Wyniki wyszukiwania - BazTech

1

Stochastic model describing evolution of microstructural parameters during hot rolling of steel plates and strips

Szeliga Danuta, Czyżewska Natalia, Klimczak Konrad, Kusiak Jan, Kuziak Roman, Morkisz Paweł, Oprocha Piotr, Pietrzyk Maciej, Poloczek Łukasz, Przybyłowicz Paweł

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e139

EN

Enhancing strength-ductility synergy of materials has been for decades an objective of research on structural metallic materials. It has been shown by many researchers that significant improvement of this synergy can be obtained by tailoring heterogeneous multiphase microstructures. Since large gradients of properties in these microstructures cause a decrease of the local fracture resistance, the objective of research is to obtain smoother gradients of properties by control of the manufacturing process. Advanced material models are needed to design such microstructures with smooth gradients. These models should supply information about distributions of various microstructural features, instead of their average values. Models based on stochastic internal variables meet this requirement. Our objective was to account for the random character of the recrystallization and to transfer this randomness into equations describing the evolution of dislocations and grain size during hot deformation and during interpass times. The idea of this stochastic model is described in the paper. Experiments composed of uniaxial compression tests were performed to supply data for the identification and verification of the model in the hot deformation and static recrystallization parts. Histograms of the grain size were measured after hot deformation and at different times after the end of deformation. Identification and validation of the model were performed. The validated model, which predicts evolution of heterogeneous multiphase microstructure, is the main output of our work. The model was implemented in the finite element program for hot rolling of plates and sheets and simulations of these processes were performed. The model’s capability to compare and evaluate various rolling strategies are demonstrated in the paper.

2

The Influence of Different Assist Gases on Ductile Cast Iron Cutting by CO2 Laser

Meško J., Nigrovič R., Zrak A.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 4

109--114

EN

This article deals with the technology and principles of the laser cutting of ductile cast iron. The properties of the CO2 laser beam, input parameters of the laser cutting, assist gases, the interaction of cut material and the stability of cutting process are described. The commonly used material (nodular cast iron - share of about 25% of all castings on the market) and the method of the laser cutting of that material, including the technological parameters that influence the cutting edge, are characterized. Next, the application and use of this method in mechanical engineering practice is described, focusing on fixing and renovation of mechanical components such as removing the inflow gate from castings with the desired quality of the cut, without the further using of the chip machining technology. Experimental samples from the nodular cast iron were created by using different technological parameters of laser cutting. The heat affected zone (HAZ), its width, microstructure and roughness parameter Pt was monitored on the experimental samples (of thickness t = 13 mm). The technological parameters that were varied during the experiments included the type of assist gases (N2 and O2), to be more specific the ratio of gases, and the cutting speed, which ranged from 1.6 m/min to 0.32 m/min. Both parameters were changed until the desired properties were achieved.

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Fatigue Properties of AlSi7Mg Alloy with Diversified Microstructure

Tupaj M., Orłowicz A. W., Mróz M., Trytek A.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 3 spec.

87--90

EN

The paper discusses the effect of microstructure on the fatigue strength of AlSi7Mg casting alloy refined conventionally with hexachloroethane without modifying and modified with TiB and Na. Castings made of both alloy variants were subjected to T6 heat treatment. It turned out that the applied refining secured satisfactory compactness of the material. In view of absence of gas and shrinkage porosity in the castings, short cracks nucleated on largest silicon precipitates and largest intermetallic phase precipitations as these were the locations where stress concentrations reached their highest values. Comprehensive modification of the alloy resulted in reduction of the value of SDAS parameter characterizing α(Al) phase dendrites, a decrease of the distance between silicone precipitates in the eutectic λE, and a decrease of the maximum size of silicone precipitates lmaxSi. The ultimate effect of these changes was an increase of the fatigue strength.

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On the influence of geometric microstructural properties of porous materials on the modelling of a tubular fuel cell

Karcz M., Kowalczyk S., Badur J.

Chemical and Process Engineering

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2010

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Vol. 31, z. 3

489-503

EN

A numerical model of tubular solid oxide fuel cell (SOFC) with simplified one-dimensional current flux prediction is examined. The model takes into account geometric properties of porous sinters used for anode and cathode. Three characteristic parameters, i.e. porosity, tortuosity and mean pore radii have been considered. The obtained numerical results allow one to estimate the influence of various geometric properties of porous materials on the fuel cell performance by means of average and local variables.

PL

Przedstawiono wyniki analizy numerycznej modelu rurkowego ogniwa paliwowego uwzględniającego podstawowe mikrostrukturalne parametry geometryczne porowatych elektrod. Rozważano trzy podstawowe parametry geometryczne: porowatość, krętość oraz średni wymiar porów. Uzyskane rezultaty umożliwiają ocenę wpływu poszczególnych wielkości charakteryzujących obszar porowaty na globalne osiągi ogniwa i lokalne wartości temperatury i gęstości prądu.