CHANGES IN THE SURFACE LAYER OF ROLLED BEARING STEEL

This paper describes changes observed in bearing steel due to roller burnishing. Hydrostatic roller burnishing was selected as the most suitable method for performing roller burnishing on hardened bearing steel. The hydrostatic roller burnishing operation was applied as an additional operation after standard finishing operations. All tests were performed on samples of 100Cr6 material (EN 10132-4), and changes in the surface layer of the workpiece were then evaluated. Several simulations using finite element methods were used to obtain the best possible default parameters for the tests. The residual stress and the plastic deformation during roller burnishing were major parameters that were tested

Design Concept of the Modular System Tools for Dynamic Testing of Materials and Cars Design Nodes

Import 29/09/2010Diplomová práce se zabývá vytvořením nového rámu pro vybrané konstrukční uzly. Dalším zájmem práce bylo vytvoření ideového návrhu modulárního systému pro dynamickou simulaci provozního zatížení nově vzniklého automobilu. K vývoji a výpočtům bylo využito počítačového modelování, konkrétně metoda konečných prvků. Bylo provedeno několik variant návrhů nového rámu automobilu. Pro výslednou vyhovující variantu rámu nového automobilu (označení RVS) jsou v práci uvedeny výsledky výpočtů pro kontrolu z hlediska pevnosti a tuhosti. V práci jsou dále uváděny dva ideové modulární systémy. První je pro testování tuhosti rámu a druhý je pro provádění laboratorních pevnostních a životnostních zkoušek. U obou modulárních systémů byly provedeny pevnostní kontroly vybraných kritických navrhovaných dílů.This diploma thesis deals with creating the new frame for the selected design nodes. Next interest of this work is creating a conceptual design for modular dynamic simulation of the operational load of the newly created car. For the development and calculations were used computer modeling, concretely the finite element method. There have been done several proposals of the new car frame. For satisfactory final variant of frame of a new car (sign RVS) there are documented the results of calculations for the control of strength and stiffness. The diploma thesis also featured two ideological modular systems. The first system is for testing stiffness of frame and the second is for laboratory tests of strength and endurance. For both modular systems have been done strenght checks of selected critical parts.339 - Katedra pružnosti a pevnostivýborn

Kalibrace Chabocheova modelu s paměťovou plochou

This paper points out a sufficient description of the stress-strain behaviour of the Chaboche nonlinear kinematic hardening model only for materials with the Masing's behaviour, regardless of the number of backstress parts. Subsequently, there are presented two concepts of most widely used memory surfaces: Jiang-Sehitoglu concept (deviatoric plane) and Chaboche concept (strain-space). On the base of experimental data of steel ST52 is then shown the possibility of capturing hysteresis loops and cyclic strain curve simultaneously in the usual range for low cycle fatigue calculations. A new model for cyclic hardening/softening behaviour modeling has been also developed based on the Jiang-Sehitoglu memory surface concept. Finally, there are formulated some recommendations for the use of individual models and the direction of further research in conclusions.Příspěvek poukazuje na dostatečný popis napěťově-deformačního chování Chabocheova modelu nelineárního kinematického zpevnění pouze pro materiály, které vykazují Masingovo chování, a to nezávisle na počtu kinematických částí. Následně jsou prezentovány dva nejpoužívanější koncepty paměťových ploch – modely Jiang-Sehitoglu (v deviátorové rovině) a Chaboche (prostor poměrných deformací). Na oceli 11523 jsou pak ukázány možnosti zachycení hysterezních smyček v rozsahu obvyklém pro nízkocyklovou oblast. Byl také vyvinut nový přístup pro modelování cyklického zpevňování/změkčování na základě paměťové plochy Jiang-Sehitoglu. V závěru jsou také formulována doporučení pro použití jednotlivých modelů a popsán směr dalšího výzkumu

Application of Linear Optimization on Parameters of 3D FDM Print

Nowadays, a fused deposition modelling (also called “FDM”) belongs to one of the most widespread additive methods of 3D print. It allows producing both models for functional verification or casts and functional components. The main advantage of this technology is an option to produce complex components of a difficult shape independent of their outer and inner surfaces. Moreover, this mentioned technology brings the decreasing of production costs in comparison with the other well-known additive methods. The final quality of a product depends on the used material and on technological conditions at the same time. The number of parameters and limits of the complete printing process is enormous. The choice of the individual parameters by a trial-and-error procedure is very time-consuming. Therefore, a use of linear optimization for finding of optimal values of chosen print parameters can be offered. For forming of the required procedures, it seems to be necessary to choose structural variables, find an appropriate objective function and deduce properly limiting conditions in a linear shape, which relates to a linear measurement. The final solution enables, on the basis of the selected initial conditions, to choose optimal parameters of the 3D print for a given material and production equipment in a relatively short period

Kazbek – The First Czech Aroma “Flavor Hops” Variety: Characteristics and Utilization

The world market of craft beer, especially dry hopped beers, has been constantly growing in the last few years. That is why new varieties of hops are still being bred. This article gives the genetic, agronomic, chemotaxonomic and brewing characteristics of Kazbek, the first “flavor hops” variety bred in the Czech Republic. Kazbek genetically belongs to a group of bitter American hops resulting from Brewers Gold variety, but the alpha acids content is relatively low, 5.0–8.0% by weight. The content of a homologous series of geranyl esters (acetate – propionate – isobutyrate) in an amount 2–4% of total essential oils (1–1.5 g/100g) is considered to be the originator of the specific, mainly citrus-like aroma of Kazbek. Moreover, the essential oil fraction contains about 25 sulfurous substances, predominantly thioesters. In the pilot scale brewing tests, the quality of Kazbek hops was proved both in kettle and dry hopping of Pilsner lagers. The overall sensory impression of kettle hopped lagers was comparable to Saaz hops, the differences were in the character of hop-derived flavor and bitterness. The best results of dry hopped beers were achieved for a 2.5 g/l hop dose and a contact time of 3 days

Determination of mechanical properties of plastic components made by 3D printing

The presented article deals with the determination of selected mechanical properties of additive materials used for 3D printing (PETG, PLA, ABS, ABS +, PLA ESD, ASA, PC / ABS). Due to the fact that 3D printing has exploded over recent years and additive manufacturing has become popular in some industries, the quality of input materials and their mechanical properties is extremely important. We used 3D printer Original Prusa MK3 to prepare samples for testing. Individual samples printed from all above mentioned materials were analyzed using selected mechanical tests (static tensile test, hardness tests). In the static tensile test, selected parameters (tensile strength limit, tensile modulus, elongation) were determined for all additive samples, which were statistically processed. The parameters for two methods of measuring hardness were also statistically evaluated, namely Shore and ball indentation. All tested additive materials were compared with the aim of obtaining the final ranking (point evaluation of tested materials with quantification of price costs). The best properties after the performed tests were achieved by the additive material PLA Filament Plasty Mladec.Univerzita Tomáše Bati ve ZlíněDepartment of Mechanical Engineering, University of Defence in Brno [SV20-216]; Project for the Development of the Organization "DZRO VAROPS"; Tomas Bata University in Zlin [VaV-IP-RO/2022/01

Influence of the shape of the filling on the mechanical properties of samples made by 3D printing

In this work, the influence of material type and sample fill density was evaluated. One PLA material was tested. Test specimens having different fill structure and density were printed from this material. Full honeycomb and gyroid shapes were used for the fill structure. The specimens had four different fill percentages for each structure: 10%, 25%, 50% and 75%. These bodies were compared to samples that were printed with 100% fill. Tensile test was performed on printed test pieces. The Zwick / Roell Z100 was used for testing and the surface hardness of the test specimens was measured by the Shore D method on a DIGI-Test II hardness tester. Fracture surfaces were evaluated on an Olympus DSX 500 optodigital microscope. The results showed that the shape of the fill did not signifi-cantly affect the values obtained by the tensile test. The hardness measurement results showed a different hardness on the bottom surface that was in contact with the printing pad and the top printing surface. Fractographic analysis revealed different types of fracture surfaces related to the printed fill structure. © 2021 Manufacturing Technology. All rights reserved

Effect of boron and vanadium addition on friction-wear properties of the coating AlCrN for special applications

Cutting tools have long been coated with an AlCrN hard coating system that has good mechanical and tribological qualities. Boron (B) and vanadium (V) additions to AlCrN coatings were studied for their mechanical and tribological properties. Cathodic multi-arc evaporation was used to successfully manufacture the AlCrBN and AlCrVN coatings. These multicomponent coatings were applied to the untreated and plasma-nitrided surfaces of HS6-5-2 and H13 steels, respectively. Nanoindentation and Vickers micro-hardness tests were used to assess the mechanical properties of the materials. Ball-on-flat wear tests with WC-Co balls as counterparts were used to assess the friction-wear capabilities. Nanoindentation tests demonstrated that AlCrBN coating has a higher hardness (HIT 40.9 GPa) than AlCrVN coating (39.3 GPa). Steels’ wear resistance was significantly increased by a hybrid treatment that included plasma nitriding and hard coatings. The wear volume was 3% better for the AlCrBN coating than for the AlCrVN coating on H13 nitrided steel, decreasing by 89% compared to the untreated material. For HS6-5-2 steel, the wear volume was almost the same for both coatings but decreased by 77% compared to the untreated material. Boron addition significantly improved the mechanical, tribological, and adhesive capabilities of the AlCrN coating. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Department of Mechanical Engineering, University of Defence in Brno [SV20-216]; Project for the Development of the Organization "DZRO Military autonomous and robotic systems"; Slovak Research and Development AgencySlovak Research and Development Agency [APVV-15-0710]Agentúra na Podporu Výskumu a Vývoja, APVV: APVV-15-071

Application of Carbon–Flax Hybrid Composite in High Performance Electric Personal Watercraft

Within the herein presented research, we studied the applicability of flax fabrics for composite parts in personal watercrafts in order to enhance damping of vibrations from the engine and noise reduction (which is relatively high for contemporary carbon constructions). Since the composite parts are intended to be exposed to humid environments requiring high levels of mechanical properties, a carbon–flax composite was selected. Samples of carbon, fiberglass, flax, and hybrid carbon–flax twill and biax fabrics were subjected to tensile and three-point bending tests. The mechanical properties were also tested after exposure of the samples to a humid environment. Damping was assessed by vibration and noise measurements directly on the complete float for samples as well as real parts. The hybrid carbon–flax material exhibited lower values of tensile strength than the carbon material (760 MPa compared to 463 MPa), but, at the same time, significantly higher than the other tested materials, or flax itself (115 MPa for a twill fabric). A similar trend in the results was observed for the three-point bending tests. Vibration tests and noise measurements showed reductions in vibration amplitude and frequency when using the carbon–flax hybrid material; the frequency response function for the watercraft part assembled from the hybrid material was 50% lower than for that made of carbon. Testing of samples located in a humid environment showed the necessity of surface treatment to prevent moisture absorption (mechanical properties were reduced at minimum by 28%). The tests confirmed that the hybrid material is satisfactory in terms of strength and its contribution to noise and vibration damping