National Repository of Grey Literature 55 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Fatigue Crack Growth Retardation Techniques for the Integral Airframe Structure
Jetela, Václav ; Růžička, Milan (referee) ; Petrásek, Miloslav (referee) ; Klement, Josef (advisor)
Při zavádění integrální letecké konstrukce vyvstal problém s rychlým růstem únavové trhliny v této konstrukci. Jednou z možností, jak zpomalit růst trhliny a zvýšit životnost konstrukce, je aplikace tzv. zastavovače trhliny. Tato disertační práce porovnává aditivně vyráběné a lepené zastavovače trhlin z hlediska životnosti, rychlosti šíření trhliny a delaminace. V případě lepených zastavovačů trhlin; doposud nebyla věnována pozornost zastavovačům z nerezové oceli. Nerezová ocel se jeví jako vhodný kandidát z důvodu koeficientu tepelné roztažnosti blízkého hliníkové slitině, vysoké tahové pevnosti a vysokého modulu pružnosti v tahu. S ohledem na aditivně vyráběné zastavovače trhlin, žádná pozornost nebyla věnována zastavovačům trhlin z materiálů odlišných od podkladové konstrukce. Za účelem doplnění současného stavu poznání byly vybrány tyto aditivní technologie: studená kinetizace a ultrazvuková konsolidace. Metodou studené kinetizace byly deponovány zastavovače z nerezové oceli a titanové slitiny. Metodou ultrazvukové konsolidace byly navařeny zastavovače z nerezové oceli. V experimentální části práce byl pozorován růst únavové trhliny v podkladové konstrukci. Delaminace zastavovače byla monitorována metodou pulzní termografie s následnou rekonstrukcí termografického signálu. Lepené zastavovače trhlin z nerezové oceli se prokázaly jako vhodná alternativa k zastavovačům s uhlíkovými vlákny. Nerezové zastavovače výrazně snížily rychlost šíření únavové trhliny, čímž značně prodloužily životnost vzorku. Bohužel, všechny zastavovače připravené metodou studené kinetizace urychlily růst únavové trhliny, čímž došlo k předčasnému selhání vzorku. Ultrazvukově konsolidované zastavovače s dvěma vrstvami oceli byly nejefektivnější z hlediska zvýšení životnosti. Tato práce navíc prokázala, že pro detekci delaminace v ultrazvukově konsolidovaném laminátu je možné použít metodu pulzní termografie.
DESIGN, STRESS ANALYSES AND LIMIT LOAD OF SANDWICH STRUCTURES
Löffelmann, František ; Pavlínek,, Vladimír (referee) ; Klement, Josef (referee) ; Píštěk, Antonín (advisor)
Disertační práce začíná rešerší výpočtů pro návrh sendvičových nosníků, desek a složitějších konstrukcí, kde zaujímá významnou roli MKP. Dále jsou popsány optimalizační metody pro ujasnění široké oblasti matematického programování a základních principů topologické optimalizace až po její implementaci na kompozitní konstrukce jinými autory. Pro názornost jsou zmíněny jak analytické, tak i numerické přístupy k optimalizaci sendvičů, kde numerické přístupy umožňují řešit daleko širší oblast úkolů. Cíl disertační práce je stanoven jako implementace zautomatizovaného algoritmu pro optimalizaci za účelem vylepšení návrhového procesu sendvičů s ohledem na napjatost a únosnost. Cíle je dosaženo prostřednictvím vlastní implementace gradientní optimalizace založené na principech topologické optimalizace, známé jako diskrétní optimalizace materiálu (Discrete Material Optimization - DMO) a jejích variant, které pomáhají najít optimální vrstvení. Přístup k materiálové interpolaci a interpolaci poruchový omezujících podmínek je vyvinut a naprogramován v pythonu za použití teorie smykových deformací prvního řádu (First Order Shear Deformation Theory - FSDT) pro vyhodnocení napětí na elementech na základě zatížení daného MKP řešičem Nastran. Gradientní optimalizér hledá nejlepší materiály pro každou vrstvu potahu sendviče a jádra z definovaných kandidátů. Program je odzkoušený na příkladech různé složitosti od nosníku tvořeného jedním elementem, kde je skutečné optimum známé, až po praktickou úlohu sendvičové kuchyňky z dopravního letadla. Výsledky ukázaly, že algoritmus je schopen dosáhnout diskrétního řešení bez (významného) narušení omezujících podmínek a může tedy být prakticky využit ke zefektivnění koncepčního návrhu sendvičů.
Relationship between tensile strength and hardness of aluminium alloys
Růžička, Martin ; Jetela, Václav (referee) ; Klement, Josef (advisor)
This thesis deals with relationship between tensile strength and hardness of aluminium alloys. The introduction provides an overview of aluminum aloys and their properties. In the following section there is an analysis of the processing of aluminum alloys. A large part is devoted to the course of precipitation hardening. The second part of the thesis contains a practical part, which describes the methodology of measuring hardness and tensile strength. The measurement process is described below. At the end, the measured data are processed into various graphs and their results are evaluated.
Smart materials in aviation
Riger, Rostislav ; Jetela, Václav (referee) ; Klement, Josef (advisor)
This bachelor thesis deals with smart materials and their applications in aviation. The theoretical part explains what we mean by the term smart materials and what we want to achieve with their use. Further, these materials are sorted according to the principle of their function and described. The practical part is focused on specific applications of smart materials in aviation. Sometimes these are only theoretical applications that have not yet been used.
Experimental evaluation of appropriate FDM technology for UAV production
Hubáček, Jan ; Klement, Josef (referee) ; Dvořák, Petr (advisor)
This bachelor thesis deals with material analysis and design of technology for Fused Deposition modelling 3D printing method of unmanned aerial vehicles. Nine materials which are suitable for this application has been tested. Tension test has been used to determine mechanical properties of each material according ISO standards for plastics. Material had to met certain criteria, which are important for 3D print of aeroplanes, to pass to the next stage of experiment. Next three-point flexural test of wing has been used. In this test has been tested two glued sections of wing root and one separate section of wing. Results of tensile test and flexural test were compared and evaluated. It was discovered that material PLA, which is commonly used for printing aeroplanes, has not been overcome. Materials that seems to have better mechanical properties has been disadvantaged for its bad properties in 3D printing process.
Age forming of aluminium alloys
Stanislav, Filip ; Petrásek, Miloslav (referee) ; Klement, Josef (advisor)
The diploma thesis is focused on the description and the verification of a relatively young creep age forming method. This method is based on a relaxation of stress and a creep of material, which occur by forming a part in the clamping tool during the artificial precipitation heat treatment at elevated temperature. After removing from the tool, the spring back and the residual stresses in the part are smaller compared to the conventional forming methods. This is mainly reflected in the increased fatigue resistance of the structure. The creep aging is only applicable to the precipitation heat treatable alloys. This thesis is focused on aluminium alloys, which are typical for the aerospace industry. The first part of the thesis describes principles of technology, its use in the aviation and material processes in the aluminium precipitation heat treatable alloys during the creep age forming. In the second part, there is a methodology of the verification of technology on samples made of the aluminium alloys ČSN EN AL-P 7075 and ČSN 424203 (approximate equivalent of ČSN EN AL-P 2024). Furthermore, a forming tool is designed, and experiments are performed according to the proposed methodology. At the end of the thesis, the experiments are evaluated and changes in the spring back of the samples are compared for three different methods of forming: the conventional cold clamping forming, the creep age forming and the creep age forming with an overaging.
Application of thermoplastic composite materials on aircraft structures
Vráblíková, Lucie ; Symonov, Volodymyr (referee) ; Klement, Josef (advisor)
This bachelor thesis deals with thermoplastic composite materials in aircraft industry. The aims of the thesis are divided into three parts. The first part contains an overview of the basic properties of fibre-reinforced thermoplastics, their structure and characteristics. In the second part, there are introduced different technologies of manufacturing thermoplastics. The last part deals with applications of thermoplastic composite materials in aircraft industry.
Evaluation of dynamic damage of composite structure
Štefanovič, Peter ; Jetela, Václav (referee) ; Klement, Josef (advisor)
The first part of the diploma thesis with name „Evaluation of dynamic damage of composite structure“ focuses on designing device for impact experiments and suitable laminate samples made from prepregs. The conditions and problems of impact tests are also demonstrated here. The second part of the thesis deals with non-destructive control of damaged specimens based on thermography. This is mainly the extent of defects in the impaired area and the evaluation of results using the pulse infrared thermography method. Finally, the relative deviation in the crack size comparison between the visual method and thermographic are compared. Consequently, the residual strength of the damaged samples against undamaged specimens are compared using bending tests.
Problém černého pasažéra v Severoatlantické alianci v období 2006 - 2016 a implikace pro fiskální politiku
Richterová, Jitka ; Maule, Petr (advisor) ; Klement, Josef (referee)
The purpose of this thesis is to examine the problem of free riding in NATO with regards to fulfilling the criteria of defence expenditures as well as econometric analysis and interpretation of the defence expenditures of the member states in the period of 2006 to 2016. Using spearman correlation test, this thesis finds a significant positive correlation between GDP of member states and their defence expenditures. Explanatory variables include main economic indicators such as GDP, GNI, share of GDP devoted to defence expenditures, average annual change in defence expenditures, etc. Main findings include the conclusion that there is a significant level of free riding in the North Atlantic Treaty Organisation and that larger member states indeed bear the larger burden. Furthermore, based on having lower average defence expenditures than NATO in the examined period, the thesis labels nineteen of the member states as free riding, given that their defence expenditures are below the NATO average. After examining and analysing free riding in NATO the thesis also highlights the implications and recommendations for fiscal policy.
Analysis of automotive industry in the Czech Republic and the Slovak Republic during years 2005 through 2016 with consideration of intervention policy of scrapping program
Tořínský, Ota ; Zeman, Martin (advisor) ; Klement, Josef (referee)
The bachelor thesis analyzes automotive industry in the Czech Republic and the Slovak Republic in the period from 2005 to 2016. The economic crisis took place during this period and the Slovak government decided to react in 2009 with the introduction of scrapping program, however the scrapping program was never introduced in the Czech Republic. The aim of the thesis is to analyze sales of passenger cars in both countries in the period from 2005 to 2016. The thesis concludes that scrapping program in Slovakia in 2009 increased the demand for passenger cars, but in 2010 this demand decreased significantly. The thesis also concludes that the scrapping program has had a negative impact for domestic sales of passenger cars in the long run.

National Repository of Grey Literature : 55 records found   1 - 10nextend  jump to record:
See also: similar author names
11 KLEMENT, Jan
2 Klement, Jakub
11 Klement, Jan
1 Klement, Jaroslav
4 Klement, Jiří
Interested in being notified about new results for this query?
Subscribe to the RSS feed.