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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.
1

A method for measuring human foot shape during running stance

Blenkinsopp, Robert January 2015 (has links)
Knowledge of the three dimensional shape of the human foot is important in the design of shoes to facilitate correct fit. Currently only the static shape of the foot is considered despite the fact that the foot undergoes changes in its shape, particularly in athletic pursuits, due to associated movements and loadings. Attempts, presented in research, have been made to measure dynamic foot shape. However, to date, measurements have been limited in detail as well as restricted to walking gait, as a result of the method. The work of this thesis aimed to develop a methodology that would be capable of measuring the three dimensional shape of the human foot during the stance phase of gait, in locomotion speeds associated with running.
2

Rozšiřování konce trubky za dynamických podmínek / Tube Flaring Technology under Dynamic Conditions

Macháček, David January 2017 (has links)
This master thesis is divided into three main parts. In first part is more closely described the method of tube flaring. Tube flaring was chosen for analysis of biaxial stress, in this thesis particularly in the presence of high strain rate. In the second part is more closely described influence of high strain rate on the forming process. There is described influence of high strain rate on behavior of the material, hardening, change of quasi-static yield strength to the dynamic yield strength, influence of high strain rate on the microstructure and more. During the description of these processes there is effort to describe the cause of these changes as well. For this task was used domestic and foreign literature, as well as peer review papers whose authors study intensively this problematic. Besides all of the above there is also derived the velocity of elastic and plastic wave. In the end is evaluated experiment, in which was done tube flaring, which is part of this master thesis. Results from the 3D optical system ARAMIS are interpreted with the help of Microsoft Excel, where the chosen results were used as the input to the equations modified for the dynamic loading.
3

Rozšiřování konce trubky za statických a dynamických podmínek / Flaring the End of a Tube Under Static and Dynamic Conditions

Šrefl, Martin January 2016 (has links)
The thesis is focused on expanding the ends of the tubes made of 1.4031 material into a cone shape for quasi-static and dynamic conditions. The aim of the research is the analysis of stress-strain condition in the area formed under the process conditions. As a technology test for expanding tubes is used a method of pushing the tube at a stationary mandrel and deformation measurement was done by 3D optical system ARAMIS. In the thesis is described in detail an experiment carried out under quasi-static conditions, the results of which yielded interesting findings. In the framework of the present study were designed and detailed engineering design and production tools designed for experimental realization of technological tests for quasi-static and dynamic conditions. Exploration in terms of the behavior of tube under dynamic conditions forming in this thesis is carried out in phase functional verification tools. The analysis of the forming process is planned in the framework of the next thesis.
4

Press Measurements and Virtual Rework of Stamping Dies / Mätningar av en Press och Virtuell Bearbetning av Pressverktyg

Palsson, Einar, Hansson, Mårten January 2017 (has links)
Stamping dies are used in the Sheet Metal Forming (SMF) process for manufacturing of car body parts. The lead time for design and manufacturing of a stamping die is long, and therefore costly. In the final step of the manufacturing process, manual rework is performed to reach a desired pressure distribution on the forming surfaces in order to achieve a robust process and an approved part within tolerance. The main purpose for this work is to study and further develop a Virtual Rework Method that alters the shape of the forming surfaces of a die to compensate for the displacements of a stamping press that occur during stamping. Measurements were performed to obtain the displacements that occur in the stamping press during stamping. These measurements were performed on a double action deep drawing press of the brand Danly, located at Volvo Cars Tool & Die department in Olofström, Sweden. The measurement yields information of how the stamping press is deflecting and deforming during operation. The measurements are recorded with a Digital Image Correlation (DIC) system that records the displacements of the press during stamping. The displacements obtained in the measurements are then used as constraints to inverse FE- model a press table with topology optimization. This optimized press table is used in the Virtual Rework Method to be able to simulate both the deformations of the press and the internal deformations that occur in the die. Pre-simulations were performed before the measurements to ensure that the blank holder plate used in the measurements would withstand the applied blank holder force. These simulations also yield if the displacements were large enough for the ARAMIS DIC system to capture. The FE-model used in this work consisted of a die, blank holder, blank holder plate, outer ram and the optimized press table. The Virtual Rework Method was applied on the FE-model, where the result concludes that the altered shape of the deformed forming surfaces is almost identical to the shape of the nominal forming surfaces. However, an inversed modelled structure that represents the behavior of the outer ram is required to apply the Virtual Rework Method on the blank holder. This inversed modelled structure could be created from the displacements obtained in the measurements. To apply the Virtual Rework method on the punch, further measurements are required, where the position of the ARAMIS DIC system is altered, or an additional ARAMIS DIC system is used. / Pressverktyg används i plåtformningsprocessen vid tillverkning av karossdelar. Ledtiden för konstruktion och tillverkning av ett pressverktyg är lång och därför kostsam. I det sista steget i tillverkningsprocessen utförs manuell bearbetning för att nå en önskad tryckfördelning på formningsytorna, vilket ger en robust process och en godkänd del inom toleranserna. Huvudsyftet med detta arbetet är att studera och vidareutveckla en virtuell fläckningsmetod som korrigerar formningsytorna på dynan för att kompensera för de förskjutningar som uppstår i en stämplingspress under stämpling. Mätningar har utfördes för att erhålla förskjutning som uppstår i en stämplingspress under stämpling. Dessa mätningar utfördes på en dubbelverkande djupdragningspress av märket Danly, som finns hos Volvo Cars Tool & Die avdelning i Olofström, Sverige. Mätningen gav information om hur pressen deformeras under stämpling. Mätningarna registreras med ett Digital Image Correlation (DIC) system som registrerar pressens förskjutningar under stämpling. Förskjutningarna som erhållits i mätningarna användes sedan som randvillkor för en inversmodell för topologioptimering av ett pressbord. Detta optimerade pressbord används sedan i den Virtuella fläckningsmetoden för att kunna simulera både pressens stelkroppsrörelse och de interna deformationer som uppstår i pressverktyget. En förstudie utfördes innan mätningarna för att säkerställa att den plåthållarplattan som användes i mätningarna skulle motstå den applicerade plåthållarkraften. Denna förstudie gjordes även för att säkerhetsställa att förskjutningarna som uppstår i plåthållarplattan var stora nog för att ARAMIS DIC systemet skulle registrera dem. FE-modellerna som användes i detta arbete bestod av en dyna, plåthållare, plåthållarplatta, yttre slid och det optimerade pressbordet. Den Virtuella fläckningsmetoden applicerades på FE- modellen, där resultatet gav slutsatsen att den korrigerade formningsytan med applicerad belastning är nästintill identisk med formen på den nominella formningsytan. En inversmodellerad struktur som representerar beteendet hos den yttre sliden krävs emellertid för att tillämpa den Virtuella fläckningsmetoden på plåthållaren. Denna inversmodellerade struktur kunde erhållas från de förskjutning som erhölls i mätningarna. För att tillämpa den Virtuella fläckningsmetoden på stansen krävs ytterligare mätningar, där ARAMIS DIC systemets position ändras eller ett ytterligare ARAMIS DIC system används. / Reduced Lead Time through Advanced Die Structure Analysis - Vinnova
5

Capacity and lifetime analysis of pre-stressed slatted floors / Kapacitetskontroll och livslängdsundersökning av förspända spaltstavar

Hermansson, Denise, Nilsson, Olivia January 2016 (has links)
This study investigates the mechanical differences between old and newly produced slatted floors through a four-point bending test. To understand to what extent the actual environment has affected the slatted floors, the carbonation depth and corrosion will be examined. The tests showed no mechanical differences between slatted floors which had been in service for a certain amount of years and newly produces ones. Corrosion could be observed on some of the samples but it was not because of the carbonation process. When comparing the calculations of reinforced and pre-stressed concrete slatted floors, the result showed that the pre-stressed floor could carry up to double the load of what the reinforced slatted floor could. The conclusion of this study is, that the pre-stressed slatted floors will certainly hold for at least thirty years and will most likely hold for many years to come.
6

Fracture prediction of stretched shear cut edges in sheets made of Dual-Phase steel

Falk, Johannes January 2017 (has links)
Dual-Phase (DP) steels, part of the group of Advanced High Strength Steels (AHSS), are used by car manufactures due to its large strength to weight ratio. The high strength of the DP steel does have a negative impact on the formability during sheet metal forming and stretch forming, e.g. fractures often appear in shear cut edges during forming of blanks made of DP steel.   The main objective with this thesis is to develop a new punch for Volvo Cars that concentrates the strain to the sheared edges of a test specimen made from different types of DP steel. This is done to be able to measure and obtain maximum fracture strain during stretch forming tests in a press. The newly developed test method is called CTEST (Concentrated Trim Edge Strain Test).   The tests are performed with DP steel specimens with three different qualities of the shear cut edges; fine cut, medium cut and worn cut. DP steels tested are DP600GI, DP600UC and DP800GI from three different suppliers. 10 different types of DP steels are tested in this study with different thickness. Thickness of specimens tested are 1 mm, 1.1 mm, 1.5 mm and 2 mm and all specimens tested have a lengthwise (RD) rolling direction.   The quality of the sheared cut edge has a great impact to the formability and maximum fracture strain of the specimen. A specimen with a fine cut endures higher fracture strain than medium cut and a worn cut for all types of DP steel with different thickness. A 1 mm thick specimen endures a lower fracture strain than 1.5 mm and 2 mm specimen for all cut qualities.   Further, the impact of the orientation of the burr zone of a shear cut edge is studied. With the burr zone facing upwards from the CTEST punch the formability of the specimens is decreased compared to a burr zone facing downwards, especially for a worn cut specimen with micro cracks and imperfections in the edge surface.   ARAMIS Digital Image Correlation (DIC) system is used to analyze the specimen edges during press experiments. The ARAMIS results unveil that several small fractures appear in the sheared edges of a specimen just before the specimens split into two pieces. This phenomenon was seen for specimen with worn and medium shear cut qualities.   Finite Element (FE) simulations of the CTEST is performed in AutoForm to determine maximum values of the true strain for the three different cut qualities. The simulation in AutoForm does show a slightly higher value of the force and press depth than the value from the press test before maximum fracture strain in reached. The small fractures seen in ARAMIS just before the specimen split into two pieces cannot be seen in the simulation in AutoForm.
7

Numerická podpora pro popis chování cementového kompozitu při únavové zkoušce / Numerical support for description of behavior of cement based composite during fatigue test

Holušová, Táňa Unknown Date (has links)
The presented dissertation thesis is focused on analysis of alternative test method for determination of mechanical parameters of cement based composites. A disk shaped specimen with diameter 150 mm, thickness 60 mm was analysed and its modification for use on compact tension test (CT). Such a test is hereinafter referred to as modified compact tension (shortly MCT or MDCT)). This test configuration was chosen for testing the static and fatigue properties of cement based composites precisely because of its traditional use for fatigue testing of metallic materials. Specimens with a different cross-sections can also be used for MCT, but the work is exclusively focused on circular specimen, for example because it could be easily cut from drill core taken directly from the existing structure, on which the properties are more relevant to the age of the used concrete of the controlled structure. The modified compact tension test was firstly calibrated by numerical simulations involved the tuning of the shape of the numerical model and used material models of concrete and steel. Then the laboratory testing of modified compact tension on several levels were performed. The adequacy of the numerical model was verified against the pilot laboratory testing of the MCT test. Furthermore, the comparison of the modified compact tension test and its suitability for determining of fracture mechanical parameters of cement based composites with the three point bending test, which is the standardized test configuration for these purposes was performed. Another laboratory testing was focused of determining of fracture mechanical parameters of concrete mixture classified in strength class C30/37 and the pilot study of fatigue parameters of the same strength class of the concrete mix. The work was also presented numerical simulations of the push-out test, focused on the connection of concrete and steel with epoxy adhesive.
8

The influence of microstructural deformations and defects on mechanical properties in cast aluminium components by using Digital Image Correlation Techniques (DICT)

Armanjo, Jahanmehr January 2015 (has links)
Digital image correlation techniques (DICT), a non-contact deformation measuring technique based on gray value digital images, have become increasingly used over the last years. By using the DIC technique during a tensile test, the deformation behavior of different engineering material under an applied load can be determined and analyzed. Digital images, acquired from a tensile test, can be correlated by using DICT software and from that the local or global mechanical properties can be calculated. The local or global mechanical properties determination of a flat test specimens are based on the displacements or changes in a previous stochastic sprayed or natural pattern. The used material for this purpose is cast silicon (Si) based aluminium (Al) component, designated as AlSi7Mg0.3 (Anticorodal-78 dv). The hypoeutectic Al- Si alloy is widely applicable for engine constructions, vehicle and aerospace constructions, shipbuilding, electrical engineering and constructions for food industry. There are many microstructural parameters in a binary system Al- Si alloys, which the mechanical properties can be depended on, for instance phase distribution, Secondary Dendrite Arm Spacing (SDAS), morphology of Si particles (Roundness) and microscopic defects or pores. All these parameters can contribute to enhance the proper mechanical performance (e.g. Strength and ductility) in the Al-Si cast components.

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