Krzysztof Zaba

Prof. Krzysztof Zaba

Non-Ferrous Metals, AGH University of Science and Technology, Kraków, Małopolskie, Poland
orcid

Research Focus & Metrics

Academic Career Length

19Years (2008-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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2 July 2021 in Materials
Verified
Journal Article
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Marcin SzpunarMarcin Szpunar
Marcin Szpunar
Tomasz TrzepiecińskiTomasz Trzepieciński
Tomasz Trzepieciński
Krzysztof ZabaKrzysztof Zaba
Krzysztof Zaba
RORobert Pawel Ostrowski
Robert Pawel Ostrowski
MZMarek Zwolak
Marek Zwolak
The aim of the research described in this paper is to analyse the synergistic effect of types of synthetic oil and their density on the value of the coefficient of friction (COF) of Ti-6Al-4V titanium alloy sheets. Lubrication performance of commercial synthetic oils (machine, gear, engine and hydraulic) was tested in a strip draw friction test. The friction tests consisted of pulling a strip specimen between two cylindrical fixed countersamples. The countersamples were placed in the simulator base mounted on a uniaxial tensile test machine. Due to the complex synergistic effect of different strip drawing test parameters on the COF, artificial neural networks were used to find this relationship. In the case of both dry and lubricated conditions, a clear trend was found of a reduction of the coefficient of friction with nominal pressure. Engine oil 10W-40 was found to be the least favourable lubricant in reducing the coefficient of friction of Grade 5 titanium sheets. The two main tribological mechanisms, i.e., galling and ploughing, played the most important role in the friction process on the test sheets. In the range of nominal pressures considered, and with the synthetic oils tested, the most favourable lubrication conditions can be obtained by using a type of oil with a low viscosity index and a high kinematic viscosity.

7 June 2021 in Materials
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PNPiotr Noga
Piotr Noga
LTLechosław Tuz
Lechosław Tuz
Krzysztof ZabaKrzysztof Zaba
Krzysztof Zaba
AZAdam Zwoliński
Adam Zwoliński
Recycling of raw materials and is crucial for the production of new products for the global economy. The aim here is, on the one hand, to reduce energy consumption, and, on the other hand, to obtain materials with similar functional properties. The study undertook research on the possibility of processing AlSi11 aluminum chips by compaction and co-extruding to obtain a product in the form of a flat bar with mechanical properties not lower than those of the cast materials. The performed tests and the developed technique allowed to obtain flat bars with more favorable mechanical properties (Yield Strength YS ≥ 155 MPa; Ultimate Tensile Strength UTS ≥ 212 MPa) than the castings (YS ≥ 70 MPa ≥ 150 MPa). The weldability evaluation tests revealed that the material is susceptible to porosity. The presence of pores, which reduces the cross-section (up to 60%), reduces the tensile strength (up to 20 MPa). The typical joint structure and plasticity is obtained, which indicate the possibility of tensile strength improvement.

16 June 2022 in Materials
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Tomasz TrzepiecińskiTomasz Trzepieciński
Tomasz Trzepieciński
Marcin SzpunarMarcin Szpunar
Marcin Szpunar
Andrzej DzierwaAndrzej Dzierwa
Andrzej Dzierwa
Krzysztof ZabaKrzysztof Zaba
Krzysztof Zaba
The article presents the results of the analysis of the influence of incremental sheet forming process parameters on surface roughness measured on both sides of conical drawpieces made from pure titanium Grade 2 sheets. The experimental plan was created on the basis of a central composite design. The study assumed the variability of feed rate, spindle speed, and incremental step size in the following range: 500–2000 mm/min, 0–600 rpm, and 0.1–0.5 mm, respectively. Two strategies differing in the direction of the tool rotation in relation to the feed direction were also analysed. Analysis of variance is performed to understand the adequacy of the proposed model and the influence of the input parameters on the specific roughness parameter. The sensitivity of the process parameter on the selected surface roughness parameters was assessed using artificial neural networks. It was found that the change in the surface roughness of the inner surface of the drawpiece is not related to the change of surface roughness of the outer side. The morphology of the outer surface of the draw pieces was uniform with a much greater profile height than the inner surface that had interacted with the tool. Taking into account the outer surface of the drawpiece, the direction of tool rotation is also most closely correlated with the parameters Sa, Sz, and Sku. Step size and feed rate provide the highest information capacity in relation to skewness and kurtosis of the inner surface of the drawpiece.

23 April 2021 in Materials
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Krzysztof ZabaKrzysztof Zaba
Krzysztof Zaba
Tomasz TrzepiecińskiTomasz Trzepieciński
Tomasz Trzepieciński
SPSandra Puchlerska
Sandra Puchlerska
PNPiotr Noga
Piotr Noga
MBMaciej Balcerzak
Maciej Balcerzak
The paper is devoted to highlighting the potential application of the quantitative imaging technique through results associated with work hardening, strain rate and heat generated during elastic and plastic deformation. The aim of the research presented in this article is to determine the relationship between deformation in the uniaxial tensile test of samples made of 1-mm-thick nickel-based superalloys and their change in temperature during deformation. The relationship between yield stress and the Taylor–Quinney coefficient and their change with the strain rate were determined. The research material was 1-mm-thick sheets of three grades of Inconel alloys: 625 HX and 718. The Aramis (GOM GmbH, a company of the ZEISS Group) measurement system and high-sensitivity infrared thermal imaging camera were used for the tests. The uniaxial tensile tests were carried out at three different strain rates. A clear tendency to increase the sample temperature with an increase in the strain rate was observed. This conclusion applies to all materials and directions of sample cutting investigated with respect to the sheet-rolling direction. An almost linear correlation was found between the percent strain and the value of the maximum surface temperature of the specimens. The method used is helpful in assessing the extent of homogeneity of the strain and the material effort during its deformation based on the measurement of the surface temperature.

27 October 2022 in Materials
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RSRyszard Sitek
Ryszard Sitek
SPSandra Puchlerska
Sandra Puchlerska
IRIlona Helena Różycka
Ilona Helena Różycka
KMKamil Majchrowicz
Kamil Majchrowicz
ZPZbigniew Pakiela
Zbigniew Pakiela
JMJarosław Mizera
Jarosław Mizera
The article presents the results of research on the influence of plastic deformation on the microstructure and tensile strength of Haynes 282 nickel superalloy produced by direct metal laser sintering (DMLS) and a conventional technique (casting). Samples were tested for dimensional accuracy using a 3D scanner. Then, the samples were subjected to plastic deformation by rolling. The microstructures of the DMLS and the as-cast samples were analysed using a scanning electron microscope. The strength properties of the samples were determined in a static tensile test. Microhardness measurements of the samples were also performed. Based on the analysis of the dimensional accuracy, it was found that the surface quality of the components produced by DMLS is dependent on the input parameters of the 3D printing process. Using the DMLS method, it is possible to produce Haynes 282 with a fine-crystalline microstructure containing dendrites. The fine-crystalline dendritic microstructure and low porosity showed very good tensile strength compared to the as-cast material. It was also found that the increase in the degree of plastic deformation of the as-cast Haynes 282 and the samples produced by the DMLS technique resulted in an increase in the strength of the tested samples, with reduced ductility.

30 December 2022 in Materials
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Krzysztof ZabaKrzysztof Zaba
Krzysztof Zaba
SPSandra Puchlerska
Sandra Puchlerska
LKLukasz Kuczek
Lukasz Kuczek
Tomasz TrzepiecińskiTomasz Trzepieciński
Tomasz Trzepieciński
PMPiotr Maj
Piotr Maj
Single Point Incremental Forming (SPIF) is an unconventional forming process that is suitable for prototype production and small lot production due to the economical tooling cost, short lead time, and the ability to create symmetrical and asymmetrical complex geometries without the use of expensive dies. This article presents the effect of the step size Δz of a forming tool made of 145Cr6 tool steel on the formability and maximum forming angle, mechanical properties, hardness, surface roughness, microstructure and texture of bimetallic Al/Cu sheets. Experiments were conducted at a constant rotational speed and feed rate, with the use of rapeseed oil as a lubricant. The tests were carried out with the use of a forming tool on both sides of the bimetallic sheet. The shape and dimensions of the formed elements are determined by non-contact optical 3D scanning. It has been proved that an increase in the step size Δz affects the deterioration of the surface quality of the specimens (an increase in the Ra parameter from 0.2 μm to approximately 3 μm for the step size of 1.2 mm), while a small step size down Δz favours the geometric stability of the samples. With increasing step size (at Δx = Δy = const.), the drawpiece wall continually thinned until the material fractured. Based on the results, it was shown that increasing the step size Δz over 1.1 mm causes cracking of the drawpieces. Furthermore, greater thinning of the Al/Cu sheet was observed in the range of step size Δz between 0.7 and 1.0 mm for aluminum side and step size Δz ≤ 0.6 mm and Δz ≥ 1.1 mm for copper side. It was also found that the mechanical properties of the bimetal sheet decreased as a result of incremental forming. The greatest decrease in strength and ductility was recorded for a pitch of 1.2 mm. Strength decreased from 230 MPa (for sheet in initial state) to approximately 80 MPa, elongation from 12% to approximately 8.5%, and hardness from 120 HV10 for Cu and 60 HV10 for Al to approximately 30 HV10 for both layers.