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1
Ishii, Kohki. « Design and Stress Analysis of Dynamic Spinal Stabilizers ». OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/270.
Texte intégralRésumé :
A dynamic lumbar spinal stabilizer with a helical machined spring element was created in the first stage. The stabilizer was built with 30 N/mm of axial stiffness because if the human body is moved to flexion and extension, this amount of a compressive and tensile load would be applied to the intervertebral disc. The stabilizer supports the loads instead of the disc. The stiffness was influenced by the number of coils, the thickness of coils, and length of the coil element. The stiffness can be determined by analytical equations or by finite element analysis (FE), such as ANSYS Workbench. In the second stage, the lumbar spine FE model was successfully constructed by using Autodesk Inventor 2010. There were three different analyzed models; (1) intact model, (2) fused model, and (3) dynamically stabilized model. This intact model is a simplified and basic model used for fused model and dynamically stabilized model. The range of motion (ROM) was the key term in this study. In other words, examination of each model was based on how much ROM was shown when the flexion, extension, and bending moments have been applied on the spine. The ROM of each model with three moments produced appropriate values compared to the references. The stress analysis is also important to optimize the design of the dynamic stabilizer. The maximum stress was 472 MPa on the stabilizer that is less than yield strength of Titanium alloy.
2
Yi, Jun 1959. « Stress compatible bimaterial interface elements with application to transient dynamic stress analysis ». Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22842.
Texte intégralRésumé :
Conventional displacement-based finite element programs do not yield unique values of stress components which ought to be continuous at element interfaces. The errors, being the differences from the correct unique values, become unacceptably large at a bimaterial interface when the moduli of the two materials are significantly different.This thesis formulates and implements new finite elements for obtaining the correct values of the stress components, both continuous and discontinuous ones, at bimaterial interface points under general dynamic loading, assuming linear, isotropic, elastic material behaviour.
The constructed finite elements programs, suitable for analyzing two-dimensional and axisymmetric three-dimensional problems, have been validated by comparing the predicted responses with the exact analytical solutions of some non-trivial impact loading (wave-propagation) problems.
The work provides a necessary tool for analyzing and designing composite structures, for example prosthetic knee and hip joints in the biomechanics field.
3
Mikucka, Vita. « Dynamic problems for interface cracks under harmonic loading ». Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=228606.
Texte intégralRésumé :
This thesis is devoted to solution of the two-dimensional elastodynamic problem for a cracked bimaterial loaded by harmonic waves. The system of boundary integral equations for displacements and tractions at the interface is obtained from Somigliana identity with the allowance for the contact interaction of the opposite crack faces. Full expressions of the integral kernels derived by the consecutive differentiation of the Green's displacement tensor are given. Due to the contact that takes place between the faces of the crack under the applied external loading, the resulting process is a steady-state periodic, but not a harmonic one. Thus, components of the stress-strain state are expanded into exponential Fourier series. The collocation method with a piecewise constant approximation on each linear continuous boundary element is used for the numerical solution. The problem is solved using the iterative algorithm. The solution is refined during the iteration process until the distribution of physical values satisfies the imposed constraints. The results are obtained for the interface crack subject to normal tension-compression, normal shear, or oblique tension-compression waves with different values of the angle of the wave incidence and the wide range of the dimensionless wave number. The distributions of the normal and tangential components of the contact forces and displacement discontinuities on the surface of the crack are investigated. The stress intensity factors are computed and analyzed for various values of the wave frequency, the friction coefficient, and material properties. The maximal stress intensity factors at the trailing crack tip differ from the SIF values at the leading crack tip showing non-symmetry of solution with respect the space and time variables. It is concluded that the crack closure and friction effect change the solution both qualitatively and quantitatively, as the difference between comparable results can achieve 30-50%.
4
Halepli, A. R. (A Reymond). « A comparative dynamic and static stress analysis of a prosthetically resurfaced tibia / ». Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63331.
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5
Shao, Qing. « Stress relaxation behavior of heat-aged Makrolon polycarbonate using dynamic mechanical analysis ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0020/MQ54645.pdf.
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6
Johnson, Catherine E. « Fragmentation Analysis in the Dynamic Stress Wave Collision Regions in Bench Blasting ». UKnowledge, 2014. http://uknowledge.uky.edu/mng_etds/16.
Texte intégralRésumé :
The first step in many mining operations is blasting, and the purpose of blasting is to fragment the rock mass in the most efficient way for that mine site and the material end use. Over time, new developments to any industry occur, and design and implementation of traditional techniques have to change as a consequence. Possibly the greatest improvement in blasting in recent years is that of electronic detonators. The improvements related to safety and increased fragmentation have been invaluable. There has been ongoing debate within the explosives industry regarding two possible theories for this. Shorter timing delays that allow interaction between adjacent shock waves or detonation waves, or the increase in accuracy associated with electronic detonators. Results exist on the improved accuracy of electronic detonators over that of electric or non-electric, but data on the relationship between the collision of dynamic stress waves and fragmentation is less understood. Publications stating that the area of greatest fragmentation will occur between points of detonation where shock waves collide exist, but experimental data to prove this fact is lacking.
This dissertation looks extensively at the head on collision of shock (in the rock mass) and detonation (in the detonation column) waves with relation to fragmentation through a number of small scale tests in concrete. Timing is a vital tool for this collision to occur and is the variable utilized for the studies. Small scale tests in solid masonry blocks, 15 x 7⅞ x 7⅞ inches in size, investigated shock and detonation wave collisions with instantaneous detonation. Blocks were wrapped in geotextile fabric and a wire mesh to contain the fragments so that in situ tensile crack formations could be analyzed. Detonating cord was used as the explosive with no stemming to maintain the shock pressure but reduce the gas pressure phase of the fragmentation cycle. Model simulations of these blocks in ANSYS Autodyn looked at the stress and pressure wave patterns and corresponding damage contours for a direct comparison with the experimental investigation.
Detonation wave collision in a single blast hole was found to positively influence the fragmentation and throw of the material. Mean fragment size decreased compared to tests with no detonation wave collision. Area of greatest throw occurred at the point of detonation collision where a buildup of gas pressure exited the block from one location. Head on collision of shock waves did not positively influence the muck pile. Largest fragments were located at the point of shock collision. The lack of particle velocity with relation to shock collision in previous literature could be attributed to the increased particle size here. Directional particle velocities could actually increase the strength and density of the rock at this location, decreasing the degree of fragmentation rather than increasing it.
7
Ye, Wei. « Nano-heteroepitaxy stress and strain analysis : from molecular dynamic simulations to continuum methods ». Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34752.
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For decades, epitaxy is used in nanotechnologies and semiconductor fabrications. So far, it's the only affordable method of high quality crystal growth for many semiconductor materials. Heterostructures developed from these make it possible to solve the considerably more general problem of controlling the fundamental parameters inside the semiconductor crystals and devices. Moreover, as one newly arising study and application branch of epitaxy, selective area growth (SAG) is widely used to fabricate materials of different thicknesses and composition on different regions of a single wafer. All of these new and promising fields have caught the interests and attentions of all the researchers around the world.
In this work, we will study the stress and strain analysis of epitaxy in nano-scale materials, in which we seek a methodology to bridge the gap between continuum mechanical models and incorporate surface excess energy effects, which can be obtained by molecular dynamical simulations. We will make a brief description of the elastic behavior of the bulk material, covering the concepts of stress, strain, elastic energy and especially, the elastic constants. After that, we explained in details about the definitions of surface/interface excess energy and their characteristic property tensors. For both elastic constants and surface excess energy, we will use molecular dynamic simulations to calculate them out, which is mainly about curve-fitting the parabola function between the total strain energy density and the strain.
After this, we analyzed the stress and strain state in nanoisland during the selective area growth of epitaxy. When the nanoisland is relaxed, the lattice structure becomes equilibrated, which means the total strain energy of system need to be minimized. Compared to other researcher's work, our model is based on continuum mechanics but also adopts the outcome from MD simulations. By combining these microscopic informations and those macroscopic observable properties, such as bulk elastic constants, we can provide a novel way of analyzing the stress and strain profile in epitaxy. The most important idea behind this approach is that, whenever we can obtain the elastic constants and surface property tensors from MD simulations, we can follow the same methodology to analyse the stress and strain in any epitaxy process. This is the power of combining atomistic simulations and continuum method, which can take considerations of both the microscopic and macroscopic factors.
8
Mahmood, Rashid. « Static and dynamic finite element stress analysis of layered composite plates and shells ». Thesis, Cranfield University, 1989. http://hdl.handle.net/1826/4048.
Texte intégralRésumé :
In this work an attempt has been made to develop
theories for finite element static and dynamic stress
analysis tailored for use with composite layered plates and
shells in this way it was hoped to provide accurate values
of the stresses particularly transverse shear stresses
through the thickness, and to perform accurate natural
frequency analysis by including non-linear effects such as
centrifugal stiffening.
Initial derivations were based upon first order facet
shell element analysis and first order curved shell element
analysis. Subsequently, derivations were produced for
higher order element analysis.
A programming package has been developed based upon
the above derivations, and containing a banded solver as
well as a frontal solver, capable of analysing structures
build up from uniform or variable thickness layers and with
a multiple number of layers having constant or variable
dimension.
Results obtained with the aid of the present package
have been compared with results derived from experimental
work as well as with results derived from available
analytical solutions. Investigations have been carried out
for existing compressor blades, made of isotropic material
and layered composite material, respectively. The results
obtained from the package have been compared with available
experimental results produced by RR or carried out at
Cranfield. It has been shown that the above mentioned
derivations produce comparable results and the package has
proved to be reliable and accurate.
9
Oet, Mikhail V. « Financial stress in an adaptive system : From empirical validity to theoretical foundations ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1459347548.
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10
Katsanis, George R. Mr. « Transient Small Wind Turbine Tower Structural Analysis with Coupled Rotor Dynamic Interaction ». DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/960.
Texte intégralRésumé :
Structural dynamics is at the center of wind turbine tower design - excessive vibrations can be caused by a wide range of environmental and mechanical sources and can lead to reduced component life due to fatigue, noise, and impaired public perception of system integrity. Furthermore, periodic turbulent wind conditions can cause system resonance resulting in significantly increased structural loads. Structural vibration issues may become exacerbated in small wind applications where the analytical and experimental resources for system verification and optimization are scarce. This study combines several structural analysis techniques and packages them into a novel and integrated form that can be readily used by the small wind community/designer to gain insight into tower/rotor dynamic interaction, system modal characteristics, and to optimize the design for reduced tower loads and cost. The finite element method is used to model the tower structure and can accommodate various configurations including fixed monopole towers, guy-wire supported towers, and gin-pole and strut supported towers. The turbine rotor is modeled using the Equivalent Hinge-Offset blade model and coupled to the tower structure through the use of Lagrange’s Equations. Standard IEC Aeroelastic load cases are evaluated and transient solutions developed using the Modal Superposition Method and Runge-Kutta 4th order numerical integration. Validation is performed through comparisons to theoretical closed form solutions, physical laboratory test results, and peer studies. Finally a case study is performed by using the tool to simulate the Cal Poly Wind Power Research Center Wind Turbine and Tower System. Included in the case study is an optimization for hypothetical guy-wire placement to minimize tower stresses and maximize the tower’s natural frequency.
11
Arefi, Mohammad Jawad. « Dynamic Characteristics and Evaluation of Ground Response for Sands with Non-Plastic Fines ». Thesis, University of Canterbury. Civil & ; Natural Resources Engineering, 2014. http://hdl.handle.net/10092/9173.
Texte intégralRésumé :
Deformational properties of soil, in terms of modulus and damping, exert a great influence on seismic response of soil sites. However, these properties for sands containing some portion of fines particles have not been systematically addressed. In addition, simultaneous modelling of the modulus and damping behaviour of soils during cyclic loading is desirable. This study presents an experimental and computational investigation into the deformational properties of sands containing fines content in the context of site response analysis. The experimental investigation is carried on sandy soils sourced from Christchurch, New Zealand using a dynamic triaxial apparatus while the computational aspect is based on the framework of total-stress one-dimensional (1D) cyclic behaviour of soil.
The experimental investigation focused on a systematic study on the deformational behaviour of sand with different amounts of fines content (particle diameter ≤ 75µm) under drained conditions. The silty sands were prepared by mixing clean sand with three different percentages of fines content. A series of bender element tests at small-strain range and stress-controlled dynamic triaxial tests at medium to high-strain ranges were conducted on samples of clean sand and silty sand. This allowed measurements of linear and nonlinear deformational properties of the same specimen for a wide strain range. The testing program was designed to quantify the effects of void ratio and fines content on the low-strain stiffness of the silty sand as well as on the nonlinear stress-strain relationship and corresponding shear modulus and damping properties as a function of cyclic shear strains.
Shear wave velocity, Vs, and maximum shear modulus, Gmax, of silty sand was shown to be significantly smaller than the respective values for clean sands measured at the same void ratio, e, or same relative density, Dr. However, the test results showed that the difference in the level of nonlinearity between clean sand and silty sands was small. For loose samples prepared at an identical relative density, the behaviour of clean sand was slightly less nonlinear as compared to sandy soils with higher fines content. This difference in the nonlinear behaviour of clean sand and sandy soils was negligible for dense soils. Furthermore, no systematic influence of fines content on the material damping curve was observed for sands with fines content FC = 0 to 30%.
In order to normalize the effects of fines on moduli of sands, equivalent granular void ratio, e*, was employed. This was done through quantifying the participation of fines content in the force transfer chain of the sand matrix. As such, a unified framework for modelling of the variability of shear wave velocity, Vs, (or shear modulus, Gmax) with void ratio was achieved for clean sands and sands with fines, irrespective of their fines content.
Furthermore, modelling of the cyclic stress-strain behaviour based on this experimental program was investigated. The modelling effort focused on developing a simple constitutive model which simultaneously models the soil modulus and damping relationships with shear strains observed in laboratory tests. The backbone curve of the cyclic model was adopted based on a modified version of Kondner and Zelasko (MKZ) hyperbolic function, with a curvature coefficient, a. In order to simulate the hysteretic cycles, the conventional Masing rules (Pyke 1979) were revised. The parameter n, in the Masing’s criteria was assumed to be a function of material damping, h, measured in the laboratory. As such the modulus and damping produced by the numerical model could match the stress-strain behaviour observed in the laboratory over the course of this study. It was shown that the Masing parameter n, is strain-dependent and generally takes values of n ≤ 2. The model was then verified through element test simulations under different cyclic loadings. It was shown that the model could accurately simulate the modulus and the damping simultaneously.
The model was then incorporated within the OpenSees computational platform and was used to scrutinize the effects of damping on one-dimensional seismic site response analysis. For this purpose, several strong motion stations which recorded the Canterbury earthquake sequence were selected. The soil profiles were modelled as semi-infinite horizontally layered deposits overlying a uniform half-space subjected to vertically propagating shear waves. The advantages and limitations of the nonlinear model in terms of simulating soil nonlinearity and associated material damping were further scrutinized.
It was shown that generally, the conventional Masing criteria unconservatively may underestimate some response parameters such as spectral accelerations. This was shown to be due to larger hysteretic damping modelled by using conventional Masing criteria. In addition, maximum shear strains within the soil profiles were also computed smaller in comparison to the values calculated by the proposed model. Further analyses were performed to study the simulation of backbone curve beyond the strain ranges addressed in the experimental phase of this study. A key issue that was identified was that relying only on the modulus reduction curves to simulate the stress-strain behaviour of soil may not capture the actual soil strength at larger strains. Hence, strength properties of the soil layer should also be incorporated to accurately simulate the backbone curve.
12
Miller, Christian [Verfasser], et Patrick [Akademischer Betreuer] Cramer. « Gene regulation during stress response transcription in Saccharomyces Cerevisiae : dynamic transcriptome analysis of osmotic stress response and mediator phosphorylation / Christian Miller. Betreuer : Patrick Cramer ». München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1032862629/34.
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Donald, Craig Hugh Maxfield. « The experience of managers responsible for retrenchment : the development of a dynamic process model and analysis of role stress ». Doctoral thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/13854.
Texte intégralRésumé :
Bibliography: leaves 317-338.Retrenchment is a widespread and frequently used strategy adopted by management to deal with the economic demands faced by organisations. The lack of a theoretical framework, however, has limited the understanding of the phenomenon. The impact of retrenchment on managers and their role in implementation has been particularly neglected, despite the fact that they are central to this process. The present study addressed the development of a dynamic retrenchment process model which could address these limitations. Development of the model was based on qualitative analysis of interview data from a sample of 50 managers involved in retrenchment announcements, in combination with other concepts and findings relating to the phenomenon, and elements of role theory. The model reflected a five phase retrenchment process-moving through decision making, design and planning, the announcement, a post-announcement phase, and concluding with an aftermath phase. The nature of the model components and the relationship between them was then examined in more depth using both qualitative and quantitative techniques. To facilitate the analysis of role dynamics, a multi-dimensional role conflict measure was developed and applied. Qualitative analysis showed indications of all types of role conflict and of role ambiguity during the retrenchment, but these manifested themselves differently during the various phases of retrenchment. Quantitative analysis demonstrated moderate relationships between person-role conflict and role ambiguity, and organisational commitment. Person-role conflict, interrole conflict and role ambiguity were also all related to a measure of mental health. Role ambiguity was the only variable displaying a significant relationship with job involvement. Qualitative analysis suggested moderating effects of personality, coping, and social support during the retrenchment process. Qualitative analysis also displayed support for the existence of adverse physiological, psychological, affective and performance outcomes resulting from involvement in the retrenchment process. The present study emphasises the importance of viewing organisational phenomena in the context of a process which changes over time. Each phase of retrenchment generates its own dynamics and demands and needs to be understood within that context. While general measures at the end of such a process give an indication of what has happened, they lack the ability to diagnose and explain perceptions and behaviour that drive the phenomenon. Also, the present study demonstrates the usefulness of specific types of role conflict in analysing the reactions of managers. Further, the study highlights the role of the psychological contract in regulating relationships and behaviour within the organisation. Both the strength of the relationship between manager and employee, as well as that between manager and organisation are demonstrated in the research. Given that retrenchment is likely to continue, the need for organisations to address specific issues within the retrenchment process is emphasised, and steps that can be taken to enhance the prospects of retrenchment assisting in organisational renewal are discussed.
14
James, Aricatt John, et Devarajan Velmurugan. « Determination of stresses and forces acting on a Granulator knife by using FE simulation ». Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-28297.
Texte intégralRésumé :
Recycling of plastics always plays an important role in keeping our environment better and safe. With the rise in usage of plastics and industrialization, the need for recycling the plastics has become a big business and is getting bigger. This thesis work was done for a company called Rapid Granulator AB, which works with the recycling of plastics as a big trade in Sweden. Like all the industries across the globe are trying to be economical in every way, Rapid Granulator AB wanted to develop an economical design of their high quality granulating knife. For achieving the economical design, they wanted to study the behaviour of the rotating knife during the process of producing plastic granules. The granulator cutting process was simulated and numerical analysis was done on the rotating knife of a plastic granulator machine by using the finite element code ABAQUS with 3D stress elements to find out the critical stresses and forces acting on the rotating knife. The bolt preload was applied by Abaqus/Standard, and the results of implicit analysis were imported to Abaqus/Explicit for the impact analysis where the flow of stresses on the rotating knife during the impact with materials were simulated and studied. The study was done on knife models of different thickness to see if the thickness of the current knife model can be reduced. Analysis were done also on a knife model assembly with a double sided cutting edge knife to see if the knife model can be used to its full extent. The simulation models and analysis results were given to the company to develop a more economical knife model.
15
Dona, Marco. « Static and dynamic analysis of multi-cracked beams with local and non-local elasticity ». Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/14893.
Texte intégralRésumé :
The thesis presents a novel computational method for analysing the static and dynamic behaviour of a multi-damaged beam using local and non-local elasticity theories. Most of the lumped damage beam models proposed to date are based on slender beam theory in classical (local) elasticity and are limited by inaccuracies caused by the implicit assumption of the Euler-Bernoulli beam model and by the spring model itself, which simplifies the real beam behaviour around the crack. In addition, size effects and material heterogeneity cannot be taken into account using the classical elasticity theory due to the absence of any microstructural parameter. The proposed work is based on the inhomogeneous Euler-Bernoulli beam theory in which a Dirac's delta function is added to the bending flexibility at the position of each crack: that is, the severer the damage, the larger is the resulting impulsive term. The crack is assumed to be always open, resulting in a linear system (i.e. nonlinear phenomena associated with breathing cracks are not considered). In order to provide an accurate representation of the structure's behaviour, a new multi-cracked beam element including shear effects and rotatory inertia is developed using the flexibility approach for the concentrated damage. The resulting stiffness matrix and load vector terms are evaluated by the unit-displacement method, employing the closed-form solutions for the multi-cracked beam problem. The same deformed shapes are used to derive the consistent mass matrix, also including the rotatory inertia terms. The two-node multi-damaged beam model has been validated through comparison of the results of static and dynamic analyses for two numerical examples against those provided by a commercial finite element code. The proposed model is shown to improve the computational efficiency as well as the accuracy, thanks to the inclusion of both shear deformations and rotatory inertia. The inaccuracy of the spring model, where for example for a rotational spring a finite jump appears on the rotations' profile, has been tackled by the enrichment of the elastic constitutive law with higher order stress and strain gradients. In particular, a new phenomenological approach based upon a convenient form of non-local elasticity beam theory has been presented. This hybrid non-local beam model is able to take into account the distortion on the stress/strain field around the crack as well as to include the microstructure of the material, without introducing any additional crack related parameters. The Laplace's transform method applied to the differential equation of the problem allowed deriving the static closed-form solution for the multi-cracked Euler-Bernoulli beams with hybrid non-local elasticity. The dynamic analysis has been performed using a new computational meshless method, where the equation of motions are discretised by a Galerkin-type approximation, with convenient shape functions able to ensure the same grade of approximation as the beam element for the classical elasticity. The importance of the inclusion of microstructural parameters is addressed and their effects are quantified also in comparison with those obtained using the classical elasticity theory.
16
Sahoo, Dipankar. « Experimental analysis of the vorticity and turbulent flow dynamics of a pitching airfoil at realistic flight (helicopter) conditions ». Diss., Texas A&M University, 2008. http://hdl.handle.net/1969.1/85893.
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Improved basic understanding, predictability, and controllability of vortex-dominated and unsteady aerodynamic flows are important in enhancement of the performance of next generation helicopters. The primary objective of this research project was improved understanding of the fundamental vorticity and turbulent flow physics for a dynamically stalling airfoil at realistic helicopter flight conditions. An experimental program was performed on a large-scale (C = 0.45 m) dynamically pitching NACA 0012 wing operating in the Texas A&M University large-scale wind tunnel. High-resolution particle image velocimetry data were acquired on the first 10-15% of the wing. Six test cases were examined including the unsteady (k>0) and steady (k=0) conditions. The relevant mechanical, shear and turbulent time-scales were all of comparable magnitude, which indicated that the flow was in a state of mechanical non-equilibrium, and the expected flow separation and reattachment hystersis was observed. Analyses of the databases provided new insights into the leading-edge Reynolds stress structure and the turbulent transport processes. Both of which were previously uncharacterized. During the upstroke motion of the wing, a bubble structure formed in the leading-edge Reynolds shear stress. The size of the bubble increased with increasing angle-of-attack before being diffused into a shear layer at full separation. The turbulent transport analyses indicated that the axial stress production was positive, where the transverse production was negative. This implied that axial turbulent stresses were being produced from the axial component of the mean flow. A significant portion of the energy was transferred to the transverse stress through the pressure-strain redistribution, and then back to the transverse mean flow through the negative transverse production. An opposite trend was observed further downstream of this region.
17
Fekrat, A. Qaium. « Calibration and Validation of EverFE2.24 : A Finite Element Analysis Program for Jointed Plain Concrete Pavements ». Ohio : Ohio University, 2010. http://www.ohiolink.edu/etd/view.cgi?ohiou1260557310.
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Šálek, Pavel. « Kontejnerový nosič ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-254302.
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This thesis deals with the design of a container carrier with interchangeable superstructures up to 3000 kg of technical weight. The introduction renders a critical review of similar devices and consecutive review of the device in terms of legislative matters. A dynamic simulation was used to calculate the loaded states. The outcome of the simulation was used to set the border conditions, which were then used for strength analysis calculations using finite element method (FEM). Blueprints of the final design are a part of the thesis.
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Jakel, Roland. « Linear Dynamic System Analyses with Creo Simulate – Theory & ; Application Examples, Capabilities, Limitations – ». Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-225992.
Texte intégralRésumé :
1. Einführung in die Theorie dynamischer Analysen mit Creo Simulate 2. Modalanalysen (Standard und mit Vorspannung) 3. Dynamische Analysen einschließlich Klassifizierung der Analysen; einige einfache Beispiele für eigene Studien (eine Welle unter Unwuchtanregung und ein Ein-Massen-Schwinger) sowie etliche Beispiele größerer dynamischer Systemmodelle aus unterschiedlichsten Anwendungsbereichen 4. Feedback an den Softwareentwickler PTC (Verbesserungsvorschläge und Softwarefehler) 5. Referenzen1. Introduction to dynamic analysis theory in Creo Simulate 2. Modal analysis (standard and with prestress) 3. Dynamic analysis, including analysis classification, some simple examples for own self-studies (shaft under unbalance excitation and a one-mass-oscillator) and several real-world examples of bigger dynamic systems 4. Feedback to the software developer PTC (enhancement requests and code issues) 5. References
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Marada, Ondřej. « Analýza kostry synchronního generátoru ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229522.
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The thesis is focused on the examination of the utility of a synchronous generator of a small hydroelectric power station in the case of a change of working position of the machine. The utility will be measured on the basis of the examination of deformations and state of stress of the frame of the generator for the present running (with vertical axis of rotation of the generator) and subsequently for modified running (with horizontal axis of rotation). This will be accomplished partly on the static shell model by finite element method and consequently on the simplified dynamic model.
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Doleček, Ladislav. « Hákový nosič kontejnerů NKH 8A340 ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230217.
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This master thesis analyses hook loader NKH 8A340. For calculation of load states was used the dynamic simulation in program MSC.ADAMS. This results were used like a input data to solve the construction with finished element method. After evaluation of results were made design changes of hook loader. Part of this thesis contains drawings of modified parts of hook loader.
22
Ota, Nadia Suemi Nobre. « O elemento finito T6-3i na análise de placas e dinâmica de cascas ». Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-23062016-162053/.
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O método dos elementos finitos é o método numérico mais difundido na análise de estruturas. Ao longo das últimas décadas foram formulados inúmeros elementos finitos para análise de cascas e placas. As formulações de elementos finitos lidam bem com o campo de deslocamentos, mas geralmente faltam testes que possam validar os resultados obtidos para o campo das tensões. Este trabalho analisa o elemento finito T6-3i, um elemento finito triangular de seis nós proposto dentro de uma formulação geometricamente exata, em relação aos seus resultados de tensões, comparando-os com as teorias analíticas de placas, resultados de tabelas para o cálculo de momentos em placas retangulares e do ANSYSr, um software comercial para análise estrutural, mostrando que o T6-3i pode apresentar resultados insatisfatórios. Na segunda parte deste trabalho, as potencialidades do T6-3i são expandidas, sendo proposta uma formulação dinâmica para análise não linear de cascas. Utiliza-se um modelo Lagrangiano atualizado e a forma fraca é obtida do Teorema dos Trabalhos Virtuais. São feitas simulações numéricas da deformação de domos finos que apresentam vários snap-throughs e snap-backs, incluindo domos com vincos curvos, mostrando a robustez, simplicidade e versatilidade do elemento na sua formulação e na geração das malhas não estruturadas necessárias para as simulações.The Finite Element Method (FEM) is the numerical method most commonly used in structural analysis. A number of shell and plate finite elements has been suggested in the last decades. Finite element formulations deal well with the displacements field, but they usually lack tests that can validate the results obtained for the stress field. This work analyzes the finite element T6-3i, a six-nodes triangular finite element derived from a geometrically exact theory, regarding its stress results, comparing them with analytic plate theories, results from tables of moments in rectangular plates and from ANSYSr, a commercial software for structural analysis, showing that T6-3i can present unsatisfactory results. In the second part of this work, the T6-3i potentialities are expanded as a dynamic formulation for nonlinear shell analysis is proposed. An updated Lagrangian framework has been used and the weak form is obtained from the Principle of VirtualWork. Several numerical examples of folding a thin dome, which present various snap-throughs and snap-backs are presented, including creased shells, showing the robustness, simplicity and versatility of the element formulation and in generation of the unstructured curved meshes indispensable for the simulations.
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Hajniš, Jan. « Analýza dynamických účinků působících na výhybky se zaměřením na stav konstrukce ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226625.
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Author´s name: Bc. Jan Hajniš School: Technical University - VUT, Brno Faculty of Civil Engineering Veveří 331/95, 602 00 Brno Program: Construction and Transportation Engineering Title: The Analysis of dynamic effects acting on the turnout with a focus on structural condition Consultant: Prof. Ing. Jaroslav Smutný, Ph.D. Number of pages: about 100 + attachments Number of attachments: about 340 Year: 2014 This work describes the size and the process of dynamic effect – vibrations and shift – cockles in crossing panel and switch panels of the turnout constructions on steel and concrete sleepers in time and frequency domain. It compares the results of the measurement between these turnout constructions. Dynamic effects are undesirable physical phenomena for operation each train. It is therefore necessary to eliminate these phenomena as much as possible. The result of this test will by means of software programm and measuring set help to determine precisely the advantages and disadvantages of using both turnout constructions, or even to propose their improvements or dimensions.
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Eiselt, Uwe, et Thomas Kelichhaus. « Dynamische Auslegung von Zahnradgetrieben mittels Mehrkörpersimulation ». Technische Universität Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A21398.
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Auf Grund wachsender Nachfrage der simulativen Beurteilung von Getrieben hinsichtlich Geräuschentwicklung, Vibration und Belastbarkeit, kommt den Berechnungsmethoden immer größere Bedeutung zu. Hier spielen nicht nur die Steifigkeit der Verzahnung, sondern auch die Steifigkeiten der Wellen, Lagerungen und Gehäuse eine wichtige Rolle.
Dazu werden unterschiedliche Simulationsmethoden vorgestellt und diese hinsichtlich Genauigkeit, Effizienz und Limitierung bewertet.
Ein wichtiger Aspekt ist in diesem Zusammenhang auch die Modellbildung, insbesondere die Ermittlung der Eingabedaten für die Beschreibung der einzelnen Komponenten und deren Verbindungselemente. Die Koppelung des Mehrkörpersystems mit einem speziellen Auslegungstool für Getriebekomponenten ist neben der Multi-Physics-Simulation und der klassischen Mehrkörperdynamik eine Methode, die die Stärken beider Tools verbindet.
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Kocourek, Petr. « Půdorysně zakřivená konstrukce z předpjatého pásu ». Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-392290.
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The theme of this doctoral thesis is research of footbridges curved in plan that are formed by stress ribbon. Recently, several noteworthy curved pedestrian bridges, which decks are suspended on their inner edges on suspension or stay cables, have been constructed. However, curved stress ribbon bridges have not been built so far. The goal of this study was to answer the question whether the use of curved stress ribbon structures is even possible. For this reason, in the first stage feasibility study of these structures has been prepared. Knowledge of both curved pedestrian bridges, which decks are suspended on their inner edge and straight stress ribbon has been used. For the mathematical modeling FEM software ANSYS was used. The obtained findings were further used to design a new type of a modern, aesthetic curved bridge for pedestrians. The structure is formed by slender reinforced deck, which is through the steel brackets on the inner side stiffened by steel section. Torsion of the deck, caused by curved structure and asymmetrical cross-section, is reduced by cable situated in the handrail. Footbridge span is 45 m, arc camber in plan is 10 m, free bridge width is 3 m. Described is a general structure effect, detail static and dynamic analysis was carried out. Designed structure including construction stages were experimentally verified on a fully physical functional 1:6 scale model. The thesis describes the model analogy used for the design of the model, its structural design and its implementation. The model was subjected to a series of load tests including the final ultimate strength test. Performed tests confirmed the good match of calculation with the reality, correctness of the design and high resistance of designed construction. Acquired results and experiences from design and realization of model form the basis for practical realization of studied structures.
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Sivathasan, Kathiravetpillai (Siva). « Dynamic site response analyses using effective stress based numerical procedure / ». For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
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Darestani, Mostafa Yousefi. « Response of concrete pavements under moving vehicular loads and environmental effects ». Queensland University of Technology, 2007. http://eprints.qut.edu.au/16662/.
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The need for modern transportation systems together with the high demand for sustainable pavements under applied loads have led to a great deal of research on concrete pavements worldwide. Development of finite element techniques enabled researchers to analyse the concrete pavement under a combination of axle group loadings and environmental effects. Consequently, mechanistic approaches for designing of concrete pavements were developed based on results of finite element analyses. However, unpredictable failure modes of concrete pavements associated with expensive maintenance and rehabilitation costs have led to the use of empiricalmechanistic approach in concrete pavement design. Despite progressive knowledge of concrete pavement behaviour under applied loads, concrete pavements still suffer from deterioration due to crack initiation and propagation, indicating the need for further research. Cracks can be related to fatigue of the concrete and/or erosion of materials in sub-layers. Although longitudinal, midedge and corner cracks are the most common damage modes in concrete pavements, Austroads method for concrete pavement design was developed based on traditional mid-edge bottom-up transverse cracking introduced by Packard and Tayabji (1985). Research presented in this thesis aims to address the most common fatigue related distresses in concrete pavements. It uses comprehensive finite element models and analyses to determine the structural behaviour of concrete pavements under vehicular loads and environmental effects. Results of this research are supported by laboratory tests and an experimental field test. Results of this research indicate that the induced tensile stresses within the concrete pavement are significantly affected by vehicle speed, differential temperature gradient and loss of moisture content. Subsequently, the interaction between the above mentioned factors and concrete damage modes are discussed. Typical dynamic amplifications of different axle groups are presented. A new fatigue test setup is also developed to take into consideration effects of pavement curvature on fatigue life of the concrete. Ultimately, results of the research presented in this thesis are employed to develop a new guide for designing concrete pavements with zero maintenance of fatigue damage.
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Loureiro, Liliana Raquel Rodrigues. « DJ-1 mutants binding partners : insights into Parkinson's Disease ». Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12583.
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Mestrado em Biotecnologia - Biotecnologia MolecularParkinson´s disease (PD), the second most common progressive neurodegenerative disorder, is a multifactorial disease caused by both genetic and environmental factors. Among the genes associated with PD, DJ-1 is a multifunctional protein involved in oxidative stress response and neuroprotection. DJ-1 mutations, such as L166P, M26I and E163K lead to loss of protein function causing early onset autosomal recessive PD. Moreover, the residue C106 is considered crucial in DJ-1 function as a sensor of oxidative stress. In this study, one missense mutations (E163K) and two engineered mutations in the residue C106 (C106A and C106DD) were produced and characterized in order to evaluate the neuroprotective effect of each mutation and also characterize their dynamic interactome. Structural analysis confirmed the production of all the mutants in the dimeric form, with a molecular weight of approximately 43kDa. Moreover, protein´s thermal stability was assessed by thermal shift and the results showed that the mutant E163K was the less stable and the C106A the most stable. Secondary structure analysis was performed by circular dichroism and revealed similar secondary structures between DJ-1 WT and mutants. In addition, a LC-MS/MS was performed to determine proteins´ contaminants and the majority of the protein contaminants were coming from the expression system and culture medium used in proteins´ production. Moreover, neuroprotection assays revealed that DJ-1 WT did not protect SH-SY5Y cells under oxidative stress conditions. The dynamic interactome of DJ-1 WT and mutants C106DD, E163K and C106A was characterized under oxidative stress conditions. A wide number of binding partners were identified and for some of them quantification in the different conditions was also determined. These interactors have a broad range of functions but the majority are associated with cellular response to oxidative stress. The study of DJ-1 mutations is very important, since it gives elucidations into DJ-1 WT functions and related disease mechanisms. In this way, the putative DJ-1 WT interactors identified still lack validation, but from these characterized dynamic interactomes further elucidations can be obtained into Parkinson’s Disease pathology and potential new targets for PD prevention and therapy, like ATP-dependent RNA helicase DDX3X herein identified as new dynamic interactor of DJ-1.
A Doença de Parkinson, a segunda doença neurodegenerativa progressiva mais comum, é uma doença multifatorial causada conjuntamente por fatores genéticos e fatores ambientais. De entre os inúmeros genes associados à Doença de Parkinson, a DJ-1 é uma proteína multifuncional envolvida na resposta ao stress oxidativo e neuroproteção. Mutações na DJ-1, tais como L166P, M26I e E136K levam à perda de função da proteína causando a forma de Parkinson autossomal recessiva com desenvolvimento precoce. De salientar que o resíduo C106 é considerado crucial na função de sensor de stress oxidativo que a DJ-1 desempenha. Neste estudo, foram produzidas e caracterizadas duas mutações sintéticas no resíduo C106 (C106A e C106DD) e uma mutação natural (E163K) de modo a avaliar o efeito neuroprotetor de cada mutação bem como caracterizar o seu interactoma dinâmico. Análises estruturais confirmaram a produção de todos os mutantes na forma dimérica, apresentando um peso molecular de aproximadamente 43kDa. A estabilidade térmica das proteínas foi ainda avaliada por thermal shift e os resultados revelaram que o mutante E163K foi o menos estável enquanto que o mutante C106A foi o mais estável. Análise da estrutura secundária foi realizada por dicroísmo circular revelando elevada semelhança entre as estruturas secundárias da DJ-1 nativa e mutantes. Por fim, foi realizada uma análise de LC-MS/MS de modo a determinar os contaminantes das proteínas produzidas e verificou-se que a maioria dos contaminantes era proveniente do sistema de expressão e meio de cultura utilizados na produção das proteínas. Seguidamente, ensaios de neuroproteção revelaram que a DJ-1 nativa não exercia um efeito neuroprotetor nas células SH-SY5Y em condições de stress oxidativo. O interactoma dinâmico da DJ-1 nativa e mutantes C106DD, E163K e C106A foi caracterizado sob condições de stress oxidativo. Um elevado número de interactores foram identificados e para alguns deles foi possível obter uma quantificação nas diferentes condições. Os referidos interactores apresentam uma enorme variedade de funções, contudo a grande maioria está associada à resposta celular ao stress oxidativo. O estudo das mutações na DJ-1 é considerado muito relevante visto que fornece importantes elucidações relativamente às funções e mecanismos da DJ-1 nativa associados à doença. Neste sentido, os supostos interactores da DJ-1 nativa identificados ainda carecem de validação, mas da caracterização dos interactomas dinâmicos, elucidações podem ser obtidas sobre a patologia da Doença de Parkinson e identificação de novos potenciais alvos para prevenção e terapia desta doença, tal como a RNA helicase DDX3X dependente de ATP aqui identificada como novo interactor dinâmico da DJ-1.
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Renou, Julien. « Observations and modeling of the seismic rupture development based on the analysis of source time functions ». Thesis, Université de Paris (2019-....), 2020. https://theses.md.univ-paris-diderot.fr/RENOU_Julien_va2.pdf.
Texte intégralRésumé :
Notre compréhension de la physique de la source sismique, qui donne naissance à des séismes de toute magnitude, requiert l’observation d’une large population d’événements. Les méthodes d’analyse systématique de la sismicité mondiale remplissent ce rôle et permettent d’extraire les propriétés des séismes puis de les confronter aux modèles de rupture sismique. La méthode SCARDEC fait partie de ces méthodes et retrouve les fonctions source d’événements sur une large gamme de magnitudes (Mw > 5.7). La fonction source, puisqu’elle décrit l’évolution tem porelle du taux de moment, est un observable privilégié pour l’analyse des propriétés transitoires de la rupture. L’objectif de notre étude est d’observer le développement de la rupture lors de ces séismes afin de plus précisément contraindre les modèles cinématiques et dynamiques de la source. La première partie de notre travail s’intéresse au développement des séismes à partir du catalogue SCARDEC. La phase menant au pic de la fonction source (“phase de dévelop pement”) est extraite pour caractériser son évolution. À partir du calcul des accélérations de moment pour des taux de moment donnés, nous observons que l’évolution du taux de moment pendant la phase de développement est indépendante de la magnitude finale. Une analyse quantitative de l’augmentation du taux de moment en fonction du temps indique que cette phase ne respecte pas la dépendance en t 2 de la loi auto-similaire, suggérant une variation transitoire de la vitesse de rupture et/ou de la chute de contrainte. Ces observations sont dans un deuxième temps confrontées aux modèles cinématiques de la source. Un modèle de crack avec des variations radiales de la vitesse de rupture, associées à une faible chute de contrainte, met en évidence que la corrélation entre vitesse de rupture et vitesse de glissement est un ingrédient nécessaire au comportement transitoire de la phase de développement vu dans les observations. Nous générons ensuite à partir du modèle composite fractal RIK des catalogues synthétiques de fonctions source. Ces derniers montrent également que la corrélation entre la vitesse de rupture et la vitesse de glissement, ainsi que la durée du temps de montée, ont une influence sur les valeurs de l’accélération de moment. Nous développons finalement des modèles dynamiques hétérogènes qui prennent en compte la physique de la rupture. Les dis tributions hétérogènes du paramètre de friction Dc et de la contrainte initiale τ0 sur la faille participent à générer des scénarios de rupture particulièrement réalistes. La propagation de la rupture est en particulier influencée par ces deux paramètres dynamiques qui entraînent une direction de propagation préférentielle couplée à une variabilité plus locale de la vitesse de rupture. La corrélation entre vitesse de rupture et vitesse de glissement, mise en lumière dans les modèles cinématiques précédents, est retrouvée et permet la reproduction des observations SCARDEC. Ces résultats devraient fournir des contraintes additionnelles pour la constitution de scenarios réalistes de la dynamique de la ruptureOur knowledge of earthquake source physics, giving rise to events of very different magnitudes, requires observations of a large population of earthquakes. The development of systematic analysis tools for the global seismicity meets these expectations, and allows us to extract the generic properties of earthquakes, which can then be integrated into models of the rupture process. Following this approach, the SCARDEC method is able to retrieve source time func tions of events on a large range of magnitude (Mw > 5.7). The source time function (which describes the temporal evolution of the moment rate) is suitable for the analysis of transient rupture properties which provide insights into the generation of earthquakes of various sizes. The purpose of our study is to observe the rupture development of such earthquakes in order to add better constraints on kinematic and dynamic source models. The first part of our work focuses on the development of earthquakes through the analysis of the SCARDEC catalog. The phase leading to the peak of the source time function (“development phase”) is extracted to characterize its evolution. From the computation of moment accelerations at prescribed mo ment rates, we observe that the evolution of the moment rate during the developement phase is independent of the final magnitude. A quantitative analysis of the moment rate increase as a function of time further indicates that this phase does not respect the steady t 2 self-similar growth, suggesting a transient variation of rupture velocity and/or stress drop. In a second part, these observations are compared with kinematic source models. A crack model with ra dial variations of the rupture velocity combined with low stress drop highlights that correlation between rupture velocity and slip velocity is a key feature for the transient behavior of the development phase previously observed. We then generate, using the composite fractal RIK model, synthetic catalogs of source time functions. This also supports that the correlation bet ween rupture velocity and slip velocity, as well as the duration of the rise-time, have a strong effect on moment acceleration values. We finally develop heterogeneous dynamic models which take into consideration rupture physics. Heterogeneous distributions of the friction parameter Dc and the initial stress τ0 contribute to generate highly realistic rupture scenarios. Rupture propagation is strongly influenced by these two dynamic parameters which induce a clear pre ferential direction of propagation together with a local variability of the rupture velocity. The correlation between rupture velocity and slip velocity highlighted by the previous kinematic models is retrieved and allows to reproduce the SCARDEC observations. These findings are expected to put further constraints on future realistic dynamic rupture scenarios
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Stephenson, Robin. « Analysing the dynamic loads in a high speed timing chain ». Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366783.
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Wei, Ling. « Experimental study of growth and protein dynamics in yeast Hog1 mutants under osmotic stress ». HKBU Institutional Repository, 2011. http://repository.hkbu.edu.hk/etd_ra/1282.
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Franklin, Paul. « Dynamic analysis and modelling of hydroecology in two Chalk streams ». Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443363.
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Mashiko, Naoto. « Comparative performance of ductile and damage protected bridge piers subjected to bi-directional earthquake attack ». Thesis, University of Canterbury. Civil Engineering, 2006. http://hdl.handle.net/10092/1159.
Texte intégralRésumé :
Incremental Dynamic Analysis (IDA) procedures are advanced and then applied to a quantitative risk assessment for bridge structures. This is achieved by combining IDA with site-dependent hazard-recurrence relations and damage outcomes. The IDA procedure is also developed as a way to select a critical earthquake motion record for a one-off destructive experiment. Three prototype bridge substructures are designed according to the loading and detailing requirements of New Zealand, Japan and Caltrans codes. From these designs 30 percent reduced scale specimens are constructed as part of an experimental investigation. The Pseudodynamic test is then to control on three specimens using the identified critical earthquake records. The results are presented in a probabilistic riskbased format. The differences in the seismic performance of the three different countries' design codes are examined. Each of these current seismic design codes strive for ductile behaviour of bridge substructures. Seismic response is expected to be resulting damage on structures, which may threaten post-earthquake serviceability. To overcome this major performance shortcoming, the seismic behaviour under bi-directional lateral loading is investigated for a bridge pier designed and constructed in accordance with Damage Avoidance principles. Due to the presence of steel armoured rocking interface at the base, it is demonstrated that damage can be avoided, but due to the lack of hysteresis it is necessary to add some supplemental damping. Experimental results of the armoured rocking pier under bi-directional loading are compared with a companion ductile design specimen.
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Urík, Tomáš. « Dynamické vlastnosti lepeno – nitovaných spojov ». Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-233922.
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The improvement of static properties of combined rivet and adhesive bonded joints have been proven by several authors [1, 2]. On the other side, dynamic properties of joints (for example fatigue and corrosion) significantly affect final function of structures during their service life. In this thesis, the combine joints created by blind rivets and hyper elastic sealant are solved. Complex description of dynamic properties of this particular combined joining technology has not been publicised, yet. Description of sealant layer influence on stress concentration in rivet hole regions is one of the main goal of this work. The next stage of the thesis is focused on the influence of above mentioned sealant layer on fatigue properties of combined blind rivet and solid countersunk rivet joints. Stress strain analysis of rivet and combined joints done by FE analysis and by experimental optical measurement of strain field proved that hyper elastic sealant layer has a positive effect on decreasing of stress peaks in rivet hole regions. This findings are in direct compliance with fatigue measurement of combined joint (AAPL). The influence of applied sealant in this combined joints improved fatigue properties by twenty percentage increasing of stress to failure in comparison with rivet joints.
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Hartnett, Kathleen A. « Streak camera analysis of dynamic characteristics of current modulated diode laser arrays / ». Full text open access at:, 1988. http://content.ohsu.edu/u?/etd,160.
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Hušek, Martin. « Londýnské oko ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227180.
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Performance of static analysis of the London Eye structure is the subject of this diploma thesis. First chapters of the thesis analyses overview of realized structures of the Ferris wheel. The main part of the thesis analyses the London Eye structure itself. Specifically are described response analyses, sensitivity analyses, analyses of ultimate limit state and serviceability, stress analyses, analyses of fatigue stress and lifetime analyses. The thesis describes among static analysis also a design of dynamic vibration absorbers. The results of each analysis are evaluated in the final chapters.
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Webb, Sarah E. « Numerical analysis of source-water dynamics for stream-bounded alluvial aquifers ». Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=3293.
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Thesis (M.S.)--West Virginia University, 2003.Title from document title page. Document formatted into pages; contains viii, 119 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references.
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Franke, Jonas. « Spatiotemporal dynamics of stress factors in wheat analysed by multisensoral remote sensing and geostatistics ». [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=986005169.
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Gao, Hao. « Carotid plaque stress analysis by fluid structure interaction based on in-vivo MRI : implications to plaque vulnerability assessment ». Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4731.
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Stroke is one of the leading causes of death in the world, resulting mostly from the sudden rupture of atherosclerotic plaques. From a biomechanical view, plaque rupture can be considered as a mechanical failure caused by extremely high plaque stress. In this PhD project, we are aiming to predict 3D plaque stress based on in-vivo MRI by using fluid structure interaction (FSI) method, and provide information for plaque rupture risk assessment. Fluid structure interaction was implemented with ANSYS 11.0, followed by a parameter study on fibrous cap thickness and lipid core size with realistic carotid plaque geometry. Twenty patients with carotid plaques imaged by in-vivo MRI were provided in the project. A framework of reconstructing 3D plaque geometry from in-vivo multispectral MRI was designed. The followed reproducibility study on plaque geometry reconstruction procedure and its effect on plaque stress analysis filled the gap in the literature on imaging based plaque stress modeling. The results demonstrated that current MRI technology can provide sufficient information for plaque structure characterization; however stress analysis result is highly affected by MRI resolution and quality. The application of FSI stress analysis to 4 patients with different plaque burdens has showed that the whole procedure from plaque geometry reconstruction to FSI stress analysis was applicable. In the study, plaque geometries from three patients with recent transient ischemic attack were reconstructed by repairing ruptured fibrous cap. The well correlated relationship between local stress concentrations and plaque rupture sites indicated that extremely high plaque stress could be a factor responsible for plaque rupture. Based on the 20 reconstructed carotid plaques from two groups (symptomatic and asymptomatic), fully coupled fluid structure interaction was performed. It was found that there is a significant difference between symptomatic and asymptomatic patients in plaque stress levels, indicating plaque stress could be used as one of the factors for plaque vulnerability assessment. A corresponding plaque morphological feature study showed that plaque stress is significantly affected by fibrous cap thickness, lipid core size and fibrous cap surface irregularities (curvedness). A procedure was proposed for predicting plaque stress by using fibrous cap thickness and curvedness, which requires much less computational time, and has the potential for clinical routine application. The effects of residual stress on plaque stress analysis and arterial wall material property characterization by using in-vivo MRI data were also discussed for patient specific modeling. As the further development, histological study of plaque sample has been combined with conventional plaque stress analysis by assigning material properties to each computational element, based on the data from histological analysis. This method could bridge the gap between biochemistry and biomechanical study of atherosclerosis plaques. In conclusion, extreme stress distributions in the plaque region can be predicted by modern numerical methods, and used for plaque rupture risk assessment, which will be helpful in clinical practice. The combination of plaque MR imaging analysis, computational modelling, and clinical study/ validation would advance our understandings of plaque rupture, prediction of future rupture, and establish new procedures for patient diagnose, management, and treatment.
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Sarker, Pratik. « Investigation of the Quenching Characteristics of Steel Components by Static and Dynamic Analyses ». ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1942.
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Machine components made of steel are subjected to heat treatment processes for improving mechanical properties in order to enhance product life and is usually done by quenching. During quenching, heat is transferred rapidly from the hot metal component to the quenchant and that rapid temperature drop induces phase transformation in the metal component. As a result, quenching generates some residual stresses and deformations in the material. Therefore, to estimate the temperature distribution, residual stress, and deformation computationally; three-dimensional finite element models are developed for two different steel components – a spur gear and a circular tube by a static and a dynamic quenching analyses, respectively. The time-varying nodal temperature distributions in both models are observed and the critical regions are identified. The variations of stress and deformation after quenching along different pathways for both models are studied. The convergence for both models is checked and validations of the models are done.
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Zhou, Pu. « A dynamic approximate representation scheme for streaming time series ». Connect to thesis, 2009. http://repository.unimelb.edu.au/10187/6766.
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The huge volume of time series data generated in many applications poses new challenges in the techniques of data storage, transmission, and computation. Further more, when the time series are in the form of streaming data, new problems emerge and new techniques are required because of the streaming characteristics, e.g. high volume, high speed and continuous flowing. Approximate representation is one of the most efficient and effective solutions to address the large-volume-high-speed problem. In this thesis, we propose a dynamic representation scheme for streaming time series. Existing methods use a unitary function form for the entire approximation task. In contrast, our method adopts a set of function candidates such as linear function, polynomial function(degree ≥ 2), and exponential function. We provide a novel segmenting strategy to generate subsequences and dynamically choose candidate functions to approximate the subsequences.Since we are dealing with streaming time series, the segmenting points and the corresponding approximate functions are incrementally produced. For a certain function form, we use a buffer window to find the local farthest possible segmenting point under a user specified error tolerance threshold. To achieve this goal, we define a feasible space for the coefficients of the function and show that we can indirectly find the local best segmenting point by the calculation in the coefficient space. Given the error tolerance threshold, the candidate function representing more information by unit parameter is chosen as the approximate function. Therefore, our representation scheme is more flexible and compact. We provide two dynamic algorithms, PLQS and PLQES, which involve two and three candidate functions, respectively. We also present the general strategy of function selection when more candidate functions are considered. In the experimental test, we examine the effectiveness of our algorithms with synthetic and real time series data sets. We compare our method with the piecewise linear approximation method and the experimental results demonstrate the evident superiority of our dynamic approach under the same error tolerance threshold.
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Anwar, Sohail. « Transient Stress and Strain Assessment of Marine Boiler : Fully Rigid Body Dynamics Coupled Finite Element Analyses ». Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-95440.
Texte intégralRésumé :
Operationally, marine components and structures such as boiler in a Ship, are exposed to varying mechanically and thermally induced forces. High-frequency mechanical loading arises from the cyclic pressure, temperature transients, and six directional Rapid Amplitude Operator (RAOs). These types of loadings are mainly in the elastic region usually denoted as high cycle fatigue (HCF), most pronounced during the start-up, and the shut-down sequence of operation, which are responsible for an astronomically reduction in Marine Boiler’s lifetime as compared to land boiler with same designed operating condition. Therefore, there is a need to determine the limitations of the engineering variables of the boiler with respect to Pressure, temperature, RAOs, and best locational point for the optimization of its designed lifetime during Operation. Detailed knowledge of this interaction between varying temperatures, RAOs and load cases is of considerable importance for precise lifetime calculations. In order to understand and analyze the material behavior under contentious stress exposure, a general-purpose linear Finite Element (FE) code, LS-DYNA software is used as a pre-processor and solver during the simulation and data are post-processed using stress-based analysis method.
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Hokeš, Filip. « Statická a dynamická analýza předpjaté mostní konstrukce ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226802.
Texte intégralRésumé :
The main objective of the thesis is to perform static and dynamic analysis of prestressed concrete bridge structures in computational system ANSYS. For the analysis was chosen footbridge over the river Svratka in Brno. In relation to this topic are solved various types of modeling prestress at a finite element level. Before analyzing the footbridge is analyzed in detail the static system and the corresponding final geometry of the structure. Knowledge of the functioning of the static system is used to build the computational model of the structure, on which is subsequently performed static and dynamic analysis.
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Malhan, Khyati. « Stellar streams as probes of dark matter : search and dynamical analysis ». Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAE027/document.
Texte intégralRésumé :
Les courants stellaires de marée sont des structures en étoile immaculées qui jouent un rôle central dans la résolution des mystères de longue date de l'archéologie galactique. Étant donné que les flux sont de nature orbitale, ils possèdent intrinsèquement les caractéristiques de résolution de la distribution de masse sous-jacente de la galaxie et peuvent être utilisés pour sonder la forme du halo de matière noire. En plus de tester le scénario de «fusion hiérarchique» de la formation de galaxies, les brèches de ruisseau peuvent également fournir une preuve indirecte de l’existence de sous-halos de matière noire (ce qui, en principe, limite la nature de la particule de matière noire elle-même). Pour toutes ces raisons, l'analyse dynamique des flux stellaires de la Voie Lactée devient naturellement l'un des problèmes les plus intéressants. Cependant, le principal défi consiste à détecter ces structures. Au cours de la thèse, l’algorithme STREAMFINDER (un algorithme à la pointe de la technologie) a été conçu pour traiter systématiquement le jeu de données Gaia (le nouveau catalogue astrophysique de l’ESA contenant des solutions astrométriques sans précédent de plus de 1,6 milliard d’étoiles) pour la détection des flux stellaires de la Voie lactée. Cette lourde entreprise a permis de détecter 10 structures de flux de confiance, dont 5 étaient considérées comme de nouvelles découvertes. Cette récolte de structures a également facilité, pour la première fois, la création d’une carte structurale et cinématique panoramique des flux stellaires de la rivière Milky. Halo, poussant notre communauté encore plus loin dans l’histoire complexe de la formation de notre galaxie. Ce projet a été immédiatement suivi de l'analyse orbitale de l'un des flux détectés (à savoir GD-1) pour explorer les améliorations des modèles de potentiel gravitationnel de notre galaxie. Les contraintes imposées à la masse de la Voie lactée et à la forme de son halo de matière noire, obtenues simplement en utilisant ce seul flux, ont révélé la puissance potentielle que l'analyse d'un ensemble de flux permettrait de sonder la distribution globale de la masse galactique de notre galaxie. Ainsi, la thèse a ouvert la voie à de nouvelles découvertes des sous-structures stellaires, soulignant également les perspectives d'avenir dans ce domaineTidal stellar streams are pristine star structures that play central role in addressing long standing mysteries of the Galactic archaeology. Since streams are orbital in nature, they inherently possess the characteristics of unravelling the underlying mass distribution of the galaxy, and can be used to probe the shape of the dark matter halo. Besides testing the ‘hierarchical merging’ scenario of galaxy formation, stream gaps can also provide indirect evidence for the existence of dark matter sub-halos (thereby, in principle, constraining the nature of the dark matter particle itself). Due to all these reasons, the dynamical analysis of stellar streams of the Milky Way Galaxy naturally becomes one of the interesting problems. However, the foremost challenge is to detect these structures. During the thesis, STREAMFINDER algorithm (a state of the art algorithm) was designed to systematically process the Gaia dataset (ESA’s novel astrophysical catalogue containing unprecedented astrometric solutions of over 1.6 billion stars) for the detection of the stellar streams of the Milky Way. This hefty endeavour led to the detection of 10 high confidence stream structures, of which 5 were reported as new discoveries.This harvest of structures also facilitated, for the first time, creation of a panoramic structural and kinematic map of the stellar streams of the Milky Way halo, taking our community a step further in unravelling the complex formation history of our Galaxy. This project was instantly followed by the orbital analysis of one of the detected streams (namely GD-1) to explore the improvements in the gravitational potential models of our Galaxy. The constraints on the Milky Way’s mass and that on the shape of its dark matter halo, that were obtained by simply employing this single stream, revealed the potential power the analysis of an ensemble of streams would hold in in probing the overall galactic mass distribtuion of our Galaxy. Thereby, the thesis paved way for new discoveries of the stellar substructures, also highlighting the future prospects in this field
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Almeida, Camila de. « Modelling of the protection mechanisms against methylgyoxal stress in Escherichia coli : dynamical analysis and experimental validation ». Thesis, University of Aberdeen, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=103942.
Texte intégralRésumé :
The main MG detoxification pathway in Escherichia coli consists of two enzymes, the glyoxalases I and II, and is dependent on glutathione (GSH). MG readily conjugates with GSH in a non-enzymatic manner. Two subsequent enzymatic reactions via the glyoxalases complete a cyclic process that recycles GSH and produces the non-toxic compound, D-lactate. An intermediate compound in the detoxification pathway, S-lactoylglutathione (SLG), activates potassium efflux systems KefB and KefC. This triggers a second mechanism of protection mediated by cytoplasmic acidification, enhancing chances of survival. Therefore, it is important to understand how cells regulate the concentration of this important intermediate compound. A deterministic model was proposed that describes the series of chemical reactions in the MG detoxification pathway, allowing one to predict the flux of all compounds produced during detoxification. Through an iterative process involving model formulation, parameter estimation, data fitting and validation against experimental data, different models were analysed and discriminated in this study. Mathematical simulations predicted that the glyoxalase pathway is not linear because it involves feedforward mechanisms for the control of SLG, the activator of the potassium efflux systems. The activities of the potassium efflux systems were investigated using deterministic models that describe the interactions between protein and ligand. From this model, it was possible to quantify the dependence of the possible binding states on the kinetic parameters of the system. Parameter estimation methods were used for the analysis of experimental data on the gating of the efflux systems, which proved useful for the design of new experimental strategies.
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Brunetti, Alessio Francesco. « Fluid dynamic analysis of trees influence in dispersion of pollutant in urban street canyon ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12041/.
Texte intégralRésumé :
degli elementi vegetali nella dinamica e nella dispersione degli inquinanti nello street canyon urbano. In particolare, è stato analizzata la risposta fluidodinamica di cespugli con altezze diverse e di alberi con porosità e altezza del tronco varianti. Il modello analizzato consiste in due edifici di altezza e larghezza pari ad H e lunghezza di 10H, tra i quali corre una strada in cui sono stati modellizati una sorgente rappresentativa del traffico veicolare e, ai lati, due linee di componenti vegetali. Le simulazioni sono state fatte con ANSYS Fluent, un software di "Computational Fluid Dynamics"(CFD) che ha permesso di modellizare la dinamica dei flussi e di simulare le concentrazioni emesse dalla sorgente di CO posta lungo la strada. Per la simulazione è stato impiegato un modello RANS a chiusura k-epsilon, che permette di parametrizzare i momenti secondi nell'equazione di Navier Stokes per permettere una loro più facile risoluzione.
I risultati sono stati espressi in termini di profili di velocità e concentrazione molare di CO, unitamente al calcolo della exchange velocity per quantificare gli scambi tra lo street canyon e l'esterno.
Per quanto riguarda l'influenza dell'altezza dei tronchi è stata riscontrata una tendenza non lineare tra di essi e la exchange velocity. Analizzando invece la altezza dei cespugli è stato visto che all'aumentare della loro altezza esiste una relazione univoca con l'abbassamento della exchange velocity. Infine, andando a variare la permeabilità delle chiome degli alberi è stata trovatta una variazione non monotonica che correla la exchange velocity con il parametro C_2, che è stata interpretata attraverso i diversi andamenti dei profili sopravento e sottovento.
In conclusione, allo stadio attuale della ricerca presentata in questa tesi, non è ancora possibile correlare direttamente la exchange velocity con alcun parametro analizzato.
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Jongchansitto, Pawarut. « Mechanical analysis of 2D composite granular materials : thermomechanical experiments and numerical simulations ». Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22592/document.
Texte intégralRésumé :
L'objectif de la thèse est d'analyser le comportement mécanique de matériaux granulaires composites bidimensionels en terme de textures granulaires en utilisant deux approches : étude expérimentale par "thermoelastic stress analysis" et étude numérique par dynamique moléculaire. Les systèmes granulaires composites sont préparés à l'aide de cylindres en polyoxyméthylène (POM) et polyéthylène haute densité (PEHD), présentant un rapport de rigidité de 4 entre eux. Différents rapports de diamètres et de nombres de particules sont considérés. Les résultats expérimentaux et numériques sont en bon accord à l'échelle macroscopique. En particulier, le réseau fort (qui est ici caractérisé par des contraintes hydrostatiques supérieures à la valeur moyenne) contient moins de 50% des particules, et présente une distribution décroissance exponentielle quel que soit le type de particules considéré pour l'analyse (particules souples, particules rigides, toutes les particules). De plus, la distribution des contacts entre particules rigides (contacts POM-POM) est anisotrope et tend à s'organiser dans le sens de la direction du chargement extérieur appliqué, tandis que les autres types de contact agissent principalement pour maintenir le système en équilibreThe main objective of our dissertation is to analyze the mechanical behavior of two-dimensional composite granular materials through the granular textures. Thermoelatic stress analysis experiments and molecular dynamics simulations are used for this purpose. The composite granular systems are prepared from polyoxymethylene (POM) and high-density polyethylene (HDPE) cylinders with a stiffness ratio of about 4 between them. Different configurations in terms of ratios of diameter size and ratio of particle numbers are systematically investigated. Experimental and numerical results are good correlated at the macroscopic scale. In particular the strong network, which is here characterized by hydrostatic stresses higher than the mean value, consists of less than 50% of all particles, and exhibits an exponential decay whatever the type of particles considered for the analysis (soft, stiff, or both types). In addition, the contact distributions between stiff particles (POM-POM contacts) is anisotropic with an effort to arrange parallel to the direction of the external applied load, whereas the other types of contacts just act to sustain the granular system in equilibrium
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Nyström, Martin, et Tainan Pantano Tomaz. « Fatigue analysis of welded joints in a forestry machine : Utilizing the notch stress concept ». Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-45003.
Texte intégralRésumé :
Welding is one of the most applied technics in the world for joining steel. Welds are liable to the phenomenon of fatigue, which is, primarily, the formation of a crack and consequently reduction of strength due to the action of time varying loads. Fatigue is one of the main causes of failure in steel structures. The aim of this thesis is to do static and dynamic analyses of a forestry crane with the purpose of using the analyses to determine the lifetime due to fatigue of welded components. Two methods for fatigue assessment are used in this work, the Hot-Spot Method and the Notch Stress Method. The first boom, which is a key component for the crane, is analyzed in a Finite Element Method (FEM) software. The found principal stress in accordance with the notch stress method in the first boom is ±165 MPa for the analyzed load case, rendering in a stress range of 330 MPa. The fatigue strength class FAT-225 (m=3), leads to an expected number of 633000 cycles, with a probability of survival of 97,7% for this case.Svetsning är en av de vanligaste teknikerna för sammanfogning av stål. Svetsar är känsliga för utmattning. Utmattningsfenomenet består primärt av en initial dislokation som genom tidsvarierande belastning formar en spricka som växer och därmed reducerar styrkan i konstruktionen. Utmattning är en av de vanligaste orsakerna till skador i stålkonstruktioner. Målet med detta arbete är att genomföra både statiska och dynamiska analyser av en skogsmaskins kran i avseende att bestämma utmattningslivslängden för dess svetsade konstruktioner. Två metoder för utvärdering används i detta arbete, hot-spot-metoden och notch-stress-metoden. Kranens första bom (lyftarmen) som är en huvudkomponent i kranen analyseras med hjälp av ett Finita Element program i enlighet med notch-metoden. Högsta funna spänningsvariationen i första huvudspänningsriktningen var ±165 MPa för ett av de analyserade lastfallen. Utmattningsklass FAT 225 (m=3) ger en uppskattning om utmattningslivslängd på 633000 cykler med en sannolikhet för överlevnad på 97.7% i detta fall.
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Gevinski, Jakerson Ricardo 1985. « Análise de tensões dinâmicas em superfícies planas a partir de parâmetros modais ». [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265202.
Texte intégralRésumé :
Orientador: Robson PederivaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: O interesse de maior produtividade e baixos custos de manutenção, associados ao desenvolvimento de produtos mais otimizados fizeram aumentar a preocupação com as falhas por fadiga em equipamentos. Neste contexto, o monitoramento da tensão dinâmica em estruturas e máquinas sujeitas à vibração adquire cada vez mais importância. Com este intuito, diversos métodos para a estimativa de tensões e deformações dinâmicas que utilizam parâmetros vibracionais vêm sendo desenvolvidos. Por estes métodos, basicamente, estima-se a deformação dinâmica pela derivação espacial do deslocamento obtido pelas técnicas de análise modal. Neste trabalho, abordam-se os conceitos da teoria da elasticidade e da análise modal para a melhor compreensão dos métodos propostos na identificação de deformação a partir dos parâmetros modais. Estudam-se os conceitos da análise modal híbrida para prever o deslocamento de pontos da estrutura e os conceitos da matriz de transformação deslocamento - deformação. Com o objetivo de avaliar esses métodos, realizam-se simulações numéricas e um experimento. Este se constitui no estudo de uma viga de alumínio, onde determinam-se as deformações de flexão da mesma, a partir das acelerações medidas e utilizando o método de diferenças finitas. As simulações e experimentos apresentaram resultados relevantes e satisfatórios no campo da determinação da tensão e deformação dinâmicas em superfícies.
Abstract: The interest of greater productivity and low costs of maintenance, combined with the development of more optimized products, have raised concern about prevention of fatigue failure of equipments. In this context, the monitoring of the dynamic stress in structures and machines under vibration has become more important. With this purpose, several methods of estimation of dynamic stress and strain using vibrational parameters have been developed. Basically, results from modal analysis are transformed from the displacement space to the strain space by use spatial differential operator. The work addresses the concepts of the theory of elasticity and modal analysis for a better understanding of the proposed methods for the identification of strain from modal parameters. It studies the concepts of hybrid modal analysis to predict the displacement of structures' points and concepts of the transformation matrix displacement to strain. In order to evaluate these methods, numerical simulations and an experiment are realized. This constitutes the study of an aluminum beam which determines the bending strain from measured accelerations and using the finite difference schemes. The simulations and experiments showed satisfactory and relevant results in the field of determination of dynamic stresses and strains on surfaces.
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
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Gevinski, Jakerson Ricardo 1985. « Determinação da deformação dinâmica em superfícies utilizando parâmetros vibracionais ». [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265177.
Texte intégralRésumé :
Orientador: Robson PederivaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-24T06:27:59Z (GMT). No. of bitstreams: 1 Gevinski_JakersonRicardo_D.pdf: 12693026 bytes, checksum: fe16190815edb5eee4a73ed3a84fa51d (MD5) Previous issue date: 2014
Resumo: Máquinas e equipamentos em condições operacionais estão susceptíveis à vibração e, consequentemente, deformações e tensões. Deformações em níveis excessivos podem ocasionar falhas por fadiga, muitas vezes catastróficas. Desta forma, o monitoramento e a caracterização da distribuição da deformação dinâmica em estruturas se tornam muito importantes. Em vista da determinação da deformação dinâmica, métodos de estimação de deformação que utilizam parâmetros vibracionais foram desenvolvidos. Por estes métodos, basicamente, estima-se a deformação dinâmica a partir da informação do deslocamento, não havendo, principalmente, a necessidade da colagem de extensômetros sobre a estrutura. Nesta tese, os métodos de estimação de deformação são aplicados utilizando funções respostas em frequência e de transmissibilidade. Os métodos de estimação da deformação são avaliados a partir de simulações numéricas e experimentos. A simulação numérica é realizada em uma viga engastada, e utilizam-se os métodos da matriz de transformação, análise modal híbrida e o método direto, baseado na análise da curvatura da viga. As avaliações experimentais são realizadas em placas de alumínio com diferentes geometrias e condições de contorno. O tensor de deformação e a distribuição da deformação dinâmica são determinados utilizando sinais de aceleração medidos em diferentes pontos da superfície das placas e os métodos de estimação. Os modos de deslocamento e de deformação, necessários para aplicação dos métodos, são obtidos por elementos finitos em ANSYS®. Na transformação deslocamento-deformação, são utilizados os métodos de diferenças finitas e de elementos finitos. Os tensores de deformação estimados são comparados com os tensores de deformação medidos por meio de extensômetros. Os modos operacionais de deformação estimados foram comparados com modos simulados. As simulações e experimentos apresentam resultados relevantes e satisfatórios no campo da determinação da deformação dinâmica
Abstract: Machinery and equipment, under operating conditions, are susceptible to vibration and hence the levels of dynamic stress and strains. The consequence of excessive vibration can be catastrophic since, high levels of stress and strain, occurring in a certain period of time can cause fatigue failures. Thus, monitoring and characterization of the dynamic strain distribution in mechanical structures becomes increasingly important. In view of the dynamic strain determination, some methods have been developed to predict the dynamic strain from vibration measurements. These methods basically consist in the numerical differentiation of displacement and, in especially, to predict the strain without the use of strain gages. In this thesis, the strain predicting methods are applied using both functions frequency responses and transmissibility. The strain predicting methods are evaluated through numerical simulations and experiments. The numerical simulation is performed on a cantilever beam, and the hybrid modal analysis, transformation matrix and the direct method, based on the analysis of the curvature of the beam matrix, are used. The experimental evaluations are performed on aluminum plates with different geometries and boundary conditions. The dynamic strain tensor and the distribution of operating strain are determined using acceleration, measured at different points on the surface of the plates, and the strain predicting methods. The strain and displacement modes, required for application of the methods, are obtained by finite element in ANSYS ®. In the displacement - strain transformation, both the finite difference methods and finite elements methods are used. The predicted strain tensors are compared with the strain measured using strain gauges. The predicted operating modes were compared with simulated strain modes. Simulations and experiments show significant and satisfactory results in the field of determining the dynamic strain
Doutorado
Mecanica dos Sólidos e Projeto Mecanico
Doutor em Engenharia Mecânica