Wyniki wyszukiwania - BazTech

1

Crystal plasticity elastic-plastic rate-independent numerical analyses of pollycrystalline materials

Wójcik Marta, Skrzat Andrzej, Stachowicz Feliks, Spišák Emil

Advances in Mechanical and Materials Engineering

|

2023

|

Vol. 40, nr 1

63--78

EN

Macroscopic analyses of plastic forming processes give only the overall description of the problem without the consideration of mechanisms of plastic deformation and the microstructure evolution. For the consideration of these processes, numerical simulations within crystal plasticity include the change of texture, anisotropy, and strain hardening of the material are used. In this paper, a crystal plasticity rate-independent model proposed by Anand and Kothari is applied for numerical analyses of polycrystalline materials. The slip was considered as the main mechanism of the plastic deformation. Basic constitutive equations of crystal plasticity for large deformation theories are presented. The selected results of elastic-plastic problems obtained using both macro- and micro- scales software for the explicit and implicit integration are featured here. The heterogeneous distribution of strain and stress in different grains are obtained, which is associated with the various crystal orientation. The crystal plasticity modelling of materials subject to plastic deformation involves not only the information about the change of a material’s shape in a macro-scale, but also describes the phenomena occurring in material in a micro-scale.

PL

Analizy makroskopowe procesów przeróbki plastycznej prezentują jedynie ogólny zarys rozważanego problemu, bez uwzględnienia mechanizmów odkształcenia plastycznego oraz ewolucji mikrostruktury. W celu rozważania procesów przeróbki plastycznej stosowane są symulacje numeryczne w ramach teorii plastyczności kryształów uwzgledniające zmianę tekstury, anizotropię oraz umocnienie odkształceniowe. W artykule zaprezentowano zastosowanie modelu Ananda i Kothari w ramach teorii plastyczności kryształów niezależnej od prędkości odkształcenia do rozwiązywania analiz numerycznych dla materiałów polikrystalicznych. W badaniach uwzględniono poślizg dyslokacyjny jako główny mechanizm odkształcenia plastycznego. Zaprezentowano wybrane rezultaty dla problemów sprężysto-plastycznych uzyskane zarówno w skali makro, jak i mikro- dla całkowania typu explicit i implicit. Uzyskano niejednorodny rozkład naprężenia i odkształcenia w poszczególnych ziarnach, związany z różną orientacją kryształów. Modelowanie numeryczne zzastosowaniem teorii plastyczności kryształów dla materiałów poddanych plastycznemu odkształceniu dostarcza nie tylko informacje o zmianie kształtu materiału w skali makro, ale także opisuje zjawiska zachodzące w materiale w skali mikro-.

2

Joining the High-Strength Steel Sheets Used in Car Body Production

Kaščák Ľuboš, Cmorej Denis, Spišák Emil, Slota Ján

Advances in Science and Technology. Research Journal

|

2021

|

Vol. 15, no 1

184--196

EN

Nowadays, there are several important reasons for using high-strength sheets in the manufacturing of car bodies. Car manufacturers choose the steel with good formability, fatigue resistance and ability to absorb impact energy. Microalloyed steels and dual-phase steels are the materials which fulfil the above-mentioned criteria. The application of high-strength sheets has led to the development of new materials joining techniques. Mechanical joining, such as clinching, is the innovative technique to join these progressive materials. Materials of different thicknesses can be joined by clinching. The paper focuses on the comparison of the properties of the joints made by clinching and resistance spot welding. The application of resistance spot welding is still the most used joining method in car body production. These properties were investigated by tensile test and metallographic observation. The HCT600X+ZF, HCT600X+Z and HX420LAD+Z steel sheets were used for the experiments. The results of tensile test show that the values of load-bearing capacity of clinched joints reached from 3900 N to 5900 N and the resistance spot welded joints reached the values of load-bearing capacity from 12000 N to 19500 N. In comparison to the resistance spot welded joints, the clinched joints reached from 32 to 48% of load-bearing capacity.

3

Management of research and development activities in the context of strategy Europe 2020

Duľová Spišáková Emília, Gontkovičová Barbora, Majerníková Janka, Spišák Emil, Pacana Andrzej

Polish Journal of Management Studies

|

2019

|

Vol. 19, No. 2

112--123

EN

The aim of the article is to evaluate the current situation of research and development management in the view of the fulfillment of the strategy of Europe 2020 by Poland and Slovakia and, based on the results of analysis, to predict the expected development of the indicator by 2020 and assesses the reaching their national targets in monitored area. Regression analysis is used to estimate the trends feature for predicting the expected development of the indicator expressing the share of expenditure on R&D of GDP in 2020. To describe and evaluate the development of monitored indicator during the 11 or 22 years period, we are using trend comparison. Based on the stated results it is possible to determine the predicted values of the indicator in the future and then evaluate whether that country will manage to achieve its set target by 2020.

PL

Celem artykułu jest ocena aktualnej sytuacji zarządzania badaniami i rozwojem przez Polskę i Słowację, pod kątem realizacji strategii „Europa 2020” oraz w oparciu o wyniki analizy, prognozowanie oczekiwanego rozwoju wskaźnika do 2020 roku i ocenę celów krajowych w monitorowanym obszarze. Analiza regresji posłużyła do oszacowania charakterystyki trendów dla prognozowania oczekiwanego rozwoju wskaźnika wyrażającego udział wydatków na B + R w PKB do 2020 r. Do opisu i oceny rozwoju monitorowanego wskaźnika w okresie 11 lub 22 lat wykorzystano porównanie trendów. Na podstawie otrzymanych wyników można określić przewidywane wartości wskaźnika w przyszłości, a następnie ocenić, czy krajowi uda się osiągnąć wyznaczony cel do 2020 roku.

4

Influence of the surface roughness of Ti6Al7Nb alloy on its behavior in biotribological systems

Piotrowska Katarzyna, Madej Monika, Spišák Emil, Ozimina Dariusz

Journal of Machine Construction and Maintenance - Problemy Eksploatacji

|

2019

|

no. 3

19--29

EN

The paper presents the results of studies of Ti6Al7Nb alloy properties used in biotribological systems. The following physicochemical treatments of the alloy were compared: polishing, sandblasting, etching as well as sandblasting and etching. Element identification was performed using a scanning electron microscope equipped with an EDS microanalyser. Scanning and confocal microscopy was used to observe surface morphology and topography. Frictional tests were carried out using a ball-disk coupling in reciprocating motion in technically dry friction and friction with lubrication with Ringer’s solution. An optical tensiometer was used to determine the contact angle. As a result of the applied physicochemical treatments, surfaces of different morphology and geometric surface structure were obtained. The polished and etched sample had the most homogeneous surface. It was found that surface roughness significantly influences tribological properties. For the samples characterized by micro roughness of the surface, the best characteristics were obtained under conditions of technically dry friction. However, under the conditions of lubrication with Ringer's solution, the properties were the best for the samples characterized by nanoroughness. Ringer's solution reduced resistance to motion by approximately 20%. A negative influence of surface development on wetting was also found.

PL

Przedstawiono wyniki badań właściwości stopu Ti6Al7Nb stosowanego w systemach biotribologicznych. Porównano ze sobą stop poddany następującym obróbkom fizykochemicznym: polerowaniu, piaskowaniu, trawieniu oraz piaskowaniu i trawieniu. Za pomocą mikroskopii skaningowej i konfokalnej obserwowano morfologię i topografię powierzchni. Identyfikację pierwiastków wykonano przy użyciu skaningowego mikroskopu elektronowego wyposażonego w mikroanalizator EDS. Badania tarciowe zrealizowano w skojarzaniu kula–tarcza w ruchu posuwisto-zwrotnym w warunkach tarcia technicznie suchego oraz tarcia ze smarowaniem płynem Ringera. Do wyznaczenia kąta zwilżania wykorzystano tensjometr optyczny. W wyniku zastosowanych obróbek fizykochemicznych uzyskano powierzchnie o zróżnicowanej morfologii oraz strukturze geometrycznej powierzchni. Najbardziej jednorodną powierzchnią charakteryzowała się próbka polerowana oraz trawiona. Stwierdzono, że chropowatość powierzchni znacząco wpływa na właściwości tribologiczne. Dla próbek charakteryzujących się mikrochropowatością powierzchni uzyskano najlepsze charakterystyki w warunkach tarcia technicznie suchego. Natomiast w warunkach smarowania płynem Ringera były one najlepsze dla próbek wyróżniających się nanochropowatością. Płyn Ringera wpłynął na zmniejszenie oporów ruchu o około 20%. Wykazano również negatywny wpływ rozwinięcia powierzchni na zwilżalność.

5

The evaluation of properties of mechanically clinched joints made of ferrous and non-ferrous materials

Kaščák Ľuboš, Spišák Emil, Kubík René, Majerníková Janka

Advances in Science and Technology. Research Journal

|

2018

|

Vol. 12, no 1

162--170

EN

Nowadays, there are several reasons for the utilization of the sheets made of aluminum in the car body production. Besides decreasing the car body weight, there is a need to reduce fuel consumption of the vehicle as well as the environmental impact by lower production of emissions. Moreover, such reasons are mutually dependent or influence each other. The application of the aluminum sheets in hybrid car body production resulted in the need for innovative joining techniques, which could make it possible to successfully join sheets from aluminum alloys. Mechanical clinching is one of the new or innovative joining techniques, which belongs to cold-forming joining process, which makes it possible to join different kinds and thicknesses of sheets. Individual materials and thicknesses can be combined. The mechanically clinched joints are durable, and the joining process duration is very fast (duration of 1s) and does not have a distinctive impact on the environment; a protective layer of the sheets remains intact. The paper focuses on the evaluation of the properties of hybrid joints that were prepared by the single stroke clinching process with a rigid die. The hot-dip galvanized steel sheets DC06 and H220PD combined with the sheets from aluminum alloys EN AW 5754 (having different values of the hardness – H11, H22, and H24) and EN AW 6082 were used for joining. The results from experiments confirmed the mechanical clinching is the suitable technique for joining such combination of sheets. However, some considerations, such as the arrangement of the sheets about the punch and die, must be regarded.

6

Forming analysis of continuosly annealed, double reduced steel sheets

Spišák Emil, Majerníková Janka, Mulidrán Peter, Kaščák Ľuboš, Slota Ján

Advances in Science and Technology. Research Journal

|

2018

|

Vol. 12, no 3

168--172

EN

The paper deals with the forming analysis of continuously annealed steel sheets double reduced. Six different metal sheet grades were evaluated in the paper, thickness was in the range from 0.15 to 0.175 mm. Described are the used methods and the results obtained by a uniaxial tensile test, biaxial test (bulge test) and a springback test.

7

Analysis of the Change in Thickness of the Thin Double Reduced Steel Sheets by Drawing of Cups

Majerníková Janka, Spišák Emil, Kaščák Ľuboš, Slota Ján

Advances in Science and Technology. Research Journal

|

2018

|

Vol. 12, no 4

28--34

EN

During the processing of the thin packaging sheets by drawing, thickness of the material changes and so does the thickness of tin layer, this has an influence on corrosion resistance. Change in material thickness of the cylindrical cups without a flange has been evaluated in this contribution. Cups were produced from the double reduced continuously annealed packaging sheets. After cupping test, the anisotropy of these sheets was evaluated too, this was expressed through the earring formation on the cups.