Solution to the mechanism of a screw jack

Předložená bakalářská práce se zabývá mechanizmem šroubové zvedáku z hlediska základních konstrukčních výpočtů, tak i z hlediska technologie výroby. V následující části je provedeno základní rozdělení dílenských zvedacích zařízení, dále pak konstrukční návrh zvedacího zařízení a v neposlední řadě návrh technologie výroby. Dále je pozornost věnována technicko - ekonomickému pohledu na výrobní proces mechanizmu šroubového zvedáku a možnosti vylepšení jak výrobního procesu, tak i samotné konstrukce.The presented bachelor thesis deals with the mechanism of the screw jack in terms of basic design calculations as well as in terms of production technology. The following part deals with basic division of the workshop lifting equipment, the design of the lifting device and, last but not least, the design of the production technology. Further attention is paid to the technical and economic view of the manufacturing process of the screw jack mechanism and the possibility of improving both the production process and the construction itself.

Structure and mechanical properties of alloys of iron aluminides with additives of zirconium, yttrium and carbon at high temperatures

katedra: KMT; rozsah: 76 s., 5 s. obr. přílohDiploma thesis deals with high-temperature behavior of iron aluminides alloys with additives of zirconium, carbon and yttrium. Fe3Al alloys have very good resistance to oxidation and sulphidation. This work deals with the improvement of their low high-temperature strength and creep resistance by alloying and heat treatment. The alloys which are compared in this work, they were prepared by vacuum melting, hot-rolling and heat treatment. The influence of heat treatment was investigated on a change in structure and hardness. The yield strength was investigated by test in tension and compression at temperatures of 600-800 °C. The creep resistance was determined by creep tests at temperatures of 600-700 °C and stress range of 80-200 MPa. It was time to rupture, time to 1% deformation and minimum creep rate.Diplomová práce se zabývá vysokoteplotním chováním slitin aluminidů železa s přísadami zirkonia, uhlíku a yttria. Slitiny na bázi Fe3Al mají velmi dobrou odolnost vůči oxidaci a sulfidaci. Tato práce se zabývá zlepšením jejich nízké vysokoteplotní pevnosti a creepové odolnosti pomoci legování a tepelného zpracování. Slitiny porovnávané v této práci byly připraveny vakuovým tavením, válcováním za tepla a tepelným zpracováním. Byl zjišťován vliv tepelného zpracování na změnu struktury a tvrdosti. Zkouškou v tahu a tlaku za teplot 600-800 °C byla zjišťována mez kluzu. Byla určena creepová odolnost creepovými zkouškami za teplot 600-700 °C a v rozmezí napětí 80-200 MPa. Byla stanovena doba do lomu, do 1% deformace a minimální creepová rychlost

Identifying the Technical Condition of Rotating Parts by Means of Vibrodiagnostics

The paper addresses the issue of identifying the technical condition of rotating parts with by means of vibrodiagnostics. This method has been developing rapidly in recent years and it is conceived to be used for predicting failure occurrence. This enables us to determine an optimum time to perform machine preventive maintenance. The aim is to determine this point in time for groups of components, such as electric motors, gear boxes, and even combustion engines. In this paper, we focus on monitoring the technical condition of the medium truck bearing box on which we simulate different field conditions. A measuring device, DEWE 50/8, including the DEWEsoft software product of the Dewetron Company, has been used for the actual measurement. Along with the vibrodiagnostics used when determining the technical condition of the bearing box, we have also applied thermography for monitoring thermal changes of individual components. The aim of the research is to determine the moment when a preventive action is to be performed or when to change components before the failure occurs and increases the costs

Machining of precise holes for bearings

Předložená diplomová práce se zabývá obráběním přesných děr pro uložení ložisek z hlediska teoretického přehledu, lícování a uložení strojních součásti. Dále pak přehledem a volbou ložisek, seznámení se s typy převodových skříní a metodami dokončování povrchů. Závěrem pak způsoby výroby děr pro uložení ložisek v převodových skříních.This diploma thesis is about machining of exact hole specifications to fit the bearings from the the theoretical overviewof the fiiting. Another purpose is to describe; the overview of machines, the choices in bearings, and the types of gearboxes. Finally, it deals with the different methods of surface finishing, how to produce the holes for the bearings to fit in gearboxes.Finally, it deals with the different methods of surface finishing and how to produce the holes for the bearings to fit in the gearboxes

The effect of endothelial cell proliferation on susceptibility to mitochondrially controlled apoptosis and oxidative stress.

Mitochondrie jsou multifunkční organely hrající rozhodující roli v energetickém metabolizmu buněk a v indukci buněčné smrti. Mitochondrie, a zvláště pak jejich respirační řetězec, jsou též hlavními producenty reaktivních forem kyslíku (ROS) v buňkách. Metabolizmus buňky může být ovlivněn jejím proliferačním stavem. Zároveň určité látky zvyšující oxidační stres vykazují antiangiogenní účinky spojené se selektivní eliminací proliferujících endoteliálních buněk (EB). Z těchto důvodů jsme v této práci zjišťovali, zda by mitochondrie mohly být zodpovědné za rozdílnou citlivost proliferujících a konfluentních (buněk v klidové fázi) EB k buněčné smrti. Zvláštní důraz byl kladen na systémy regulující hladinu ROS nebo apoptózy: respirační řetězec (produkce ROS), antioxidačních ochrana (detoxifikace ROS) a proteiny rodiny Bcl-2 (regulace apoptózy). Nejdříve jsme vystavili EB s normálně fungujícím a defektním respiračním řetězcem působení rozličných látek vyvolávajících oxidační stres a apoptózu a stanovili produkci ROS a citlivost k apoptóze v proliferujícím a klidovém stavu. Tyto experimenty ukázaly, že funkční respirační řetězec do značné míry zvyšuje citlivost proliferujících EB k indukci tvorby ROS a apoptóze, zatímco v buňkách v klidovém stavu funkční řetězec naopak proti buněčné smrti chrání. Vzhledem...Mitochondria are multifunctional organelles playing a key role in energy metabolism and cell death induction. Mitochondria, and specifically their respiratory chain, are also the main producers of reactive oxygen species (ROS) in cells. Metabolism can be affected by the state of cellular proliferation and certain ROS-inducing agents have an antiangiogenic effect based on the preferential elimination of proliferating endothelial cells (EC). Therefore, in this work we investigated, whether mitochondria could be responsible for different sensitivity of proliferation and confluent EC to cell death. We mainly focused on systems that regulate ROS level and apoptosis: respiratory chain (ROS production), antioxidant defense (ROS detoxification) and Bcl-2 family of proteins (apoptosis regulation). First, we treated EC with functional and nonfunctional respiratory chain with various oxidative stress- and apoptosis-inducing agents and determined ROS production and susceptibility to apoptosis in proliferating and confluent cells. Our results show that functional respiratory chain greatly increases the susceptibility of proliferating cells to ROS induction and apoptosis, whereas in qiescent cells it protects against cell death. Given these findings, we assessed the activity of respiratory chain in proliferating...Katedra biochemieDepartment of BiochemistryPřírodovědecká fakultaFaculty of Scienc

Experimental Study of the Volumetric Error Effect on the Resulting Working Accuracy—Roundness

Currently, various types of software compensations are applied to machine tools. Their aim is to increase the working accuracy of the tools. The improvement in working accuracy is then further assessed according to the increase in the dimensional and shape accuracy or the surface quality of the workpiece. This publication describes the effects of the volumetric accuracy of a machine tool on the working accuracy of a workpiece, where total roundness (RONt) is evaluated in multiple cuts. In the experiment, two test workpieces are manufactured on a three-axis milling machining centre. The first is made using a standard machine setup while the second with activated volumetric compensation. The LaserTRACER self-tracking laser interferometer is used to compensate for volumetric accuracy. In the second part, verification measurements are performed with a Ballbar, where roundness error is evaluated according to ISO 230-4. Then two test workpieces are machined, and, in the last part, measurement is performed on Talyrond 595S roundness measuring equipment. Finally, the results are analysed and the dependence between the volumetric accuracy, the circularity error of the machine and the working accuracy of the CNC machine tool is established, represented by the RONt of the workpiece. This paper presents new and unpublished relations between the volumetric accuracy of the machine tool and the RONt of the workpiece

Capability of measurement with a touch probe on CNC machine tools

Increasing the productivity of high-precision manufacturing requires efficient product inspection, for example, using integrated scanning systems on CNC machine tools (MT). However, measuring the dimensional and shape accuracy of workpieces using a touch probe (TP) on MT is negatively affected by the geometric accuracy setting of the MT, thermal stability of the MT and its surroundings, type of scanning system. The aim of this paper was to examine the possibilities of assessing the capability of touch probe measurements on MT, to define the size of the permissible controlled tolerance of the workpiece and to assess the influence of the geometric accuracy of the machine on the size of the permissible tolerance parameter of the inspected workpiece. In the presented experiments, the calculation of the TP measurement capability is based on a new approach respecting the VDA5 standard extended by the minimum tolerance (TOLmin) conformity assessment procedure according to ISO 14253-1:2017

Finite Element Analysis of Osteosynthesis Screw Fixation in the Bone Stock: An Appropriate Method for Automatic Screw Modelling

The use of finite element analysis (FEA) has grown to a more and more important method in the field of biomedical engineering and biomechanics. Although increased computational performance allows new ways to generate more complex biomechanical models, in the area of orthopaedic surgery, solid modelling of screws and drill holes represent a limitation of their use for individual cases and an increase of computational costs. To cope with these requirements, different methods for numerical screw modelling have therefore been investigated to improve its application diversity. Exemplarily, fixation was performed for stabilization of a large segmental femoral bone defect by an osteosynthesis plate. Three different numerical modelling techniques for implant fixation were used in this study, i.e. without screw modelling, screws as solid elements as well as screws as structural elements. The latter one offers the possibility to implement automatically generated screws with variable geometry on arbitrary FE models. Structural screws were parametrically generated by a Python script for the automatic generation in the FE-software Abaqus/CAE on both a tetrahedral and a hexahedral meshed femur. Accuracy of the FE models was confirmed by experimental testing using a composite femur with a segmental defect and an identical osteosynthesis plate for primary stabilisation with titanium screws. Both deflection of the femoral head and the gap alteration were measured with an optical measuring system with an accuracy of approximately 3 µm. For both screw modelling techniques a sufficient correlation of approximately 95% between numerical and experimental analysis was found. Furthermore, using structural elements for screw modelling the computational time could be reduced by 85% using hexahedral elements instead of tetrahedral elements for femur meshing. The automatically generated screw modelling offers a realistic simulation of the osteosynthesis fixation with screws in the adjacent bone stock and can be used for further investigations

L'Hydroptère: A story of a dream

In 2009, l’Hydroptère broke the symbolic barrier of 50 knots and became the world fastest sailing boat over both 500 meters and 1 nautical mile. This major achievement relied on the high skills of the sailing team but also on technical advances of the boat, resulting from long years of studies and development. This achievement is also an open window to a new goal: flying around the world. In the present article, we present this long and incredible story, highlighting the different steps, the technology involved, and the background of that project.