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1
Lucas, Davidson Glenn. „High Frequency Direct Excitation of Small-Scale Motions in Planar Shear Flows“. Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/10579.
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The effect of direct, small-scale excitation on the evolution of a plane shear layer which forms at the edge of a backward facing step is investigated experimentally using high resolution particle image velocimetry and hot-wire anemometry. Actuation is effected at frequencies that are over an order of magnitude higher than the characteristic (or natural) formation frequency of the layer by a spanwise array of piezoelectrically-driven synthetic jet actuators
that are placed near the edge of the step. The actuation has significant effects on the evolution of both large- and small-scale motions within the shear layer inducing an increase in small-scale dissipation and simultaneous suppression of turbulence production. While the fundamental instabilities that lead to the formation of large scale motions are typically suppressed, low-frequency amplitude-modulation of the actuation signal allows the formation of large scale motions and entrainment which, in concert with the small-scale actuation, lead to enhancement of the turbulent shear stresses throughout the shear layer. Amplitude
modulation is also used to assess the effect of flow transients that are induced by step or low duty cycle actuation. The present findings suggest strategies for controlled suppression or
enhancement of mixing in the near field of the shear layer.
2
Frascoli, Federico. „Chaotic and rheological properties of liquids under planar shear and elongational flows“. Swinburne Research Bank, 2007. http://hdl.handle.net/1959.3/22416.
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Thesis (PhD) - Swinburne University of Technology, Centre for Molecular Simulation - 2007.Dissertation submitted in fulfilment of requirements for the degree Doctor of Philosophy, Centre for Molecular Simulation, Faculty of Information and Communication Technologies, Swinburne University of Technology, 2007. Typescript. Includes bibliographical references (p. 151-161).
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Rara, Angela Dominique Sarmiento. „Rolling Shear Strength and Modulus for Various Southeastern US Wood Species using the Two-Plate Shear Test“. Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104017.
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Cross-Laminated Timber (CLT) is an engineered wood product made by laminating dimensional or structural composite lumber in alternating orthogonal layers. Compared to Canada and Europe, CLT is a novel product to the US. With the additions included in the 2021 International Building Code (IBC), CLT material properties, especially rolling shear, would need to be explored. The increasing demand for softwood lumber, along with the increase of demand of CLT panel production, could place a burden and surpass the domestic softwood supply. Rolling shear is a phenomenon that occurs when the wood fibers in the cross-layers roll over each other because of the shearing forces acting upon a CLT panel when it is loaded out-of-plane. This study used the two-plate shear test from ASTM D2718 to measure the rolling shear properties of various southeastern US wood species: southern pine, yellow-poplar, and soft maple. A secondary study was conducted, using the same two-plate shear test, to measure the rolling shear properties of re-manufactured southern pine for CLT cross-layer application. The soft maple had the greatest average rolling shear strength at 5.93 N/mm2 and southern pine had the lowest average rolling shear strength at 2.51 N/mm2. Using a single factor analysis of variance (ANOVA), the rolling shear strength values from soft maple were significantly greater than yellow-poplar, which was significantly greater than the southern pine. For the rolling shear modulus, the southern pine and soft maple were of equal statistically significant difference, and both were greater statistically significant different compared to the yellow-poplar. The most common failure found from testing was rolling shear.Master of Science
Cross-Laminated Timber (CLT) is an engineered wood panel product, similar to plywood, constructed with solid-sawn or structural composite lumber in alternating perpendicular layers. The additions included in the incoming 2021 International Building Code (IBC) has placed an importance in expanding the research related to the mechanical and material properties of CLT. Also, with the increasing demand for softwood lumber and CLT panel production, the demand for the domestic softwood lumber could place a burden and surpass the domestic softwood supply. Rolling shear is a failure type that occurs when the wood fibers in the cross-layers roll over each other because of the shearing forces acting upon a CLT panel. This study used the two-plate shear test to measure the rolling shear properties of various southeastern US wood species: southern pine, yellow-poplar, and soft maple. A secondary study was conducted, using the same two-plate shear test, to measure the rolling shear properties of re-manufactured southern pine for CLT cross-layer application. The soft maple had the greatest average rolling shear strength at 5.93 N/mm2 and southern pine had the lowest average rolling shear strength at 2.51 N/mm2. Using a single factor analysis of variance (ANOVA), the rolling shear strength values from soft maple were significantly greater than yellow-poplar, which was significantly greater than the southern pine. For the rolling shear modulus, the southern pine and soft maple were of equal statistically significant difference, and both were greater statistically significant different compared to the yellow-poplar. The most common failure found from testing was rolling shear.
4
Papazoglou, Sebastian. „Elucidation of isotropic and anisotropic shear elasticity of in vivo soft tissue using planar magnetic resonance elastography“. Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16136.
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Die Magnetresonanzelastographie (MRE) stellt ein nichtinvasives Verfahren dar, welches die Bestimmung der in vivo Scherelastizität weicher Gewebe ermöglicht. Im Rahmen diese Arbeit wurden Methoden zur Bestimmung isotroper und anisotroper Scherelastizitäten anhand von MRE Wellenbildern entwickelt und evaluiert. Alle in dieser Arbeit vorgestellten Methoden basieren auf planarer MRE, d.h. auf der Aufnahme einer einzelnen Auslenkungskomponente innerhalb der Bildschicht. Dadurch wird die MRE erheblich beschleunigt. Allerdings stellen sich dadurch auch besondere Anforderungen an die Datenauswertung zur Bestimmung aussagekräftiger elastischer Kenngrößen. Anhand von planaren MRE-Experimenten an Gewebephantomen und menschlicher Skelettmuskulatur sowie mittels numerischer Simulation wird gezeigt, dass bei Beachtung weniger experimenteller Randbedingungen und einer darauf abgestimmten Datenauswertung, korrekte Elastizitäten ermittelt werden können. Ein besonderer Schwerpunkt der Arbeit liegt in der Analyse experimenteller Einflüsse wie Bildrauschen und -auflösung auf die ermittelten elastischen Kenngrößen. Des Weiteren werden Methoden zur Bestimmung anisotroper Elastizitäten sowie zur Analyse von Streueffekten im MRE-Wellenbild vorgestellt. Die behandelten Einflüsse auf die Amplituden und Wellenlängen im MRE-Bild, werden vergleichend diskutiert und zusammengefasst, um ein einfaches Verfahrensprotokoll zur Analyse experimenteller in vivo MRE-Daten zu entwickeln. Alle in dieser Arbeit verwendeten Methoden und Programme sind im Anhang zusammengefasst und auf Anforderung erhältlich.Magnetic resonance elastography (MRE) is a noninvasive method that allows the determination of in vivo shear elasticity of soft tissues. In this thesis methods for the determination of isotropic and anisotropic shear elasticities from MRE wave data were developed and evaluated. All methods presented in this work are based on planar MRE, i.e. they are based on the measurement of a single displacement component in the image plane. This way measurement time in MRE is greatly reduced. However, this imposes specific requirements on data evaluation in order to determine significant elastic constants. On the basis of planar MRE experiments on tissue mimicking gels, human skeletal muscle and numerical simulations it is demonstrated that correct shear elasticities can be determined, taking into account a small set of experimental boundary conditions as well as the employment of complementary data evaluation strategies. This thesis is particularly focussed on the analysis of noise and image resolution on the determined elastic constants. Moreover, methods for determining anisotropic elasticity and analyzing shear wave scattering effects on MRE wave data are introduced. The investigated influences on wave amplitudes and wave lengths are compared and discussed to develop a simple measurement protocol for the evaluation of in vivo MRE data. All methods employed in this work are summarized in the appendix along with the corresponding computer code, which is available on demand.
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Hyensjö, Marko. „Fibre Orientation Modelling Applied to Contracting Flows Related to Papermaking“. Doctoral thesis, KTH, Mekanik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4762.
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The main goal of this work was to develop numerical models for studying the behaviour of fibres in an accelerated flow. This is of special interest for e.g. papermaking. The early stage of the paper manufacturing process determines most of the final properties of a paper sheet. The complexity of studying the flow of fibre suspensions both experimentally and numerically emphasises a need for new ideas and developments. By means of solving the evolution of a convective-dispersion equation, i.e. the Fokker-Planck equation, a fully 3D approach with respect to the position and the two fibre angles, polar and azimuthal angles, following a streamline is presented. As an input to the fibre orientation model the turbulent flow field is solved by Computational Fluid Dynamics (CFD) with second-order closure in the turbulence model. In this work two new hypotheses have been presented for the variation of the non-dimensional rotational diffusivity with non-dimensional fibre length, Lf /η and the Reynolds number based on the Taylor micro-scale of the turbulence, Reλ Parameters for the two new hy- potheses and earlier models are determined with the aim of achieving a general relation and a value of the rotational dispersion coeffcient of stiff fibres in an anisotropic turbulent fluid flow. Earlier modelling work has been focused on solving the planar approach, i.e. assuming all fibres to be in one plane. This planar approach is discussed and compared with the fully 3D approach and its validity is evaluated. The optimization of parameters for the different hypotheses correlated on a central streamline, showed a good agreement with an independent experimental result in the undisturbed region. Moreover, it is particularly interesting that the boundary layer region and the wake region are predicted fairly well and the phenomena are well described, which has not been the case earlier. It seems that the new hypothesis based on the variation of the non-dimensional fibre length, Lf /η gives the best correlation in these shear-layer regions. Further- more it was established that the planar approach fails to predict shear layers, i.e. the boundary layer and the wake regions. As emphasized in the theory section, the planar formulation is strictly valid only if all fibres are oriented in one plane, which is not the case in the shear layers. In the undisturbed region, the 3D and the planar approaches, agree in their results. This leads to the conclusion that both approaches are suitable when shear layers are not studied.QC 20100812
6
Howell, Jaron A. „Distribution of Particle Image Velocimetry (PIV) Errors in a Planar Jet“. DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7004.
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Particle Image Velocimetry (PIV) is an optical fluid measurement technique used to obtain velocity measurements. Two PIV systems were used to capture data simultaneously and measurement error for the MS PIV system is calculated. An investigation of error distribution is performed to determine when uncertainty estimations fail for the CS PIV-UQ method. Investigation of when results from multi pass PIV processing are achieve were performed so that reliable uncertainty estimations are produced with the CS method. An investigation was also performed which determined that error distributions in PIV systems are correlated with flow shear and particle seeding density. Correlation of random errors in space was also performed at the jet core and shear regions of the flow.
It was found that in flow regions with large shear that error distributions were non-Gaussian. It was also found in regions of large shear that CS uncertainty results did not match the error. For multi-pass PIV processing with 50% and 75% IW overlap it was found that 4 and 6 passes should be used, respectively, in order for CS uncertainty estimations to be reliable. It was also found that the correlation of random errors in space is much larger in shear regions of the jet flow than in the jet core.
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Vezirov, Tarlan Azad [Verfasser], Sabine [Akademischer Betreuer] Klapp und Michael [Akademischer Betreuer] Zaks. „Non-equilibrium dynamics and feedback control of strongly confined colloidal suspensions in a planar shear flow / Tarlan Azad Vezirov. Gutachter: Sabine Klapp ; Michael Zaks. Betreuer: Sabine Klapp“. Berlin : Technische Universität Berlin, 2015. http://d-nb.info/1075807522/34.
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Heczko, Martin. „Počítačové modelování hranic dvojčatění ve slitinách s tvarovou pamětí“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-416633.
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This Master‘s thesis is focused on theoretical study of twinning in magnetic shape memory alloys based on Ni2MnGa using ab initio calculations of electronic structure within the projector augmented wave method. In particular, the effect of increasing concentration of manganese at the expense of gallium was studied on total energy and stress profiles along different deformation paths in the (10-1)[101] shear system of non-modulated martensite. Further, this work deals with the effect of the concentration of manganese on the energy of planar fault caused by presence of partial dislocation due to motion of twin boundary. The results show that the shear modulus in studied shear system increases with the increasing concentration of manganese as well as energy barrier and deformation characteristics along shear deformation paths increases, which makes the shear more difficult in Mn-rich alloys. Increasing concentration of manganese also leads to rising the planar fault energy. All these effects can be responsible for lower mobility of twin boundaries in alloys with higher concentration of manganese.
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Petersen, Spencer Ray. „A System for Foot Joint Kinetics – Integrating Plantar Pressure/Shear with Multisegment Foot Modeling“. BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8456.
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Introduction: Instrumented gait analysis and inverse dynamics are commonly used in research and clinical practice to calculate lower extremity joint kinetics, such as power and work. However, multisegment foot (MSF) model kinetics have been limited by ground reaction force (GRF) measurements. New technology enables simultaneous capture of plantar pressure and shear stress distributions but has not yet been used with motion capture. Integrating MSF models and pressure/shear measurements will enhance the analysis of foot joint kinetics. The purpose of this study was to develop methodology to integrate these systems, then analyze the effects of speed on foot joint kinetics. Methods: Custom software was developed to synchronize motion capture and pressure/shear data using measured offsets between reference frame origins and time between events. Marker trajectories were used to mask pressure/shear data and construct segment specific GRFs. Inverse dynamics were done in commercial software. Demonstrative data was from 5 healthy adults walking unshod at 3 fixed speeds (1.0, 1.3, and 1.6 m/s, respectively) wearing retroreflective markers according to an MSF model. Plantar shear forces and ankle, midtarsal, and first metatarsophalangeal (MTP) joint kinetics were reported. Speed effects on joint net work were evaluated with a repeated measures ANOVA. Results: Plantar shear forces during stance showed some spreading effects (directionally opposing shear forces) that relatively were unaffected by walking speed. Midtarsal joint power seemed to slightly lag behind the ankle, particularly in late stance. Net work at the ankle (p = 0.024), midtarsal (p = 0.023), and MTP (p = 0.009) joints increased with speed. Conclusions: Functionally, the ankle and midtarsal joints became more motorlike with increasing speed by generating more energy than they absorbed, while the MTP joint became more damperlike by absorbing more energy than it generated. System integration appears to be an overall success. Limitations and suggestions for future work are presented.
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Hosein, Riad. „An investigation of in-shoe plantar pressures and shear stresses with particular reference to diabetic peripheral neuropathy“. Thesis, King's College London (University of London), 1996. https://kclpure.kcl.ac.uk/portal/en/theses/an-investigation-of-inshoe-plantar-pressures-and-shear-stresses-with-particular-reference-to-diabetic-peripheral-neuropathy(b0ebff48-2d9e-4fb7-8730-4ae42704ad0b).html.
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Jeong, Hwigeum. „Short-Term Effects of Increased Body Mass and Distribution on Plantar Shear, Postural Control, and Gait Kinetics: Implications for Obesity“. BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8609.
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Context: Obesity is a growing global health concern. The increased body mass and altered mass distribution associated with obesity may be related to increases in plantar shear that putatively leads to physical functional deficits. Therefore, measurement of plantar shear may provide unique insights on the effects of body mass and body distribution on physical function or performance. Purpose: 1) To investigate the effects of body mass and distribution on plantar shear; 2) To examine how altered plantar shear influences postural control and gait kinetics. Hypothesis: 1) a weighted vest forward distributed (FV) would shift the center of pressure (CoP) location forward during standing compared with a weighted vest evenly distributed (EV); 2) FV would increase plantar shear spreading forces more than EV during standing; 3) FV would increase postural sway during standing while EV would not; and 4) FV would increase peak braking force, plantar impulses, and plantar shear spreading forces during walking more than EV. Methods: Twenty healthy young males participated in four different tests: 1) static test (for measuring plantar shear and CoP location without acceleration; 2) two-leg standing postural control test; 3) one-leg standing postural test; and 4) walking test. All tests were executed in three different weight conditions: 1) unweighted (NV); 2) evenly distributed vest (EV) with 20% added body mass; and 3) front-loaded vest (FV), also with 20% added body mass. Plantar shear stresses were measured using a pressure/shear device, and several shear and postural control metrics were extracted. Repeated measures ANOVAs with Holms post hoc test were used to compare each metric among the three conditions (α = 0.05). Results: FV and EV increased both anterior-posterior and medial-lateral plantar shear forces in single-foot trials compared to NV. FV shifted CoP forward. FV and EV showed decreased CoP range and velocity and increased time-to-boundary (TTB) during postural control compared to NV. While EV increased medial-lateral plantar shear spreading force, FV increased anterior-posterior plantar shear spreading force during walking. Conclusion: Added body mass increases plantar shear spreading forces. Body mass distribution had greater effects during dynamic tasks. In addition, healthy young individuals seem to quickly adapt to external stimuli to control postural stability. However, the interactive effects between body mass and distribution may disrupt physical function and/or performance in other populations—such as elderly, obese, and diabetes. Plantar shear may play a critical role in clinical diagnosis. However, as it is the first step study, follow-up studies are necessary to further support the clinical role of plantar shear.
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Lukassen, Laura Johanna [Verfasser], Martin [Akademischer Betreuer] Oberlack und Dieter [Akademischer Betreuer] Bothe. „A colored-noise Fokker-Planck equation for non-Brownian particles in shear-induced diffusion / Laura Johanna Lukassen. Betreuer: Martin Oberlack ; Dieter Bothe“. Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2015. http://d-nb.info/1111909989/34.
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Reimnitz, Marc. „Shear-slip induced seismic activity in underground mines : a case study in Western Australia“. University of Western Australia. School of Civil and Resource Engineering, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0062.
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Mining induced seismic activity and rockbursting are critical concerns for many underground operations. Seismic activity may arise from the crushing of highly stressed volumes of rock around mine openings or from shear motion on planes of weakness. Shear-slip on major planes of weakness such as faults, shear zones and weak contacts has long been recognized as a dominant mode of failure in underground mines. In certain circumstances, it can generate large seismic events and induce substantial damage to mine openings. The Big Bell Gold mine began experiencing major seismic activity and resultant damage in 1999. Several seismic events were recorded around the second graphitic shear between April 2000 and February 2002. It is likely that the seismic activity occurred as a result of the low strength of the shear structure combined with the high level of mining induced stresses. The stability of the second graphitic shear was examined in order to gain a better understanding of the causes and mechanisms of the seismic activity recorded in the vicinity of the shear structure as mining advanced. The data were derived from the observation of the structure exposures, numerical modelling and seismic monitoring. The numerical modelling predictions and the interpreted seismic monitoring data were subsequently compared in order to identify potential relationships between the two. This thesis proposes the Incremental Work Density (IWD) as a measure to evaluate the relative likelihood of shear-slip induced seismic activity upon major planes of weakness. IWD is readily evaluated using numerical modelling and is calculated as the product of the average driving shear stress and change in inelastic shear deformation during a given mining increment or step. IWD is expected to correlate with shear-slip induced seismic activity in both space and time. In this thesis, IWD was applied to the case study of the second graphitic shear at the Big Bell mine. Exposures of the second graphitic shear yielded information about the physical characteristics of the structure and location within the mine. Numerical modelling was used to examine the influence of mining induced stresses on the overall behaviour of the shear structure. A multi-step model of the mine was created using the three- dimensional boundary element code of Map3D. The shear structure was physically incorporated into the model in order to simulate inelastic shear deformation. An elasto-plastic Mohr-Coulomb material model was used to describe the structure behaviour. The structure plane was divided into several elements in order to allow for the comparison of the numerical modelling predictions and the interpreted seismic data. Stress components, deformation components and IWD values were calculated for each element of the shear structure and each mining step. The seismic activity recorded in the vicinity of the second graphitic shear was back analysed. The seismic data were also gridded and smoothed. Gridding and smoothing of individual seismic moment and seismic energy values resulted in the definition of indicators of seismic activity for each element and mining step. The numerical model predicted inelastic shear deformation upon the second graphitic shear as mining advanced. The distribution of modelled IWD suggested that shear deformation was most likely seismic upon a zone below the stopes and most likely aseismic upon the upper zone of the shear structure. The distribution of seismic activity recorded in the vicinity of the shear structure verified the above predictions. The seismic events predominantly clustered upon the zone below the stopes. The results indicated that the seismic activity recorded in the vicinity of the second graphitic shear was most likely related to both the change in inelastic shear deformation and the level of driving shear stress during mechanical shearing. Time distribution of the seismic events also indicated that shear deformation and accompanying seismic activity were strongly influenced by mining and were time-dependant. Seismic activity in the vicinity of the second graphitic shear occurred as a result of the overall inelastic shear deformation of the shear structure under mining induced stresses. A satisfactory relationship was found between the spatial distribution of modelled IWD upon the shear structure and the spatial distribution of interpreted seismic activity (measured as either smoothed seismic moment or smoothed seismic energy). Seismic activity predominantly clustered around a zone of higher IWD upon the second graphitic shear as mining advanced. However, no significant statistical relationship was found between the modelled IWD and the interpreted seismic activity. The lack of statistical relationship between the modelled and seismic data may be attributed to several factors including the limitations of the techniques employed (e.g. Map3D modelling, seismic monitoring) and the complexity of the process involved.
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Godoy, Tatiane Corrêa de. „Modelagem de placas laminadas com materiais piezoelétricos conectados a circuitos shunt resistivo-indutivo“. Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18149/tde-12062008-112524/.
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Este trabalho apresenta uma modelagem de placas laminadas com sensores/atuadores piezoelétricos integrados e conectados a circuitos tipo shunt resistivo-indutivo (RL). O modelo faz uso de duas teorias de placa, FSDT (First-order Shear Deformatíon Theory) e TSDT (Third-order Shear Deformatíon Theory), e considera a possibilidade de inserção de pastilhas piezoelétricas trabalhando nos modos de extensão e cisalhamento. Um modelo de elementos finitos para placas laminadas piezoelétricas, em camada equivalente (Equivalent Single Layer), foi desenvolvido usando como graus de liberdade os deslocamentos mecânicos generalizados e a carga elétrica gerada nos circuitos acoplados. Após, uma implementação computacional foi realizada e validada através de comparações com resultados encontrados na literatura. Então, foram realizados estudos para configurações de placa laminada com diferentes quantidades de pastilhas piezoelétricas através de uma análise paramétrica para obtenção das posições de maior acoplamento entre pastilhas e estrutura para os primeiros modos de vibração da placa. Estes resultados possibilitaram a otimização da eficiência do acoplamento eletromecânico através da distribuição das pastilhas piezoelétricas para uma placa com maior quantidade de pastilhas bem como a comparação dos resultados obtidos entre as duas teorias utilizadas.This work presents the modeling of laminate plates with embedded piezoelectric sensors and actuators connected to resistive-inductive (RL) shunt circuits. The model considers two plate theories, FSDT (First-order Shear Deformation Theory) and TSDT (Third-order Shear Deformation Theory) and allows embedded piezoelectric patches in extension and thickness-shear modes. A finite element model for piezoelectric laminate plates, using equivalent single layer (ESL), was developed considering the generalized mechanical displacements and the electric charges induced in the coupled electric circuits as degrees of freedom. Then, the model was implemented and validated by means of comparisons with results found in the literature. Thereafter, some laminate plate configurations with different numbers of piezoelectric patches were studied through a parametric analysis to obtain the positions that maximize the electromechanical coupling between patches and structure for the first vibration modes. These results allowed the optimization of the electromechanical coupling efficiency through piezoelectric patches distribution for a plate with a larger number of patches and the comparison between the results obtained with the two plate theories considered.
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Guo, Tianyi. „Using Light to Study Liquid Crystals and Using Liquid Crystals to Control Light“. Kent State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=kent1595210881250992.
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RODRIGUES, David Rosa. „Comparação experimental entre tipos de armadura de cisalhamento para combate à punção em lajes cogumelo de concreto armado: Stud rails e Double headed studs“. Universidade Federal de Goiás, 2009. http://repositorio.bc.ufg.br/tede/handle/tde/683.
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Previous issue date: 2009-09-29This research presents the results of an experimental comparison between the types of shear reinforcement "stud rails" and "double headed studs" to combat the punching shear of a reinforced concrete flat slabs. It also presents a comparison of experimental results with those provided under the ACI 318/2005, CEB-FIP MC/1990, EUROCODE 2/2004 and NBR 6118:2003. The motivation was to investigate the efficiency of these shear reinforcement for the differences between them. It was tested six slabs of concrete to concentric load, with dimensions of 2400 mm x 2400 mm x 150 mm. It was concreted a column of section 500 mm x 200 mm to 850 mm total height next to the slab. The main variables were the type of shear reinforcement "stud rails" x "double headed studs, the "studs" diameter and the shear reinforcement area per layer. The slabs were tested until the failure. It was monitored the deflection, reinforcement deformation of bending and shear. All slabs failed by punching with internal surface rupture. The experimental results after being compared with the expected standard in each individual calculation showed conservative values. Slabs of Group 1 with "stud rails" presented failed loads greater than those in Group 2 with "double headed studs. Codes/standards 318/2005 ACI, CEB-FIP MC/1990, EUROCODE 2 / 2004 and NBR 6118:2003 safely predict the failed loads of all slabs. The base of the shear reinforcement type "stud rails" moving inside the column may have reduced the failed load of the slab L3. Shear reinforcement type stud rails it is easer of assembly and play than the type double headed studs .
Esta pesquisa apresenta os resultados de uma comparação experimental entre os tipos de armadura de cisalhamento stud rails e double headed studs para combate à punção em lajes cogumelo de concreto armado. Apresenta, também, uma comparação dos resultados experimentais com os previstos segundo o ACI 318/2005, CEB-FIP MC/1990, EUROCODE 2/2004 e a NBR 6118:2003. A motivação foi investigar a eficiência destas armaduras de cisalhamento a procura de diferenças entre elas. Foram ensaiadas seis lajes maciças de concreto armado à punção centrada, com dimensões 2400 mm x 2400 mm x 150 mm. Foi concretado junto à laje um pilar de seção 500 mm x 200 mm com altura total 850 mm. As principais variáveis foram o tipo de armadura de cisalhamento: stud rails x double headed studs , o diâmetro dos studs e a área de armadura de cisalhamento por camada. As lajes foram ensaiadas até a ruptura. Foram monitoradas as flechas, deformações da armadura de flexão e cisalhamento. Todas as lajes romperam por punção com superfície de ruptura interna. Os resultados experimentais após serem comparados com os esperados segundo cada norma de cálculo apresentaram valores conservadores. As lajes do Grupo 1 com stud rails apresentaram cargas de ruptura maiores que as do Grupo 2 com double headed studs . Os códigos/normas ACI 318/2005, CEB-FIP MC/1990, EUROCODE 2/2004 e a NBR 6118:2003 previram com segurança as cargas de ruptura de todas as lajes. A base da armadura de cisalhamento tipo stud rails avançando dentro do pilar pode ter reduzido a carga de ruptura da Laje L3. A armadura de cisalhamento tipo stud rails apresenta maior facilidade de montagem e execução que a tipo double headed studs .
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McKellar, Dougan Kelk. „A dislocation model of plasticity with particular application to fatigue crack closure“. Thesis, University of Oxford, 2001. http://ora.ox.ac.uk/objects/uuid:45183b90-017f-4ac1-9550-94772a0ca88b.
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The ability to predict fatigue crack growth rates is essential in safety critical systems. The discovery of fatigue crack closure in 1970 caused a flourish of research in attempts to simulate this behaviour, which crucially affects crack growth rates. Historically, crack tip plasticity models have been based on one-dimensional rays of plasticity emanating from the crack tip, either co-linear with the crack (for the case of plane stress), or at a chosen angle in the plane of analysis (for plane strain). In this thesis, one such model for plane stress, developed to predict fatigue crack closure, has been refined. It is applied to a study of the relationship between the apparent stress intensity range (easily calculated using linear elastic fracture mechanics), and the true stress intensity range, which includes the effects of plasticity induced fatigue crack closure. Results are presented for all load cases for a finite crack in an infinite plane, and a method is demonstrated which allows the calculation of the true stress intensity range for a growing crack, based only on the apparent stress intensity range for a static crack. Although the yield criterion is satisfied along the plastic ray, these one-dimensional plasticity models violate the yield criterion in the area immediately surrounding the plasticity ray. An area plasticity model is therefore required in order to model the plasticity more accurately. This thesis develops such a model by distributing dislocations over an area. Use of the model reveals that current methods for incremental plasticity algorithms using distributed dislocations produce an over-constrained system, due to misleading assumptions concerning the normality condition. A method is presented which allows the system an extra degree of freedom; this requires the introduction of a parameter, derived using the Prandtl-Reuss flow rule, which relates the magnitude of slip on complementary shear planes. The method is applied to two problems, confirming its validity.
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Júnior, Faustino Sanches. „Desenvolvimento de modelos numéricos para a análise de estruturas de pavimentos de edifícios“. Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-31032016-121303/.
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Este trabalho fornece uma contribuição à análise estrutural não-linear de pavimentos de edifícios de concreto armado com o emprego do Método dos Elementos Finitos. A deformação por esforço cortante é considerada, portanto as teorias de Timoshenko e de Reissner-Mindlin são empregadas nas formulações dos elementos de barra e de placa, respectivamente. As posições dos elementos de barra e de placa são independentes e, portanto, podem ser definidas em diferentes planos. Em conseqüência do exposto, o efeito de membrana deve ser necessariamente considerado na modelagem do pavimento. Para completar o modelo mecânico, as não-linearidades físicas descrevem o comportamento do concreto e do aço. A deterioração do concreto no cisalhamento é também considerada através de um modelo simplificado que é proposto para a modelagem do cisalhamento em condições de serviço.This work gives a contribution to the non-linear structural analysis of reinforced concrete buildings floors using the Finite Element Method. The shear strain components are taken into account by adopting the Timoshenko\'s beam theory together with and the Reissner-Mindlin\'s theory for plate bending. Bar and plate element position are independent and therefore can be defined at different planes. As several level are considered when defining the structure membrane effects are necessary considered. In order to complete the mechanical model, physical non-linearities are also assumed to describe concrete and steel behaviours. The deterioration of the concrete material in shear is also taken account. For this purpose, a simplified model is adopted to compute approximately the damaged shear component in the steel direction.
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Muehlemann, Anton. „Variational models in martensitic phase transformations with applications to steels“. Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:bb7f4ff4-0911-4dad-bb23-ada904839d73.
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This thesis concerns the mathematical modelling of phase transformations with a special emphasis on martensitic phase transformations and their application to the modelling of steels. In Chapter 1, we develop a framework that determines the optimal transformation strain between any two Bravais lattices and use it to give a rigorous proof of a conjecture by E.C. Bain in 1924 on the optimality of the so-called Bain strain. In Chapter 2, we review the Ball-James model and related concepts. We present some simplification of existing results. In Chapter 3, we pose a conjecture for the explicit form of the quasiconvex hull of the three tetragonal wells, known as the three-well problem. We present a new approach to finding inner and outer bounds. In Chapter 4, we focus on highly compatible, so called self-accommodating, martensitic structures and present new results on their fine properties such as estimates on their minimum complexity and bounds on the relative proportion of each martensitic variant in them. In Chapter 5, we investigate the contrary situation when self-accommodating microstructures do not exist. We determine, whether in this situation, it is still energetically favourable to nucleate martensite within austenite. By constructing different types of inclusions, we find that the optimal shape of an inclusion is flat and thin which is in agreement with experimental observation. In Chapter 6, we introduce a mechanism that identifies transformation strains with orientation relationships. This mechanism allows us to develop a simpler, strain-based approach to phase transformation models in steels. One novelty of this approach is the derivation of an explicit dependence of the orientation relationships on the ratio of tetragonality of the product phase. In Chapter 7, we establish a correspondence between common phenomenological models for steels and the Ball-James model. This correspondence is then used to develop a new theory for the (5 5 7) lath transformation in low-carbon steels. Compared to existing theories, this new approach requires a significantly smaller number of input parameters. Furthermore, it predicts a microstructure morphology which differs from what is conventionally believed.
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FENG, DE-ZHI, und 馮德智. „Nonlinear analysis of planar curved beam with shear deformation“. Thesis, 1992. http://ndltd.ncl.edu.tw/handle/17811086600384537619.
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Pickett, Lyle M. „Structure of a planar reacting shear layer using hydrocarbon fuels“. 2000. http://www.library.wisc.edu/databases/connect/dissertations.html.
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Medronho, Bruno Filipe Figueiras. „Shear-induced transitions in complex fluids : planar lamellae and multilamellar vesicles“. Doctoral thesis, 2009. http://hdl.handle.net/10316/12183.
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Yi-TsungYeh und 葉宜璁. „Mixing of shear-thinning fluids in a zigzag planar microchannels with baffles“. Thesis, 2010. http://ndltd.ncl.edu.tw/handle/59166046862100198896.
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碩士國立成功大學
機械工程學系碩博士班
98
In this work, we investigate the mixing behavior of shear-thinning fluids in a zigzag planar microchannel with baffles. The shear-thinning fluids considered in this work are the aqueous solution of Carboxymethyl Cellulose Sodium. The power-law has been employed for modelling the relation between shear stress and shear rate of the shear-thinning fluid. Then, we apply the commercial package, CFD-ACE+, to simulate the 3-D flow field and mixing behavior in the micromixer. Numerical simulation is performed for various distances between bends, flow rates, fluid properties and the positions of baffles to investigate the effects of these parameters on the mixing behavior in the micromixer. The fabrication process of the micromixer includes applying the photolithography method to fabricate SU-8 mold, replicating PDMS (polydimethysiloxane) mold and bonding the PDMS with a cover glass. Add Rhodamine B to one of the inlet fluids of the micromixer ; the fluid mixing is observed by a laser confocal spectral microscope, Leica TCS SP2. Reasonable agreement of simulation and experiment results is found for the cases considered. From the results of this work the following trends may be observed. (i) Adding buffles to the channel wall before bending enhances the mixing of fluids most significantly. (ii) As the Reynolds number increase, the mixing efficiency increases. (iii) An optimum distance between bends can be found for the mixing of fluids. (iv) The increase of the Reynolds number enlarges the discrepancy between shear-thinning fluid and Newtonian fluid.
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Brunetti, Jonathan A. „Examining a Role for Planar Cell Polarity Signaling in Endothelial Cell Alignment and Organization“. Thesis, 2012. http://hdl.handle.net/1807/33497.
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Endothelial cells (ECs) respond to flow but the exact mechanism producing alignment is not completely understood. We characterized EC alignment in microfluidic channels, 4 mm wide by 350 um high, to generate shear of 20 dynes / cm2 across the cell surface. In microchannels, ECs aligned perpendicular under flow. Analytical tools were developed to quantify nuclear alignment at 67% for human umbilical vein endothelial cells (HUVECs); cell elongation under shear flow shifted aspect ratio from 2.41 to 2.86.
We next sought to probe the mechanism through which ECs communicate during realignment. The planar cell polarity (PCP) signaling pathway is involved in cell organization and coordination during development. A number of genes are known to affect the formation and organization of cellular structures through PCP signaling in human ECs. Higher expression of Vangl1 and Dvl1 proteins did not alter cell reorganization; knockdown of Vangl1 expression decreased EC alignment.
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Papazoglou, Sebastian [Verfasser]. „Elucidation of isotropic and anisotropic shear elasticity of in vivo soft tissue using planar magnetic resonance elastography / von Sebastian Papazoglou“. 2009. http://d-nb.info/1007738316/34.
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Shen, Fu-Chiun, und 沈富群. „Plantar Pressure/Shear Sensor Array with Bluetooth Low Energy“. Thesis, 2013. http://ndltd.ncl.edu.tw/handle/9p83da.
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碩士國立臺北科技大學
機電整合研究所
101
Plantar pressure/shear force array sensor are placed at the bottom of the shoe-pads. When user walks with them, the soles of shoes touch the ground. The Sensing unit perceives different level of pressure and adopts a set of four sensors to detect the Shear force direction. The analog signal is transformed to digital data through the microprocessor in the circuit. The digital signal will then be transmitted to mobile phones or computers through wireless transmission by bluetooth module. As a mobile phone or a computer receives the data, it shows the corresponding position of the foot on the APP. The color which displays on the mobile or computer changes from light to dark with the different perceived level of pressure and represents the current plantar pressure situation of user. Besides, the APP calculates the center of gravity of user according to the numerical value and position of the 16 Sensing unit and it is presented by red star.
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Kang, Wei-Shui, und 康維訓. „The development of plantar pressure and shear force measuring technologies“. Thesis, 2011. http://ndltd.ncl.edu.tw/handle/7yq4mg.
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碩士國立臺北科技大學
製造科技研究所
99
This study is to develop the plantar pressure and shear force measuring technologies. There are two parts of this study. The first part is the planter pressure and shear force recording plate based on micro structure imprint. The second part is the image based planter pressure measuring and shear force calculation. For the recording plate, it is fabricated by hard poly and soft PU. There are many different geometric designs have been tested. For the image based measuring system, a way to calculate the shear force based on the normal pressure distribution has been proposed. By the combination of the above two measuring method, the plantar pressure and the shear force of the bear feet and wear shoes can be measured. Different from conventional foot pressure technologies, the new system brings a new foresight in foot diagnostic by bring the foot pressure together with shear force measuring.
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Lukassen, Laura Johanna. „A colored-noise Fokker-Planck equation for non-Brownian particles in shear-induced diffusion“. Phd thesis, 2015. http://tuprints.ulb.tu-darmstadt.de/4587/7/Dissertation_Lukassen.pdf.
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The topic of the present work are non-Brownian particles in shear flow. As reported in
literature, the occurring phenomenon in this context is shear-induced diffusion which
takes place in the absence of the well-known Brownian diffusion. Diffusive processes
can be described stochastically in terms of a stochastic differential equation (Langevin
equation or Langevin-like equation) or a differential equation for the probability
density, in second order referred to as Fokker-Planck equation. It is known that in
contrast to Brownian diffusion, the shear-induced diffusion is a long-time diffusion
which poses a challenge to the stochastic description of this phenomenon. The present
work analyzes the problem of non-Brownian particles in shear-induced diffusion
with regard to the Markov property of the treated variables. This concludes that the
Fokker-Planck equation so far derived in pure position space may not be sufficient. In
order to ensure the Markov process property, a Fokker-Planck equation extended to
coupled position colored-noise velocity space is derived. Throughout the extension,
the colored-noise velocity is modeled as an Ornstein-Uhlenbeck process. These first
two steps were also treated in the author’s Master thesis (Lukassen 2012). A detailed
substantiation of this approach is published in (Lukassen & Oberlack 2014b) including
a new multiple time scale analysis and a Gaussian solution. The multiple time scale
analysis results in the dimensionless form of the equation of motion which serves as a
starting point for the derivation of the new colored-noise Fokker-Planck equation. As
a next step, this coupled Fokker-Planck equation is integrated over velocity space and
approximated to yield a reduced position-space Fokker-Planck equation. It is shown
that such a reduction as in the present work is only possible under certain conditions
concerning the correlation time. The resulting position-space equation is analyzed
and compared to the traditional position-space models. The reduced form exhibits
additional correction terms. In an outlook, possible extensions of the presented model
are discussed with exemplary simulation results. Chapter 5 and 6 as a whole are based
on the author’s publication (Lukassen & Oberlack 2014b).
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Leite, Tiago Maurício de Pinho. „Optical fiber solutions to physical rehabilitation systems and e-Health applications“. Master's thesis, 2018. http://hdl.handle.net/10773/25194.
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In this dissertation a biaxial optical fiber sensor, based on Bragg gratings, is proposed for simultaneous monitoring of plantar and shear pressures.
This work begins with the definition of the problem: the consequences of pathologies associated with diabetic foot and lower limbs disorders. It was analysed several previously published studies on plantar pressure sensors, the several methodologies and applications that already exist.
A biomechanical research was carried out, with particular focus on gait pattern and human foot anatomy, in order to understand the different gait phases and points of greatest interest for foot pressure monitoring.
Thus, the response of sensors based on Bragg gratings was studied in several configurations of sensing cells, then integrated in insoles. The sensitivities obtained for normal pressure were between 0.56 and 2.16 pm/kPa and, for shear pressure, between 0.51 and 3.98 pm/kPa.
Those prove to be a non-invasive solution with potential to be included in e-health systems for real-time gait monitoring. They can be prepared for daily medical use, serving as important tools in aiding prevention and diagnosis, especially of foot diseases.Nesta dissertação é proposto um sensor biaxial em fibra ótica, baseado em redes de Bragg, para monitorização simultânea de pressões plantar e de cisalhamento. Este trabalho começa com a definição do problema: as consequências de patologias associadas ao pé diabético e distúrbios na sincronização dos membros inferiores. Foram analisados vários estudos publicados anteriormente sobre sensores de pressão plantar, as diversas metodologias e aplicações já existentes. Foi realizada uma pesquisa na área da biomecânica, com particular foco no padrão de marcha e na anatomia do pé humano, de forma a compreender as diferentes fases da marcha e os pontos de maior interesse para monitorização da pressão do pé. Assim, foi desenvolvido um estudo sobre a resposta de sensores baseados em redes de Bragg à pressão, em várias configurações de células sensoriais, culminando na integração desses sensores em palmilhas. Foram obtidas sensibilidades para pressão normal entre 0,56 e 2,16 pm/kPa e, para pressão de cisalhamento, entre 0,51 e 3,98 pm/kPa. Estas demonstram ser uma solução não invasiva, com potencial de ser incluída em sistemas e-Health, para monitorização da marcha em tempo real. Podem ser preparadas para uso médico diário, servindo como importantes ferramentas no auxílio para a prevenção e diagnóstico, em especial de doenças do pé.
Mestrado em Engenharia Física
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Barroso, Viviane Setti. „A consistent linear two-dimensional mathematical model for thin two-layer plates with partial shear interaction“. Master's thesis, 2020. http://hdl.handle.net/10316/92236.
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Dissertação de Mestrado Integrado em Engenharia Civil apresentada à Faculdade de Ciências e TecnologiaThis dissertation presents a consistent derivation, from three-dimensional linear elasticity, of a two-dimensional mathematical model describing the bending and in-plane stretching behaviours, under a general system of quasi-static distributed loads, of thin two-layer plates with partial shear interaction. The following key assumptions are made:(i) Each layer, when considered separately, behaves as a Kirchhoff plate.(ii) The interlayer (with non-zero thickness), when considered separately, behaves as a transverse shear-only Mindlin plate.(iii) Each layer is bonded to the interlayer in such a way that both sliding and detachment are prevented.The dimensional reduction stage of the derivation, from three spatial dimensions to just two, is accomplished by means of Podio-Guidugli’s method of internal constraints. This is followed by a process of assembly or aggregation, in which the continuity of displacements and certain stress components across each layer/interlayer interface is enforced. A problem with closed-form analytical solution illustrates the application of the two-dimensional model and its capabilities. In particular, the solution is proven to be continuous across the whole range of zero, partial and full interaction between the layers. The problem is then generalized and a Navier-type solution is obtained. The results are compared with those reported in the literature. Possible applications of the model include the analysis of laminated glass plates under quasi-static short-term loads in service conditions and within a limited temperature range.
Nesta dissertação apresenta-se uma dedução consistente, a partir da teoria da elasticidade linear tridimensional, de um modelo matemático bidimensional que descreve o comportamento à flexão e no plano, sob um sistema geral de cargas distribuídas quase-estáticas, de placas finas de duas camadas com interação de corte parcial. Admitem-se as seguintes hipóteses fundamentais:(i) Cada camada, quando considerada isoladamente, comporta-se como uma placa de Kirchhoff.(ii) A intercamada (com espessura não nula), quando considerada isoladamente, comporta-se como uma placa de Mindlin e apresenta apenas resistência ao corte transversal.(iii) A ligação entre cada camada e a intercamada é perfeita, considerando-se assim impedidos tanto o deslizamento como o afastamento nessas superfícies de descontinuidade material. A etapa de redução do número de dimensões espaciais de três para duas é realizada por intermédio do método de restrições internas proposto por Podio-Guidugli. Segue-se um processo de agregação, no qual se impõe, em cada interface camada/intercamada, a continuidade dos deslocamentos e de certas componentes de tensão. Um problema com a solução analítica ilustra as potencialidades do modelo desenvolvido. Em particular, mostra-se que a solução é contínua em toda a gama de interação entre camadas, desde a interacção nula até à interacção total. Este problema é depois generalizado e obtém-se uma solução do tipo Navier. Os resultados são comparados com os disponíveis na literatura. De entre as possíveis aplicações do modelo, destaca-se a análise de placas de vidro laminado sob a acção de cargas quase-estáticas de curta duração, em condições de serviço e dentro de uma gama de temperaturas limitada.