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The Use of the Aluminium Alloy in the Bicycle Industry
Hudec, Jiří ; Liškutín, Petr (referee) ; Liškutín, Petr (referee) ; Němec, Karel (advisor)
Bachelor's thesis deals with the aluminum alloys in the cycling industry. It contains information on the properties of aluminum and its alloys and the distribution of aluminum alloys according to certain criteria. It is discussed in more detail in the work of most alloys in the cycling industry - Al-Cu-Mg, Al-Mg-Si, Al-Mg-Zn and Al-Zn-Mg-Cu with examples, for which components are suitable alloys. Everything is accompanied by images in the enclosure at the end of work.
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Mechanical Properties of Plastics
Suchý, Marek ; Němec, Karel (referee) ; Molliková, Eva (advisor)
This bachelor thesis deals with the plastics in terms of their internal structures. Analyzes the impact of these characteristics on the resulting mechanical properties of materials. Furthermore, examining the external influences significantly on the polymer chain operates. Concludes two basic methods for the detection of mechanical properties - tensile test and 3-point bend tests.
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Fatigue Properties of Stainless Austenitic Steel
Sedlák, Martin ; Němec, Karel (referee) ; Věchet, Stanislav (advisor)
Final bachelor thesis „Fatigue characteristics of anti-corrosion austenitic steels" is aimed at problematic of mechanics and fatigue properties of Chrome-Nickel austenitic steel CSN EN X2CrNiMo 18-14-3. Thesis aim is to pass judgment on influence of stress cycle asymmetry on fatigue characteristics on high cyclic loading on above mentioned steel. Design Haigh and Smith diagrams. Component of the thesis is metallographical and chemical analysis, mathematical values processing obtained from fatigue tests and also determine primary mechanical properties. Further Wohler´s curves are stated at different stress cycle asymmetry. According to mathematical values processing is designed Haigh and Smith diagrams and fatigue index is calculated. From obtained data result that medium stress of cyclic stress, has of principle influence on appreciate fatigue limit of engaged material.
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The Material Selection for Bicycle Frames
Šály, Peter ; Petrenec, Martin (referee) ; Němec, Karel (advisor)
Bachelor's thesis summarises basic information about materials that are used for production of bicykle's frames. It concerns not only with common materials that are the most used nowadays, thus aluminium alloys and composite materials – carbon in the concrete, but it also pointed on the other, alternative materials. It also explains specific terms that relate to concrete materials or to their technological treating. Each material has listed characteristic which is objective thus measurable and it results from physical-chemical's properties and treating possibilities of concrete materials. It conveys assumption of frame behaviour made from this material. Subjective characteristic is also listed and it results from practice – from the feelings by real ride. Comparison of these two approaches resulted in conclusion which may help in choosing material for bicykle's frame which we have specific requirements on. Next thesis concerns with usage of concrete materials by various producers whether world producers or national ones, with orientation on brands which are interesting because of their treating of unusual materials or they are interesting because of their specific treating of common materials. There is a brief review of most used materials for concrete types of bicycle's frames at the end of the thesis.
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Static and Fatigue Properties of Selected Al - alloy
Skoumalová, Zuzana ; Němec, Karel (referee) ; Věchet, Stanislav (advisor)
The present bachelor thesis focuses on material properties of wrought aluminium alloy AlZn4Mg1. The thesis deals with the interrelations between the alloy structure and its static as well as fatigue properties, especially with the latter. The first part of the thesis provides a summary of current knowledge in the studied field, experimental results can be found in the second part. Static properties of the alloy were examined with the help of measurements of hardness and a tension test, fatigue properties on the basis of experiments in high- and low-cycle regions.
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Influence of Loading Frequency on Fatigue Properties of Structural Materials
Kašpar, Jan ; Němec, Karel (referee) ; Věchet, Stanislav (advisor)
This thesis analyse the influence of loading frequency on the fatigue of the structural materials. Low frequency loading (to the 200 Hz) has nearly no influence on the fatigue properties in almost all cases. Hight frequency loading (1 and more kHz) has major influence on the fatigue limit of the structural materials. This interference will disply like increasing of the fatigue limit. For example fatigue limit of steel is more affected by hight frequency loading than the cast-iron. Important aspect at hight frequency loading is rising temperature in the loading process. Rising temperature has negative influence on the fatigue limit of materials. Important aspect of the loading high frequency is possibility to achieved gigacycle regime of the fatigue (109 and more cycles), where should appear crack from below surface. This crack is call „ fish eye".
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Food competition between common carp (Cyprinus carpio) and topmouth gudgeon (Pseudorasbora parva)
NĚMEC, Karel
Small cyprinid fish, the topmouth gudgeon (Pseudorasbora parva Schlegel, 1842) is considered as an undesirable fish species because it represents an important food competitor for commercial non-predatory fishes. This study was performed under pond conditions (four ponds in South Moravia and two ponds in South Bohemia) during the growing seasons in 2006 {--} 2007. The purpose of my work was to determinate the level of food competition between topmouth gudgeon and common carp (Cyprinus carpio) as a dominating pond fish species. Food selectivity was evaluated using Ivlev´s electivity index (Jacobs, 1974). The level of food competition between common carp and topmouth gudgeon was used to evaluate the index of food similarity according to Shorygin (1952). The diet of topmouth gudgeon consisted mainly of chironomid larvae and zooplankton, mostly cladocerans (Daphnia, Bosmina), detritus and periphyton (Oscillatoria, Scenedesmus, Sphaerotilus). Macrophytes, copepods and Brachionus were also ingested by P.parva but in comparatively low proportions. In contrast, carp diet consisted mainly of bottom items including chironomid larvae, macrophytes and organic debris, mainly detritus and periphyton. The food items of lesser importance were dragon fly (Anisoptera) larvae, cladocerans (Bosmina, Daphnia) and ostracods. Topmouth gudgeon competed with common carp for chironomid larvae, periphyton and detritus, for zooplankton (mainly cladocerans Daphnia, Bosmina). The highest valuation the food competition was registered in fish from the Vracovický pond (South Moravia) and the Podsedek pond (South Bohemia), when it amounted from 24.02 to 34.78 % food similarity.
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