminum Alloys." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/96308297710863583127.
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碩士中興大學
材料科學與工程學系所
99
Aluminum alloy is mass-produced in the market for its material extrusion due to high opposite strength, light in weight and high heated electric conductivity and excellent superconductivity and it is easily shaped to be manufactured and it is broadly used in many fields, such as operational medical equipments, aircrafts, 3C products, mobile devices, bicycles, automobiles, all kinds of sport rackets and linear rails. The study is mainly discussed to experiment different natural aging by using over-aged ways and ends up getting the impact towards aluminum alloy 7050 microstructure and machinery property. The experiment targets Al-Zn-Mg-Cu of 7050 test bar and divides A and B groups. A group will proceed 475°C and stay for one hour and quickly quenches to room temperature. There are four different natural agings-0 hr, 50 hr, 150 hr and 250 hr. The process of B group will proceed 475°C and stay for one hour , and quickly quenches to room temperature with four different natural agings-0 hr, 50 hr, 150 hr and 250 hr, and final T73 artifictial aging 120℃ for 10 hr and 177℃ for 8 hr. I proceed the research and analysis via the observation of OM,SEM,EDS and XRD. Analysis of components, tensile test, hardness and electrical conductivity and etc. According to the result of the experiment, A group owns more precipitant as the natural aging is increased. When natural aging at 250Hr, precipitant quantities and hardness are the maximum, but the electric conductivity is the minimum. So this process the base speed of precipitant. For B group after T73, with OM observation, the precipitant is the densest and smallest at natural aging 50Hr. much dense, so the hardness reaches HRB 88, the ultimate tensile strength reaches 589.2 MPa and the yield strength reaches 545.2 MPa. The lowest conductivity is 38.9%IACS. When the test is conducted at 150 hr and 250 hr after natural aging 50 hr, both the hardness is 579.2 MPa、572.6 MPa and UTS gradually decline. Electric is 39.3%IACS and 39.6%IACS conductivity increases and the stretch remains the same. Therefore, with natural aging without artificial aging treatment, the hardness grows as time increased. After artificial aging treatment, the optimum strength is at natural aging 50 hr.The grain size is almost the same. Therefore, the main concern to influence the strength is the particle size of the second phase and volume percentage.
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Chou, Jyh-cyen, and 周志勤. "The Influence of Mean Stress and Loading Frequency on the Corrosion Fatigue Properties of 7050-T6 and 7050-T73 Aluminum Alloys." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/09314847651074574942.
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碩士國立中央大學
機械工程學系
86
This study investigated the influence of mean stress and loading frequency on the corrosion fatigue properties of 7050-T6 and 7050-T73 in 3.5 wt% NaCl solution. Crack opening levels were measured under different loading conditions in order to understand the effects of mean stress and loading frequency on the oxide-induced crack closure levels. Furthermore, the roles of SCC and mechanical fatigue mechanisms in influencing the corrosion fatigue properties of such alloys were investigated by subtracting the Results showed that an increase in mean stress level of cyclic loading resulted in faster crack growth rate and shorter fatigue life for 7050 aluminum alloys tested in salt water. The corrosion fatigue life was reduced as a result of decreasing loading frequency. However, as the loading frequency decreased, the fatigue crack growth rate increased at intermediate and high stress intensity factor ranges (DKs) and decreased at low DK. The reverse frequency dependence of the fatigue crack growth rate is attFractography analyses indicate that corrosion fatigue cracks of 7050-T6 and 7050-T73 initiated mostly from the corrosion pits and propagated transgranularly under various loading conditions applied in this study.
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Chung, cc, and 鍾群敏. "The study of microstructure on strength and stress corrosion resistance of 7000-series aluminum alloys." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/33546911841389107268.
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碩士國立中央大學
機械工程學系
84
This research proceeds to control the microstructure of the alloys by heat treatment in the manufacturing process of aluminum alloys for aerospace.Furthermore,the effects of the microstructure on the stress corrosion cracking properties will be investigated.Therefore,the high strength and high stress corrosion cracking resistance of aluminum alloys for aerospace will be obtained by adjusting the heat treatment in the manufacturing process.Thus,by controlling the quenching rate after solution treatment and retrogression and reaging treatment will also be used to control the precipitation structure.The result shows strength and stress corrosion cracking resistance can be obtained by the above ways.
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Kumar, K. "Studies On Friction Stir Welding Of Precipitation Hardenable Aluminium Alloys." Thesis, 2009. http://hdl.handle.net/2005/720.
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Friction Stir Welding (FSW) is an emerging solid state welding process. It has been a proven method for welding high strength aluminium alloys which were previously not recommended for conventional fusion welding. Since the invention of the process by The Welding Institute, United Kingdom, in 1991, a number of studies have been conducted on the material flow, microstructural evolution and mechanical properties of friction stir welds. However, there is not enough conceptual background available on FSW process for physical understanding of the mechanism of weld formation. In addition to that, FSW welds of high strength precipitation hardenable aluminium alloys suffer from reduced joint efficiency due to overaging in the heat affected zone. In the present investigation, experimental analysis has been carried out to understand the mechanism of weld formation and parameter optimization for aluminium alloys 7020-T6 and 6061-T6. For this purpose the investigations have been made on both the process aspects and the material aspects.
The process aspects are analyzed with the objective of learning the mechanism to produce defect free welds. For this purpose experiments have been carried out to analyze the effect of FSW parameters, material flow and the frictional characteristics between the tool and base metal. Preliminary experiments are conducted on aluminium alloy 7020-T6 with different tool geometries to analyze the interaction of the tool with the base metal using a knee-type vertical milling machine. Then, the tool geometry which produced defect-free weld is used for further experimentation. The role of tool pin, shoulder and axial load on the formation of defect free weld is analyzed in an innovative experiment, where the tool and base metal interaction is continuously increased by continuously increasing the interference between the tool and base metal. In another experiment the initial abutting interface position with respect to the tool is continuously varied to study the interaction of the tool with the initial interface and to find the positional information where the initial interface is completely eliminated. Further, the tool metal interface condition is studied using a specially designed tribological experiment which simulates the FSW condition.
From the base metal point of view, due to the strain, strain rate and temperature imposed on the base metal during the process, the microstructure is altered. In precipitation hardenable aluminium alloys the strengthening precipitates are dissolved or overaged in the weld region depending on the peak temperature in the region, which reduces the joint efficiency. However, the dissolution and overaging are kinetic process. In order to analyze this time dependant softening behavior of the base metal 7020-T6 and 6061-T6, isothermal annealing and differential scanning calorimetric studies are performed.
In order to obtain FSW welds with maximum joint efficiency, the welding temperature should not exceed the “softening temperature” of the base metal. But, to produce defect free welds favorable material flow in the weld nugget is necessary. The material flow and consolidation depend on the process temperature. Hence, for a given tool to produce defect free weld there is a need for minimum temperature. If the weld formation temperature is less than the base metal softening temperature, the weld can be made with 100% joint efficiency. In order to optimize the FSW parameter which gives defect free weld with lowest possible temperature, an instrumented programmable FSW machine is designed and developed. The machine is designed in such a way that welding parameters – rotation speed, traverse speed and plunging depth – can be continuously varied from the start to end of the weld between given two values. This reduces the number of experimental trials, material and time.
Based on the experimental results the following conclusions are derived.
1.The minimum diameter of the pin required for FSW depends on the base metal and tool material property for a given set of parameters. If the pin diameter is insufficient for a given set of welding parameters, it fails during plunging operation itself.
2.There is a minimum diameter of the shoulder for a given diameter of the pin which produces defect free weld. The ratio of pin to shoulder to produce a defect free weld is not a constant value. It changes with tool geometry and process parameters.
3.Increasing the area of contact between the tool and shoulder for a given set of parameters increases the heat input and results in increased weld nugget grain size.
4.Initial abutting interface of the base metal is eliminated at the leading edge of the tool. However, new surfaces are generated due to interaction with the tool and the newer surfaces are consolidated at the trailing edge of the tool. Importantly, the weld strength is controlled by the defects generated due the improper elimination of newly generated surfaces.
5.Optimal axial load is required to generate the required pressure to consolidate the transferred material at the trailing edge of the tool and should be equal to the flow stress of the material at the processing temperature. The optimal axial load is 8.1kN for a tool having 20mm diameter shoulder with 6mm diameter frustum shaped pin.
6.Only the material that approaches the tool at the leading edge on the advancing side is stirred and the remaining material is simply extruded around the tool. Further, the initial abutting interface is completely removed only when it is located in the stirring zone, otherwise the initial abutting interface is not eliminated. In the present study the interface is completely stirred when it is located on the advancing side of the tool between 0.5mm away from the centerline and edge of the tool.
7.The temperature and pressure at the tool–base metal interface is above the temperature and pressure required for seizure to occur for given tool material (H13) and base metal (7020-T6). Hence, it is clear that during FSW the base metal transfers on to the tool and interaction occurs between transferred layer on tool and base metal. The coefficient of friction between the given tool material and base metal in FSW condition is in the range of 1.2 – 1.4.
8.The minimum temperature requirement for FSW of 7020-T6 is 400oC and 6061-T6 is 430oC. However, 7020-T6 and 6061-T6 softens at lower temperatures than that of the minimum FSW temperature. 7020-T6 softens 30% in 7min at 250oC, 4min at 300oC, 2min at 350oC and 1min at 400oC. After softening 30%, there is 10% recovery in hardness and the hardness remains constant thereafter. Whereas 6061-T6 softens gradually up to 47% in 7min at 350oC and 400oC, below the temperature of 250oC for 7020-T6 and 350oC for 6061-T6 there is no softening observed in 7min.
9.The maximum joint efficiency of the 7020-T6 weld is 82% and 6061-T6 weld is 60%.
10. The reduction in joint efficiency is attributed to overaging of the material in the heat affected zone.
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Huang, Cheng-Chia, and 黃呈加. "Determination of the solidification curve of 7000 series Aluminum alloys by using DTA and mathematical modelling." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/92451755677882134922.
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Martins, José Pedro Ramos. "Análise do efeito de pré-deformação nas propriedades mecânicas cíclicas da liga de alumínio 7050-T6." Master's thesis, 2019. http://hdl.handle.net/10316/86444.
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Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e TecnologiaAs ligas de alumínio da série 7000 são usadas num vasto número de aplicações, devido,principalmente, ao facto de combinarem elevada resistência específica, e boa resistência àcorrosão. A liga 7050 é particularmente atrativa para a conceção de componentesaeronáuticos, o que se deve às suas excelentes propriedades mecânicas, elevada resistênciaà corrosão, e boa tenacidade à fratura. Os componentes aeronáuticos são, muitas vezes,sujeitos a ciclos de carga complexos, variáveis ao longo do tempo, quer em termos de gamade tensão, quer em termos de razão de tensão. A existência de ciclos de carregamento comtensões médias não nulas pode causar deformação plástica adicional, o que pode culminarem falhas prematuras por fadiga, fenómeno responsável por cerca de 90% das roturas ocorridas em serviço.O objetivo deste trabalho é quantificar o impacto da acumulação de deformação nocomportamento da liga de alumínio 7050-T6 em regime da fadiga oligocíclica. Numa primeirafase, são efetuados ensaios em controlo de tensão, que visam a acumulação controlada dedeformação plástica. Numa segunda, são efetuados ensaios em controlo de deformação, comamplitudes variáveis entre 0.5 e 2.0%. Os resultados obtidos são posteriormente comparadoscom resultados para iguais condições de carregamento, mas estes sem pré-deformação aplicada. Após a realização dos ensaios, as superfícies de fratura são analisadas por microscopia eletrónica devarrimento (SEM) para identificação dos principais mecanismos de fratura. É também feita uma análise energética à gama de energia de energia de deformação plástica e total, bem como uma análise à microestrutura do material por difração de raios-x.
The 7000 series aluminum alloys are used in a wide range of applications,mainly because they combine high specific resistance, and good resistance tocorrosion. The alloy 7050 is particularly attractive for the design of componentsaeronautics, which is due to its excellent mechanical properties, high resistancecorrosion, and good fracture toughness. The aeronautical components are,are subject to complex load cycles, varying over time, or in terms of rangeof stress, or in terms of the stress ratio. The existence of charging cycles withtensions can cause additional plastic deformation, which mayin premature failures due to fatigue, a phenomenon responsible for about 90% of the breaks that occurred in service.The objective of this work is to quantify the impact of deformation accumulation onbehavior of the 7050-T6 aluminum alloy under the low-cycle fatigue regime. In a first stress-controlled tests are carried out, aiming at the controlled accumulation ofplastic strain. In a second, strain-controlled tests are carried out, withamplitudes between 0.5 and 2.0%. The results obtained are then comparedwith results for equal loading conditions, but these without pre-deformation applied. After the tests, the fracture surfaces are analyzed by electron microscopy of(SEM) to identify the main fracture mechanisms. An energy analysis is also performed on the energy range of plastic and total deformation energy, as well as an analysis of the microstructure of the material by XRD and microscopy.
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Peng, Huan-Chih, and 彭煥之. "The Effects of Heat Treatment on the Microstructure and Mechanical Properties of 7050 Aluminum Alloys Containing Scandium." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/69994709790602232830.
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碩士元智大學
機械工程學系
96
7000 series aluminum alloys has excellent properties in precipitation hardening. When scandium added that could modify mechanical properties. This study was to investigate the influence of precipitation hardening effect and the mechanical properties on aging treatment during the different heat treatment of 7050 aluminum alloys containing scandium. This study was divided into two parts. First parts of this study investigated the precipitation hardening effect on 7050 aluminum alloys containing scandium during aging treatment. Second part of this study discussed the mechanical properties of this alloy on aging treatment. It is proposed that the optimal aging treatment parameters were aging at 150℃ for 6h followed with 120℃ for 6 h. The microhardness was Hv285 and the ultimate tensile strength and elongation were 666MPa and 6%, respectively. The microstructure of this alloy after aging possessed uniform and fine precipitate in the matrix.
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Shahzad, Majid. "Influence de la rugosité et des traitements d’anodisation sur la tenue en fatigue des alliages d’aluminium aéronautiques 2214 et 7050." Phd thesis, 2011. http://oatao.univ-toulouse.fr/5804/1/Chaussumier_5804.pdf.
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The fatigue of materials and structures is a phenomenon in which surface condition plays an important role; specially in initiating the micro-cracks. Moreover, the structural components are also subjected to aggressive environments and hence are susceptible to corrosion phenomenon. Therefore, it is necessary to protect them against the corrosion phenomenon. For aluminium alloys used in aeronautical applications, anodization is widely used surface treatment to increase the corrosion resistance. Despite the benefits obtained in terms of enhanced corrosion resistance, the anodizing process has a damaging effect on the fatigue performance of the base material. One of the reasons for this decrease in fatigue life is associated to the degradation of surface condition during the anodizing process. In this work, we have studied the influence of machining and anodization on fatigue behaviour of aluminium alloys 2214 and 7050. We showed experimentally that for 2214 alloy the process of anodization-sealing reduced the fatigue life considerably while for 7050 alloy the process of pickling is the major cause in decreasing the fatigue life. We have also developed life prediction model for anodized alloys. The model is based on determination of concentration of stress ‘Kt’ generated by the surface condition. The developed model integrates the aspects of multi-site initiation, coalescence and regime of short crack propagation.
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Balsas, Andreia Cação. "Modelo constitutivo para previsão do comportamento cíclico da liga 7050-T6." Master's thesis, 2019. http://hdl.handle.net/10316/93629.
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Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e TecnologiaEsta dissertação teve como principal objetivo a implementação de um modelo constitutivo que caracterizasse a resposta elastoplástica cíclica da liga de alumínio AA 7050-T6 utilizando o software de elementos finitos ADINA®.A modelação do comportamento cíclico da liga foi feita com base em resultados experimentais obtidos através de ensaios de fadiga oligocíclica efetuados em controlo de amplitude de deformação total, entre 0,6% e 1,75%, e com razões de deformação de -1, 0 e 0,5. O modelo aplicado define o comportamento plástico cíclico do material através do critério de cedência de von Mises, de duas leis de encruamento: isotrópico e cinemático, e de uma regra de fluxo associada ao critério de von Mises. Através das leis de encruamento, respetivas ao modelo constitutivo, e pela metodologia abordada por Prates, [20], obteve-se uma aproximação inicial dos parâmetros de encruamento do material, tendo-se procedido com simulações numéricas dos ensaios de fadiga num sólido cúbico tridimensional. Posteriormente efetuou-se o ajustamento dos parâmetros através da análise comparativa entre as curvas de histerese de tensão-deformação experimentais e as resultantes das simulações numéricas, tendo-se conseguido simular com sucesso a resposta cíclica da liga quando solicitada em controlo de amplitude de deformação de 1,5% a 1%, com razão de deformação -1, 0 e 0,5 e de 1,75% e 0,8%, com razão de deformação de -1 e 0. Conclusivamente, o procedimento desenvolvido é suficientemente robusto para simular satisfatoriamente as formas dos circuitos estáveis, assim como, para determinar as densidades de energia de deformação plástica e total para as diferentes amplitudes e razões de deformação.
The main objective of this study was the implementation of a constitutive model able to characterize the cyclic elastoplastic response of the AA 7050-T6 aluminum alloy using the ADINA® finite element software. The modelling of the alloy's cyclic behavior was based on experimental results from low-cycle fatigue tests performed under strain-controlled mode with total strain amplitudes between 0,6% and 1,75% and strain ratios of -1, 0 and 0,5. The model defines the cyclic plastic behavior of the material according to the von Mises yield criterion, a flow rule related to it, and two hardening laws - isotropic and kinematic. Through the respective constitutive model hardening rules and the methodology used by Prates, [20], an initial estimate of the material hardening parameters was obtained, followed by numerical simulations of the fatigue tests on a tridimensional cubic solid.Afterwards, an adjustment was made to the parameters by means of a comparative analysis between the experimental stress-strain hysteresis loops and those obtained from the numerical simulations, resulting in the successful simulation of the alloy’s behavior, of low cyclic fatigue tests, in constant amplitude strain control of 1,5%, 1,25%, 1% (with strain ratios of -1, 0, 0,5), 1,75% and 0,8% (with strain ratios of -1 and 0). In conclusion, the procedure developed is sufficiently accurate to satisfactorily simulate the stable circuits shapes, as well as to determinate the total and plastic strain energy densities for the several amplitude and strain ratios.
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Branco, Mário Gabriel Ferreira. "Estudo do fenómeno de relaxação de tensões na liga de alumínio 7050-T6." Master's thesis, 2018. http://hdl.handle.net/10316/86043.
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Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e TecnologiaAs ligas de alumínio da série 7000 são usadas num vasto número de aplicações estruturais, devido, principalmente, ao facto de combinarem elevada resistência específica, e boa resistência à corrosão. A liga 7050 é particularmente atrativa para a conceção de componentes aeronáuticos, o que se deve, de uma forma geral, às suas excelentes propriedades mecânicas, elevada resistência à corrosão, e boa tenacidade à fratura. Para além disso, a maioria destes componentes está sujeita a ciclos de tensão e deformação variáveis ao longo do tempo, o que os torna particularmente vulneráveis a falhas por fadiga. Nessa perspetiva, quer o desenvolvimento de novos componentes, quer a definição de intervalos de inspeção adequados, pressupõe a utilização de modelos de previsão de vida tão exatos quanto possível. Ora, o desenvolvimento de um modelo adequado pressupõe, em primeira instância, a utilização de propriedades de fadiga do material rigorosas. A presente tese tem como objectivo principal caraterizar o comportamento da liga de alumínio 7050-T6 no regime da fadiga oligocíclica, dando-se ênfase especial ao efeito da razão de deformação (Rε). Os ensaios são efetuados em controlo de deformação, para amplitudes de deformação (∆ε/2) entre 0.5% e 1.5%, considerando valores de Rε iguais a -1, 0 e 0.5. Após os ensaios, as superfícies de fratura são analisadas por microscopia eletrónica de varrimento, para identificar os principais mecanismos de fratura. .
Aluminum alloys of the 7000 series are used in a wide number of structural applications, mainly because they combine high specific strength and good corrosion resistance. The 7050 alloy is particularly attractive for the design of aeronautical components, which is generally due to its excellent mechanical properties, high corrosion resistance, and good fracture toughness. In addition, most of these components are subject to varying stress and strain cycles over time, which makes them particularly vulnerable to fatigue failure.In this perspective, both the development of new components and the definition of adequate inspection intervals presuppose the use of life expectancy models as accurate as possible. However, the development of an appropriate model presupposes, in first instance, the use of stringent fatigue properties of the material. The main objective of this thesis is to characterize the behavior of the 7050-T6 aluminum alloy in the regime of low-cycle fatigue, with special emphasis on the effect of the strain ratio (Rε). The tests are performed under strain-controlled conditions for strain amplitudes (Δε /2) between 0.5% and 1.5%, considering values of Rε equal to -1, 0 and 0.5. After the tests, the fracture surfaces are analyzed by scanning electron microscopy to identify the main fracture mechanisms. .
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Silva, Paula Isabel Oliveira da. "Comportamento à fadiga de peças entalhadas da liga de alumínio 7050-T6 sujeitas a carregamentos multiaxiais de flexão-torção." Master's thesis, 2021. http://hdl.handle.net/10316/98203.
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Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e TecnologiaAs ligas de alumínio da série 7xxx têm elevada aplicabilidade em engenharia, graças às suas propriedades, nomeadamente baixa densidade, custo relativamente baixo, elevada resistência e boa tenacidade à fratura. Estas propriedades fazem destas ligas um dos materiais ideais para componentes expostos a ciclos de carga resultantes de condições de serviço complexas e em ambientes desfavoráveis.Estes componentes estruturais, devido às condições de serviço a que serão sujeitos, são suscetíveis à ocorrência de falhas em serviço, que muitras vezes estão associados à acumulação de deformação plástica nas descontinuidades geométricas. É, por isso, fundamental estudar e compreender o fenómeno de fadiga nestas ligas para várias geometrias, de modo a desenvolver componentes mais seguros e fiáveis.O objetivo deste trabalho consiste em analisar o comportamento à fadiga em provetes com entalhes laterais concebidos a partir da liga de alumínio 7050-T6, quando sujeitos a esforços combinados de flexão e torção. Serão feitos ensaios experimentais de fadiga para diferentes relações entre as tensões normais e as tensões de corte, considerando diferentes níveis de tensão para uma razão de tensão próxima de zero.Com os dados experimentais, far-se-á o estudo da evolução da fenda de fadiga, desde o local e a trajetória de iniciação de fenda por fadiga. Analisar-se-ão as superfícies de fratura e comparar-se-ão estes resultados com outros trabalhos desenvolvidos sobre o tema.Posteriormente, desenvolver-se-ão modelos numéricos de previsão dos locais de iniciação e das direções de propagação de fenda, os quais se compararão com os resultados experimentais obtidos.
7xxx aluminium alloy series are widely used in engineering due to their properties, such as low density, low price, high strength and good fracture toughness. All the mentioned properties make these alloys ideal materials for components subjected to cycle loading, resulting from complex operational conditions and an adverse environment. These structural components, due to the specific service conditions, are susceptible to in-service failure, which may result premature fatigue failure, especially in critical geometric discontinuities, where accumulation of plastic deformation can occur. These reasons make important the understanding of fatigue behavior for these alloys, in order to improve fatigue design of engineering components.The purpose of this study is to analyze the fatigue behavior 7050-T6 alluminium alloy components subjected to multiaxial loading. Fatigue test will be performed for different bending-torsion relations, considering several stress levels, for a stress ratio close to zero.With experimental data, fatigue behavior will be analyzed, namely the crack initiation sites fatigue crack paths in the early stage of growth and fracture surfaces. These results will be compared to those obtained for other studies.Finally, a numerical model will be used to predict the fatigue crack initiation sites ans fatigue crack angles in the early stage of growth, and the results will be compared to the experimental observations.