Leszek Frąś, M.Sc., Eng.

Department of Theory of Continuous Media and Nanostructures (ZTOCiN)
Division of Polymer Physics (PFP)
position: specialist
telephone: (+48) 22 826 12 81 ext.: 260
room: 233
e-mail: lfras

Recent publications
1.Frąś T., Frąś L.J., Faderl N., RUBBER AND MAGNETORHEOLOGICAL FLUID APPLIED AS THE INTERLAYER IN COMPOSITE ARMOURS AGAINST HIGH-VELOCITY LOADINGS, DIAGNOSTYKA, ISSN: 1641-6414, Vol.18, No.3, pp.63-68, 2017
Abstract:

Monolithic, homogenous ballistic shields consisting of a single thick, high-hardness and high-strength steel plate are rarely applied in modern combat vehicles. Currently, a popular armour concept is a multilayered shield since it is expected that the kinetic energy of a threat may be dissipated by transmission through materials with different properties and also by multiple interface reflections. Searching for a maximum ballistic protection at minimum weight inspires applications of various materials which complementary behaviour provides a high protective efficiency without excessive mass. The preliminary experimental investigation presented in the paper aimed to verify behaviour of two prototyped laminated armours under impacts of small-calibre projectiles (cal. 7.62). The main interest lied in impact properties of materials proposed as the intermediate layer. The first tested concept was a laminated steel armour with the 10 mm thick rubber interlayer. In the second armour, the intermediate layer consisted of a magnetorheological fluid.

Keywords:

energy absorption, rubber, magnetorheological fluid, protective properties

Affiliations:
Frąś T.-other affiliation
Frąś L.J.-IPPT PAN
Faderl N.-French-German Research Institute of Saint-Louis (DE)
2.Frąś L.J. , The Perzyna Viscoplastic Model in Dynamic Behaviour of Magnetorheological Fluid under High Strain Rates, ENGINEERING TRANSACTIONS (ROZPRAWY INŻYNIERSKIE), ISSN: 0867-888X, Vol.63, No.2, pp.233-243, 2015
Abstract:

The extension of viscoplastic model of Perzyna for the field of magnetorheological materials is proposed. Perzyna’s approach is adopted to identify the mechanisms of microscopic rearrangement of ferroelements producing visible increase of material stiffness, in particular increase of shear modulus. The project of laboratory test stand is presented. It is based on Split-Hopkinson pressure bar set-up equipped with container for magnetorheological fluid and coil to control it

Keywords:

magnetorheological fluid, magnetorheological gel, Perzyna viscoplastic model, Split-Hopkinson pressure bar

Affiliations:
Frąś L.J. -IPPT PAN

Conference abstracts
1.Frąś L.J., Pęcherski R.B., DYNAMIC BEHAVIOUR OF MAGNETHOREOLOGICAL MATERIALS , MatCel’2017 & DynMatCel’2017, Cellular Materials: Structural Behaviour, Modelling and Characterisation, 2017-09-25/09-27, Aveiro (PT), pp.17-18, 2017
Abstract:

The magnethoreological material is based on the ferroparticles immersed in carrying fluid. The acting magnetic field is forcing ferroelements to connect into characteristic structure - braids. Behaviour of the magnethoreological material at the high strain rates will be described by Perzyna model. The created model will be verified with use of dedicated laboratory set up.

Keywords:

magnethoreological material, viscoplasticity model, dynamic behaviour, ferroelements.

Affiliations:
Frąś L.J.-IPPT PAN
Pęcherski R.B.-IPPT PAN
2.Chrzanowska J., Denis P., Mościcki T., Hoffman J., Garbiec D., Frąś L.J. , Szymański Z., Characterization of tungsten boride layers deposited in pulsed laser ablation process, SolMech 2016, 40th Solid Mechanics Conference, 2016-08-29/09-02, Warszawa (PL), No.P257, pp.1-2, 2016
Abstract:

Tungsten boride compounds are very promising new hard and super - hard materials. This kind of materials could be used in production of high-speed tools, durable bearings and nonabrasive surfaces. The hardness of tungsten borides strongly depends on boron content as well as material microstructure. For example hardness of W2B is about 12.4 GPa, WB hardness is 18 – 36 GPa, WB2 hardness is 28.5–39.7 GPa and WB3 hardness is 28.6 – 36.9 GPa. Moreover production of tungsten borides in the form of layers or nano -grained structured increase its hardness even above 40 GPa. Although the properties of tungsten boride structures are known from theoretical calculations, the data concerning structures produced experimentally are scare. Therefore, the properties of tungsten boride layers deposited by pulsed laser deposition (PLD) process are investigated in this paper. Layers were deposited using two types of targets: with boron to tungsten ratio of 2.5:1 and 4.5:1 and with the use of two laser wavelengths: 355 and 1064 nm.

Keywords:

pulsed laser deposition, tungsten borides

Affiliations:
Chrzanowska J.-IPPT PAN
Denis P.-IPPT PAN
Mościcki T.-IPPT PAN
Hoffman J.-IPPT PAN
Garbiec D.-other affiliation
Frąś L.J. -IPPT PAN
Szymański Z.-IPPT PAN
3.Frąś L.J., Jarząbek D., Dziekoński C., Pęcherski R.B., Viscoplastic deformation of magnethoreological solids, SolMech 2016, 40th Solid Mechanics Conference, 2016-08-29/09-02, Warszawa (PL), No.P244, pp.1-2, 2016
Abstract:

The microsized (~10µm) ferroelements build the structure of magenthoreological (MR) fluid. This two phase material in neutral state behaves as a fluid but in magnetic field becomes a solid and has properties of elasto-viscoplastic material. This is due to the skeleton made by ferrolements connected into braids. The aim of the paper is to identify the physical mechanisms of deformation of such a structure with use of own set up for in situ microscopic observations.

Keywords:

magnethoreological solids, viscoplasticity, ferroelements, compression test, shear banding

Affiliations:
Frąś L.J.-IPPT PAN
Jarząbek D.-IPPT PAN
Dziekoński C.-IPPT PAN
Pęcherski R.B.-IPPT PAN
4.Nowak M., Pęcherski R.B., Nowak Z., Frąś L.J., Numeryczna rekonstrukcja struktury pianek otwartokomórkowych z wykorzystaniem tomografii komuterowej, OMIS'2015, XI Konferencja Odkształcalność Metali i Stopów, 2015-11-17/11-20, Łańcut (PL), pp.61-62, 2015
Abstract:

Przedmiotem badań niniejszej pracy jest numeryczna rekonstrukcja struktur rzeczywistych pianek otwartokomórkowych w celu wygenerowania reprezentatywnego elementu objetości. Analizowane są dwa rodzaje pianek (ceramiczna i polimerowa), których porowatość wynosi odpowiednio 90% i 94%. Oba rodzaje pianek zostały przebadane z użyciem mikrotomografu komputerowego. Uzyskane dane zostały zaimportowane do programu ScanIP, przy pomocy którego przeprowadzono cyfrową obróbkę uzyskanych obrazów oraz wydzielono fazę reprezentującą szkielet pianki.

Keywords:

numeryczna rekonstrukcja, struktury otwartokomórkowe, pianki metaliczne, mikrotomografia komputerowa

Affiliations:
Nowak M.-IPPT PAN
Pęcherski R.B.-IPPT PAN
Nowak Z.-IPPT PAN
Frąś L.J.-IPPT PAN
5.Frąś L.J., Konowrocki R., Pęcherski R.B., Niesprężyste deformacje materiałów magnetoreologicznych. Doświadczalna wizualizacja i model fizyczny, OMIS'2015, XI Konferencja Odkształcalność Metali i Stopów, 2015-11-17/11-20, Łańcut (PL), pp.13-14, 2015
Abstract:

Magnetorheological materials are commonly used in technical devices because of specific behaviour in magnetic field. The magnetoactive particles are immersed in the carried fluid. The material becomes solid under the influence of magnetic field. The structure of solid material consists of the chains of the particles lying along the direction of magnetic field and the material under the stress is deforming as a solid body. The present studies are focused on the microscopic and phenomenological models of non-newtonian fluid. However, the mechanisms of deformation in solidified material under magnetic field require further investigations. The aim of the paper is to present the experimental visualization of the rearrangements of the particles in the activated by magnetic field chains. Basing on microscopic observations, the hypothesis is formulated that the mechanism of micro-shear banding is responsible for inelastic deformation of magnetorheological material. The discussed physical model makes the basis of the material description within the framework of the Perzyna viscoplasticity theory.

Keywords:

magnetorheological fluid, magnetorheological gel, Perzyna viscoplastic model

Affiliations:
Frąś L.J.-IPPT PAN
Konowrocki R.-IPPT PAN
Pęcherski R.B.-IPPT PAN
6.Frąś L.J., Pęcherski R.B., Viscoplasticity of magnetorheological materials - theoretical description and experimental investigations, PCM-CMM 2015, 3rd Polish Congress of Mechanics and 21st Computer Methods in Mechanics, 2015-09-08/09-11, Gdańsk (PL), pp.673-674, 2015
Abstract:

The extension of viscoplasticity Perzyna's model for the field of magnetorheological materials is proposed. The model is adopted to identify the mechanisms of microscopic rearrangement of ferroelements producing visible increase of material stiffness, in particular increase of shear modulus. The project of laboratory test stand is presented. It is based on Split Hopkinson Pressure Bar set-up equipped with container for magnetorheological fluid and coil to control it.

Keywords:

magnetorheological fluid, magnetorheological gel, Pezryna viscoplasticity model, Split Hopkinson Pressure Bar

Affiliations:
Frąś L.J.-IPPT PAN
Pęcherski R.B.-IPPT PAN
7.Pęcherski R.B., Nowak M., Frąś L.J. , Numerical simulations of auxetic metallic foam fabrication process, PCM-CMM 2015, 3rd Polish Congress of Mechanics and 21st Computer Methods in Mechanics, 2015-09-08/09-11, Gdańsk (PL), pp.857-858, 2015
Abstract:

The subject of te study are metallic open-cell foams. In particular, the foam of Cu skeleton is considered. To simulate the deformation process of such a material the finite element program ABAQUS is used. The tomogram reconstructing the 3D virtual volume of a real foam structure with the use of computed tomography is applied to formulate the finite element model of the convex open-cell foam cube of the edge of 800 voxels created with application of ABAQUS/CAE. The initial cube of convex open-cell skeleton is subjected to three-axial compression applied as uniform displacements normal to the surface of cube faces in order to simulate numerically auxetic foam fabrication process.

Keywords:

auxetic foam, micro-tomography, tomograms, negative Poisson's ration, numerical simulation, metallic foam, open-cell foam, foam fabrication

Affiliations:
Pęcherski R.B.-IPPT PAN
Nowak M.-IPPT PAN
Frąś L.J. -IPPT PAN

Patents
Numer/data zgłoszenia patentowego
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Twórca / twórcy
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pdf
421696
2017-05-24
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Frąś L., Kołbuk-Konieczny D., Pręgowska A.
Uchwyt pomiarowy do Dzielonego Pręta Hopkinsona oraz sposób pomiaru zachowania materiału, w którym stosuje się Dzielony Pręt Hopkinsona
PL, Instytut Podstawowych Problemów Techniki PAN
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