Дисертації з теми "Joints"

Hip joint is one of the important load bearing joints and has been extensively studied to investigate contact mechanics and tribology. It has known to experience high contact forces and stresses. However, cartilage shows remarkable lubricating and wear properties, and survives the lifetime of a person. Biphasic lubrication based on the principle of fluid load support has provided an explanation for this. However, when, the cartilage fails the part or whole of the joint needs to be replaced and hemiarthroplasty is one such remedy. Three-dimensional finite element models with elastic/hyperelastic cartilage have been used to investigate contact mechanics of the hip joint. However, to understand the role of interstitial fluid in contact mechanics and tribology, cartilage has to be modelled as biphasic material. Interventions such as hemiarthroplasty may alter this phenomenon and hence it is also important to know the extent of this effect. This study was thus an attempt to address these issues. An algorithm developed earlier for 2-D problems was refined, adapted and tested for 3-D problems to detect nodes in contact to impose surface fluid flow conditions. This was then used in natural hip joint where fluid load support was found to be very high (~94%). Three-dimensional hemiarthroplasty was then experimentally verified using porcine hips. The methodology was then used to investigate the effect of clearance in hemiarthroplasty which confirmed the earlier findings that undersizing of the femoral head increases both contact and shear stresses probably leading to cartilage erosion. The investigation of the activities of daily living showed lower contact stresses when compared to the outcomes of clinical studies and depended not only on the magnitude of the load but also on their locations. In all the models the total fluid load support was very high and was between ~90% which supported the biphasic lubrication hypothesis.

Istanbul is a city on the water and historically has been a link between East and West. Unlike most cities, ferry boats are one of the most commonly used means of travel, along with rail and bus lines. There is a contrast between the grandeur of the historic buildings as seen from the water and the unpleasantness of disembarking from the ferry, which berths at a small shed-like structure on the edge of the water which has old tires attached to piles driven into the bank of the Golden Horn. Some distance away there is a bus terminal and train stop. The paths of travel between these are unclear and the area is chaotic. Architecture has the potential to join and connect people, physical forces, the past and present at various scales. This project seeks to accomplish this connection on a particular site by building a new structure out in the water as a central focal point and joining it to rail and bus links with a tunnel and elevated covered walkways.
Master of Architecture

Articular stiffness is an important symptom in most arthritic diseases and appears to be a useful marker of disease activity in rheumatoid arthritis. Attempts to obtain a reliable objective measure of articular stiffness span the last 30 years but a meaningful measure of this symptom remains elusive. A number of reasons have been suggested to explain the discrepancy between objective and subjective stiffness in arthritis and these can be summarised as: a semeiological confusion, aberrant mechano-receptor thresholds and concurrent muscle wasting. This thesis examines each of these hypotheses. Some patients may confuse pain and stiffness or may wish to use other words to describe their joint symptoms. A questionnaire was developed which enabled patients to express their joint symptomatology using a wide range of descriptors. No differences were found between health professionals and patients in their definition of each of the descriptors. The questionnaire discriminated clearly between groups of patients with rheumatoid arthritis, ankylosing spondylitis and non-articular rheumatism. Movement perception threshold was measured in the finger but it was found that subjects relied on cutaneous information. Vibration perception threshold was used as an alternative measure of mechano-receptor thresholds: no abnormalities were found in 50 patients with rheumatoid arthritis. Muscle cross-sectional area was calculated from anthropometric data and the results compared with measurements obtained from computed tomographic scans. A significant decrease in forearm muscle cross-sectional area was found in rheumatoid arthritis but the decrease was not sufficient to explain the reduction in grip strength observed, some of the variation being explained by deformity and pain in the joints. From this study it was possible to make a correction for muscle wasting in previously published stiffness data, revealing significant increases in metacarpo-phalangeal joint stiffness in rheumatoid arthritis. This result was confirmed in new data based on the resonant frequency of the wrist. Further data on the qualitative aspects of muscle were obtained by relating dynamic angular wrist stiffness to level of contraction of forearm muscles. Although arthritic subjects differed significantly from normals at maximum activation, when the results were expressed in terms of absolute grip strength no differences were found, suggesting inhibition of muscle activation in rheumatoid arthritis. It is concluded that symptomatic stiffness is objectively quantifiable in arthritis providing measurements are made in relationship to the equilibrium position of the joint and providing a correction is made for muscle wasting.

Rock joint surface roughness is characterized by using statistical parameters and fractal parameters estimated by various methods. It was found that at least two parameters are required to quantify joint surface roughness. By limiting only to statistical parameters, an average I angle is suggested to capture the large-scale undulations (non-stationary part of roughness) and Z₂' is suggested to capture the small-scale roughness (stationary part of roughness). Fractal parameters estimated by different method were used to describe the stationary part of surface roughness. Relation between fractal dimension estimated by the divider method and roughness was investigated by introducing a new term called specific length. With the help of the specific length it was proved that even though fractal dimension is a useful parameter, it alone is not sufficient to describe roughness. Two fractal roughness parameters, K(d) and D are suggested to quantify the stationary roughness. Available box methods were found not suitable for quantification of roughness of non-self-similar profiles. Using the initial portion of the variogram function a relation between the fractal dimension and a variogram parameter is presented. It is clear that at least two variogram/fractal related parameters are needed to describe at least two variogram/fractal related parameters are needed to describe stationary roughness. The fractal dimension D and Kᵥ are suggested to quantify stationary roughness. The power spectral density function is used to obtain spectral parameters to quantify stationary roughness. The relation between the fractal dimension and a spectral parameter is given. It is shown that the fractal dimension alone is insufficient to characterize stationary roughness of non-self-similar profiles. The fractal dimension and the spectral intercept K(s) are suggested to quantify stationary roughness. Four new equations are suggested to predict peak shear strength of joints incorporating one or two aforementioned parameters to capture stationary roughness and I angle to capture non-stationary roughness. Roughness parameters should be calculated in different directions to capture the anisotropic roughness that exist in most of rock joint surfaces. The validation exercise performed showed clearly that the new equations have a good capability of predicting anisotropic peak shear strength of joints.

Asphalt joints are inevitable parts of every pavement. They are constructed for different reasons. Although much attention is dedicated to the construction joints (hot with hot pavement), a scientific approach for cold joints (cold with hot pavement) with respect to large patch constructions is still missing. This report tries to evaluate existing construction techniques and to suggest new testing methods of tests. Although, indirect tensile tests IDT and direct tension tests DTT are familiar in the field of asphalt pavement characterization, they have not been used for the assessment of joint quality so far. In this report, these two test types are evaluated and the results are analyzed using finite element software ABAQUS. The results of the comparison of joint compaction techniques on a laboratory scale suggest that joints with angles seem to show more promising behavior than vertical joints. Also, starting compaction from the hot side generally produces better results than compaction starting from cold side.

Complex systems composed of many substructures include various structural joints connecting the substructures together. These mechanical connections play a significant role in predicting the dynamic characteristics of the assembled systems accurately. Therefore, equivalent dynamic models of joints that consist of stiffness and damping elements should be developed and the joint parameters should be determined for an accurate vibration analysis. Since it is difficult to estimate joint parameters accurately by using a pure analytical approach, it is a general practice to use experimental measurements to model joints connecting substructures. In this study an experimental identification method is suggested. In this approach the frequency response functions (FRFs) of substructures and the coupled structure are measured and FRF decoupling method is used to identify equivalent dynamic characteristics of bolted joints. Since rotational degrees of freedom (RDOF) in connection dynamics is very important, a structural joint is modeled with translational, rotational and cross-coupling stiffness and damping terms. FRF synthesis and finite-difference formulations are used for the estimation of unmeasured FRFs and RDOF related FRFs, respectively. The validity and application of the proposed method are demonstrated both numerically and experimentally. In simulation studies, simulated experimental values are used, and it is seen that the identification results are prone to high errors due to noise in measurement and the matrix inversions in the identification equations. In order to reduce the effect of noise, it is proposed to extract the joint properties by taking the average of the results obtained at several frequencies in the frequency regions sensitive to joint parameters. Yet, it is observed in practical applications that experimental errors combine with the measurement noise and the identification results still may not be so accurate. In order to solve this problem, an update algorithm is developed. In the approach proposed, the identified dynamic parameters are used as initial estimates and then optimum dynamic parameters representing the joint are obtained by using an optimization algorithm. The application of the proposed method is performed on a bolted assembly. It is shown with experimental studies that this method is very successful in identifying bolted joint parameters. The accuracy and applicability of the identification method suggested are illustrated by using a dynamically identified bolt in a new structure, and showing that the calculated FRFs in which identified joint parameters are used, match perfectly with the measured ones for the new structure. In this study, the effects of bolt size and quality of bolts, as well as the bolt torque on the joint properties are also studied by making a series of experiments and identifying the joint parameters for each case.

All but the simplest physical systems contains mechanical joints. The behavior of these joints is sometimes the dominant factor in over all system behavior. The potential for occurence of microslip and macroslip normally makes the behavior of joints non-linear. Accurate modeling of joints requires a non-linear ramework. As clamping pressures are typically random ad variable, the behavior of the joints becomes random. Joint geometries are random along with other unknowns of the joints. Two different methods for measuring the energy dissipation are explained. In the experimental method, the energy dissipation of a non-linear joint is calculated from the slope of the envelope of the time response of acceleration. The simulation work is carried out by considering a smooth hysteresis model with the help of Matlab programming. Finally, the parameters are extracted for a specific non-linear system by comparing analytical and experimental results.
0736988322

Bolted joints provide one of the most common means of joining two structural components together. The joints themselves use friction to transmit force, torque and motion across a common interface from one component to another. In many cases a pretensioned bolt, running through a common hole at the joint interface, provides the clamping force. The friction force at a joint interface is highly nonlinear. This makes the analysis of dynamic systelTIS with joints unrealistic with conventional linear techniques. It has also been shown that the contact pressure at a joint interface is not necessarily uniform. A variable contact pressure results in a variable limiting friction load. Where the contact pressure can be shown to be smallest on an interface, local microslip can take place whilst the joint maintains its sticking contact elsewhere. Microslip is responsible for the dissipation of energy from within bolted joints that otherwise maintain their integrity. The level of energy dissipation caused by microslip can be significantly larger than that provided by other dissipative mechanisms within a structure. This provides an incentive to be able to describe and predict the energy losses and overall joint behaviour accurately. Difficulties arise when considering 3-Dimensional contact, changing contact conditions during dynamic loading and the nonlinear nature of friction phenomena. To investigate microslip behaviour in bolted joints a detailed finite element model of an isolated lap joint interface was constructed. The joint interface was subjected to a variety of preloads and applied torque. Output from the joint is in the form of hysteresis loops that reveal information about the energy dissipated and overall joint stiffness during a loading cycle. Representative models are presented that reduce the complexity of the joint, yet still maintain the defining characteristics of the hysteretic behaviour. The first representative model uses Jenkins elements that match the physical response of the joint at a number of discrete points during the loading cycle. Good agreement between the finite element model and the Jenkins element model is illustrated. The Jenkins element model is also capable of predicting the response of the finite element model when different magnitudes of preload and applied torque are applied. The second representative model is the Bouc-Wen representation of hysteresis. This model offers significant gains in efficiency when approximating the smooth transition from a fully sticking interface to the onset of joint failure. All of the hysteresis can be described using just four parameters, and matching with the finite element model is demonstrated. To demonstrate microslip behaviour physically an individual joint was experimentally analysed. A cantilever beam with a single lap joint near the clamped end is resonated to generate the dynamic joint hysteresis. The joint behaviour is monitored by local time domain measurements at a number of different preloads and excitation amplitudes. Microslip is demonstrated in the joint when the preload is reduced from a maximum "rigid" clamping value. Notably at low preloads the spectral content of the response reveals a large contribution from the superharmonics of the excitation frequency. Both the Jenkins element model and the Bouc-Wen model are successfully matched to the hysteresis output of the experimental joint.

This thesis is concerned with an experimental investigation of the behaviour of lapped joints in reinforced concrete. A review of existing literature highlights the need to establish the longitudinal strain distribution along lap joints. This has been achieved experimentally, with detailed strain measurements being taken using a technique of internally gauging the reinforcing rods. In some specimens, strain concentration gauges were installed at the tip of the lap to permit the acquisition of particularly localised information. Computer programs were developed to process the substantial amounts of data generated during the course of each test. Two series of tests were undertaken, both using axially loaded specimens, and dealing with tension and compression lap joints respectively. The laps ranged in length from 125 to 750 mm, and comprised bars of either 12 or 20 mm diameter. Transverse reinforcement was provided in two of the tension specimens. Greater emphasis was placed on the first series, with fifteen tension specimens being tested. Thirteen of these tests were each completed within a single day but, additionally, two long-term tests were undertaken. In the latter, a constant load was sustained for up to 81 days. The measurements clearly showed the changing behaviour of the specimens, first as transverse cracks developed and subsequently as failure of the lap joint was approached. The comprehensive analysis of the test results includes a comparison of the ultimate behaviour of these joints with existing design proposals and regulations. The detailed information provided by the strain measurements enables the justification of design assumptions regarding lap joint behaviour, and thus lends greater confidence to existing design regulations. The results from five compression specimens were analysed and compared with the tension tests. The significant contribution to force transfer made by the bearing of the free end of the steel against the concrete was evident. The specimens were loaded to the rig capacity without failing. Additional strain measurements were taken in one tension and one compression specimen by casting embedment gauges within the concrete. These gauges were arranged to measure the circumferential strains in the specimen, and were complemented by strain gauges mounted on the surface of the concrete. The data thus obtained permitted a comparison of the bursting forces set up inside and outside the lap joints. The work showed that some aspects of lap joint behaviour require clarification. Suggestions for further work are included.

Des tests de fissuration ont été réalisés sur des joints collés asymétriques. Ces assemblages asymétriques sont constitués de deux substrats de nature et/ou d’épaisseur différentes liés par un adhésif. Cette géométrie d’éprouvette semble peu utilisée pour effectuer des essais de fissuration. Elles présentent certains inconvénients et de ce fait n’ont fait l’objet d’aucune normalisation. Dans le cadre cette géométrie d’éprouvette d’essai a été néanmoins été retenue et utilisée dans trois configurations différentes pour la caractérisation mécanique des assemblages collés. Des protocoles d’essai et les schéma d’analyse associés ont été définis pour des essais de fissuration à vitesse de déplacement imposé (CRT : Constant Rate Test), à force imposée (CFT : Constant Force Test) ainsi qu’à déplacement imposé (CDT : Constant Displacement Test). Les analyses ont pu être étalonnées au moyen d’un étau matérialisant artificiellement la position d’un fissure. De nombreuses configurations ont été étudiées à l’occasion de ce travail tant du point de vue des adhésifs utilisés (epoxy, cyanoacrylate, acrylic mastic, PSA) que du point de vue des substrats encollés (alliage d’aluminium, composite à matrice organique, polycarbonate). Ces nouveaux tests s’avèrent prometteurs car ils permettent de suivre de façon continu et précision la propagation de fissure au sein de la liaison. En outre, l’analyse des déformations mesurées par extensométrie lors d’essai réalisés à déplacement imposé (CDT) permet un suivi précis de la réponse de la couche adhésive dans la zone contrainte et d’estimer la taille de cette dernière, y compris lorsque la colle est dans un état métastable. Un autre résultat important de ce travail concerne l’analyse de la modification du front de fissure celle-ci voit une diminution de l’adhésion entre les deux substrats. Enfin, un calcul plus précis du taux de restitution d’énergie a été proposé pour prendre en compte le caractère élastique de la couche adhésive, mais permettant aussi de mieux appréhender la redistribution des contraintes dans la colle, et ainsi mieux interpréter les essais mécaniques réalisés. Des analyses par Microscopie à Force Atomique (AFM) ainsi qu’au microscope électronique à balayage (MEB) ont été effectués sur les substrats encollés pour évaluer l’impact des traitements de surface. Des simulations numériques par la method des éléments finis ont été réalisées pour determiner l’état de contrainte dans nos éprouvette d’essai et ainsi expliquer la courbure du front de fissure et les faciès de rupture observés. Les nouvelles configurations expérimentales décrites dans ce manuscript nous paraissent prometteuses car elle offrent une amelioration très significative en terme de fiabilité et précision comparativement aux tests présentés habituellement pour ce type de travaux
Adhesion was studied in asymmetric bonded joints using fracture mechanics tests. The asymmetric bonded joints consist of two different type and/or thickness materials bonded by an adhesive. Mentions of asymmetric bonded joint tests employed so far are rare in the literature. They are imperfect and therefore are not standardized. Accordingly three new tests were introduced in this work to study bonded joints. The new metrological routines and models were built for the CRT (Constant Rate Test), CFT (Constant Force Test) and the CDT (Constant Displacement Test). The routines were validated with the new Artificial Crack Tip test developed in this thesis. Different bonded systems were examined: the adhesives - epoxy, cyanoacrylate, acrylic mastic, PSA; the bonded adherends - aluminium alloys, CFRP composites and polycarbonate. The results obtained in the new tests are very promising in terms of the accuracy and continuous observation of crack kinetics. In addition it was found that the novel strain gauge technique, introduced in the CDT, test allows precise joint monitoring when the adhesive is in a metastable state and a precise estimation of process zone. Another interesting achievement of this work was describing the phenomenon of double crack curvature in the vicinity of the strong – weak adhesion transition zone. The next achievement was derivation of the strain energy release rate from the elastic foundation model, which gives better understanding of the mechanics and the measurements behind adhesive bonding. Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM) studies were made of the bonded substrates to estimate the surface treatment effects. The stress state in asymmetric geometry was studied using finite element analysis (FEA), which explained the formation of the curved crack front and the origin of river patterns. The new tests developed in this study appear promising since they offer accurate and reliable results for the materials tested
W pracy przedstawiono wyniki badan asymetrycznych zlaczy adhezyjnych z wykorzystaniem prób mechaniki pekania. Asymetryczne zlacza klejone powstaja przez polaczenie dwóch dowolnych materialów, o innym wskazniku na zginanie, za pomoca kleju. Zaproponowano trzy nowe metody eksperymentalne dla których zaprojektowano i zbudowano stanowiska badawcze. Poprawnosc modeli fizycznych i matematycznych wykorzystanych do interpretacji badanych zjawisk potwierdzono wykorzystujac opracowana w pracy próbe ze sztucznym frontem pekniecia. Próby przeprowadzono na zlaczach klejonych wykorzystujac kleje: epoksydowe, cjanoakrylowy, typu Mastic i PSA, laczonymi materialami byly: stopy aluminium, kompozyt weglowy oraz poliweglan. Wyniki badan uzyskane przy wykorzystaniu nowych metod wskazuja na ich pewnosc i dokladnosc, dodatkowo umozliwiaja ciagla obserwacje propagujacego pekniecia. Nowa metoda pomiaru parametrów mechaniki pekania oparta na pomiarach tensometrycznych zostala z powodzeniem zastosowana do zlaczy w których klej znajduje sie w stanie metastabilnym. W pracy zaobserwowano i przeanalizowano zjawisko powstawania podwójnego frontu pekniecia na granicy osrodków o róznych silach adhezji, dotad nie opisanego. Po raz pierwszy wyprowadzono równanie szybkosci uwalniania energii sprezystej wykorzystujac model belki na sprezystym podlozu, co umozliwia lepsze zrozumienie zachowania sie zlaczy klejonych. Przeprowadzone badania z uzyciem mikroskopii sil atomowych (AFM) oraz skaningowej mikroskopii elektronowej (SEM) umozliwily ocene efektów obróbki powierzchniowej stopów aluminium. W pracy dokonano analizy naprezen w asymetrycznych zlaczach adhezyjnych z wykorzystaniem metody elementów skonczonych (FEM). Analiza FEM pozwolila na wyjasnienie zjawiska powstawania zakrzywionego frontu pekniecia w badanych przelomach. Zaproponowane nowe metody badan zlaczy asymetrycznych zapewniaja dokladnosc i pewnosc pomiaru dla materialów wykorzystanych w badaniach

One of the most important requirements of an adhesive joint is the ability to retain a significant proportion of its load-bearing capability for the long periods under the wide variety of environmental conditions encountered during its service-life. There exists a need to improve the understanding of the mechanics and mechanisms associated with the durability of adhesive joints in hostile environments, such as one of the most potentially damaging and frequently encountered, water, to further their future extensive use in engineering applications. In the present research, four important aspects in relation to the durability of adhesive joints have been investigated. These were: (a) developing sound short-term accelerated test methodologies to assess the durability of adhesive joints; (b) understanding the mechanisms of environmental attack on different types of surface pretreated adhesively bonded aluminium alloy substrates; (c) developing adhesive/primer/pretreatment systems which possess excellent long-term durability; and (d) investigating the potential of environmentally-friendly organosilanes as primers to enhance the intrinsic adhesion of adhesive joints. The results from these studies showed that: (a) constant displacement rate and cyclicfatigue tests provide excellent quantitative durability test methodologies; (b) fracture mechanics and advanced surface analysis of adhesive joints have proven surface pretreatments using phosphoric acid anodising (PAA) are far superior to those employing a grit blasting and degreasing (GBD) pretreatment which can be attributed to the increased surface area and excellent bonding morphology of the anodised oxide surface, allowing deep penetration of the viscous adhesive and impeding water ingress at the adhesive/substrate interface; (c) the durability performance of PAA pretreated adhesive joints employing a primer (PAAP) are superior to those without a primer specifically in water, and acid-based surface pretreatments are significantly advanced compared to simple GBD; and (d) the self assembling long carbon-chain silanes enhance the durability of adhesive joints via the formation of covalent bonds between the adhesive and the activated silane monolayer deposited on the substrate.

Rail joints have been in existence for a long time of which their design has remained primarily unchanged over this period. Rail joints are a typical example of bolted joints. Like other bolted joints, their integrity depends on the quantitative representation of the contact pressure distribution at the interface during design. In service, rail joints are subjected to complex operating stresses, and they demand high maintenance cost because they are safety critical and have the lowest service life of the components on the rail tracks. In this study, non-intrusive ultrasonic techniques have been employed to investigate the parameter relevant to their design, operation and condition monitoring. The effect of variation in plate thickness and diameter of the bearing surface of the bolt head on the contact pressure distribution at bolted interfaces under varying axial loads was investigated. While it was observed that the contact pressure at the interface increases as the applied load increases, the distance from the edge of the bolt hole at which the distribution becomes stable is independent of the applied load on the bolted joint. However, the contact pressure distribution was observed to vary with the plate thickness. Although the variation in the peak value of average contact pressure distribution in bolted joints does not depend on the plate thickness, the distance from the edge of bolt hole at which the value of the distribution becomes stable increases as the plate thickness is increased. It was revealed that the peak value of the contact pressure distribution decreases as bearing diameter of the bolt head increases, and that the distance at which the normalised average contact pressure distributions become fairly constant also increases as the bearing diameter of the bolt head increases. In the majority of the cases, the distance falls between 3 and 4 of the bolt radius from the edge of the bolt hole. It was also observed that the edge of the bolt head has a pronounced effect on the position of the peak value of the contact pressure distribution at the interface. Furthermore, a model based on a Weibull distribution has been proposed to fit the experimental data, and a good correlation was observed. Non-intrusive experimental techniques were simultaneously used to investigate the relaxation of contact pressure and loosening of bolted joints subjected to cyclic shear loading. Three critical areas: the contact interface of bolted component, the bolt length and the rotation of the bolt head, were monitored during loosening of the joints. The results show that loosening of bolted joints can be grouped into four stages. The early stage of the loosening of bolted joints is characterised by cyclic strain ratcheting- loosening of the bolted joint during vibration without rotation of the bolt head. The higher the rate of relaxation at this early stage the lower is the resistance of the bolted joint to vibration induced loosening of bolted joints. Furthermore, the rate of loosening at the bolted joint interface is not the same but increases away from the bolt hole. While the rate of loosening of bolted joints largely depends on the amplitude and the number of cycles of the applied dynamic shear load, it is independent of the frequency of the applied load. In addition, increasing the bolt torque was found to increase the loosening resistance of the bolted joint. When joints are subjected to a constant shear load in addition to the dynamic shear load, the loosening rate increase, and this rate depend on the magnitude of this constant shear load. A normal incidence pulse-echo ultrasonic technique was used to monitor de-bonding at the interface of adhesive bonded insulated lap joints and insulated block joints, subjected to a shear load induced failure. The results revealed that the insulated joint exhibited elastic behaviour before a sudden failure (rupture) of the joint. The de-bonding of adhesive/insulating layer on the web sides of IBJs was found to occur earlier than at any other parts of the joint when the applied load was only a fraction of the peak of the shear load. However, the de-bonding at the top and foot of the rail occurred almost at the peak of the shear load. This same technique was used to monitor the degradation, and eventual failure of IBJs subjected to cyclic shear loading. The results showed that the degradation of the adhesive insulating layer has commenced, and was in progress when the joint was virtually intact and displayed elastic behaviours. The failure at the adhesive interface is indicated by a sudden change in the value of the measured reflection coefficient. After this, the failure of the joint is preceded by plastic behaviour of the joint. In addition, the change in the length of the bolts can also be monitored directly, as a complete failure at the interface of the bolted joints can be highlighted before the failure occurred. The results of this study have shown that, with further development, ultrasound can be used to monitor the condition of IBJs while in service.

Aprés un bref historique du probléme chapitre I nous avons analysé dans le chapitre II à l'aide de la théorie des mécanismes les différentes solutions possibles de transmission cinématique entre le différentiel et la roue. On montre qu'il existe 3 familles possibles :1) L'une avec une seule boucle cinématique 2)La deuxième utilise 2 boucles cinématiques 3) La troisième utilise 3 boucles cinématiques et conduit aux différents tripodes. Dans le chapitre III on étudie la géome��trie complète des transmissions envisagées. On montre que le joint tripode à point fixe est approché par un mouvement dont l'axe décrit un cône et qu'il est quasi homocinétique. Dans chapitre IV, V, VI nous analysons la transmission des efforts avec frottements en fonction de l'angle d'entrée pour les tripodes de type GI (Glaenszer intérieur), FTJ (Fraa Tripode Joint) et AAR (Angular Adjusted Roller). On met en évidence l' effort de martèlement, ses variations en fonction de l'angle d' entrée, de la géométrie et des coefficients de frottement de glissement. On calcile le rendement. On compare ces résultats théoriques avec des données expérimentales issues de la bibliographie
After a brief background of the subject, chapter 1, is developed in chapter 2,the analysis of all possible solutions of cinematic transmission between the driveshaft and the wheel, based on the theory of mechanisms. It is shown that there are 3 possibilities : 1. The first with only one cinematic loop 2. The second uses 2 cinematic loops. 3. The third is based on 3 cinematic loopps and leads to various tripots. In chapter 3, a complete geometric study of transmissions is approached. It is shown that a tripot with a fixed point is approximated by a movement with an axis describing a cone and it is a constant velocity joint. In chapters 4, 5 and 6 transmission of friction efforts is analyzed in function of the angular input , for tripots of type GI (Glaenser Interior). , FTJ (Free Tripot Joint) and AAR (Angular Adjusted Roller). Hammering forces are yeld and their dependency on the angular input on geometry and on sliding friction coefficients are studied. Efficiency is calculated. Theoretic results are compared to experimental data issued to bibliography

Kissing bonds (KBs) refer to the situation where two surfaces are only partially bonded or are debonded but touching or in very close proximity. This may be the consequence of poor adhesion, environmental degradation or impact damage. This defect is not visible macroscopically and because of their intimate contact which makes it more difficult to detect using a non destructive technique (NDT) than conventional defects such as voids or cracks etc. The success of NDT evaluation and widespread use of adhesive bonding rely greatly upon comprehensive knowledge of morphology, surface chemistry and mechanics associated with KBs. Two approaches were successfully taken to produce reliable and repeatable KBs: by surface contamination using a mould release agent (Frekote®700-NC); and by weakening the electrically-debonding adhesive, ElectRelease™, with a low voltage. Significant changes in morphology and elemental distribution of the contaminant at/near the Frekote contaminated interfaces were found. Some morphological and chemical changes at/near the anodic metal/ElectRelease™ interface were also evident. Additional information about chemical interactions at/or near the contaminated interface due to the presence of Frekote and the application of the electric field confirmed the changes in morphology and elemental distribution. Double-lap joints with KBs were tested in tension with local strains captured by strain gauges and extensometer. Significant reduction in failure strength was apparent when using Frekote and ElectRelease™ subjected to the electric field. The tests were simulated using finite element analysis. Cohesive elements were introduced along the predicted failure interfaces taking into account the adhesion loss associated with KBs. The experimental failure load and local strain results were in good agreement with the finite element predictions. The ways that KBs were produced and the understandings in morphology, surface chemistry and their failure mechanisms contributed to the modified criteria of KBs and the development of the non-linear ultrasonic technique investigated by the NDT group at the University of Bristol. The morphology, surface chemistry and failure mechanisms of KBs in adhesive joint are now better understood.

Ce mémoire présente une étude théorique et expérimentale de joints annulaires à bague flottante ainsi que de joints rainurés segmentés, destinés à assurer l’étanchéité dynamique au sein de machines tournantes à haute vitesse dans les domaines aéronautique et aérospatial. Des joints annulaires à bague flottante ont été testés sur un banc d’essais dédié au sein de l’institut Pprime pour de multiples configurations de vitesse de rotation et de différence de pression étanchée. La réponse dynamique des joints par rapport aux vibrations du rotor a été étudiée pour différentes amplitudes de l’excitation. Certains résultats issus de cette étude ont été confrontés à une modélisation numérique basée sur les équations de mouvement d’un joint soumis aux forces d’inertie, aux forces hydrodynamiques dans son étanchéité principale et aux forces de frottement à l’étanchéité secondaire. Le coefficient de frottement à l’étanchéité secondaire a été estimé à partir du modèle de Greenwood et Williamson, appliqué au cas d’un régime de lubrification mixte. Les comparaisons réalisées valident le modèle numérique utilisé, qui reproduit le comportement d’un joint soumis à une excitation rotorique donnée. Un autre modèle est proposé pour le cas des joints rainurés segmentés. Les écoulements au sein des différentes parties d’un tel joint ont été modélisés par des méthodes distinctes. Les forces de frottement sont étudiées par un modèle similaire à celui utilisé dans le cas des bagues flottantes. Une étude paramétrique sur différentes caractéristiques géométriques et de fonctionnement du joint a été menée
This thesis presents a theoretical and experimental study of floating ring annular seals and radial segmented seals. These seals are designed to prevent leakage inside high-speed rotating machinery used in aeronautics and aerospace applications. Floating ring annular seals were tested on a dedicated test rig inside the Institut Pprime. Various rotation speed and pressure difference configurations were used. The behavior of the floating rings when submitted to rotor vibrations was studied for different excitation amplitudes. Results from this study were confronted to a numerical model based on the equations of motion of the seal. The seal is driven by inertia forces, hydrodynamic forces in the main seal and friction forces on the secondary seal. The friction coefficient on the secondary seal was estimated by Greenwood and Williamson’s model for mixed lubrication. The analysis validates the theoretical model, which reproduces the dynamic behavior of a seal driven by a given rotor excitation. Another model was used to study segmented seals. The flow in each part of such a seal was modeled with various methods. Friction forces were studied with a model similar to that used for floating rings. A parametric study was performed on various geometric and operating parameters

Thesis (M.S.)--West Virginia University, 2004.
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In performing manual tasks, muscles are voluntarily contracted in order to produce force and orient the limb in the desired direction. Many occupational tasks are associated with frequent musculoskeletal disorders. In tasks involving skilful manipulation, very frequently the forces are focused on the upper limb and neck. Upper extremity cumulative trauma disorders are among the more common worker related injuries. These muscle disorders may be related to repetitive exertions, excessive muscle loads and extreme postures. One of the major challenges is to quantify the muscle load and researchers have tried various measures to quantify muscle load. Joint mechanical impedance can be a robust method to quantify muscle load. Joint mechanical impedance characterizes the dynamic torque-angle relationship of the joint. Joint impedance has been measured by earlier researchers, for limited tasks, by imparting force (or angle) perturbations on the joint and relating resultant angular (or force) changes. The joint impedance gives a quantitative measure related to muscle co-contraction level. Measurement of the mechanical impedance at the workplace may provide useful information relevant to the understanding of upper limb disorders. Electromyogram (EMG) is the electrical activity of the muscle. Usually, an estimate of the EMG amplitude is obtained from the raw waveform recorded from the surface of the skin. EMG amplitude estimates can be used to non-invasively estimate torque about joints. Presently, there exists no means by which mechanical impedance can be estimated non-invasively (i.e., without external perturbations). Therefore, we proposed the use of EMG to noninvasively estimate the joint mechanical impedance. Our objective in this project was to determine the extent to which surface EMG can be used to estimate mechanical impedance. Simulation studies were first performed to understand the extent to which this tool could be useful and to determine methods to be used for the experiment. The simulations were followed by evaluating and estimating mechanical impedance using data collected from one experimental subject. Simulations helped to devise processing techniques for the measured signals and also to determine the length of data to be collected. Low pass filters for derivatives (used in the development of impedance estimates) were designed. Subtracting out a polynomial was the best approach to attenuate a low frequency drift (artifact) that occurs in torque measurements. Thirty seconds of data provided impedance estimates with a relative error of 5% when EMG amplitude estimates with SNR of 15 were used. Experimental data from constant-posture, slowly force-varying background torque level showed that the elbow joint system behaved like a second order linear system between 2 Hz and 10 Hz. Co-contraction by subjects during experiments caused impedance estimates to be unexpectedly high even at low background torque. Further experiments would need to be conducted with the subjects being instructed to avoid co-contraction.

Le comportement mécanique en cisaillement sous contrainte normale constante de joints rocheux est étudié en utilisant une approche numérique par éléments discrets (DEM Discrete Element Model). Les influences respectives de la rugosité des surfaces des joints, de l'élasticité des épontes, de la rupture des aspérités de surface et du niveau de contrainte de compression sur les comportements en fermeture et cisaillement des joints rocheux sont particulièrement analysées. Pour la première fois la rugosité des joints considérée comme auto-affine est utilisée avec DEM pour étudier le frottement des joints rocheux. Cette rugosité est décrite par l’intermédiaire de trois paramètres :exposant de rugosité auto-affine, longueur de corrélation auto-affine et variance des fluctuations de hauteur. Sur la base d’un algorithme fondé sur la méthode spectrale, huit surfaces auto-affines isotropes correspondant à différentes rugosités ont été générées. Ces surfaces numériques sont utilisées comme moules permettant de générer les surfaces composées d’éléments discrets utilisées dans la suite de l’étude. La modélisation par éléments discrets s’appuie sur une calibration des propriétés élastiques effectuée à partir d’un volume élémentaire représentatif suivie de l’implémentation d’un critère elliptique de contraintes de rupture (au niveau des lois d’union entre éléments) permettant de simuler les grandes lignes du comportement quasi-fragile d’un mortier(utilisé lors d’expérimentations antérieures). Sur cette base et une fois les surfaces rugueuses implémentées dans les modèles DEM, les essais de fermeture (test de compression) des huit joints sont effectués sous deux niveaux de contrainte de compression : 14 MPa et 21 MPa. Par la suite, les joints sont cisaillés selon deux directions perpendiculaires. Pour chaque direction de cisaillement et chaque niveau de contrainte de compression, les joints sont testés en utilisant trois modèles mécaniques différents : 1) modèle rigide dans lequel, à l’exception des surfaces de joint en contact,les épontes ne peuvent pas se déformer, 2) modèle élastique dans lequel les épontes peuvent se déformer dans leur volume et 3) modèle élastique-fracture dans lequel les épontes peuvent se déformer dans leur volume et les liens entre les particules peuvent rompre selon le critère elliptique de contrainte. L'utilisation de ces trois modèles mécaniques différents permet d'étudier de façon systématique l'influence de la rugosité seule (modèle rigide), l'influence de l'élasticité et de la rugosité (modèle élastique) et enfin, l'effet combiné de la rugosité, de l'élasticité et de la rupture(modèle élastique-fracture). L’étude des résultats obtenus lors des simulations DEM est accompagnée d’une analyse énergétique permettant d’estimer l’évolution de l’énergie élastique stockée dans le système, de l’énergie de friction, du travail associé à la dilatance du joint et de l’énergie dissipée au cours de l’essai de cisaillement
The shear behavior of rock joints under constant normal stress is studied using Discrete Element Method (DEM). The respective influences of joint surface roughness, elasticity of medium, fracture of surface asperities, and level of compression load on the closure and shear behaviors of rock joints are particularly analyzed. For the first time the roughness of the joints considered as self-affine is use dwith DEM to study the friction of rock joints, the roughness is described through three parameters:self-affine roughness exponent, self-affine correlation length and height variance. Using a numerical algorithm based on spectral method, eight isotropic self-affine surfaces corresponding to different roughness are generated. Latter, numerical surfaces are used as molds to generate the discrete elements surfaces. The discrete element modeling is premised on a preliminary calibration of the elastic properties performed on a representative elementary volume and on the implementation of the fracture properties (elliptic fracture criterion expressed in stress) describing with a reasonable accuracy the quasi-brittle fracture behavior of mortar (used in previous experimental tests). On this basis and once the roughness surfaces implemented in DEM, the simulations of the compression/closure test are performed on the eight joints and this for two compression stress levels: 14 MPa and 21 MPa. Then, the eight DEM joints are sheared along two perpendicular directions. For each shear direction and each level of compression stress, the joints are tested through three different mechanical models: 1) rigid model in which the medium cannot deform excepted at the contact surface of joints, 2) elastic model in which the medium can deform in its volume and 3) elastic-fracture model in which the medium can deform in its volume and the bondsbetween discrete elements can failed according to the elliptic fracture criterion. The use of these three mechanical models allows studying systematically the influence of the roughness alone (rigidmodel), the influence of elasticity and roughness (elastic model) and finally, the combined effect ofthe joint roughness, of the elasticity and of the fracture (elastic-fracture model). The study of the results obtained from the DEM simulations is followed by an energetic analysis allowing theestimation of the evolutions, as a function of the shear displacement, of the elastic energy stored inthe system, of the friction energy, of the work related to the joint dilatancy and of the energy dissipated by internal damping of the DEM
En esta tesis se estudia la fricción en juntas rocosas utilizando el Método de Elementos Discretos (DEM). En particular, se estudia la influencia de la rugosidad de las superficies de la junta, la elasticidad, la fractura, y el nivel de carga de compresión sobre el comportamiento de cierre y de cizalla de las juntas rocosas. Por primera vez la rugosidad de las juntas considerada como auto-afín esutilizada para estudiar la fricción de juntas rocosas, la rugosidad se describe mediante tres parámetros: el exponente de rugosidad, la longitud de correlación auto-afín y la varianza de alturas. Mediante un algoritmo de computadora basado en métodos espectrales, ocho superficies autoafines isotrópicas con diferente rugosidad fueron creadas. Posteriormente, las ocho superficies fueron utilizadas como moldes para generar las juntas utilizando elementos discretos. Antes de realizar las simulaciones de compresión y cizallaura, se calibraron las propiedades elásticas y defractura (criterio de fractura elíptico basado en esfuerzos) de las juntas numéricas a los datos experimentales (obtenidos previamente) de unas muestras de mortero mediante la utilización de un volumen elemental representativo (REV). Una vez que las propiedades mecánicas de las juntas se obtuvieron mediante la calibración del REV, se realizaron las pruebas de cierre (prueba de compresión) de las ocho juntas DEM. Se utilizaron dos niveles de esfuerzo de compresión para laspruebas de cierre: 14 MPa y 21 MPa. Después, las ocho juntas DEM fueron cizalladas en dos direcciones mutuamente perpendiculares. Para cada dirección de cizalla y cada nivel de esfuerzo decompresión (14 y 21 MPa), las juntas fueron cizalladas usando uno de los tres modelos mecánicos siguientes: 1) un modelo rígido, en el que las juntas no se pueden deformar, excepto en su superficie,2) un modelo puramente elástico, en el que las juntas se pueden deformar en todo su volumen y 3)un modelo elástico con fractura en el que las juntas se pueden deformar en su volumen y, si elesfuerzo sobre las uniones entre partículas excede cierto nivel de esfuerzo máximo, las uniones se rompen de una manera irreversible. El uso de estos tres modelos mecánicos nos permitirá estudiar de manera sistemática: la influencia de la rugosidad (modelo rígido), la influencia de la elasticidad y rugosidad (modelo puramente elástico) y, finalmente, el efecto combinado de la rugosidad de las juntas, la elasticidad y la fractura (modelo elástico con fractura). El estudio de los resultados obtenidos de las simulaciones DEM es seguido por una análisis energético el cual permite estudiar la evolución de los diferentes tipos de energía en función del desplazamiento de cizalla: energía elástica almacenada en el sistema, energía de fricción entre elementos discretos, el trabajo relacionado conla dilatación de la junta y la energía disipada por el amortiguamiento interno del DEM

Le carbure cémenté (WC-Co) est un système biphasé constitué de grains de carbure de tungstène enrobés dans un liant à base de cobalt. Dans ce matériau composite, qui allie donc la dureté du carbure à la résilience du cobalt, la maîtrise de la microstructure est un paramètre clef pour l’optimisation des propriétés mécaniques.Le but de ce travail est de mettre au jour les mécanismes régissant le développement des joint de grain et des joints de phase lors du frittage. L’effet de la teneur en liant, du taux de carbone et du temps de frittage ont été particulièrement étudiés.Ce travail est basée sur la caractérisation du matériau par EBSD (Electron BackScattered Diffraction), une méthode qui facilite la séparation des grains et donc l’utilisation de techniques d’analyse d’image pour étudier la microstructure. En outre un programme basé sur les données d’orientation des grains collectées par EBSD et permettant l’analyse de la texturation des joints de grain et des joints de phase a été développé pour cette étude.L’étude de la contiguité montre qu’elle ne dépend pas du taux de frittage ni de la teneur en carbone du liant, mais essentiellement de la fraction volumique de liant. Cela implique que l’encombrement et l’imbrication des particules sont les principaux paramètres entrant en compte dans l’établissement de la contiguité. Un grossissement plus rapide et plus marqué a été observé dans les échantillons riches en carbone, ainsi que dans ceux présentant un fort taux de liant. Un grossissement anormal a été observé dans les échantillons riches en carbone et à fort taux de liant. La désorientation aux joints de grains est caractérisée par un couple axe/angle décrivant la rotation liant les deux cristaux. L’étude de la distribution des axes a révélé que trois rotations sont particulièrement abondantes : celles autour de [101 ̅0], [21 ̅1 ̅0] et [0001]. Elles représentent environ 30% de la surface totale des joints de grains. Pour chacune des rotations particulières ont été détectées : [101 ̅0]/90°, [21 ̅1 ̅0] / (48°- 60°- 90°) et [0001]/90°. L’étude de la géométrie de ces joints suggère que leur remarquable stabilité est due au fort taux de cohérence dans le plan de joint. L’analyse statistique des plans de joint de grain et de joint de phase montre que la plupart d’entre eux correspond à un plan basal ou prismatique pour au moins l’un des deux grains (70% environ de la surface totale de joint de grain, et 50% environ de la surface totale de joint de phase). Sur la base de ces résultats, un scénario décrivant l’évolution de la microstructure durant le frittage est finalement proposé
WC-Co cemented carbide is a two phase system constituted of a cobalt based binder matrix embedding hard tungsten carbide grains. This material is especially used in fields such as metal cutting or mining, where high mechanical properties are required. Therefore, the microstructure is a key parameter to control to optimize the mechanical properties of the alloy.This work aims at understanding the mechanisms of grain boundary and phase boundary development during sintering, and how they may influence the final microstructure. The effect of the binder content, carbon content and sintering time was especially investigated.Electron BackScattered Diffraction characterization was chosen to conduct this study. First because the precise separation of grains in the resulting images makes possible automation of the measurements, and thus allows a statistical analysis of several microstructural parameters (as grain size, contiguity) on numerous samples. Secondly because orientation data collected by this way make possible the analysis of grain boundary and phase boundary texture. To this end, an automated method was developed for analysis of grain boundaries and estimation of remarkable boundary planes fraction from 2D EBSD measurements.The study of contiguity shows that it does not depend on sintering time or carbon content in the binder, but essentially of the carbide grain volume fraction. This result implies that impingement is the first order parameter in the evolution of contiguity. Grains appear to grow faster and in a larger extent in samples with a carbon rich binder, as well as in high binder content samples. Abnormal grain growth seems to be favored by high binder content in carbon rich samples. All grain boundaries were characterized by a couple of rotation axis and misorientation angle. Three particular rotation axes were identified: [101 ̅0], [21 ̅1 ̅0] and [0001]. They represent around 30% of the total grain boundary surface area. In addition, specific rotations were found to be particularly abundant in the microstructure: [101 ̅0]/90°, [21 ̅1 ̅0] / (48°- 60°- 90°) and [0001]/90°.A study of their geometry suggests that their stability would be due to a particularly coherent boundary plane. A statistical analysis shows that most grain boundaries and phase boundaries have a habit plane parallel to a basal or prismatic plane (about 70% of the total grain boundary surface area and 50% of the total phase boundary area. Finally, a scenario is proposed for the microstructure development model during sintering of cemented carbides on the basis of the results

La structure cristallographique des principaux defauts presents dans les lingots bruts de silicium polycristallin de type polix a ete etudiee par microscopie electronique en transmission (met). Une methode analytique a permis de determiner de facon tres precise des parametres qui caracterisent les joints de grains et les sous-joints. Les precipites presents dans ce materiau ont ete egalement caracterises. Parallelement a cette description structurale, l'activite electrique de ces defauts a ete etudiee au moyen de la microscopie electronique a balayage (meb) par la technique du courant induit par faisceau d'electrons (ebic). Des mesures quantitatives de vitesses de recombinaison des porteurs de charge electrique minoritaires sur les defauts ont ete realisees. Il a ete mis en evidence le role determinant des facteurs chimiques, la segregation d'impuretes et surtout la precipitation sur l'activite ebic des defauts. Ces phenomenes sont cependant modules par les facteurs structuraux

The fracture behaviour of polymer composite-metal joints has been investigated within the context of two real joint applications. A joint intended for the joining of a glass-fibre reinforced vinylester composite (GRP) superstructure to the steel deck of a naval vessel was the starting point for the project. The novel technique lies in the manufacture of the joint in that a steel adherend is incorporated into the superstructure panel during the manufacture of the panel itself by a resin infusion moulding process. One end of this adherend protrudes from the finished panel which can then be welded to the steel deck. The vinylester matrix resin thereby acts as the sole source of adhesion at the composite-metal interface. Characterisation of the mechanical response of this joint highlights the influence of the toughness of the GRP on the joint behaviour. The fracture behaviour of this interface is then investigated to establish the effects of steel surface roughness and heating. Accelerated ageing of the joint in salt and distilled water is carried out and the effect of the GRP mechanical properties and joint mechanical response evaluated. A second application considered has been the joining of a titanium adherend to a carbon-fibre reinforced epoxy composite adherend for use in a racing car suspension system. A comparison of the effectiveness of different titanium surface treatments is made in terms of the surface profile and oxide thickness. A range of adhesive layer thicknesses are used in the manufacture of the joints and the effects of this and the surface treatment on the fracture behaviour are determined. The main conclusions drawn are that the principal factors affecting fracture behaviour of metal-composite joints are adherend surface chemistry, moisture absorption, exposure to elevated temperature, and joint design.

Adhesives can enable significant weight reductions in automotive constructions. However, the performance of adhesive joints and the energy absorption of bonded structures needs to be well understood. This thesis describes the perfonnance of a number of automotive adhesive joints using a fracture mechanics approach. The fracture energy, Gc ' was used to characterise the joint perfonnance during different modes of loading at low and high r,ates. A detailed analysis strategy was developed to account for the different types of crack propagatidn observed and the high rate effects encountered. This analysis also included the use of load-independent equations and incorporated the effects of kinetic energy. A high-speed video system was used to study the fracture behaviour and to measure accurately the deformation ofthe joint and the crack growth. During mode I tests the values of Gc decreased as the test rate was increased. The increase in test rate did not induce significant variations in the initiation values of Gc in mode II and mixed-mode VII when load independent methods were used. Delamination of the composite substrates in some tests complicated the interpretation of the results and made some mixed-mode failure criteria difficult to apply. However, an analytical model was introduced to predict the composite delamination observed in the different tests and this showed an excellent agreement with the observed failure paths. The results obtained for mode I demonstrated that neither test velocity nor crack speed was the parameter controlling the toughness. Instead the time parameter rl/2 appeared to describe the variation in G/c more closely. This parameter relates to the adiabatic heating at the crack tip, which causes a material softening. Thermographic measurements were performed to support this proposal. Finally, structural tests on composite crush tubes showed that adhesively bonded structures can indeed be used with confidence in automotive applications.

This thesis details the work carried out under two research projects at the University of Surrey. The first project titled The Design of Structural Adhesive Joints', was of three years duration from September 1985 to August 1988 and was sponsored by the Science and Engineering Research Council. The second project, sponsored by Ford UK Ltd, and tided 'A General Joint Analysis Facility extended certain aspects of the analysis work initiated In the first period of research. The objective of the work was to address the problem of integrating structural adhesives Into the design process and to provide procedures that would facilitate this integration in a quantitative, rather than the more usual qualitative way. To be effective, such an approach needed to consider not only a means of analyzing a proposed joint but also a way of predicting the actual failure of that joint. An extensive literature survey of analyses available to the design engineer has been completed. The analyses investigated were found to be lacking in several critical respects, and as part of this research, methods of analysis overcoming some of these limitations have been developed. The analyses produced are based on earlier approaches but extended and modified as appropriate. The work on all the analyses produced has been carried out by considering a simple adherend-adhesive sandwich configuration. Five different analyses, considering the sandwich to be modelled with differing degrees of complexity, have been produced. In all of the analyses the adherends are assumed to behave as cylindrically bent plates capable of sustaining both tensile and shear forces and bending moments, with the adhesive transmitting both tensile and/or shear loads. Initially an elastic solution was obtained, adopting a relatively simple approach. This enabled the subsequent enhancement of including non-linear material behaviour to utilize the same governing equations, thus maintaining consistentcy. The General Elastic Analysis (GEA) has been extensively simplified to produce a number of two parameter design formulae suitable for use by an engineer at an early stage in the design process. The two analyses produced by this simplification are called the Simplified Peel Analysis (SPA) and the Simplified Shear Analysis (SSA), so called because they consider the named component of stress in the adhesive layer only. The GEA was then extended to include non-linear material properties in the adhesive layer, and an analysis called the Non-linear Adhesive Analysis (NLAA) was produced. A programme of validation using the NLAA and a non-linear finite element analysis of similar joint configurations was carried out. Additional comparisons with existing analyses have also been undertaken where possible. The NLAA has been shown to produce extremely accurate results for the stresses in the adhesive layer when compared with the component stresses predicted by the finite element method (FEM). The NLAA has been used successfully to determine the spread of yield in a single-lap joint, giving dose agreement with results from analysis using the FEM, but with much reduced computer and operator time. The final stage of the work was concerned with the Inclusion of non-linear adherend material properties, and an analysis called the Full Non-linear Analysis (FNLA) has been produced which Incorporates this refinement to the general model. Again the finite element method has been used to assess the accuracy of this new analysis, and the results from this work are presented here. Derivations of both forms of the elastic analysis and of the non-linear and full non-linear analyses are reported in Chapters 4 and 5 and the software appropriate to each Is described fully. The Initial survey of available literature has shown that there Is considerable lack of knowledge about possible causes of joint failure. Specifically, It Is noted that a criterion by which joint failure can be measured has not been uniquely defined. In an attempt to provide a criterion or criteria to enable the prediction of joint failure a 'Failure Criteria' test and analysis programme has been completed. Joint configurations were manufactured using a range of adhesives with different levels of ductility, and adherends of different stiffnesses. Batches of these test coupons were tested to failure under both predominantly mode I and mode 11ty pes of loading. Both FEM and FNLA analyses of each test configuration have been carried out, and the stress and strain distributions at the levels of failure load were established for each batch and studied to establish any correlation between various proposed failure criteria. Close agreement between certain factors and the equivalent bulk material properties was noted for test batches. The applicability of various failure criteria for both the mode I and mode II test configurations and possible general criteria are discussed. The failure of the mode I test configurations has been shown to be governed by the local level of maximum principal stress at the end of the overlap. The mode II test configurations also show dose agreement in terms of the maximum principal stress, but agreement with bulk data Is poor. Therefore, a further failure criterion is proposed for the mode II joints in terms of the 'global yielding' of the adhesive layer. The bulk property testing of the adherend and adhesive materials to establish their physical properties for use in the finite element analysis of the test programme Is also fully documented.