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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.
61

Analýza mechanických vlastností polymerů a polymerních kompozitů z videozáznamu tahové zkoušky / Analysis of mechanical properties of polymers and polymer compsites from video record of tensile test

Ščudlová, Jolana January 2010 (has links)
This thesis described mechanical tests with monitoring of camera. The aim of this work is to obtain additional information about material behavior during the test. The mechanical tests were monitored high-definition (HD) digital video-camera and camera with high resolution. The method was applied to the tensile test and Pennsylvania notch test (PENT test). The videorecordings were processed with the assistance image analysis method. The marks were placed on both of these specimens, mutual movement these marks were used to obtain following characteristics. It was Poisson’s ratio and true stress by tensile test. By PENT test it was rate growth crack. The investigated material was elastomeric polyurethane filled by biodegradable polyhydroxybutyrate for tensile test. Second material was polypropylene for PENT test. The camera is adding to the test gives extended information about the material and better interpretation results.
62

Mechanické vlastnosti smršťovacích LLDPE fólií v závislosti na jejich složení / Influnce of chemical composition on mechanical properties of LLDPE stretch film

Vojáček, Jakub January 2015 (has links)
Thesis summarizes the problems of production and use of stretch film. The change of strength, ductility and relative relaxation effect in different times of drawing from role in three weeks was observed. Further, change of strength and ductility due to changes in the rate of deformation, exposure to accelerated aging in a UV chamber and changes in the loading direction were observed. Mechanical tests were realized on a tensile tester, relaxation tests on DMA and crystallinity changes were observed on the DSC. Relationship between chemical composition of stretch film and mechanical and thermomechanical properties were studied. It was found that chemical composition essential for stretch film properties. However, due to the impossibility to distinguish effects of chemical composition and process parameters was impossible to find clear relation describing this relationship.
63

Výpočtové modelování mechanických zkoušek izolovaných buněk / Computational modelling of mechanical tests of isolated cells

Sůkal, Petr January 2009 (has links)
The master’s thesis deals with computational modelling of mechanical testing of isolated cells, particularly of single-axle tensile test. The aim is to imitate the real deformed shape known from experiments. At first, the structure of each cell component is described and analyzed according to their significance for mechanical behavior. The outline of basic mechanical tests used for cell testing is discussed next. A structural computational model comprising all components significant for mechanical purposes is created for the modelling. Those components are nucleus, cytoplasm, cell membrane and cytoskeleton. Due to the problems with convergence the model was divided into two parts. The first one treats separately the shape of cytoskeleton and the second one treats the shape of communicating components (nucleus, cytoplasm and cell membrane). Both of those partial models succeed in reaching the deformations according to the experiments.
64

Testování pryžových těsnících prvků podrobených různým vnějším vlivům / Testing of commercial rubber sealing components exposed to different ambient conditions

Jančaříková, Marie January 2016 (has links)
Diploma thesis studies the effect of temperature (75 and 105 °C) and the effect of 3 kinds of liquids (silicone and hydraulic oil and coolant) at room temperature and at 105 °C on change of the structure of 3 species butadiene-acrylonitrile (NBR) seals (o-ring and two types of bolts). The seals are inspected by the thermogravimetric analysis, differential scanning calorimetry and infrared spectroscopy, the influence of 105 °C on the o-rings is also evaluated in terms of changes in tensile properties. The greatest changes in the composition and structure are observed on o-rings particularly due to temperature of 105 °C, there was a significant reduction in dilatability and an increase in stiffness and glass transition temperature. The root cause is the surface and centre additive decomposition and oxidation. The bolts have suffered from decomposition of the protective surface layer and the additives in the centre, structural change was minor. Exposure to 75 °C has resulted in a gradual loss of low molecular weight substances. Liquids at room temperature didn‘t affect the structure of the seals, at 105 °C it caused a loss of weight due to decomposition of the protective surface layer and release of additives and the products of their decomposition. Results showed that the common use of the NBR seals at 105 °C is unsuitable, at 75 °C it leads to gradual changes, loss in mechanical and sealing properties.
65

Zpevnění polymerních kompozitů uhlíkovými nanotrubkami / Hardenning of polymeric composites by nanotubes

Kuběna, Martin January 2013 (has links)
This diploma thesis focuses on the influence of carbon nanotubes (CNTs) on the mechanical properties of a composite material with polyurethane (PU) matrix. The material was supplied in the form of thin films with thickness from 0.2 mm to 1.2 mm. The theoretical part of this thesis describes the production technology, properties and applications of composite materials PU/CNTs, and also deals with preparation technology and properties of both components of this composite material separately. The theoretical part also describes the principle of tensile testing of polymer materials. The experimental part of the thesis was primarily focused on comparing the tensile properties of a composite material PU/CNTs with tensile properties of pure PU. At first, tensile properties of pure PU were investigated, while the influence of various factors like strain rate, specimen thickness, heat treatment and aging was examined. In adition, stress relaxation tests and tests with strain rate jumps were performed on pure PU specimens. Then composite PU/CNTs was tested in tension and the results were compared with the results of tensile tests of pure PU. Composite material PU/CNTs was prepared with various concentrations, so it was possible to determine the effect of CNTs content on the tensile properties of the composite. The last part of this thesis deals with tensile tests of PU composite material with functionalized carbon nanotubes (PU/FCNTs), where the influence of surface modification (functionalization) of CNTs on the tensile properties composites was investigated. It was shown that the effect of both CNT and FCNT on mechanical properties of the composite is not significant. This conclusion was discussed on basis of the works of other authors, which do not unambiguously proved the positive effect of CNT or FCNT on mechanical properties of composites with polymer matrix.
66

Protlačovací zkouška konstrukčních ocelí za snížených teplot / Small-punch test of structural steels at low temperatures

Němčíková, Eva January 2013 (has links)
Diploma thesis is focused on comparison of small punch test results and tensile test results. For experiments were chosen steel P91, 10Ch2MFA, 20CrNi2MoV, 11 416 and 42 2707. These steel are used in nuclear power engineering, or they were developed for this purpose. Basic mechanical characteristics, namely ultimate tensile stress and yield stress, were evaluated from small punch test records of observed materials. This is done via convenient correlation relationships. Obtained values were compared with values obtained by conventional tensile tests. There are mentioned own suggested correlation relationships and comparison of temperature curves gained from small punch test and tensile test in the thesis. Assessment of microstructure of observed materials and analysis of fracture surfaces was provided as well. It was found out, that for assessing basic mechanical characteristics (ultimate tensile stress and yield stress) is the best to suggest own correlation relationships, instead of using universal relationships from literature. The fracture mechanism of all types of assessed steel was ductile in entire temperature range (up to -40 °C).
67

Characterization and Processing Evaluation of Starch/High-Density Polyethylene Materials in Extrusion Blow Molding

Bacigalupi, Bradley Dale 01 December 2013 (has links) (PDF)
The growing negative impacts of non-biodegradable plastics derived from non-renewable materials have created increasing interest throughout the world for new materials that are both biodegradable and renewable, that can be combined with or replace traditional plastics. Plant-based thermoplastic starch (TPS), a promising alternative material to traditional petroleum based resin, is both biodegradable and renewable and has great potential for use in plastic manufacturing processes. Two major obstacles that prevent more widespread use of TPS include; TPS base material, which is typically manufactured in a flake or powder, is incompatible with standard plastics production equipment that require pelletized resin, the second reason is that TPS is difficult to mix with standard plastic materials such as High Density Polyethylene (HDPE). BiologiQ of Blackfoot Idaho through a unique manufacturing process has created a new type of TPS called EcoStarch™ Resin (ESR) that overcomes these two obstacles the material can be both pelletized and combined with various standard base plastics such as HDPE. This study evaluated and characterized the processability materials properties of ESR and HDPE blends in the Extrusion Blow Molding (EBM) by measuring wall thickness, tensile strength, tensile elongation, modulus of elongation and formability compared to 100% HDPE bottles. As the ESR content increased the uniformity of the wall thickness increased. The tensile strength increased from ESR content of 30% to 50% while the elongation decreased. Bottles were successfully extrusion blow molded with ESR content of 50%.
68

Implementation of the SuperPave IDT analysis procedure

Du, Guangli January 2010 (has links)
Cracking is one of the most severe distress modes of asphaltpavements. Thus characterising the fracture resistance properties of asphaltmixtures is the key issue for improving the performance relatedmixture design. The present master thesis project addresses the implementationof the theoretical framework, which is used to characterise thefracture resistance of mixtures based on the SuperPave indirect tensiletest (IDT). An open source Matlab-based software for analysing resilientmodulus, Poisson’s ratio, creep parameters and fracture resistance parametershas been developed. The software analyses the the IDT results, toestimate mixture’s fracture resistance based on hot mix asphalt FractureMechanics. Predictions form the field specimens concerning the fractureresistance obtained from IDT are compared with observed field performance.
69

Investigation of the basic mechanics of edge cracking in sheet aluminum forming

Bayat, Hamidreza, Abbasi, Mohammad January 2023 (has links)
As technology is developing in all automotive companies, car body designers have also investigated new materials such as composite and aluminum alloys. Designing modern car structures has also created various challenges in the production process, including formability limitations. The main purpose of this research work was to develop a test setup for an open-hole uniaxial tensile test and investigate the effect of the cutting tool on the shearing edge quality of the series 6000 aluminum alloy and materials formability as a result. To approach this significant issue, detecting the onset of necking and forming limit curves FLC using 3D digital image correlations (DIC) capabilities were studied. Two methods based on strain rate for evaluating the instability through 3D DIC and Matlab were applied. Eighteen specimens in rolling, transverse, and diagonal directions were investigated. Although the results of the tensile test machine are close for all tests, due to 3D DIC limitations, detecting the onset of necking was hard to obtain.
70

Review of Earlier Thesis work at BTH Related to Packaging and Packaging Field

Ahmad, Abu ul Hasnat January 2021 (has links)
This work aims at giving a systematic review of the numerical approaches and obtained results published in recent years. Focus is set on both the recent trends and achievements as well as challenges and open questions. Thesis critically reviews work done in previous thesis related to food packaging material and design, at Blekinge Institute of Technology with the collaboration of Tetra Pak liquid food packaging company. Here, 27 numbers of master’s thesis are critical review all the while using 4 PHD works for referencing.  Focus of these thesis works relates to the mechanics and its sub-branch fracture mechanics. Due to this all the theory related to mechanics and fracture mechanics, which is compulsory to know for understanding is defined initially. Main material which are under consideration throughout the work are PP, LDPE, PET-LDPE, and aluminum foil. As three materials are used in the liquid food packaging which are PE, paper board and aluminum. Uses of this material and there required physical properties are measured. Testing methods which are used to check whether the material meets the required parameters are tensile testing, tear testing, peel testing and shear test.  Also, some methods are used along with these tests to perform the test more precisely, to evaluate and compare result i.e., Nakajima test, Digital image correlation. DIC testing technique is used to compare the results obtained from simulation. It is also understood that DIC method provided the user with increased quality of obtained results.  Most of the topics of discussions have been reviewed for corresponding thesis, displaying the used ideas, theory, applied experimentation and realized conclusions. Using these above it was able to derive a conclusion based on the developed research questions and hypothesis. Defined problems in previous work are studied also solution as a future work is suggested to overcome these problems. Mainly the slippage issue while holding PE in clamps. Furthermore, various development is discussed which is done to introduce new material which is more possible being used in the future.

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