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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

A Study on the Design and Analysis of Coronary Stents

Chen, Yi-an 26 July 2004 (has links)
Coronary stents are generally tubular-shaped expandable devices which function to hold open a segment of a blood vessel. They are particularly suitable for use to support and hold back a dissected lumen. This study aims to improve the existing designs of coronary stents through geometry design. This study focuses on the flexible mechanism and planar strut of a thin wall tubular stent to design a new type of coronary stent. A good coronary stent has to meet various requirements. First of all, a coronary stent has to be strong enough to support the wall of the blood vessel. Secondly, it has to be elastic enough. Thirdly, the longitudinal length shorten with dilatation should be as less as possible, otherwise it is difficult to implant precisely. Computer aided design software Pro Engineer is used to build the solid model and then CAE software ANSYS is used to analyze the dilatation of the new stent. After several modifications, a new type of stent with no longitudinal shortening is designed.

Thermo-Mechanical Deformation and Stress Analysis of Flip-Chip Ball Grid Array

Guo, Yu-Lun 01 July 2003 (has links)
The thesis investigates the thermo-mechanical deformation and stress of a flip-chip package (FCBGA) via both experiment and simulation. First, Shadow Moiré is used to evaluate the warpage of a package at elevated temperature. Then we adopt the finite element method incorporated with the software ANSYS to simulate the warpage of a package and compare the obtained results with experiment at data. Then, the material properties of underfill, the thickness of die and the substrate are considered as important parameters. Their effects on stress and strain fields of package are studied. In case of FCBGA with and without underfill, we find that FCBGA with underfill can reduce stress concentration and increase warpage of a package in comparion with FCBGA without underfill. As for FCBGA with and without heat slug, it is observed that the warpage of FCBGA with heat slug is smaller than that of FCBGA without heat slug. Both stress and strain in the packages of above two cases are similar. The parametric study about the underfill, we find that smaller modulus and CTEs of underfill can reduce the stress and strain of package. However in the consideration of thicknesses of both die and substrate, it is shown that thinner die can reduce stress and strain of package, but thinner substrate does not. So it is suggested that thicknesses of die are the thinner the better.

Design and Impact Effect Analysis of CFRP Golf Head

Hsieh, Wen-long 28 January 2008 (has links)
Abstract With the innovation of materials, many producers verify their golf heads. To improve the energy transmission and to keep stability while batting, the researcher tried to design golf head with a composite material and enlarge sweet spot zone. In addition, the researcher utilized the CAD software to construct and analyze data. He also applied the finite element of LS-DYNA software to simulate the impact question of a golf club head. Let¡¦s understand the change of geometry, impact effects and stresses of golf head by modifying the thickness of head. From the result of simulation, the CFRP impact face of a golf head has better velocity of a golf ball after impact than the Ti impact face. When the CFRP thickness of an impact face is 2.4~ 2.6 mm and the initial velocity is 45 m/s, the speed of the ball is 68.4~67.8 m/s and the angular velocity is about 2860~2570 rpm after impact. In a vertical direction, the zone of sweet spot is about ¡V30~25mm distance from the center of golf head face, in horizontal direction about -15~25mm. In the same basis of ball speed, when the face of golf head is CFRP, the zone of sweet spot will be wider than the Ti face. When the impact velocity is 55 m/s, the thickness of face about 2.6~ 2.8 mm is better, in 35 m/s, the thickness of face about 2.2~ 2.4mm is also better.

Impact Analysis of the Structure Variation on the Golf Club Impact Face

Chen, Ying-chuag 03 September 2009 (has links)
Currently, golf club design has been widespread. No matter the appearance changed, designed for center of gravity, material application, etc, they are all pursuing better efficiency of hitting. However, there will be no optimal design with emphasize on one of them. Thanks to the parameter design of golf head with simulating and analyzing golf ball trajectory, and modifying M.O.I., center of gravity, etc, the optimal performance of club head can be achieved. In this thesis, golf club models were set up by SolidWorks. The weight of club head model was decided by different class of users, and each class of club head had four types of hitting face structures individually. Then, their impact effect was simulated by LS-Dyna solver system. In this thesis, the hitting effect for different types hitting face was analyzing by including professional Male, Female, amateur Male, and Female four different tyes of users. Then the influences on ball linear velocity, the angular velocity and the trajectory were verified. The Men¡¦s PGA Tour suitable club is reticulate face. The Ladies¡¦ LPGA Tour suitable club face is uniform slab. The Typical Men suitable club face is concentric circle. The Typical Lady suitable club faces are concentric circle and reticulate face.

Stress Study of Silicon Die for Filp-Chip Package Under Different Types of Stress Loading

Cheng, Mao-Chuan 22 January 2007 (has links)
Over the past years, there are many studies discusses different modes of die cracking and improvement. Die cracking is one of the crucial issues that influence the reliability of flip chip assemblies. Die cracking depends on a combination of several factors, such as residual bending stresses generated in the package due to mismatches in the coefficients of thermal expansion(CTE) of the various materials in the assembly or wafer dicing process . In this study, the stresses in the chip of a FCBGA (Flip-Chip Ball Grid Array) induced by the temperature raising and by the mechanical load of different pressures on an automatic test handler are investigated by using commercial finite element software ANSYS, while the FCBGA is subjected to the high temperature electrically test. The causes and precautions corresponding to the die cracking are studied in order to improve the reliability of products.

Finite Element Analysis of the Pressure Vessel Skirt Support

Ko, I-Feng 23 January 2009 (has links)
This research investigates the stress anslysis of a tower skirt support respectively by the earthquake and the wind pressure loading. The researcher used the computer-aided design software Solidworks to set up the tower model and he used finite element software ANSYS to analyze the structure. This study aims to analyze the safety of a tower support for different models. By the finite element analysis, this study found the largest displacement of tower, the von Mises stresses, and the safety factor for the skirt support. Among them, the butted-flared skirt support has the smallest displacement. According to the analysis result, the empty crate type design of skirt support revealed the safety factor of stress greater than two, which ensure that the equipment safety and material-savings. It is expected the study findings can provide a reference for designing or repairing a tower skirt support.

Επεξεργασία εικόνων αξονικού τομογράφου με τη χρήση του λογισμικού VASCULAR MODELING TOOLKIT (VMTK)

Σιδεράκης, Απόστολος 12 November 2007 (has links)
Η παρούσα διπλωματική εργασία εκπονήθηκε στο εργαστήριο Ιατρικής Φυσικής του τμήματος Ιατρικής του Πανεπιστημίου Πατρών, υπό την επίβλεψη του Καθηγητή Ιατρικής Φυσικής Γεώργιου Νικηφορίδη. Ασχολείται στο πρώτο μέρος με το θεωρητικό υπόβαθρο σχετικά με τη δημιουργία αθηρωματικών πλακών στα αιμοφόρα αγγεία και το ρόλο που παίζει η υπολογιστική ρευστοδυναμική στην επίλυση του συγκεκριμένου προβλήματος. Στο εισαγωγικό αυτό κεφάλαιο δίνονται επίσης βιβλιογραφικά κάποιες μελέτες, που έχουν γίνει σχετικά με τη λύση του προβλήματος. Το δεύτερο μέρος της εργασίας ασχολείται με την επεξεργασία και τρισδιάστατη ανακατασκευή ιατρικών εικόνων DICOM (Digital Imaging and Communications in Medicine) τεσσάρων μοντέλων, που προέρχονται από αξονικό τομογράφο, με τη χρήση του λογισμικού VMTK (Vascular Modeling ToolKit). Οι ιατρικές εικόνες που χρησιμοποιήθηκαν προέρχονταν από δύο πειραματικά μοντέλα κόνικλων φυσιολογικά και με υποκείμενη αθηρωματική στένωση της νεφρικής αρτηρίας (Renal Artery Stenosis, RAS) και δύο ανθρώπινων με στένωση ουρήθρας. Η συγκεκριμένη διαδικασία υλοποιείται με τη χρήση του λογισμικού VMTK και παρατίθεται στο Παράρτημα της εργασίας. / This postgraduate thesis was accomplished on the laboratory of Medical Physics, University of Patras, with Professor Nikiforidis G. as the supervisor. The first part deals with the theoretical background for the construction of atheromatic plates in the blood cells, together with the state of the art of computational fluid dynamic methods concerning the field. This introductory chapter also includes studies as references, which deal with similar problems. The second part relates to three-dimensional reconstruction of medical images (Digital Imaging and Communications in Medicine, DICOM). Four models coming from a CAT (Computerized Axial Tomography) are processed with the use of VMTK (Vascular Modeling Toolkit) software. The images under use came from 2 experimental rabbit models which showed no pathology, 2 subjected to RAS (Renal Artery Stenosis) and 2 human models with urethra stenosis. The process took place using the VMTK software platform and is given analytically in the annex.

Optimalizace konstrukčního spoje dřevěného mostu

Hudeček, Martin January 2010 (has links)
No description available.

Modální analýza rezonanční desky kytary

Lukeš, Martin January 2013 (has links)
No description available.

Análisis computacional del torque en función de la tasa de giro en la turbina Tesla de aire

Abarca González, Francisco Andrés January 2012 (has links)
Ingeniero Civil Mecánico / El presente trabajo de título entrega un análisis computacional de fluidos (CFD) sobre una turbina tipo Tesla, máquina que tiene como principal objetivo desarrollar potencia sobre el eje para diversos usos. Las razones principales que motivaron el desarrollo de este trabajo de título, fueron la necesidad de investigar sobre máquinas más económicas y eficientes (en determinadas aplicaciones) que las actuales. La Turbina Tesla, en vista que no posee álabes, sino que discos para transferir la energía al eje, la convierte en una de las máquinas más económicas en su campo, lo que llama la atención de los investigadores y genera la necesidad de conocer el comportamiento del equipo antes de su construcción, con respecto a su torque y rendimiento, siendo estos factores de suma importancia al momento de seleccionar un equipo para una determinada aplicación. Si bien es claro que el fluido de trabajo a utilizar es un factor muy importante para desarrollar el diseño y conocer el desempeño de la máquina, se ha decidido trabajar con un único fluido, el cual es aire. Lo anterior se debe a que es un fluido que puede ser considerado como un gas ideal con respecto a algunas propiedades; además, con el aire la máquina podría alcanzar mayores revoluciones por minuto (RPM) que con vapor o agua (otros dos fluidos interesantes de estudiar), lo que según investigaciones anteriores favorece el rendimiento de la turbina. El desarrollo del presente trabajo comenzó con la recopilación de información sobre la turbina tipo Tesla, abarcando también bombas y compresores tipo Tesla, lo que sirvió de base para el estudio a realizar. Posteriormente se investigó acerca del software utilizado para la modelación en CFD (la herramienta Fluent de ANSYS), de manera de escoger el modelo matemático iterativo más adecuado y las suposiciones oportunas para desarrollar el trabajo en el tiempo establecido para el mismo. En este trabajo, se modeló un único espacio inter-disco representativo de los demás que posee la máquina. Se efectuaron simulaciones para tasas de giro entre 1.000 y 18.000 RPM, logrando así simular distintas cargas en el eje, obteniendo de esta forma el torque, la potencia y el rendimiento, entre otros resultados. Dentro de las conclusiones importantes, se destaca la linealidad del decaimiento del torque, a medida que aumentan las RPM, notándose también un aumento de la potencia y el rendimiento hasta las 13.000 RPM, tasa de giro desde la que éstos comienzan a disminuir. Una vez finalizada la lectura de este trabajo, se espera que el lector no sólo adquiera información acerca de la simulación realizada, sino que también este informe le pueda servir como guía para simulaciones similares en CFD a realizar con el software ANSYS y su interfaz Fluent. Es así como en la sección en la que se explica el ajuste el software, se ha prestado gran atención en representar la mayor cantidad de detalles posibles.

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