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1	Thermomechanical modeling of a shape memory polymer Ghosh, Pritha B. 15 May 2009 (has links) The aim of this work is to demonstrate a Helmholtz potential based approach for the development of the constitutive equations for a shape memory polymer undergoing a thermomechanical cycle. The approach is motivated by the use of a simple spring-dashpot type analogy and the resulting equations are classified as state-equations and suitable kinetic equations for the recoverable-energy elements and the dissipative elements in the model respectively. These elements have mechanical properties which vary with temperature. The governing equations of the model are developed starting from the basic conservation laws together with the laws of thermodynamics. The entire set of equations are written in a state-evolution form as a set of ordinary differential equations to be solved using Matlab. It is shown that the results of the simulation in Matlab are in qualitative and quantitative agreement with experiments performed on polyurethane. Subsequently, we study the dependence of the yield-stress on temperature to be similar and different functions of heating or cooling processes. thermodynamics shape memory polymer modeling spring-dashpot helmholtz potential dissipation
2	Synchronized assessment ofcompression of corrugatedboard : Mechanics and visualization Bürger, Johan January 2023 (has links) Flexographic printing involves driving a paper substrate through the gap between two cylinders, where one of the cylinders has a print form layer covered in ink. The ink transfer from the print form to the paper is dependent on the pressure between the paper substrate and the cylinders. Knowledge about how the paper substrate reacts to compression is therefore important when aiming for high quality flexography printing. In this project the paper substrate in focus is corrugated board consisting of a top liner, a bottom liner and a fluted paper material in between the liners. To gain knowledge about the compression dynamics of the boards they are subjected to compression experiments with and without print form. The compression experiments are filmed and the videos are then analyzed using thresholding and tracking methods. The developed thresholding method is able to measure the thickness of each material separately in each frame while the developed tracking method is able to track the movement of the top and bottom metal blocks compressing the materials. The strains calculated from the image analysis measurements are then used as input values to the Maxwell spring-dashpot model with the intention of modelling the stress. Analysis of the compression experiment videos shows that the material properties of thecorrugated board may not be constant for the duration of the compression. This is because the fluting changes its shape when being compressed. Comparing the modelled stress to the stress measured by the press used in the experiments shows that the Maxwell spring-dashpot model is not able to model the stress accurately when the corrugated board goes through multiple stages of compression. The model works better for compression where the shape of the fluting is not significantly changed. corrugated board compression image analysis thresholding modelling Maxwell spring dashpot Materials Engineering Materialteknik
3	遮断器用油圧操作装置の動作時間安定化に関する研究 / シャダンキヨウユアツソウサソウチノドウサジカンアンテイカニカンスルケンキュウ山下透, Tohru Yamashita 02 March 2017 (has links) 電力用遮断器の油圧操作装置において，油圧回路内の気泡が操作装置の動作に及ぼす悪影響を解消するために，新しい油圧回路方式である常時高圧安定回路方式を提案し，油圧回路内の流れおよび可動部の定式化と解析および実測を行った．本方式の動作特性と動作安定性，ピストンの制動特性，複数の油圧操作装置の駆動特性について検討し，本方式が有効かつ安定的に機能することを確認した．以上により，油圧操作装置の動作時間安定化技術を開発することができた． / We proposed and studied a hydraulic operation stabilizing system for a hydraulic operating device of a circuit breaker to eliminate the influence of air bubbles created in hydraulic fluid. We formulated the flow of hydraulic circuit and the motion of moving parts, which were numerically simulated and experimentally confirmed. We confirmed that this stabilizing system functioned effectively and stably through the investigation: operation characteristics and stability of the stabilizing system, braking characteristics of a piston-dashpot system and operation characteristics of two hydraulic operating devices. Based on the results, we could perform an engineering development for stabilizing operation time of the hydraulic operating device. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University 遮断器油圧操作装置常時高圧安定回路方式数値解析一次元流れ気泡油柱分離駆動特性動作安定性油圧振動ダッシュポット制動特性同期駆動順次駆動 Circuit breaker Hydraulic operating device Hydraulic operation stabilizing system Numerical analysis One-dimensional flow Air bubble Hydraulic column separation Operation characteristics Motion stability Hydraulic vibration Dashpot Braking characteristics Synchronous drive Sequential drive

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