Instytut Podstawowych Problemów Techniki
Polskiej Akademii Nauk


dr inż. Kajetan Wojtacki

Zakład Mechaniki Materiałów (ZMM)
Zespół Modelowania Materiałów (ZeMM)
stanowisko: adiunkt
telefon: (+48) 22 826 12 81 wewn.: 430
pokój: 238
ORCID: 0000-0002-7520-8274

Ostatnie publikacje
1.  Majkut M., Kwiecińska-Piróg J., Wszelaczyńska E., Pobereżny J., Gospodarek-Komkowska E., Wojtacki K., Barczak T., Antimicrobial activity of heat-treated Polish honeys, Food Chemistry, ISSN: 0308-8146, DOI: 10.1016/j.foodchem.2020.128561, pp.1-6, 2020

Bactericidal properties of honey depend on botanical and geographical origin, where thermal treatment can have a significant affect. The aim of this study was to investigate the effect of temperature on minimum bactericidal concentration (MBC), vitamin C content, total polyphenols content and antioxidant capacity of ferric reducing antioxidant potential (FRAP) of several nectar honey varieties from northern Poland (lime, rapeseed, multifloral and buckwheat). The honeys were subjected to thermal treatment at 22 °C, 42 °C, 62 °C, 82 °C and 100 °C for two exposure times. The results showed a significant reduction of antimicrobial properties (MBC 50%) at 82 °C and 62 °C after 15 and 120 min exposure time for most samples. Short time exposure reduced vitamin C content (50 %) but increased total polyphenols content (27%) and FRAP value (106%).

Słowa kluczowe:
honey, vitamin C, polyphenols, antioxidant properties, antibacterial activity, temperature treatment

Afiliacje autorów:
Majkut M. - UTP University of Science and Technology (PL)
Kwiecińska-Piróg J. - Nicolaus Copernicus University (PL)
Wszelaczyńska E. - UTP University of Science and Technology (PL)
Pobereżny J. - UTP University of Science and Technology (PL)
Gospodarek-Komkowska E. - Nicolaus Copernicus University (PL)
Wojtacki K. - IPPT PAN
Barczak T. - University Paris-Saclay - LIMSI laboratory (FR)
2.  Wojtacki K., Vincent P.G., Suquet P., Moulinec H., Boittin G., A micromechanical model for the secondary creep of elasto-viscoplastic porous materials with two rate-sensitivity exponents: application to a mixed oxide fuel, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2018.12.026, Vol.184, pp.99-113, 2020

This study deals with the secondary creep of a porous nuclear fuel. This material is composed of an isotropic matrix, weakened by randomly distributed clusters of pores. The viscous strain in the matrix is described by two power-law viscosities corresponding to two different creep mechanisms. The material microstructure is analyzed and appropriate descriptors of its morphology are identified. Representative Volume Elements (RVE's) are generated according to these descriptors. The local fields and overall response of these realizations RVE's are simulated within the framework of periodic homogenization using a full-field computational method based on Fast Fourier Transforms. An analytical model based on appropriate approximations of the effective potential governing the overall response of porous materials under creep is proposed. The accuracy of the model is assessed by comparing its predictions with full-field simulations and the agreement is found to be quite satisfactory.

Słowa kluczowe:
porous media, viscoplasticity, FFT method, homogenization, mathematical morphology, microstructures

Afiliacje autorów:
Wojtacki K. - IPPT PAN
Vincent P.G. - Institut de Radioprotection et de SûretéNucléaire (FR)
Suquet P. - Aix-Marseille Université (FR)
Moulinec H. - Aix-Marseille Université (FR)
Boittin G. - Aix-Marseille Université (FR)
3.  Wojtacki K., Daridon L., Monerie Y., Computing the elastic properties of sandstone submitted to progressive dissolution, INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, ISSN: 1365-1609, DOI: 10.1016/j.ijrmms.2016.12.015, Vol.95, pp.16-25, 2017

We present a numerical method for estimating the stiffness-to-porosity relationships for evolving microstructures of Fontainebleau sandstone. The proposed study is linked to geological storage of CO 2 and focuses on long-term and far field conditions, when the progressive degradation of the porous matrix can be assumed to be homogeneous at the sample scale. The method is based on microstructure sampling with respect to morphological descriptors extracted from microtomography. First, an efficient method of generation of accurate numerical media is proposed. The method is based on grain deposit, compaction and diagenesis and allows to reproduce user-defined morphological parameters. Second, two simple numerical models that mimic chemical degradation of porous aquifers are presented. Effective elastic properties are estimated within the framework of periodic homogenization and finite element approach. A fixed-point method on a self-consisted outer layer allows to consider non-periodic representative volume elements. Accurate predictions of elastic properties over a wide range of porosity are obtained. The overall evolutions of elastic behaviour due to the increase of porosity are in excellent agreement both, with experimental data and the results obtained by Arns et al. [1].

Słowa kluczowe:
Porous media, X-ray microtomography, Numerical dissolution, Fontainebleau sandstone, Self-consisted numerical method, Homogenization

Afiliacje autorów:
Wojtacki K. - inna afiliacja
Daridon L. - Université de Montpellier (FR)
Monerie Y. - Université de Montpellier (FR)

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