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The temperature dependence of tensile characteristics and fracture toughness of the standardly heat-treated low-alloyed steel OCHN3MFA along with three additionally heat-treated grades was experimentally studied. In the temperature range of 196; 22 °C, all the additional heat treatments transferred the standard steel from a high- to ultra-high strength levels even with improved tensile ductility characteristics. This could be explained by a reduction of the inclusion content, refinement of the martensitic blocks, ductile retained austenite content, and homogenization of the shape ratio of martensitic laths as revealed by metallographic, X-Ray, and EBSD techniques. On the other hand, the values of the fracture toughness of all grades were found to be comparable in the whole temperature range as the cause of a high stress triaxiality in the pre-cracked Charpy V-notch samples. The values of the fracture toughness of the standard steel grade could be predicted well using the fracture model proposed by Pokluda et al. based on the tensile characteristics. Such a prediction failed in the case of additionally heat-treated grades due to the different temperature dependence of the fracture mechanisms occurring in the tensile and fracture-toughness tests. While the tensile samples fractured in a ductile-dimple mode at all temperatures, the fracture-toughness specimens exhibited a transition from the ductile to quasi-brittle fracture mode with decreasing temperature. This transition could be interpreted in terms of a transfer from the model proposed by Rice and Johnson to the model of Tvergaard and Hutchinson.

Shape memory alloys (SMAs) are being increasingly applied as thermally driven actuators. The commercially available SMA elements, however, frequently contain stress risers, either due to internal or surface defects or due to the required component shape. Stress risers represent a potential danger for the preliminary fatigue failure of such actuators but its actual mechanism is not very clear. This paper presents a combined experimental (2D DIC analysis of surface strains) and numerical analysis (SMA model with plastic deformation) of the stress, strain and phase fraction fields evolving in a thin NiTi shape memory ribbon with an artificial notch subjected to cyclic cooling-heating through transformation range under constant external force. It appeared that, even if only very low tensile stress is externally applied upon thermal cycling, local tensile stress at the notch tip sharply increases during the first cooling due to the forward martensitic transformation (MT) proceeding heterogeneously in space. This heterogeneity gives rise to plastic deformation at the notch-tip, which gradually accumulates upon thermal cycling and shields the notch tip from tensile overloading. Hence, fatigue performance of thermal NiTi actuator with stress riser depends very much on the plastic deformability of the alloy.

The fatigue properties of thermo-mechanically treated and machined aluminum alloy 7475-T7351 have been studied. The applied advanced machining strategy induced intensive plastic deformation on the machined surface under defined cutting conditions. Therefore, a detailed study of 3D surface topography was performed. Advanced characterization of the material structure and electron back scattered diffraction mapping of selected chemical phases were performed, as well as energy dispersive X-ray analysis of the surface. Advanced mechanical properties of the material were investigated in situ with a scanning electron microscope that was equipped with a unique tensile fixture. The fatigue results confirmed an evident dispersion of the data, but the mechanism of crack nucleation was established. Fracture surface analysis showed that the cracks nucleated at the brittle secondary particles dispersed in the material matrix. The surface topography of samples that had been machined in wide range of cutting/deformation conditions by milling has not proved to be a decisive factor in terms of the fatigue behavior. The incoherent interface and decohesion between the alumina matrix and the brittle secondary phases proved to significantly affect the ultimate strength of the material. Tool engagement also affected the fatigue resistance of the material.

Pavel Šandera: Technologický postup montáže schodiště VŠB – Technická Univerzita Ostrava, Fakulta stavební, Katedra pozemního stavitelství 2015, 185 stran Vedoucí diplomové práce: Ing. Jiří Teslík Předmětem mé diplomové práce je zpracování projektové dokumentace novostavby multifunkčního objektu včetně tepelně technického posouzení jeho obvodových konstrukcí. V návaznosti na ni pak vytvoření 2 variantních technologických postupů realizace vnitřního schodiště z 1.PP do 1.NP (monolitický železobeton, ocelobeton), návrhu opatření „Bezpečnosti a ochrany zdraví při práci“ a dokumentace zařízeni staveniště pro montáž tohoto schodiště. Dále pak vypracování podrobných položkových rozpočtů s výkazy výměr a řádkových harmonogramů postupu stavebních prací pro obě varianty. Hlavním cílem tohoto projektu je ukázat 2 možné varianty realizace schodiště, vzájemně je porovnat a stanovit, která z nich je pro daný objekt výhodnější., Pavel Šandera: Technological procedure of staircase installation VŠB – Technical University of Ostrava, Faculty of Civil Engineering, department of Building Constructions 2015, 185 pages Thesis supervisor: Ing. Jiří Teslík The object of the thesis is a processing of a project documentation of a new multifunctional building including a thermal-technical appraisal of its perimeter constructions. In connection with it also a creation of two variant technological procedures of the inside staircase installation from the ground floor to the first floor (monolithic ferroconcrete, steel-concrete), a proposal of measures "Occupational Safety and Health" and a documentation of the equipment of a construction site for the staircase installation, and finally, drawing up detailed itemized budgets with measurement sheets and line schedules of construction work procedures for both variants. The main aim of this project is to demonstrate two possible variants of the staircase installation; draw a mutual comparison and determine which one is better for the given building., Ve zpracování, Import 20/01/2016, Import 11/02/2016

Pavel Šandera: Projekt stavební části administrativní budovy včetně podrobného položkového rozpočtu a časového harmonogramu postupu prací - Bakalářská práce VŠB – Technická Univerzita Ostrava, Fakulta stavební, Katedra pozemního stavitelství 2014, 60 stran Vedoucí bakalářské práce: ing. Zdeněk Peřina, Ph.D. Předmětem mé bakalářské práce je vytvořit projekt adaptace stávajícího fiktivního objektu skladu na novou administrativní budovu smyšlené firmy Lampa, s.r.o., podrobný položkový rozpočet na danou stavbu a časové harmonogramy prací pro vybranou část budovy. Součástí projektu je dokumentace bouracích prací a dokumentace stavební části včetně příslušných textových a výkresových částí. Dokumentace slouží pro realizaci výstavby. Podrobný položkový rozpočet je sestaven pro bourací a pro stavební práce. Je zpracován ve verzi s cenami a s výkazem výměr. Tento rozpočet slouží zejména jako podklad pro investora. Lze jej však upravit na rozpočet slepý, který je možno využít při výběrovém řízení. Dva časové harmonogramy postupu stavebních prací jsou navrženy pro realizaci přístavby k objektu. Jeden počítá s jednosměnnou výstavbou, druhý počítá s dvousměnnou výstavbou. Harmonogramy jsou určeny jako vodítko pro rozvržení plánovaných nákladů a výnosů v čase, pro operativní řízení výstavby a pro včasné zajištění stavebních materiálů a lidských zdrojů pro jednotlivé etapy realizace. V neposlední řadě mají sloužit jako orientační kalendář pro předávky konstrukčních výztuží technickému dozoru investora před betonáží. Cílem tohoto projektu je ukázat jednu z možných variant přestavby stávajícího částečně nevyužitého objektu na novou moderní a plně funkční administrativní budovu. Dále má pak ukázat finanční náklady na tuto akci a časovou potřebu pro provedení přístavby k tomuto objektu., Pavel Šandera: Project of a constructional part of an administrative building including a detailed budget and a time schedule of progress of work – Bachelor thesis VŠB – Technical University of Ostrava, Faculty of Civil Engineering, Building Construction Department 2014, 60 pages Thesis supervisor: Ing. Zdeněk Peřina, Ph.D. The objective of the bachelor thesis is a creation of a project of a fictitious storehouse renovation to a new administrative building of a fabricated company Lampa, s.r.o., a detailed budget for this building and a time schedules of work for the selected part of the building. Part of the project is a documentation of demolishing and building operations including relevant text and drawing documentation. The documentation serves for a realization of the construction. The detailed budget is drawn up for demolishing and building operations. It is processed in two versions, with prices and with a bill of quantities. This budget serves mainly as a basic document for the investor. It is possible to adjust it to a blind budget with a possible use during a selection procedure. Two time schedules of progress of work are designed for the realization of an addition to a building. One of them supposes one-shift construction; the other supposes two-shift construction. The schedules are determined to be a guideline for a distribution of planned costs and earnings in time, for operating management of the construction and for timely arrangement of a construction material and human resources for the individual stages of realization. Last but not least, they are supposed to serve as an orientation calendar for handovers of constructional supports to an engineering supervision of the investor before concreting. The aim of this project is to point out to one of the possible variants of the reconstruction of the partly idle premises to the new modern and fully functional administrative building. It should also point out to the financial charges for this action and a, Ve zpracování, Import 05/08/2014

Byly připraveny lomové plochy vznikající při ohybově-torzním namáhání vzorků připravených z vysokopevnostních nízkopříměsových Cr-Al-Mo ocelí. Byly analyzovány topologické charakteristiky těchto ploch., Fracture surfaces generated under combined bending-torsion fatigue loading in both the low-cycle fatigue and the high-cycle fatigue regions of specimens made of high-strength low-alloy Cr-Al-Mo steel are analysed in terms of topographical characteristics. Parameters reported here are the root mean square roughness, the number of peaks per unit length and the Hurst exponent quantifying various aspects of surface topography. As a main result of the analysis, the critical portion of torque beyond which the character of fracture topography significantly changes is estimated to be within the range of 40-50% of a total loading. (C) 2007 Published by Elsevier Ltd.