Dissertations / Theses on the topic 'Deformation phase'
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1
Singh, Shiv Brat. "Phase transformations from deformed austenite." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246513.
2
Sandala, Rebecca Sarah. "Deformation mechanims of two-phase titanium alloys." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/deformation-mechanims-of-twophase-ttitanium-alloys(50a395c3-70f6-49f7-a3df-41d2f899a851).html.
Abstract:
Two-phase Ti6246 alloy is a light weight material exhibiting very high strength at higher temperatures compared to the commonly used Ti64 alloy. This particular alloy is used at the later stages of compressor discs within the aero engines. However, compressor discs undergo a number of cyclic stresses, which could eventually lead to fatigue failure. In order to optimize the microstructure for design and lifing models, an improved understanding of the localised deformation mechanisms is crucial, particularly at the surface, as cracks can be initiated leading to failure and in turn affect the life expectancy of the component. Two-phase alloys in use have very complex lamellar microstructures comprising of a mixture of coarse and fine phases and their role in deformation can be very complex and difficult to understand. The focus of this study was particularly based on the importance of the beta phase in strengthening two-phase microstructures. Therefore, this study has been simplified to compare model lamellar microstructures, which have particular sizes of beta phase in between alpha lamellae. Digital Image Correlation along with high resolution imaging was used to develop a detailed understanding of the localised deformation in these microstructures. Widening the beta phase in-between alpha lamellae caused a more homogenous deformation, while ageing the beta phase with fine secondary alpha strengthened the microstructure. However, all microstructures showed that the single continuous alpha layer at beta grain boundaries depicted the highest amount of deformation, which can be detrimental for the life of the component. The behaviour of slip at the α/β interface not only depended on the size of the phases but also depended on the neighbouring crystallographic orientations and the relationship of the two phases, specifically the alignment of the close packed slip directions. Strain maps of these microstructures were subsequently related to corresponding Schmid factor maps and crystal plasticity models to improve this understanding.
3
Djazeb, Mohammad Reza. "High temperature deformation of two-phase Al-alloys." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46282.
4
Hedström, Peter. "Deformation and martensitic phase transformation in stainless steels /." Luleå : Department of Applied Physics and Mechanical Engineering, Division of Engineeing Materials, Luleå University of Technology, 2007. http://epubl.ltu.se/1402-1544/2007/67/.
5
Kismarahardja, Ade Wijaya. "The Deformation-Induced Phase Transformation in Gold Nanoribbons." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23034.
Abstract:
The tensile experiment for nanomaterials in a transmission electron microscope (TEM) has become a very important tool to study the atomic deformation of material at nanoscale. An enormous amount of effort has been spent to perform the tensile experiments on nanomaterials. They revealed new discoveries that have never been observed in bulk materials and eventually lead to further applications. In this thesis, experimental reports of tensile test on gold nanoribbons in TEM were reported. The gold nanoribbons have 4H structure but the FCC structure could coexist in some areas. Gold nanoparticles have been studied intensively in the past decades due to their extraordinary properties and promising applications. The rise of chemical syntheses technology has stimulated further exploration of gold nanoparticles in recent years. The wet chemical technique has successfully created more closed-packing structures that have never been discovered before, including 4H gold nanoribbons. Even though the latest syntheses techniques have created many interesting structures, the investigation of their mechanical properties seems to be very difficult to perform. The tensile experiment on gold nanoribbons has never been performed. This thesis reports the first investigation of the mechanical properties of gold nanoribbons by using tensile test in TEM. Phase transformation from 4H to FCC or vice versa were observed. The dislocation in the structures leads to the phase transformation. Furthermore, necking has also been observed during tensile test, particularly in the FCC structure which eventually lead to ductile fracture. However, necking was also observed in 4H structure. In addition to this, coalescence between two nanoribbons was also observed during tensile.
6
Sinclair, Chad. "Co-deformation of a two-phase FCC/BCC material /." *McMaster only, 2001.
7
Jenkins, Brent Allan. "Phase transformations and deformation metallography in dilute uranium alloys." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670343.
8
Yamaguchi, Masashi. "Phase-field simulation of dendritic growth under externally applied deformation." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/2792.
Abstract:
Defects, i.e. hot tears, macrosegragation, and pores, formed in metal castings are a result of stresses and strains in the solid-liquid mushy zone. Numerical simulation of solidification of deforming dendrite crystal promises to improve insight into the mechanical behavior of mushy zones under an applied load. The primary goal of this thesis is to develop numerical methodologies for performing solidification simulation of deforming dendrites. Such simulation encounters difficulties associated with the interface dynamics due to phase change or interaction among the dendrites, and large visco-plastic deformation applied to them. Phase-field simulation of dendritic solidification is promising for the treatment of the complex interface dynamics. Free energy based formulation allows the model to incorporate bridging and wetting phenomena occurring at grain boundaries through an extra energy term which arises from a mismatch of the crystallographic orientation. The particle method would be attractive to handle large inelastic deformation without suffering mesh entanglement. In order to investigate the effect of solid deformations on the evolving microstructure, the material point method with elasto-visco-plasticity constitutive model is developed to couple to a phase-field model of solidification. The changes in the crystallographic orientation of a growing dendrite crystal due to solid deformation are carefully accounted for through the coupling methodology. The developed numerical framework is applicable to the simulation for single and multiple crystals, and is capable of handling complex morphological change. The wide variety of validations and practical problems solved in this thesis demonstrates the capability of investigating deformation behavior of growing crystals.
9
Hill, Thomas. "Evolution of second phase particles with deformation in aluminium alloys." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/evolution-of-second-phase-particles-with-deformation-in-aluminium-alloys(e87af2eb-bf04-46d5-9b51-d44d4584c579).html.
Abstract:
The effect of high temperature, high strain rate deformation on the evolution of second phase particles in commercial aluminium alloys has been investigated. Three model alloys provided by Novelis have been examined, and the evolution of particles during deformation has been examined for the alloy that most closely resembles the composition of alloys used in commercial applications. The effect of deformation mechanisms was expected to be an enhancement of diffusion controlled processes; therefore the first part of the work was to develop a heat treatment that would produce a fine distribution of dispersoid particles. This heat treatment was then used to prepare material for torsion testing, at strain rates similar to those found during the hot rolling stage of commercial production. Testing was performed at both the end of heat treatment temperature, to remove thermal effects, and at a lower temperature which more closely represents the temperature during commercial rolling. Material was examined by optical microscopy, FEGSEM and TEM and the particle populations were characterised by backscattered FEGSEM imaging and image analysis. This demonstrated that the disperoid particle population develops in multiple ways. Along with the enhancement of coarsening there is a significant shape change to the dispersoid particles, suggesting a change in the character of their interface. It has also been demonstrated that there is nucleation of new particles, despite a long prior hold time, in material deformed at the same temperature as the heat treatment. Material deformed at lower temperatures also demonstrated a larger increase in the volume fraction of dispersoid than material with the same thermal history. A constitutive model for diffusion enhancement and a model for particle evolution have been combined to simulate the effects of thermomechanical processing on the particle population.
10
Zhang, Nianxian. "Processing of a two-phase alloy by severe plastic deformation." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/388051/.
Abstract:
This thesis presents a systematic study on evolutions of microstructure, microhardness and superplasticity of a Pb-62% Sn alloy processed by both equal-channel angler pressing (ECAP) and high-pressure torsion (HPT) and the subsequent self-annealing process at room temperature (RT). The Pb-Sn alloy exhibits characteristics with significant grain refinement after processing by ECAP and HPT but with a reduction in the hardness values by comparison with the initial as-cast condition. For HPT processing, it is shown that there are generally smaller grains at the edges of the discs by comparison with the disc centres. The hardness results are different from those generally reported for conventional single-phase materials where a hardening trend was commonly observed after HPT processing. The significance of this difference is examined. The microstructures of the alloy after HPT were repeatedly investigated during the course of self-annealing by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and scanning electron microscopy (TEM). A significant grain growth combined with increase of microhardness was observed. It was demonstrated that there was a large fraction of twin boundaries with a twin relationship of 62.8°<100> in the microstructure for the as-cast condition. Owing to the presence of high pressure, the mobility of Ʃ21 boundaries at 71° was greatly favoured during processing by HPT. But the mobility of the dislocation-twin boundary near 62.8°<100> was favoured during self-annealing at RT once the high pressure was removed. The HPT processing significantly increased the solubility of Sn in Pb phase. This supersaturated state of Sn in Pb is, however, not stable at RT during self-annealing and therefore a decomposition of Sn from Pb-rich phase was observed after 16 days of storage. Lattice diffusion should be considerable as the main mechanism for the decomposition. Moreover, abnormal grain growth was observed to be greatly favoured during self-annealing when the introduced strain was relatively low, i.e. 2 passes by ECAP and the centre region of a HPT-processed disc after one turn. Consequently, a series of HPT-processed samples with different storage time was tested in tension at RT and at 1.0 × 10-4 - 1.0 × 10-1 s-1. The results demonstrated that, despite the storage time, all processed alloy exhibited excellent RT superplasticity at 1.0 × 10-4 s-1 and the highest elongation of 630% was recorded in the processed alloy after storage for 4 days at RT. The detailed investigation showed, due to the high strain rate sensitivity of the processed alloy, a transition strain rate of ~1.0 × 10-2 s-1 was observed in which stain softening with ductile behaviour is apparent due to active GBS below the transition point but high strength is observed because of grain boundary strengthening above the transition during plastic deformation at RT in the Pb-Sn alloy after HPT. Nanoindentation tests were then performed applying both indentation depth-time (h-t) relationship at holding stage and the hardness, H, at various loading rates to explore the evolution of strain rate sensitivity (SRS), m. The results obtained by both tensile test and nanoindentation show that the relatively fast self-annealing of the HPT-processed Pb-62% Sn eutectic alloy is occupying by an unambiguous changing-tendency of strain rate sensitivity. The results confirm the validity of using nanoindentation for measuring strain rate sensitivity.
11
Belchev, Borislav Stefanov, and University of Lethbridge Faculty of Arts and Science. "Deformation quantization for contact interactions and dissipation." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy, c2010, 2010. http://hdl.handle.net/10133/2490.
Abstract:
This thesis studies deformation quantization and its application to contact interactions
and systems with dissipation. We consider the subtleties related to quantization
when contact interactions and boundaries are present. We exploit the idea that discontinuous
potentials are idealizations that should be realized as limits of smooth
potentials. The Wigner functions are found for the Morse potential and in the proper
limit they reduce to the Wigner functions for the infinite wall, for the most general
(Robin) boundary conditions. This is possible for a very limited subset of the
values of the parameters -- so-called fine tuning is necessary. It explains why Dirichlet
boundary conditions are used predominantly. Secondly, we consider deformation
quantization in relation to dissipative phenomena. For the damped harmonic oscillator
we study a method using a modified noncommutative star product. Within this
framework we resolve the non-reality problem with the Wigner function and correct
the classical limit.iii, 188 leaves ; 29 cm
12
Kalu, Peter Nwankwo. "The deformation of some two-phase Al-alloys at elevated temperatures." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38061.
13
Mazinani, Mohammad. "Deformation and fracture behaviour of a low-carbon dual-phase steel." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/30951.
Abstract:
The primary goal of this study was to evaluate the effect of martensite plasticity on the
deformation and fracture behaviour of an intercritically annealed commercial low carbon (0.06
wt.%) dual phase steel. The volume fraction and the morphology (banded and almost equiaxed)
of the martensite phase were systematically varied by control of the intercritical annealing
temperature and the heating rate to this temperature. It was observed that the yield and tensile
strengths were dependent on the martensite content but not on the martensite morphology. On
the other hand, the true uniform strain, fracture strain and fracture stress were found to have a
significant dependence on martensite morphology.
An Eshelby based model, which allowed for the calculation of the stress in the martensite
islands, was employed in order to rationalize the tensile properties of the dual-phase steel
samples with different martensite contents and morphologies. In addition, by comparing the
calculated stress in the martensite with an estimate of yield stress, it was possible to examine
the conditions under which martensite plasticity occurs. The work hardening behaviour and the
fracture properties of the steel samples were rationalized by the implications of martensite
plasticity. For the cases where martensite showed significant plasticity (or co-deformed with
the ferrite matrix), the void nucleation rate during post-necking deformation decreased
considerably and hence, the final fracture properties were dramatically improved.
The deformation of martensite in different dual-phase steel samples was examined both
qualitatively (using optical micrographs of the undeformed and deformed sections of fractured tensile samples) and quantitatively (through image analysis of the microstructures before and
after tensile deformation). The tensile stress-strain responses of different dual-phase steel
samples were modeled using the modified Eshelby method. This approach was found
appropriate for modelling the stress-strain behaviour of the steels with equiaxed morphology
and martensite contents below approximately 30%. In the case of banded morphology, the
stress-strain behaviour of the steel sample with 17% martensite was successfully predicted by
the model. However, the model overestimated the flow stress of the steel with 30% martensite.
For the martensite contents greater than 30%, the overestimation of the flow stress of the steel
samples with banded morphology was greater than that for the equiaxed samples.
Finally, the void formation process during tensile deformation was examined quantitatively
through image analysis of the fracture surface of the steels. The experimental results showed
very little void growth during ductile fracture of the steel samples with 17% and 41%
martensite. Modelling the void formation process in these steels assuming no void growth stage
resulted in the same observation. This confirmed the quantitative observation that void
nucleation is the dominant effect during ductile fracture of these steels.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
14
Gayle, Frank Wentzel. "Phase transformations and deformation behavior in the aluminum-lithium-zirconium system." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15262.
Abstract:
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Vita.
Includes bibliographical references.
by Frank Wentzel Gayle.
Sc.D.
15
Pelemo, David Ayo. "High temperature deformation of a two phase titanium alloy IMI-550." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47217.
16
Sircar, S. "The deformation and annealing behaviour of some two-phase aluminium alloys." Thesis, University of Manchester, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488374.
17
Wang, Liu Sheng. "Shape and deformation measurement of 3D surface using phase stepping speckle interferometry." Thesis, Nottingham Trent University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386409.
18
Lainé, Steven John. "The role of twinning in the plastic deformation of alpha phase titanium." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/267425.
Abstract:
The optimisation of compressor stage aerofoil and fan blade design remains an important area of titanium alloy research and development for aerospace gas turbines. Such research has important implications for critical and sensitive component integrity and efficiency. In particular, a better understanding of how deformation twinning interacts with microstructural features in titanium alloys is required, because such twinning facilitates plastic deformation at a higher strain rate than dislocations. To investigate this behaviour, commercial purity titanium and the titanium alloy Ti–6Al–4V were subjected to ballistic impact testing at room temperature with a high strain rate of 10³s⁻¹. In addition, a detailed analysis was conducted of three manufacturing processes of Ti–6Al–4V (wt. %) that are likely to cause deformation twinning: metallic shot peening, laser shock peening and deep cold rolling. The results presented in this thesis have furthered the understanding of the role of deformation twinning in the plastic deformation of α-phase titanium. Key findings of the research include the characterisation of deformation twinning types and the conditions that favour certain deformation twinning types. From the analysis of the ballistic testing of commercial purity titanium, the first definitive evidence for the existence of {112‾4} twinning as a rare deformation twinning mode at room temperature in coarse-grained commercial purity titanium is presented. In addition, the ballistic testing results of the Ti–6Al–4V alloy highlighted very different deformation twinning characteristics. Commercial purity titanium deformed plastically by a combination of {101‾2} and {112‾1} tensilve twinning and {112‾4} and {112‾2} compression twinning modes. By contrast, the deformation twinning of Ti–6Al–4V was limited to only the {101‾2} and {112‾1} tensile twinning modes. The two tensile deformation twinning types have very different morphologies in equiaxed fine grained Ti–6Al–4V. {112‾1} deformation twins span multiple grain boundaries and {101‾2} deformation twins reorient entire grains to a twinned orientation. This observation provides evidence for whole grain twinning of equiaxed fine grained Ti–6Al–4V by {101‾2} twinning. Grain boundary interactions between various deformation twinning types and alpha phase grain boundaries in commercial purity titanium and Ti–6Al–4V are reported and analysed. In commercial purity titanium {101‾2} as well as other deformation twinning types were observed interacting across alpha phase boundaries and higher angle alpha phase grain boundaries. The analyses of the manufacturing processes of Ti–6Al–4V highlight the very different dislocation and deformation twinning structures in surfaces processed by these techniques. A notable feature of material processed by laser shock peening is the almost complete absence of deformation twinning, contrasting with the frequent observation of extensive deformation twinning observed in the material processed by metallic shot peening and deep cold rolling. Therefore, the findings suggest that there is a strain rate limit above which deformation twinning is suppressed. The implications of this research are that a better understanding of the conditions that that favour certain deformation twinning types or propagation behaviours will enable more accurate plasticity modelling and better alloy design. This is important for the design and the manufacturing of titanium components and the high strain rate deformation to which titanium components in aerospace gas turbines can be subjected because of bird strike, foreign object debris ingestion or fan blade failures.
19
Хоменко, Олексій Віталійович, Алексей Витальевич Хоменко, Oleksii Vitaliiovych Khomenko, Дар`я Сергіївна Трощенко, Дарья Сергеевна Трощенко, Dar`ia Serhiivna Troshchenko, Л. С. Метлов, Л. С. Метлов, and L. S. Metlov. "Modeling of phase dynamics and kinetics of fragmentation at severe plastic deformation." Thesis, Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна Національної академії наук України, 2015. http://essuir.sumdu.edu.ua/handle/123456789/41631.
20
Al-Sawai, Wael. "Non-equilibrium Phase Transitions in Interacting Diffusions." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7660.
Abstract:
The theory of thermodynamic phase transitions has played a central role both in theoretical physics and in dynamical systems for several decades. One of its fundamental results is the classification of various physical models into equivalence classes with respect to the scaling behavior of solutions near the critical manifold. From that point of view, systems characterized by the same set of critical exponents are equivalent, regardless of how different the original physical models might be. For non-equilibrium phase transitions, the current theoretical framework is much less developed. In particular, an equivalent classification criterion is not available, thus requiring a specific analysis of each model individually. In this thesis, we propose a potential classification method for time-dependent dynamical systems, namely comparing the possible deformations of the original problem, and identifying dynamical systems which share the same deformation space. The specific model on which this procedure is developed is the Kuramoto model for interacting, disordered oscillators. Studied in the mean-field limit by a variety of methods, its associated synchronization phase transition appears as an appropriate model for cooperative phenomena ranging from coupled Josephson junctions to self-ordering patterns in biological and social systems. We investigate the geometric deformation of the dynamical system into the space of univalent maps of the unit disk, related to the Douady-Earle extension and the Denjoy-Wolff theory, and separately the algebraic deformation into the space of nonlinear sigma models for unitary operators. The results indicate that the Kuramoto model is representative for a large class of non-equilibrium synchronization models, with a rich phase-space diagram.
21
DE, KERMERCHOU GUERBERT SYLVIE. "Les hematies en contraste de phase dans les hematuries : experience amienoise et revue de la litterature." Amiens, 1992. http://www.theses.fr/1992AMIEM030.
22
Kiwanuka, Robert. "Micro-deformation and texture in engineering materials." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:3c924d01-7501-4d59-bb53-07e6584e50c5.
Abstract:
This DPhil project is set in the context of single crystal elasticity-plasticity finite element modelling. Its core objective was to develop and implement a methodology for predicting the evolution of texture in single and dual-phase material systems. This core objective has been successfully achieved. Modelling texture evolution entails essentially modelling large deformations (as accurately as possible) and taking account of the deformation mechanisms that cause texture to change. The most important deformation mechanisms are slip and twinning. Slip has been modelled in this project and care has been taken to explore conditions where it is the dominant deformation mechanism for the materials studied. Modelling slip demands that one also models dislocations since slip is assumed to occur by the movement of dislocations. In this project a model for geometrically necessary dislocations has been developed and validated against experimental measurements. A texture homogenisation technique which relies on interpretation of EBSD data in order to allocate orientation frequencies based on representative area fractions has been developed. This has been coupled with a polycrystal plasticity RVE framework allowing for arbitrarily sized RVEs and corresponding allocation of crystallographic orientation. This has enabled input of experimentally measured initial textures into the CPFE model allowing for comparison of predictions against measured post-deformation textures, with good agreement obtained. The effect of texture on polycrystal physical properties has also been studied. It has been confirmed that texture indeed has a significant role in determining the average physical properties of a polycrystal. The thesis contributes to the following areas of micro-mechanics materials research: (i) 3D small deformation crystal plasticity finite element (CPFE) modelling, (ii) geometrically necessary dislocation modelling, (iii) 3D large deformation CPFE modelling, (iv) texture homogenisation methods, (v) single and dual phase texture evolution modelling, (vi) prediction of polycrystal physical properties, (vii) systematic calibration of the power law for slip based on experimental data, and (viii) texture analysis software development (pole figures and Kearns factors).
23
Marco, Breda. "Phase stability in Duplex stainless steels." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423521.
Abstract:
This thesis summarizes the work performed during the research activities developed in the three-years course of scientific training for the attainment of the Doctor of Philosophy degree. The research was mainly focused on the study of the physical metallurgy of Duplex stainless steels, a particular class of stainless steels having a biphasic austeno-ferritic microstructure, with the aim to characterize their microstructural stability as a consequence of heat treatments and cold plastic deformation.
The choice of the research topic was dictated by the increasing use of these steels for industrial applications, being able to provide high-strength features and elevated performances against corrosive attacks, making them particularly suitable and competitive in aggressive environments, also as structural materials. However, there are limitations to the use of Duplex steels, owing to the occurrence of microstructural modifications, either during high-temperature exposures or as a result of cold working, which can compromise their interesting features.
The thesis is organized into three main parts; the first chapter is focused on properties, problems and applications of Duplex stainless steels, providing a general introduction about these materials and in which particular emphasis was given to those metallurgical variables that affect the production process and the microstructural stability. In Chapter 2 and 3, the research activities concerning the effects of heat treatments (Chapter 2) and cold rolling (Chapter 3) the on the Duplex properties are presented and discussed. It was considered appropriate to report a brief summary of literature at the beginning of the second chapter, aimed to provide the reader with the “state of art” on the effects of thermal cycles on Duplex steels properties, whereas the remaining sections of the chapter are a constitutive part of the research activities. In addition, the experimental part discussed in Chapters 2 and 3 has been integrated with a section devoted to the study of Duplex application at an industrial scale (Appendix A), aimed to the employment of these materials in marine environment. Finally, Appendix B reports the results concerning archaeometallurgical studies, which has contributed to the scientific training of the candidate, even if it was not related to the main research topic.
Experiments and training courses were mainly carried out in facilities and laboratories pertaining to the Industrial Engineering Department (DII ) of the University of Padua – and particularly those belonging to the DII “metallurgy group” – under the supervision of Prof. Irene Calliari and Prof . Emilio Ramous. However, certain specific activities have required the involvement of other structures external to the University of Padua; among these, the neutron diffraction measurements were carried out in the INES diffractometer, located at the ISIS facility in the Rutherford Appleton Laboratory (Didcot, UK), in collaboration with Dr. Antonella Scherillo and Dr. Francesco Grazzi (CNR of Florence), while the magnetic measurements were performed in the laboratories of the University of Budapest (BME), in collaboration with Prof. István Mészáros. Moreover, the EBSD analysis on the deformed materials were executed by Dr. Paola Bassani (CNR of Lecco), while the mechanical impact tests were carried out in collaboration with Dr. Cinzia Menapace (University of Trento), in the university laboratories, and with Eng. Marco Pizzo (Unilab Laboratori Industriali srl), in the Exova CTR srl laboratories.
The results of the studies pertaining to the research period and reported in this thesis have contributed to enhance the knowledge about Duplex stainless steels, in relation to the effects that microstructural modifications can induce on the materials properties, and were of appropriate scientific relevance to allowing their presentation in international conferences and their publication in scientific journals.La presente tesi riassume il lavoro eseguito durante l’attività di ricerca svolta nel corso del triennio di formazione scientifica per il conseguimento del titolo di Dottore di Ricerca. L’obiettivo principale è stato lo studio della metallurgia fisica degli acciai inossidabili Duplex, una particolare categoria di acciai inossidabili a struttura bifasica austeno-ferritica, con lo scopo di caratterizzarne la stabilità microstrutturale a seguito di trattamenti termici e deformazione plastica a freddo. La scelta del tema di ricerca è stata dettata dal sempre più crescente utilizzo di questi acciai in ambito industriale, grazie alle loro elevate caratteristiche meccaniche e di resistenza agli attacchi corrosivi che li rendono particolarmente adatti e competitivi per applicazioni in ambienti aggressivi, anche come materiali ad uso strutturale. Tuttavia, esistono delle limitazioni all’impiego degli acciai Duplex, dovute a trasformazioni microstrutturali che possono insorgere durante l’esposizione del materiale a temperature elevate o che possono verificarsi a seguito di deformazioni a freddo, compromettendone le interessanti caratteristiche. La tesi è suddivisa in tre parti principali. Nel primo capitolo è riportata un’introduzione generale sugli acciai Duplex, focalizzata sulle loro proprietà, problematiche e applicazioni, in cui è stata data particolare enfasi alle variabili metallurgiche che ne influenzano il processo produttivo e la stabilità microstrutturale. Nei Capitoli 2 e 3, invece, sono presentate e discusse le attività oggetto di ricerca riguardanti lo studio degli effetti dei trattamenti termici (Capitolo 2) e della laminazione a freddo (Capitolo 3) sulle caratteristiche dei Duplex. Si è ritenuto opportuno esporre all’inizio del secondo capitolo un breve riassunto di lavori presenti in letteratura, con lo scopo di fornire al lettore lo “stato dell’arte” in merito alle conoscenze sugli effetti dei cicli termici sulle proprietà dei Duplex, mentre le restanti sezioni del capitolo sono parte costitutiva dell’attività di ricerca svolta dal candidato. Inoltre, la parte sperimentale discussa nei Capitoli 2 e 3 è stata integrata con una sezione dedicata allo studio dei Duplex in ambito industriale (Appendice A) e riguardante le applicazioni di questi materiali in ambiente marino. Infine, in Appendice B si riportano i risultati ottenuti da uno studio archeometrico di carattere metallurgico, sviluppato nel corso del periodo di Dottorato e che ha contribuito alla formazione scientifica del candidato, seppure il tema in oggetto non sia strettamente correlato all’attività di ricerca principale. Le attività di ricerca, sperimentali e di formazione, sono state principalmente svolte presso i locali e i laboratori del Dipartimento di Ingegneria Industriale (DII) dell’Università degli Studi di Padova, ed in particolare in quelli pertinenti al gruppo di metallurgia del DII, sotto la supervisione della Prof.ssa Irene Calliari e del Prof. Emilio Ramous. Tuttavia, alcune attività hanno richiesto il coinvolgimento di altre strutture esterne all’Università di Padova. Nella fattispecie, le misurazioni di diffrazione di neutroni sono state effettuate nella stazione diffrattometrica INES, situata presso la struttura ISIS nel Rutherford Appleton Laboratory (Didcot, UK) in collaborazione con la Dott.ssa Antonella Scherillo ed il Dott. Francesco Grazzi del CNR di Firenze, mentre le misure magnetiche sono state condotte presso i laboratori dell’Università di Budapest (BME), in collaborazione con il Prof. István Mészáros. Le analisi EBSD sui materiali deformati sono invece state realizzate dalla Dott.ssa Paola Bassani del CNR di Lecco, mentre le prove meccaniche di tenacità ad impatto sono state effettuate in collaborazione con la Dott.ssa Cinzia Menapace dell’Università di Trento, presso i laboratori universitari, e con l’Ing. Marco Pizzo (Unilab Laboratori Industriali srl), presso i laboratori Exova CTR srl. I risultati riportati nella presente tesi hanno contribuito ad ampliare la conoscenza degli effetti delle modificazioni microstrutturali sulle caratteristiche e proprietà degli acciai Duplex e, pertanto, presentano una rilevanza scientifica tale da averne permesso la presentazione in convegni internazionali e la pubblicazione in riviste scientifiche di settore.
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Sjögren, Torsten. "Influences of the Graphite Phase on Elastic and Plastic Deformation Behaviour of Cast Irons." Doctoral thesis, Linköpings universitet, Konstruktionsmaterial, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8776.
Abstract:
The amount and morphology of the graphite phase largely controls the resulting properties of cast iron. For instance, in flake graphite cast irons the mechanical properties are low while the thermal conductivity is high. This is in contrast with spheroidal graphite cast irons where the mechanical properties are high and the thermal conductivity is low. These differences are due to the different graphite morphologies and must be accounted for in the design work and material selection of cast iron components. In this work the influence of the graphite phase on the elastic and plastic deformation behaviour of cast irons has been studied. The material grades studied originate from castings for marine diesel engine piston rings with different chemical analyses. Two groups of pearlitic cast iron materials were studied; one with differences in graphite morphology and one with grey irons that differed in graphite content. For these different material grades the mechanical properties were correlated to microstructural parameters. In addition to standard uniaxial tensile tests, acoustic emission measurements were used for the study of deformation. When studying the modulus of elasticity of the cast iron it was found that the modulus of elasticity of the inherent graphite phase depends on the roundness of the graphite particles and is due to the strong anisotropy of the graphite phase. A linear correlation between nodularity and the modulus of elasticity of the graphite phase was derived. This correlation made it possible to account for the anisotropy of the graphite phase in the model used. By applying the linear function when modelling the effective modulus of elasticity, a high accuracy between experimental and theoretical values was achieved. Another factor affecting the elastic response when subjecting a cast iron component to tensile load was found to be the plastic deformation that actually occurs at very low strains for all of the studied cast iron grades. It was observed that the plastic deformation in the low strain elastic region, quantified by using acoustic emission measurements, increased linearly with decreasing modulus of elasticity. These measurements showed that the amount of plastic deformation in the elastic region was largely controlled by the graphite morphology. It was concluded that as the roundness of the graphite particles increases, the plastic deformation activity in the elastic region decreases. The plastic deformation activity continued linearly into the pronounced plastic region of the tensile tests. A decrease in roundness or increase in graphite fraction resulted in an increase of the amount of plastic deformation and the strain hardening exponent. A dependence between strength coefficient and graphite fraction was observed. Models for the flow curves for pearlitic cast irons were developed and shown to accurately reproduce the observed experimental curves. The surveys performed and conclusions from this thesis will be helpful in the design of new cast iron materials.
25
Sjögren, Torsten. "Influences of the graphite phase on elastic and plastic deformation behaviour of cast irons /." Jönköping : Linköping : Department of Mechanical Engineering, School of Engineering, Jönköping University ; Department of Management and Engineering, Linköping University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8776.
26
Dair, Benita Jean 1973. "Characterization, orientation, and deformation behavior of the double gyroid phase in elastomeric triblock copolymers." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85251.
27
Wang, Haopeng. "Confined crystallization, crystalline phase deformation and their effects on the properties of crystalline polymers." Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1246041849.
28
Hou, Duen-Huei. "Phase stability, mechanical properties and deformation mechanisms in B2-ordered Nb-Ti-Al alloys /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487857546385251.
29
Feng, Zhiyao. "The Deformation-induced Martensitic Phase Transformation in Low Chromium Iron Nitrides at Cryogenic Temperatures." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1526306156203016.
30
Monserrat, Hernández Oriol. "Deformation measurement and monitoring with Ground-Based SAR." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/81557.
Abstract:
The Ground-Based Synthetic Aperture Radar (GB-SAR) is a relatively new technique,
which in the last ten years has gained interest as deformation measurement and
monitoring tool. The GB-SAR technique is based on an imaging radar-based sensor, which
o ers high sensitivity to small displacements, in the region of sub-millimetres to
millimetres, long-range measurements, which can work up to some kilometres, and massive
deformation measurement capability. These features confer to the GB-SAR technique
interesting advantages with respect to other point-wise deformation measurement
techniques.
The process of estimating deformation from the GB-SAR data is not straightforward:
it requires complex data processing and analysis tools. This dissertation is focused on
these tools, covering the whole deformation estimation process. This thesis collects the
main research results achieved on this topic during my work at the Active Remote Sensing
Unit of the Institute of Geomatics. Two di erent approaches for measuring deformation
with GB-SAR data are described and discussed. The irst one is the interferometric
approach, based on the exploitation of the phase component of the GB-SAR data, which
is the commonly used GB-SAR method. The second one is a non-interferometric approach,
which exploits the amplitude component of the GB-SAR data, o ering an interesting
alternative way to exploit the GB-SAR data.
This dissertation has two main objectives. The first one is presenting, step by step, a
complete interferometric GB-SAR procedure for deformation measuring and monitoring.
The second one is presenting two new algorithms, which represent the most innovative
part of this thesis. The first algorithm faces the phase unwrapping problem, providing an
automatic solution for detecting and correcting unwrapping errors, which is called 2+1D
phase unwrapping. The second algorithm is the base of the above mentioned non-
interferometric approach, which overcomes some of the most critical limitation of GB-SAR
interferometry, at the expense of getting less precise deformation estimates.
The dissertation is divided in 6 chapters. The first one is the introduction, while the
second one provides an overview of GB-SAR interferometry, introducing the main aspects
that are the basics of the subsequent chapters. Chapter 3 describes a complete GB-SAR
processing chain. Chapters 4 and 5 contain the most original part of the dissertation, i.e.
the 2D+1 phase unwrapping algorithm, and the non-interferometric approach. Finally, in
Chapter 6 the conclusions are discussed and further research is proposed.El radar terrestre d’obertura sintètica (GB-SAR) és una tècnica relativament nova que, en els últims deu anys, ha guanyat interès com a eina per a mesurar i monitorar deformacions. La tècnica GB-SAR es basa en un sistema radar amb capacitat per proporcionar imatges, que ofereix una alta sensibilitat a petits desplaçaments, d’ordre mil·limètric o submil·limètric, que és capaç de mesurar a llargues distàncies (alguns km) i que té una alta capacitat per fer mesures massives. Aquestes característiques donen a la tècnica interessants avantatges respecte a altres tècniques clàssiques de mesura de deformacions, típicament basades en mesures puntuals. Derivar mesures de deformació a partir de dades GB-SAR no és un procés senzill, ja que requereix uns procediments complexos de processat i anàlisi de dades. Aquesta tesi es centra en aquests processos. Aquesta tesi recull alguns dels resultats més destacats de la investigació que he desenvolupat sobre aquest tema a la unitat de Teledetecció Activa de l'Institut de Geomàtica. Al llarg del document es descriuen dues aproximacions diferents per mesurar deformacions amb GB-SAR. Una es basa en la explotació de la tècnica de la interferometria, és a dir explotant la component de la fase de les imatges GB-SAR: és la tècnica GB-SAR usada habitualment. La segona, anomenada tècnica no-interferomètrica, es basa en la component de l’amplitud de les dades GB-SAR i ofereix una interessant alternativa a la primera. La tesi acompleix dos objectius principals. En primer lloc presenta un procediment complet per la mesura i monitoratge de deformacions mitjançant interferometria GB-SAR. En segon lloc, descriu dos nous algorismes que resolen problemes específics de la interferometria clàssica aplicada al GB-SAR i que representen la part més innovadora d’aquesta tesi. El primer algorisme aborda un dels problemes oberts de la interferometria, el phase unwrapping, proposant un mètode automàtic per detectar-ne i corregir-ne els errors. El segon algorisme proposa un nou mètode per a l'explotació de les dades GB-SAR per mesurar deformacions sense utilitzar la interferometria. La estructura de la tesi consisteix en sis capítols. Després de la introducció, el Capítol 2 proporciona una visió general de la interferometria GB-SAR, introduint els conceptes principals utilitzats en la tesi. En el tercer capítol es descriu una cadena de processament basada en GB-SAR interferomètric. Els capítols quart i cinquè contenen la part més original de la tesi: l'algorisme de phase unwrapping i el mètode no-interferomètric per la mesura de deformacions. Finalment, es discuteixen les conclusions principals i es proposen futures línies d’investigació.
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Karewar, Shivraj. "Atomistic Simulations of Deformation Mechanisms in Ultra-Light Weight Mg-Li Alloys." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc801888/.
Abstract:
Mg alloys have spurred a renewed academic and industrial interest because of their ultra-light-weight and high specific strength properties. Hexagonal close packed Mg has low deformability and a high plastic anisotropy between basal and non-basal slip systems at room temperature. Alloying with Li and other elements is believed to counter this deficiency by activating non-basal slip by reducing their nucleation stress. In this work I study how Li addition affects deformation mechanisms in Mg using atomistic simulations. In the first part, I create a reliable and transferable concentration dependent embedded atom method (CD-EAM) potential for my molecular dynamics study of deformation. This potential describes the Mg-Li phase diagram, which accurately describes the phase stability as a function of Li concentration and temperature. Also, it reproduces the heat of mixing, lattice parameters, and bulk moduli of the alloy as a function of Li concentration. Most importantly, our CD-EAM potential reproduces the variation of stacking fault energy for basal, prismatic, and pyramidal slip systems that influences the deformation mechanisms as a function of Li concentration. This success of CD-EAM Mg-Li potential in reproducing different properties, as compared to literature data, shows its reliability and transferability. Next, I use this newly created potential to study the effect of Li addition on deformation mechanisms in Mg-Li nanocrystalline (NC) alloys. Mg-Li NC alloys show basal slip, pyramidal type-I slip, tension twinning, and two-compression twinning deformation modes. Li addition reduces the plastic anisotropy between basal and non-basal slip systems by modifying the energetics of Mg-Li alloys. This causes the solid solution softening. The inverse relationship between strength and ductility therefore suggests a concomitant increase in alloy ductility. A comparison of the NC results with single crystal deformation results helps to understand the qualitative and quantitative effect of Li addition in Mg on nucleation stress and fault energies of each deformation mode. The nucleation stress and fault energies of basal dislocations and compression twins in single crystal Mg-Li alloy increase while those for pyramidal dislocations and tension twinning decrease. This variation in respective values explains the reduction in plastic anisotropy and increase in ductility for Mg-Li alloys.
32
Hofmann, Tobias [Verfasser], and Heiko [Akademischer Betreuer] Andrä. "Phase-Field Methods for Deformation Processes in Lithium-Ion Batteries / Tobias Hofmann ; Betreuer: Heiko Andrä." Kaiserslautern : Technische Universität Kaiserslautern, 2018. http://d-nb.info/1156901499/34.
33
Benafan, Othmane. "Deformation and Phase Transformation Processes in Polycrystalline NiTi and NiTiHf High Temperature Shape Memory Alloys." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5123.
Abstract:
The unique ability of shape memory alloys (SMAs) to remember and recover their original shape after large deformation offers vast potential for their integration in advanced engineering applications. SMAs can generate recoverable shape changes of several percent strain even when opposed by large stresses owing to reversible deformation mechanisms such as twinning and stress-induced martensite. For the most part, these alloys have been largely used in the biomedical industry but with limited application in other fields. This limitation arises from the complexities of prevailing microstructural mechanisms that lead to dimensional instabilities during repeated thermomechanical cycling. Most of these mechanisms are still not fully understood, and for the most part unexplored. The objective of this work was to investigate these deformation and transformation mechanisms that operate within the low temperature martensite and high temperature austenite phases, and changes between these two states during thermomechanical cycling. This was accomplished by combined experimental and modeling efforts aided by an in situ neutron diffraction technique at stress and temperature. The primary focus was to investigate the thermomechanical response of a polycrystalline Ni49.9Ti50.1 (in at.%) shape memory alloy under uniaxial deformation conditions. Starting with the deformation of the cubic austenitic phase, the microstructural mechanisms responsible for the macroscopic inelastic strains during isothermal loading were investigated over a broad range of conditions. Stress-induced martensite, retained martensite, deformation twinning and slip processes were observed which helped in constructing a deformation map that contained the limits over which each of the identified mechanisms was dominant. Deformation of the monoclinic martensitic phase was also investigated where the microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were captured and compared to the bulk macroscopic response of the alloy. This isothermal deformation was found to be a quick and efficient method for creating a strong and stable two-way shape memory effect. The evolution of inelastic strains with thermomechanical cycling of the same NiTi alloy, as it relates to the alloy stability, was also studied. The role of pre-loading the material in the austenite phase versus the martensite phase as a function of the active deformation modes (deformation processes as revealed in this work) were investigated from a macroscopic and microstructural perspective. The unique contribution from this work was the optimization of the transformation properties (e.g., actuation strain) as a function of deformation levels and pre-loading temperatures. Finally, the process used to set actuators, referred to as shape setting, was investigated while examining the bulk polycrystalline NiTi and the microstructure simultaneously through in situ neutron diffraction at stress and temperature. Knowledge gained from the binary NiTi study was extended to the investigation of a ternary Ni-rich Ni50.3Ti29.7Hf20 (in at.%) for use in high-temperature, high-force actuator applications. This alloy exhibited excellent dimensional stability and high work output that were attributed to a coherent, nanometer size precipitate phase that resulted from an aging treatment. Finally, work was initiated as part of this dissertation to develop sample environment equipment with multiaxial capabilities at elevated temperatures for the in situ neutron diffraction measurements of shape memory alloys on the VULCAN Diffractometer at Oak Ridge National Laboratory. The developed capability will immediately aid in making rapid multiaxial measurements on shape memory alloys wherein the texture, strain and phase fraction evolution are followed with changes in temperature and stress. This work was supported by funding from the NASA Fundamental Aeronautics Program, Supersonics Project including (Grant No. NNX08AB51A). This work has also benefited from the use of the Lujan Neutron Scattering Center at LANSCE, which is funded by the Office of Basic Energy Sciences DOE. LANL is operated by Los Alamos National Security LLC under DOE Contract No. DE-AC52-06NA25396.Ph.D.
Doctorate
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering
34
UEHARA, Takuya, Takato TAMAI, and Nobutada OHNO. "Molecular Dynamics Simulations of Shape-Memory Behavior Based on Martensite Transformation and Shear Deformation." The Japan Society of Mechanical Engineers, 2006. http://hdl.handle.net/2237/9014.
35
Nippress, Stuart. "Subduction body force stresses, deformation and mantle seismic anisotropy at the 410 and 660km phase transitions." Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420748.
36
Zhao, Yuchen. "Multi-scale study of mechanical behaviour of two-phase materials during large deformation and ductile damage." Thesis, Troyes, 2017. http://www.theses.fr/2017TROY0018.
Abstract:
Cette thèse est dédiée à l’étude du comportement élasto-plastique des matériaux polycristallins multiphasés ainsi que de l’endommagement ductile à différentes échelles. Les hétérogénéités microscopiques ont une influence importante sur la réponse mécanique macroscopique des matériaux. Et l’endommagement ductile est encore difficile à mesurer aux échelles fines. Cette thèse traite des problématiques suivantes : 1. L’évolution du comportement des phases et des grains sous chargements jusqu’à la rupture.2. L’influence de l’hétérogénéité intrinsèque au niveau micro, sur le comportement macroscopique des matériaux biphasés.3. L’influence de la striction et de l’endommagement sur le comportement de familles d’orientation de grains.4. La mesure indirecte de l’endommagement échelle fine par diffraction. Afin d’enquêter sur ces questions, l’acier duplex et le titane biphasé sont testés. La diffraction est utilisée pour effectuer des mesures in situ non-destructive au cours d’essais de traction et jusqu’à la rupture. Des simulations sont réalisées grâce à un modèle auto-cohérent élasto-plastique, dans lequel est introduite la modélisation de l’endommagement ductile. Les données expérimentales aux différentes échelles y sont comparées. En outre, des tests de nano-indentation et observation micrographiques sont effectués pour observer l’évolution spatiale des propriétés mécaniques des phases le long de la striction et jusqu’à la surface de ruptureThe thesis is dedicated to the study of elasto-plastic behavior of multiphase polycrystalline materials and ductile damage at different scales. The microscopic heterogeneities have important influence on the macroscopic mechanical behavior of materials. Ductile damage is still difficult to measure at small scales. The following issues are the main topic involved in this thesis: 1. The evolution of mechanical behavior in phases and groups of grains, under external load until fracture.2. The influence of intrinsic heterogeneity on the macroscopic behavior of two-phase materials.3. The influence of necking and ductile damage, on the behavior of grains with different orientation families.4. The indirect measurement of ductile damage at small scales by diffraction. To answer these questions, duplex steels and two-phase titanium are tested. The diffraction method is used to perform in situ measurements during tensile test until fracture. Predictions are carried out by an elasto-plastic self-consistent model, in which ductile damage have been integrated. Experimental data on different scales are compared with these predictions. In addition, nano-indentation tests are carried out to study the evolution of phases’ mechanical properties along the neck until fracture edge. Microscopic images were also taken in order to observe the fracture surfaces of studied materials
37
Gérard, Yves. "Etude experimentale des interactions entre deformation et transformation de phase : exemple de la transition calcite-aragonite." Rennes 1, 1987. http://www.theses.fr/1987REN10146.
38
Lv, Duchao. "A Multi-Scale Simulation Approach to Deformation Mechanism Prediction in Superalloys." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469009668.
39
Mraizika, Florence. "Evolutions microstructurales en compression à chaud des alliages de titane betacez et 6246 et influence du forgeage sur la transformation [beta] -> [alpha]." Grenoble INPG, 1996. http://www.theses.fr/1996INPG4206.
Abstract:
Les relations entre les gammes thermomecaniques et les microstructures des alliages de titane sont encore insuffisament connues. Ce travail se propose d'ameliorer la connaissance des etats structuraux resultant du forgeage beta et de ceux resultant de la transformation beta vers alpha-beta ulterieure. Les influences des deux parametres taux et vitesse de deformation sur les evolutions microstructurales et texturales se produisant lors du forgeage ainsi que de la transformation beta/alpha sont systematiquement explorees. Les evolutions texturales mettent en evidence une augmentation de la composante <111> lorsque la vitesse de deformation augmente. Les mecanismes qui president a la formation des microstructures de deformation ont ete mis en evidence. Aux fortes vitesses de deformation, le dentellement des joints par sibm et la desorientation des parois par recristallisation continue sont a l'origine de la formation des nouveaux grains. Les nouveaux grains ont toujours une orientation qui peut etre reliee a celle des grains parents et l'orientation <111> des grains initiaux est favorable a la germination. La formation de petits grains aux ex-joints beta entre deux taux de deformation 0. 25 et 1. 5 provoque une augmentation de la densite de joints et de la valeur de la desorientation moyenne. Cette germination induit une hausse du nombre de sites de germination et donc une acceleration de la cinetique de precipitation beta/alpha ulterieure entre deux taux de deformation 0. 25 et 1. 5. Aux faibles vitesses de deformation, la stabilite des microstructures du fait de l'intervention des mecanismes de restauration et de migration des parois est responsable de la non influence du taux de deformation sur les cinetiques de precipitation. A faible taux de deformation, lorsque la vitesse de deformation augmente, entre 10#-#1 et 10#-#3 s#-#1 la cinetique de precipitation augmente ; ceci est relie a l'efficacite des joints et a la densite des sous-joints qui augmentent avec la vitesse de deformation. A fort taux de deformation, entre 10#-#1 et 10#-#3 s#-#1 l'augmentation du nombre de sites de germination s'ajoute aux deux autres facteurs cites pour accroitre la cinetique de facon plus accusee
40
Wehrenberg, Christopher. "Phase transformations in shock compacted magnetic materials." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43595.
Abstract:
Shock compaction experiments were performed on soft magnetic phases Fe₄N and Fe₁₆N₂, and hard magnetic phases Nd₂Fe₁₄B and Sm₂Fe₁₇N₃ in order to determine their thermo-mechanical stability during shock loading and explore the possibility of fabricating a textured nanocomposite magnet. Gas gun experiments performed on powders pressed in a three capsule fixture showed phase transformations occurring in Fe₄N, Fe₁₆N₂, and Nd₂Fe₁₄B, while Sm₂Fe₁₇N₃ was observed to be relatively stable. Shock compaction of FCC Fe₄N resulted in a partial transformation to HCP Fe₃N, consistent with previous reports of the transition occurring at a static pressure of ~3 GPa. Shock compaction of Fe₁₆N₂ produced decomposition products alpha-Fe, Fe₄N, and FeN due to a combination of thermal effects associated with dynamic void collapse and plastic deformation. Decomposition of Nd-Fe-B, producing alpha-Fe and amorphous Nd-Fe-B, was observed in several shock consolidated samples and is attributed to deformation associated with shock compaction, similar to decomposition reported in ball milled Nd-Fe-B. No decomposition was observed in shock compacted samples of Sm-Fe-N, which is consistent with literature reports showing decomposition occurring only in samples compacted at a pressure above ~15 GPa. Nd-Fe-B and Sm-Fe-N were shown to accommodate deformation primarily by grain size reduction, especially in large grained materials. Hard/Soft composite magnetic materials were formed by mixing single crystal particles of Nd-Fe-B with iron nanoparticles, and the alignment-by-magnetic-field technique was able to introduce significant texture into green compacts of this mixture. While problems with decomposition of the Nd₂Fe₁₄B phase prevented fabricating bulk magnets from the aligned green compacts, retention of the nanoscale morphology of the alpha-Fe particles and the high alignment of the green compacts shows promise for future development of textured nanocomposite magnets through shock compaction.
41
Oberson, Paul Gregory. "An experimental and theoretical Investigation of the low temperature creep deformation behavior of single phase titanium alloys." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3983.
Abstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Material Science and Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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MIRJALILI, Mojtaba. "Numerical Analysis of a Large-Scale Levee on Soft Soil Deposits Using Two-Phase Finite Deformation Theory." 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/126785.
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Ceccato, Francesca. "Study of large deformation geomechanical problems with the Material Point Method." Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424697.
Abstract:
The numerical simulation of real geomechanical problems often entails an high level of complexity; indeed they are often characterized by large deformations, soil-structure interaction and solid-fluid interaction.
Moreover, the constitutive behavior of soil is highly non-linear.
Landslides, dam failure, pile installation, and undrground excavation are typical examples of large deformation problems in which the interaction between solid a fluid phase as well as the contact between bodies are essential.
This thesis addresses the challenging issue of the numerical simulation of large deformation problems in geomechanics.
The standard lagrangian finite element methods are not well suited to treat extremely large deformations because of severe difficulties related with mesh distortions.
The need to overcome their drawbacks urged researchers to devote considerable effort to the development of more advanced computational techniques such as meshless methods and mesh based particle methods.
In this study, the Material Point Method (MPM), which is a mesh based particle method, is exploited to simulate large deformation problems in geomechanics.
The MPM simulates large displacements with Lagrangian material points (MP) moving through a fixed mesh.
The MP discretize the continuum body and carry all the information such as mass, velocity, acceleration, material properties, stress and strains, as well as external loads.
The mesh discretizes the domain where the body move through; it is used to solve the equations of motion, but it does not store any permanent information.
In undrained and drained conditions the presence of water can be simulated in a simplified way using the one-phase formulation.
However, in many cases the relative movement of the water respect to the soil skeleton must be taken into account, thus requiring the use of the two-phase formulation.
The contact between bodies is simulated with an algorithm specifically developed for the MPM at the beginning of the century.
This algorithm was originally formulated for the frictional contact. It extension to the adhesive contact is considered in this thesis, which is well suited to simulate soil-structure interaction in case of cohesive materials.
In this thesis typical geomechanical problems such as the collapse of a submerged slope and the simulation of cone penetration testing are considered.
Numerical results are successfully compared with experimental data thus confirming the capability of the MPM to simulate complex phenomena.La simulazione numerica di molti problemi geotecnici è spesso caratterizzata da un elevato grado di complessità, infatti tipici fenomeni come frane, collasso di rilevati e installazione di pali necessitanto di tener conto delle grandi defromazioni del materiale, dell'accoppiamento meccanico tra fase solida e fase liquida e dell'interazione terreno-struttura. Questa tesi si occupa della simulazione numerica di tali problemi attraverso il Material Point Method, in particolare vengono considerati il collasso di un pendio sommerso e la penetrazione del piezocono. I classici metodi lagrangiani agli elementi finiti, ampiamente utilizzati da decenni, non sono adatti alla simulazione di grandi deformazioni per i severi problemi conseguenti le estreme defromazioni della mesh. La necessità di superare i limiti dei classici FEM, diversi gruppi di ricerca si sono impegnati, negli ultimi anni, a sviluppare nuovi metodi numerici tra cui si ricorda SPH, MPM e PFEM. Nel Material Point Method il continuo deformabile è rappresentato da un insieme di punti materiali che si spostano attraverso una mesh fissa di elementi finiti. I punti materiali trasportano tutte le informazioni del corpo come velocità, tensioni, deformazioni, proprietà del mateiale e carichi, mentre la mesh è utilizzata solo per risolvere le equazioni del moto, ma non memorizza alcuna informazione permamente; in questo modo si evitano problemi di distorsione degli elementi finiti. L'interazione con l'acqua o altri fluidi interstiziali è determinante nel comportamento del terreno nella maggior parte delle condizioni di carico. In condizione drenate e non drenate, la presenza dell'acqua può essere tratta in modo semplificato cos' che gli spostamenti del terreno possono essere calcolati con l'uso delle equazioni del continuomo monofase. In molti casi è essenziale tener conto del movimento relativo tra lo scheletro solido e l'acqua, questo necessita dell'uso della formulazione bifase. Entrambe queste possibiltà di simulare il terreno saturo vengono utilizzate nello studio dei problemi oggetto di questo studio. Nel MPM problemi caratterizzati dal contatto fra corpi possono essere simulati con un algoritmo sviluppato specificatamente per l'MPM all'inizio del secolo; tale algoritmo viene ripreso in questa tesi ed esteso al caso dei terreni coesivi per la simulazione dell'interazione terrno-struttura.
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Nechaev, Yury S. "Stimuli and mechanisms of diffusion mass-transport in the processes of structural-phase changes in metallic materials under high-rate deformation: Stimuli and mechanisms of diffusion mass-transport in the processesof structural-phase changes in metallic materials under high-rate deformation." Diffusion fundamentals 2 (2005) 52, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14385.
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Okitsu, Yoshitaka. "FABRICATION OF ULTRAFINE GRAINED STEELS WITHOUT SEVERE PLASTIC DEFORMATION AND THEIR APPLICATION TO AUTOMOBILE BODY STRUCTURES." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157630.
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Schappert, Klaus Bernhard [Verfasser], and Rolf [Akademischer Betreuer] Pelster. "Confinement effects in nanopores : elastic properties, phase transitions, and sorption-induced deformation / Klaus Bernhard Schappert. Betreuer: Rolf Pelster." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2014. http://d-nb.info/1054328056/34.
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Gläser, Dennis [Verfasser], and Bernd [Akademischer Betreuer] Flemisch. "Discrete fracture modeling of multi-phase flow and deformation in fractured poroelastic media / Dennis Gläser ; Betreuer: Bernd Flemisch." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2020. http://d-nb.info/1218532319/34.
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Lours, Philippe. "Mecanismes de deformation plastique de la phase gamma prime du superalliage cmsx2 : etude par microscopie electronique "in situ"." Toulouse 3, 1989. http://www.theses.fr/1989TOU30059.
Abstract:
La phase gamma prime du superalliage cmsx2 a la structure l12 ordonnee. Elle presente un accroissement de limite elastique avec la temperature contrairement aux materiaux classiques. Le memoire comporte quatre parties: - la premiere rappelle les principales caracteristiques des superalliages. - la deuxieme partie presente la technique de deformation in situ: elle consiste a reproduire, a l'interieur meme du microscope electronique et dans une large gamme de temperatures (25c a 1000c), les conditions reelles de l'essai de traction. - la troisieme partie propose une simulation numerique de la repartition des contraintes dans la microeprouvette in situ. Nous avons choisi pour cela une approche par la methode des elements finis. - enfin la quatrieme presente les resultats experimentaux. Les essais in situ font apparaitre que: le mouvement des superdislocations dans les plans octaedriques se produit de maniere brutale et heterogene par formation d'empilements; trois mecanismes sont responsables de l'accroissement de la limite elastique: a basse temperature, les dislocations se deplacent par un mouvement de blocage/deblocage; a haute temperature, les dislocations se bloquent par glissement devie dans les plans cubiques selon la transition de kear&wilsdorf; a toute temperature, la formation et l'evolution sous contrainte des boucles de dislocation contribuent au durcissement. Au voisinage et au-dela de la temperature du pic de limite elastique, nous avons analyse l'etalement sous contrainte des fautes d'empilement intrinseque. Nous avons de plus realise quelques essais de traction et de relaxation macroscopiques. L'ensemble de nos resultats sont finalement confrontes aux caracteristiques des differents modeles proposes
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YU, DAPENG. "Etude des defauts et de la deformation plastique de la phase quasicristalline t2 du systeme al-li-cu." Paris 11, 1993. http://www.theses.fr/1993PA112274.
Abstract:
Notre etude a ete consacree a l'analyse d'une part des defauts de structure et d'autre part du comportement de la deformation plastique de la phase quasicristalline t2 du systeme al-li-cu, aussi bien que des imperfections induites par la deformation. De veritables defauts ont ete observes et etudies par microscopie electronique a transmission dans les echantillons non deformes. Ces defauts se presentent soit sous la forme de defauts lineaires (dislocations), de defauts planaires (sous-joint de grains et faute d'empilement) ou encore sous la forme de structures modulees. Un essai de deformation de la phase t2 a ete realise a temperature ambiante. Il parait donc vraisemblable que les dislocations dans les quasicristaux ne sont pas mobiles a temperature ambiante et que les mecanismes de deformation des phases cristallines ne sont pas controles a basse temperature par un glissement des dislocations, mais plutot par un rearrangement local de type phasonique. Les dislocations ont ete observees et analysees dans la phase quasicristalline t2 apres deformation. La direction de la composante du vecteur de burgers dans l'espace physique b et la composante correspondante du vecteur de burgers dans l'espace perpendiculaire b d'une des dislocations observees fut determinee etant parallele a l'axe de symetrie d'ordre 2, <0/0, 0/0, 0/2>, et parallele a la direction <0/0, 0/0, 2/0> respectivement. Une structure modulee selon un axe de symetrie d'ordre 3 et a periodicite variable a ete observee dans un echantillon deforme par une analyse des diagrammes de diffraction electronique et des images en haute resolution
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Тищенко, Костянтин Володимирович, Константин Владимирович Тищенко, Kostiantyn Volodymyrovych Tyshchenko, Ірина Михайлівна Пазуха, Ирина Михайловна Пазуха, Iryna Mykhailivna Pazukha, Наталія Іванівна Шумакова, Наталия Ивановна Шумакова, and Nataliia Ivanivna Shumakova. "Strain Properties of Nanodimentional Film Systems Based on Fe and Pt." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35200.
Abstract:
The results of research structural, phase state and strain properties of nanodimentional film systems
based on Fe and Pt at deformation intervals l1 = (0 - 1)%, l2 = (0 - 2)% and l3 = (0 - 3)% are presented.
After condensation in films occurred initiation disordered solid solution fcc-FePt with the mean value of
lattice parameter ā = 0,385 nm. The analysis of experimental deformation dependence at different Fe thickness,
which changes in the range from 4 to 57 nm, while the thickness of Pt = 18 nm = const, were presented.
It was shown that the value of mean strain coefficient depends on total film thickness and Fe concentration.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35200