Thermomechanically bonded spunbond nonwoven fabrics contain discrete bonds that are formed by melted and fused fibers. Through equi-biaxial tensile testing and simultaneous image capture, the mechanical response of individual bonds was studied through loading in the preferential fiber direction, the machine direction, and in the direction that is perpendicular, the cross direction, of the fabric web. Independent biaxial force and displacement data were collected and analyzed, and the maximum force and stiffness of the bonds in the machine and cross directions were found to be statistically different. After scaling the maximum force and stiffness by a relative basis weight parameter, a fiber orientation parameter, and the width of the bond itself, the peak force and stiffness in the machine and cross directions were found to no longer be statistically different. This indicates that basis weight, fiber orientation, and bond size dictate the biaxial mechanical behavior of the bonds. Furthermore, significant fiber debonding was observed in all the bonds tested, effectively suggesting bond disintegration into the individual component fibers during testing. Digital image correlation, using the captured images, was utilized to calculate local and average Eulerian strains of the bond during the initial stages of the test. The strain experienced by the bonds in the machine direction was always positive and increasing as the biaxial load increased. The strain in the cross direction, however, experienced increasing and decreasing strain. Local strain maps revealed the highly inhomogeneous strain response of the bonds under biaxial loading. / Master of Science

The uterosacral ligaments (USLs) are important anatomical structures that support the uterus and apical vagina within the pelvis. As these structures are over-stretched, become weak, and exhibit laxity, pelvic floor disorders such as pelvic organ prolapse occur. Although several surgical procedures to treat pelvic floor disorders are directed toward the USLs, there is still a lot that is unknown about their function. These surgeries often result in poor outcomes, demonstrating the need for new surgical approaches and biomaterials. The first chapter of this dissertation presents a review of the current knowledge on the mechanical properties of the USLs. The anatomy, microstructure, and clinical significance of the USLs are first reviewed. Then, the results of published experimental studies on the {emph{in vivo}} and {emph{ex vivo}}, uniaxial and biaxial tensile tests are compiled. Based on the existing findings, research gaps are identified and future research directions are discussed. The second chapter proposes the use of planar biaxial testing, digital image correlation (DIC), and optical coherence tomography (OCT) to quantify the deformations of the USLs, both in-plane and out-of-plane. Using virgin swine as an animal model, the USLs were found to deform significantly less in their main direction (MD) of {emph{in vivo}} loading than in the direction perpendicular to it (PD) at increasing equibiaxial stresses. Under constant equibiaxial loading, the USLs deformed over time equally, at comparable rates in both the MD and PD. The thickness of the USLs decreased as the equibiaxial loading increased but, under constant equibiaxial loading, the thickness increased in some specimens and decreased in others. The third chapter presents new experimental methods for testing the {emph{ex vivo}} tensile properties of the uterosacral ligaments (USLs) in rats. USL specimens were carefully dissected to preserve their anatomical attachments, and they were loaded along their main {emph{in vivo}} loading direction (MD) using a custom-built uniaxial tensile testing device. This chapter reports the first mechanical data on the rat USLs in isolation from surrounding organs. It is also the first experimental study to provide measurements of the inhomogeneous deformations of the USLs during loading along their main textit{in vivo} loading direction, revealing that the USLs may behave as auxetic structures. The fourth and final chapter presents preliminary findings on novel imaging applications to characterize the evolving structure of the USLs before, during, and after tensile pulling along the ligaments' main textit{in vivo} axis of loading. Rat USLs were excised using the proposed novel dissection method and pulled uniaxially as was performed in the previous chapter. Before and after mechanical testing, second harmonic generation (SHG) was used to image collagen and muscle within the three anatomical regions of the USLs. During mechanical testing, OCT was used to collect out-of-plane images of the cervical/intermediate regions of the USL specimens, resulting in 3D volume scans of the regions. SHG images showed the USLs to have complex microstructures with significant wavy collagen bundles interwoven with muscle bundles. Preliminary observation of the microstructure during testing revealed interwoven sections of tissue with collagenous fibers that reoriented in all directions illustrating how the USLs may expand laterally during uniaxial loading, causing the auxetic properties documented in the previous chapter. Though more quantitative work remains to be done, the findings presented in this dissertation improve our understanding of how the USLs deform with increasing load, such as what occurs during pregnancy. Together, these studies serve as a springboard for future investigations on the supportive function of the USLs in animal models by offering guidelines on testing methods that capture their complex mechanical behavior. / Doctor of Philosophy / The uterosacral ligaments (USLs) are important anatomical structures that support the uterus and vagina and are often used to restore the support of pelvic organs during surgeries for pelvic organ prolapse. These surgeries often result in poor outcomes, demonstrating the need for new surgical approaches and graft materials. Due to their supportive role, the mechanical properties of the USLs are important for their physiological function, and they must be investigated to improve current treatment strategies for pelvic organ prolapse. To this end, we designed new equipment, dissection, and testing methods to characterize the mechanical behavior of the USLs using swine and rats as animal models. We provided the first three-dimensional characterization of time-dependent deformations of swine USLs as they were pulled along their two physiological loading directions using advanced imaging methods, including digital image correlation and optical coherence tomography. We isolated the USLs from rats with their anatomical attachments and mechanically tested them along their main physiological loading direction, reporting the first mechanical data on the rat USLs in isolation from surrounding organs. Finally, we used the advanced imaging techniques optical second harmonic generation microscopy and optical coherence tomography to determine how the microstructure (e.g., collagen and muscle) of the rat USLs evolves before, during, and after mechanical testing. These findings advance our understanding of the three-dimensional, nonlinear, heterogeneous, elastic, and viscoelastic deformations of the USLs. Our work may serve as a springboard for future investigations on the supportive function of the USLs by offering guidelines on testing methods that capture their complex mechanical behavior.

Most strength grading machines on the European market use an averagemodulus of elasticity (MOE), estimated on a relatively large distance along awood member, as the indicating property (IP) to bending strength. Theaccuracy of such grading machines in terms of coefficient of determination israther low at R2 ≈ 0.5. This research is motivated by a desire to increase theaccuracy of the strength grading in the industry today. The aim of the presentstudy is to contribute knowledge of local variation in bending stiffness/MOEwith high resolution and thus locate weak sections due to stiffness reducingfeatures (the most important is knots) for structural timber.The present study introduces three methods that involve structural dynamics,classical beam theory and optical measurement to assess local wood stiffness.Specifically: The dynamic method, in which a wood member is treated as an ordinaryphysical structure and the local stiffness is studied by exploring itsdynamic properties. In Method II, a bending MOE profile is established based on local fibre angle information. The local fibre orientation is detected through highresolution laser scanning based on the tracheid effect.  For Method III, a bending MOE profile is established using surfacestrain information under four-point bending. A high resolution strainfield is obtained using the digital image correlation (DIC) technique. From the present study, the two latter methods are more favourable inevaluating the local stiffness within a piece of structural timber. Moreover, thestudy reveals that the established bending MOE profiles using the two lattermethods, i.e. based on information of the local fibre angle and surface strain,agree reasonably well. However, for some patterns of knot clusters, the localbending MOE, calculated on the basis of fibre angles, is significantly higherthan the local bending MOE estimated on the basis of surface strain. / De flesta av de utrustningar för hållfasthetssortering som utnyttjas på deneuropeiska marknaden använder ett medelvärde på elasticitetsmodulen(MOE), beräknat på en relativt stor längd av en sågad planka, som indikativparameter (IP). Sådan hållfasthetssortering ger en noggrannhet i termer avförklaringsgrad på R2 ≈ 0.5, vilket är ganska lågt. Arbetet i denna studiemotiveras av en önskan att öka noggrannheten i hållfasthetssorteringen. Syftetmed denna studie är att bidra med kunskap om lokala variationer iböjstyvhet/MOE med hög upplösning och att lokalisera veka snitt (där kvistarär den viktigaste försvagande faktorn) för konstruktionsvirke.Den aktuella studien introducerar tre metoder som omfattar strukturdynamik,klassisk balkteori och optisk mätning vid bedömningen av lokal styvhet imaterialet. Specifikt:  Metod I, där den lokala böjstyvheten studerades genom de dynamiskaegenskaperna såsom egenfrekvens och modform.  Metod II, där en MOE profil beräknas på basis av information om lokalafibervinklar på ett virkesstyckes ytor. Den lokala fiberorienteringen mätsmed högupplöst laserskanning baserad på den så kallade trakeideffekten.  Metod III, där en MOE-profil fastställdes med hjälp avtöjningsinformation för en hel flatsida av en planka belastad med konstantböjmoment. Det högupplösta töjningsfältet erhölls med hjälp av teknikför Digital Image Correlation (DIC). Studien visar att de två sistnämnda metoderna är mycket lämpade för attutvärdera den lokala styvheten i ett virkesstycke. Dessutom visar studien att deMOE-profiler som togs fram med hjälp av de två sistnämnda metoderna,vilka baseras på information om lokala fibervinklar och töjningsfältet på ytan,stämde överens för större delen av virkesstycket. För visa kvistgrupper kan dock den lokala böjstyvheten högre med metoden baserad på fibervinklar.

The context of this thesis is a research project focused on the investigation of a renewable biopolymer-poly(lactic acid) (PLA) as a potential replacement of petroleum-based polymers in advanced nanocomposites reinforced with Microfibrillated cellulose (MFC). MFC is extracted from wood, which is a renewable, sustainable, carbon neutral and recyclable material. This advanced MFC-PLA bio- based composite material is expected to allow for the substitution of petroleum-based plastics in various markets and applications. The specific objectives of the thesis are: 1) to describe the morphological characterization of MFC used for prototype MFC-PLA composites, and 2) to determine the mechanical properties of the prototype MFC-PLA nanocomposites formulation generated in form of thin transparent films. In order to meet this objective it was necessary to: 2.1) develop a methodology for optical strain measurement in transparent thin films; and 2.2) develop an effective methodology for obtaining multiple mechanical properties from small number of specimens of prototype materials subjected to tensile tests. Two types of MFC, one obtained by courtesy of University of Maine and the other purchased from Innventia AB company, were investigated under a field emission scanning electron microscopy (FESEM). The micrographs obtained from FESEM showed that both types of MFC were of complex hierarchical structures, which did not allow qualitative characterization of the morphological features in terms of particulate composites nor cellular solids. Since prototype formulations of MFC-PLA composites were generated in small amounts (typically one Petri dish) in a form of thin transparent films, there was a need for quick and efficient assessment of their key mechanical properties that would provide feedback and guide further prototyping work. An optical measurement method based on digital image correlation (DIC) principle was developed to measure the deformation and strains of the tensile film samples. In our study, the accuracy and precision of the measurement of deformation were ±1.5 µm and 0.4 µm respectively. The corresponding accuracy and precision in terms of strains were ±30 µstrain and 75 µstrain respectively. This method can be successfully used to determine the critical mechanical properties, such as elastic modulus, toughness and Poisson's ratio, of transparent thin films by a single tensile test, all of which require precise strain measurement. In addition, this optical measurement method makes it possible to significantly simplify the testing for measuring essential work of fracture (EWF), an important material property of thin transparent films. In traditional method, measurement of EWF requires large amount of notched specimens. However, our study showed that only a small amount of notched specimens were needed to measure the EWF of a material. This method could not be successfully used to determine EWF from un-notched tensile specimens. / Graduation date: 2012 / Folder labeled "UMaine MFC aerogel" contains SEM micrographs of MFC from University of Maine (referred as type A MFC in the thesis). Two pieces of leaf-like flakes at different locations were cut by Focused Ion Beam (FIB) in order to observe the internal structure of the flakes. Folder "FIB_01 ": a series of SEM micrographs of FIB-cut flake at different magnification levels. Folder "FIB_02 ": another series of SEM micrographs of FIB-cut flake at various magnification levels. Folder labeled "Swedish MFC aerogel" contains SEM micrographs of MFC from Innventia AB company, Sweden (referred as type B MFC in the thesis). There is a series of SEM micrographs of type B MFC aerogel at various magnification levels in this folder.

Much of North America’s reinforced concrete infrastructure is reaching the end of its service life and careful inspection and assessment is required to ensure the appropriate capacity is maintained in these structures. The research conducted herein seeks to further the development of two new sensor technologies: fibre optic strain sensors and digital image correlation, which have the potential to provide comprehensive performance data for structures to a level of accuracy previously not possible. The research involves determining the accuracy of these sensor systems to monitor both strain and crack widths in reinforced concrete compared to conventional techniques, such as electrical resistance strain gauges. Preliminary work was also undertaken on correcting the sensor results for temperature. It was determined that temperature variations in the range of +21 °C to 20 °C, result in significant strain errors for both sensor systems. Once the results obtained from the sensors systems are corrected for temperature, crack widths are monitored in four small-scale reinforced concrete tension specimens, and strain and crack width behaviour is monitored in four full-scale beams under four point bending. One of the major problems faced when using the digital image correlation technique is out of plane movement which results in significant error. Techniques to lower this error are addressed. In addition, obtaining a more robust understanding of the effects of temperature on crack widths, stiffness, strength and short term creep behaviour of reinforced concrete elements is explored to improve structural monitoring and numerical models used for analysis. Four full-scale beams, two at room temperature and two at 20 °C, were loaded to failure under four point bending. A comparison of the room temperature and low temperature test results show that the cracks tend to close up at lower temperatures in members that are free to expand and contract. This behaviour results in a potential increase in shear capacity for beams at lower temperatures. The low temperature beams also saw a minor increase in strength, but saw no noticeable increase in stiffness. Lastly, short term creep behaviour was reduced in the low temperature beams once the formation of ice occurred. / Thesis (Master, Civil Engineering) -- Queen's University, 2012-10-31 11:08:32.631

Nos casos de perda óssea vertical severa, principalmente em áreas posteriores da mandíbula, o uso de implantes curtos associado a próteses fixas metaloplásticas esplintadas pode ser uma alternativa às cirurgias de enxerto ósseo e a melhor transmissão de tensões ao osso adjacente, respectivamente. Dentre os métodos que avaliam a distribuição de tensões em torno dos implantes, a Correlação de Imagem Digital (CID) leva vantagens no que diz respeito à possibilidade de avaliar a distribuição das tensões de forma contínua por meio de imagens obtidas ao longo do tempo, durante carregamento oclusal. Diante disso, este trabalho avaliou qualitativa e quantitativamente o desempenho biomecânico de próteses fixas metaloplásticas parafusadas, unidas e isoladas, sobre implantes de diferentes comprimentos, posicionados na região posterior da mandíbula, por meio do método de CID. A partir de quatro modelos mestres, foram confeccionados quatro modelos em resina de poliuretano F16, simulando extremidade livre mandibular, com o dente 44 em resina (Luxatemp) e os dentes 45, 46 e 47 substituídos por implantes curtos (4 x 5 mm) e/ou convencionais (4 x 11 mm). Os grupos (G) deste estudo foram: G1 (dois implantes convencionais [45 e 46] e um curto [47]), G2 (um implante convencional [45] e dois curtos [46 e 47]), G3 (três implantes curtos) e G4 (três implantes convencionais). Próteses fixas metaloplásticas unidas e isoladas foram parafusadas sobre os intermediários e submetidas a diferentes carregamentos oclusais de 250N: puntiforme (distal do 47 e mesial do 45) e oclusal distribuído. Tensões na direção horizontal (&epsilon;xx) foram calculadas e comparadas qualitativa e quantitativamente pelo software de CID (Davis 8.0, LaVision GmbH). Em geral, houve uma concentração de tensões em maior intensidade nas áreas onde os implantes curtos estavam posicionados. No carregamento puntiforme no segundo molar, houve uma predominância de tensões de compressão e tração nos planejamentos com coroas unidas e isoladas, respectivamente, e as tensões de maior magnitude foram encontradas no G2, G3 e G4 com coroas isoladas (p>0,05), apresentando valores mediados (&mu;S) equivalentes a 396,08, 360,45 e 354,04, respectivamente. No carregamento puntiforme envolvendo o segundo pré-molar, houve predominância de tensões de compressão em todos os planejamentos, com magnitudes mais elevadas nos grupos com coroas unidas (p<0,05). As simulações com carga oclusal distribuída revelaram, também, predominância de tensões de compressão em todos os planejamentos, com maior magnitude nos grupos com coroas unidas, sobretudo no G1 (-464,05±106,43) e G3 (-474,39±179,54) e com diferenças estatisticamente significantes em relação aos demais grupos (p<0,05). Dentro das limitações deste estudo, pode-se concluir que a esplintagem das coroas sobre múltiplos implantes promoveu maior concentração de tensões em torno dos implantes durante os carregamentos puntiforme no segundo pré-molar e oclusal distribuído, reforçando a necessidade de contato interproximal e ajuste oclusal efetivos para promover melhor distribuição das tensões. Adicionalmente, a combinação de implantes curtos e convencionais parece ser uma alternativa viável na reabilitação de áreas edêntulas posteriores com altura óssea reduzida. / In cases of severe vertical bone loss, especially in the posterior region of the mandible, the use of short implants associated with splinted resin-veneered fixed dental prostheses (FDPs) can be an alternative to bone graft surgery and better force transmission to the adjacent bone, respectively. Among the methods to evaluate the stress distribution around the implants, the digital image correlation (DIC) has advantages as regards the possibility of evaluating the stress distribution continuously using images taken over time, during occlusal loading. Thus, this study evaluated qualitatively and quantitatively the biomechanical behavior of splinted and non-splinted resin-veneered FDPs, screw-retained on implants of different lengths positioned in the posterior region of the mandible with the aid of the DIC method. Four F16 polyurethane resin models were fabricated to simulate half of the mandibular arch containing tooth 44 in resin (Luxatemp) and teeth 45, 46 and 47 replaced by short (4 x 5 mm) and/or conventional (4 x 11 mm) implants. Groups (G) of this study were: G1 (two conventional implants [45 and 46] and one short implant [47]), G2 (one conventional implant [45] and two short implants [46 and 47]) G3 (three short implants) and G4 (three conventional implants). Splinted and non-splinted FDPs were screwed to the implant abutment and subjected to different oclusal loads of 250N: punctiform (45 mesial and 47 distal) and balanced occlusal load. Strains in the horizontal direction (&epsilon;xx) were calculated based on displacement and compared qualitatively and quantitatively by the DIC software (Davis 8.0, LaVision Inc.). In general, there was a stress concentration at higher intensity in those areas where short implants were placed. In punctiform load on the second molar, there was a compressive and tensile stresses predominance when splinted and non-splinted crowns were used, respectively, and the stresses of greater magnitude were found in the G2, G3 and G4 with non-splinted crowns (p>0.05), showing median values (&mu;S) equivalent to 396.08, 360.45 and 354.04, respectively. In punctiform load involving the second premolar, there was a compressive stress predominance in all planning with highest magnitudes in groups with splinted crowns (p<0.05). The oclusal load distributed simulations also revealed compressive stresses predominance in all planning, with greater magnitude in groups with splinted crowns, especially in G1 (-464.05 ± 106.43) and G3 (-474.39 ± 179.54), both with statistically significant differences when compared to the other groups (p<0.05). Within the limitations of this study, it can be concluded that splinting multiple adjacent implant supported provided a high stress concentration around the implants during punctiform (45 mesial) and balanced occlusal load, reinforcing the need for effective interproximal contact and oclusal adjustment to promote better stress distribution. Additionally, the combination of short and conventional implants seems to be a viable alternative in the rehabilitation of mandibular free end with reduced bone height.

Les joints adhésifs sont de plus en plus utilisés dans des structures industrielles critiques. Ils sont donc susceptibles de subir des chargements dynamiques complexes. Les méthodes de caractérisation dynamiques existantes ne caractérisent pas seulement le joint adhésif, mais l'assemblage collé tout entier. Cette thèse propose une méthode innovante pour caractériser un joint adhésif sous sollicitations dynamiques multiaxiales. La méthode expérimentale repose sur trois éléments principaux: i) un système de barres d'Hopkinson conventionnel (SHPB), ii) une nouvelle géométrie d'éprouvette, nommée DODECA, qui permet d'appliquer trois chargements multiaxiaux différents et iii) des mesures locales de déformation et de contrainte par corrélation d'images. La contrainte et la déformation dans le joint adhésif sont estimées directement à partir des données expérimentales pendant le chargement jusqu'au point de rupture. Une autre approche basée sur la méthode FEMU (Finite Element Model Updating) a été utilisée pour compléter le modèle du joint adhésif. Une méthode inverse numérique a été développée pour obtenir les paramètres élastiques, plastiques et de rupture du joint adhésif. De plus, des outils qualitatifs ont été proposés pour estimer les incertitudes sur les paramètres identifiés. Ce travail a prouvé l'intérêt de l'imagerie rapide locale pour caractériser les joints adhésifs.Cette méthode innovante a été validée sur une autre éprouvette nommée BIADH45. Cette dernière étude a aussi mis l'accent sur de nouveaux domaines de recherche : en particulier, le rôle des interfaces dans la rupture du joint adhésif et l'intérêt des substrats en CMO dans la caractérisation dynamique des joints adhésifs. / Adhesive joints are increasingly employed for bonding critical parts of industrial structures. Therefore, they are subject to complex dynamic loadings. Existing dynamic characterization techniques do not characterize only the adhesive joint, but the complete assembly. This thesis proposes an innovative experimental technique for the characterization of adhesive joints under dynamic multiaxial loadings. The experimental method relies on three main components: i) a conventional split Hopkinson pressure bar (SHPB) apparatus, ii) a novel specimen, denoted as DODECA, which enables testing of three distinct multiaxial loadings using the same method and iii) local strain and stress measurements performed by digital image correlation (DIC). The stress and strain in the adhesive joint are estimated directly from the experimental data both during loading and at the failure point. Another approach based on the Finite Element Model Updating method (FEMU) has been used to complete the adhesive joint model. A numerical inverse method has been developed to obtain elastic, plastic and fracture parameters. Besides, qualitative tools have been proposed to estimate uncertainties on identified parameters. This work has proven the value of local high-speed imaging to characterize adhesive joints.This innovative method has been validated on another specimen denoted as BIADH45. This last study has also emphasized new research interests : in particular, the role of the interfaces in the adhesive joint failure and the benefit of substrates in CMO in dynamic characterization of adhesive joints.

Three dimensional (3D) woven composites have attracted the interest of academia and industry thanks to their damage tolerance characteristics and automated fabric manufacturing. Although much research has been conducted to investigate their out-of-plane "through thickness" properties, still their in-plane properties are not fully understood and rely on extensive experimentation. The aim of this work is to study the electromechanical behaviour of three different fibre architectures of 3D woven composites "orthogonal (ORT), layer-to-layer (LTL) and angle interlock (AI)" loaded, in three different orientations "warp (0º), weft (90º) and off-axis (45º)", in quasi-static tension. Stress/strain response is captured as well as damage initiation and evolution up to final failure. The ORT architecture demonstrated a superior behaviour, in the off-axis direction, demonstrated by high strain to failure (~23%) and high translaminar energy absorption (~40 MJ/m3). The z-binder yarns in ORT suppress delamination and allow larger fibre rotation during the fibre "scissoring motion" that enables further strain to be sustained. In-situ electrical resistance variation is monitored using a four-probe technique to correlate the resistance variation with the level of damage induced while loading. Monotonic and cyclic "load/unload" tests are performed to investigate the effect of piezo-resistivity and residual plasticity on resistance variation while damage is captured by X-ray scanning during interrupted tests at predefined load levels. In addition, this study investigates the potential of using 3D woven composites in joint assemblies through open-hole tension and "single fastener double-lap joint" bearing strength tests. 3D woven composites in the off-axis orientation, especially ORT, demonstrate a potential for overcoming some of the major challenges for composite joints' applications which are the pseudo-ductility, stress redistribution away from the notch and notch insensitivity. Finally, the study proposes a micro-mechanics based damage model to simulate the response of 3D orthogonal woven composites loaded in tension. The proposed model differs from classical damage mechanics approaches in which the evolution law is obtained by retrofitting global experimental observations.

L'objectif ultime de ce travail de thèse consiste à établir un bilan énergétique à l'échelle du grain afin de caractériser et de vérifier la cohérence thermodynamique de modèles de comportement utilisés pour rendre compte du développement de la plasticité cristalline dans les matériaux métalliques. La première partie de ce travail a consisté à mettre en place un protocole d'élaboration du matériau permettant d'obtenir la microstructure souhaitée, compatible avec des moyens d'observations macroscopiques. Les échantillons d'aluminium à très gros grains (centimétriques) ainsi obtenus sont utilisés pour effectuer des essais cycliques durant lesquels les champs cinématiques et thermiques sont mesurés au moyen de techniques de Corrélation d'Images Numériques et de Thermographie Infra-rouge. Deux techniques de traitement d'image spécifiques ont été proposées. Elles permettent d'introduire des hypothèses sur les champs cinématiques et thermiques qui soient adaptées à la microstructure (ici continuité intra-granulaire du déplacement, de la température et du flux). Ces méthodes permettent d'accéder à des mesures complètement indépendantes d'un grain à l'autre tout en améliorant la robustesse des méthodes de mesure. Ces méthodes ont été validées numériquement en utilisant des images de synthèse sur lesquelles ont été appliqués des champs hétérogènes. Une campagne d'essais cycliques a enfin été menée sur les multi-cristaux d'aluminium élaborés. Les méthodes développées ont permis d'observer le développement de la plasticité intra-granulaire et le développement de la fissuration inter-granulaire. / The main objective of this PhD thesis is to establish an energy balance at the grain scale in order to assess the thermomechanical consistency of material models used to predict the development of crystal plasticity of metals.The first part of this work consists in setting a protocol allowing the material elaboration with the desired microstructure which is to be compatible with the use of classical macroscopic observation devices. The obtained coarse-grained aluminum samples (with centimeter grains) are used in cyclic tensile tests. During these tests, the kinematic and thermal fields are recorded with Digital Image Correlation and Infra-Red Thermography techniques.Two specific imaging techniques were developed. They allow introducing ad hoc hypotheses (i.e. consistent with microstructure) on the kinematic and the thermal fields. In this work, these hypotheses consist in intra-granular continuity conditions on the displacement, temperature and heat flux fields. These methods give independent measures on each grain while improving the robustness of the measurement methods. These methods were numerically validated using computer-generated images heterogeneously loaded.Cyclic tests were finally performed on the processed aluminum multi-crystals. The developed methods allowed the observation of the development of intra-granular plasticity and the development of inter-granular cracking.

Nos casos de perda óssea vertical severa, principalmente em áreas posteriores da mandíbula, o uso de implantes curtos associado a próteses fixas metaloplásticas esplintadas pode ser uma alternativa às cirurgias de enxerto ósseo e a melhor transmissão de tensões ao osso adjacente, respectivamente. Dentre os métodos que avaliam a distribuição de tensões em torno dos implantes, a Correlação de Imagem Digital (CID) leva vantagens no que diz respeito à possibilidade de avaliar a distribuição das tensões de forma contínua por meio de imagens obtidas ao longo do tempo, durante carregamento oclusal. Diante disso, este trabalho avaliou qualitativa e quantitativamente o desempenho biomecânico de próteses fixas metaloplásticas parafusadas, unidas e isoladas, sobre implantes de diferentes comprimentos, posicionados na região posterior da mandíbula, por meio do método de CID. A partir de quatro modelos mestres, foram confeccionados quatro modelos em resina de poliuretano F16, simulando extremidade livre mandibular, com o dente 44 em resina (Luxatemp) e os dentes 45, 46 e 47 substituídos por implantes curtos (4 x 5 mm) e/ou convencionais (4 x 11 mm). Os grupos (G) deste estudo foram: G1 (dois implantes convencionais [45 e 46] e um curto [47]), G2 (um implante convencional [45] e dois curtos [46 e 47]), G3 (três implantes curtos) e G4 (três implantes convencionais). Próteses fixas metaloplásticas unidas e isoladas foram parafusadas sobre os intermediários e submetidas a diferentes carregamentos oclusais de 250N: puntiforme (distal do 47 e mesial do 45) e oclusal distribuído. Tensões na direção horizontal (&epsilon;xx) foram calculadas e comparadas qualitativa e quantitativamente pelo software de CID (Davis 8.0, LaVision GmbH). Em geral, houve uma concentração de tensões em maior intensidade nas áreas onde os implantes curtos estavam posicionados. No carregamento puntiforme no segundo molar, houve uma predominância de tensões de compressão e tração nos planejamentos com coroas unidas e isoladas, respectivamente, e as tensões de maior magnitude foram encontradas no G2, G3 e G4 com coroas isoladas (p>0,05), apresentando valores mediados (&mu;S) equivalentes a 396,08, 360,45 e 354,04, respectivamente. No carregamento puntiforme envolvendo o segundo pré-molar, houve predominância de tensões de compressão em todos os planejamentos, com magnitudes mais elevadas nos grupos com coroas unidas (p<0,05). As simulações com carga oclusal distribuída revelaram, também, predominância de tensões de compressão em todos os planejamentos, com maior magnitude nos grupos com coroas unidas, sobretudo no G1 (-464,05±106,43) e G3 (-474,39±179,54) e com diferenças estatisticamente significantes em relação aos demais grupos (p<0,05). Dentro das limitações deste estudo, pode-se concluir que a esplintagem das coroas sobre múltiplos implantes promoveu maior concentração de tensões em torno dos implantes durante os carregamentos puntiforme no segundo pré-molar e oclusal distribuído, reforçando a necessidade de contato interproximal e ajuste oclusal efetivos para promover melhor distribuição das tensões. Adicionalmente, a combinação de implantes curtos e convencionais parece ser uma alternativa viável na reabilitação de áreas edêntulas posteriores com altura óssea reduzida. / In cases of severe vertical bone loss, especially in the posterior region of the mandible, the use of short implants associated with splinted resin-veneered fixed dental prostheses (FDPs) can be an alternative to bone graft surgery and better force transmission to the adjacent bone, respectively. Among the methods to evaluate the stress distribution around the implants, the digital image correlation (DIC) has advantages as regards the possibility of evaluating the stress distribution continuously using images taken over time, during occlusal loading. Thus, this study evaluated qualitatively and quantitatively the biomechanical behavior of splinted and non-splinted resin-veneered FDPs, screw-retained on implants of different lengths positioned in the posterior region of the mandible with the aid of the DIC method. Four F16 polyurethane resin models were fabricated to simulate half of the mandibular arch containing tooth 44 in resin (Luxatemp) and teeth 45, 46 and 47 replaced by short (4 x 5 mm) and/or conventional (4 x 11 mm) implants. Groups (G) of this study were: G1 (two conventional implants [45 and 46] and one short implant [47]), G2 (one conventional implant [45] and two short implants [46 and 47]) G3 (three short implants) and G4 (three conventional implants). Splinted and non-splinted FDPs were screwed to the implant abutment and subjected to different oclusal loads of 250N: punctiform (45 mesial and 47 distal) and balanced occlusal load. Strains in the horizontal direction (&epsilon;xx) were calculated based on displacement and compared qualitatively and quantitatively by the DIC software (Davis 8.0, LaVision Inc.). In general, there was a stress concentration at higher intensity in those areas where short implants were placed. In punctiform load on the second molar, there was a compressive and tensile stresses predominance when splinted and non-splinted crowns were used, respectively, and the stresses of greater magnitude were found in the G2, G3 and G4 with non-splinted crowns (p>0.05), showing median values (&mu;S) equivalent to 396.08, 360.45 and 354.04, respectively. In punctiform load involving the second premolar, there was a compressive stress predominance in all planning with highest magnitudes in groups with splinted crowns (p<0.05). The oclusal load distributed simulations also revealed compressive stresses predominance in all planning, with greater magnitude in groups with splinted crowns, especially in G1 (-464.05 ± 106.43) and G3 (-474.39 ± 179.54), both with statistically significant differences when compared to the other groups (p<0.05). Within the limitations of this study, it can be concluded that splinting multiple adjacent implant supported provided a high stress concentration around the implants during punctiform (45 mesial) and balanced occlusal load, reinforcing the need for effective interproximal contact and oclusal adjustment to promote better stress distribution. Additionally, the combination of short and conventional implants seems to be a viable alternative in the rehabilitation of mandibular free end with reduced bone height.