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Microstructural Investigation and Mechanical Testing of an Ultrafine-grained Austenitic Stainless Steel
Chlupová, Alice ; Man, Jiří ; Polák, Jaroslav ; Karjalainen, L. P.
Special thermomechanical treatment based on high degree deformation followed by reversion annealing was applied to 301LN austenitic stainless steel to achieve ultrafine-grained (UFG) structure with considerably enhanced mechanical properties. Two different conditions of the thermomechanical treatment were adopted and resulting microstructures with different grain sizes were characterised by optical and high resolution scanning electron microscopy (SEM-FEG). Hardness measurements and tensile tests were performed to characterize mechanical properties. To reveal structural changes induced during thermomechanical treatment and during tensile tests a magnetic induction method was additionally applied. Experimental study validated the ability of the above special treatment to produce austenitic stainless steel with grain size about 1.4 m which exhibits tensile strength about 1000MPa while ductility remains on level about 60 %. The results obtained for both thermomechanical conditions are compared and the relationship between microstructure refinement, phase content and mechanical properties is discussed.
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Measurement of material hardness focused on metallic materials by dynamic method and using mobile hardness tester DHT-100
KOCH, Karel
During introduction this work describes dynamic method of hardness measurement particularly with focus on DHT-100 hardness tester. In the next part, history and development of hardness testing is being mentioned. Practical part of this work is dedicated to comparison of dynamic method with other known methods of hardness testing. Aim of this work was also to create work instructions for usage and measurements done by DHT-100 hardness tester. The work instructions are being described and introduced in practical part as well.
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Microstructure and hardness of TiB2
Halasová, Martina ; Bača, L. ; Šajgalík, P. ; Chlup, Zdeněk ; Dlouhý, Ivo
MICROSTRUCTURE AND HARDNESS OF TIB2 TiB2 in its pure form is extremely hard material with high melting point. This behaviour predetermines it to be used as e.g. nozzles, armour or wear parts. It is also very brittle and the effort is to decrease brittleness trough addition of various dopants. This contribution deals with the TiB2 dopped with Ta and Ni in various ratio. For observing the microstructure was used SEM and Vickers hardness was calculated by measuring the diagonals of indents. For comparison the values obtained by machine were shown in graph, too.
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Processing technology and quality of meat smoked mackerel
KÖLBL, Antonín
The technological process of smoked mackerel (Scomber scombrus) manufacture was described in detail with a focus on quality of muscle. The smoked mackerel brined in 6%, 12% and 15% of brine was monitored by texture profile analysis (TPA) using a cylindrical probe P 75 and spherical probe P 1S. Textural properties of muscle, such as hardness, cohesiveness, springiness and chewiness were evaluated. With increasing concentrations of brine muscle hardness and chewiness significantly decreases. In texture measuring, using a cylindrical probe P 75, in 6% of brine approximately 10.4 % higher hardness can be achieved, about 1 % higher chewiness and about approximately 5 % lower springiness expect, than when brined in 12% of brine. When brined in 15% of brine about 6.7 % lower hardness, about approximately 11.2 % lower chewiness and about 6.5 % lower springiness expect, than when brined in 12% of brine. When using a spherical probe P 1S is at brined in 6% of brine about approximately 6.5 % higher hardness and about approximately 11 % lower chewiness that brined in 12% of brine. When brined in 15% of brine about approximately 13 % lower springiness and approximately 21.7 % lower chewiness expect, than when brined in 12% of brine. To a lesser extent springiness was influenced, cohesiveness with increasing concentrations of salt in brine was unchanged. Texture measurements were supplemented by microbiological analysis of the total count of microorganisms (TCM). This analysis confirmed that with increasing concentrations of salt brine the count of microorganisms decreases (on 103 using 6% of brine and on 102 using 12% and 15% of brine) as a result of reduced water activity (aw).
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The effect of chemical degradation of surface layers on mechanical properties of wood
Drdácký, Miloš ; Kloiber, Michal ; Frankl, Jiří ; Bryscejn, Jan ; Tippner, J.
The aim of the research was the determination of the effect of chemical degradation on the surface layers of wooden constructional elements and their mechanical properties and also the depth which the damage reaches. The degradation of wood surface layers was caused by chemical reactions of some compounds contained within fire-prevention coatings applied repeatedly on wooden constructions of historic buildings in the past. These include e.g. ammonium sulphate and ammonium phosphate. This paper presents experimental procedures and results obtained through measuring of mechanical properties in the damaged layer of fibrillated wood and in wood without damage. The observed properties were wood compressive and tensile strength and wood hardness. The results proved a loss in cohesion and changes in mechanical properties only in a thin surface layer.
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Fractural based microstructural damane evaluation in Ni-based superalloy gas turbine blades
Tarafder, M. ; Dlouhý, Ivo ; Hore, S. ; Das, S. K.
A fractal based evaluation of microstructural damage in Ni based superalloy cast IN 738 LC used in gas turbine blades is presented in the paper. Non-destructive in-situ replica method was used without damaging the blades for the evaluation of microstructure. The theoretical life of the stator blades of the gas turbine, which was exposed to temperature varying between 1060°C to 1100°C, was approximately 100,000 hours. In order to assess the suitability of the stator blades after 50% of the service life, fractal based microstructural damage evaluation has been conducted. The fractal dimensions of the in situ metallographic images can be correlated to the progressive deterioration of hardness at various locations of the blades. The extent of damage is inversely proportional to the fractal dimension. For fractal dimension below 2.4, the material can be classified as substantially damaged.
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Studium mechanických vlastností DLC tenkých vrstev deponovaných v jedno a dvoufrekvenčním kapacitním výboji
Buršíková, V. ; Stoica, A. ; Sobota, Jaroslav ; Grossman, Jan ; Fořt, Tomáš ; Klapetek, P. ; Buršík, Jiří ; Bláhová, O.
Nanostructured diamond-like carbon coatings were deposited on several different substrate materials (silicon, glass, polycarbonate and steel) in single (13.56 MHz) and dual capacitive r.f. discharges (LF=100-300kHz, HF =13.56 MHz). The objective of our study was to find the optimum combination of the high and low frequency (continuous or pulsed) excitation enabling to cover uneven substrate surfaces and significant lowering of the internal stress in films.
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Studium mechanických vlastností gradovaných amorfních DLC povlaků deponovaných PECVD
Buršíková, V. ; Stoica, A. ; Sobota, Jaroslav ; Grossman, Jan ; Fořt, Tomáš ; Klapetek, P. ; Buršík, Jiří ; Peřina, Vratislav ; Bláhová, O.
For optimisation of performance of the coating there is necessary to optimise the following materials parameters: the elastic modulus, hardness, surface strength, film fracture toughness and film-substrate adhesion. We proposed to protect the substrate surface with graded coating, which has monotonically graded elastic modulus and Poisson's ratio.
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