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1
Content available Enceladus as a place of origin of life in Solar System
Czechowski L.
Geological Quarterly
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2018
|
Vol. 62, No. 1
172--180
EN
Enceladus, a satellite of Saturn, with its radius of 250 km, is the smallest geologically active celestial body in the Solar System. My model of core origin and evolution indicates that for hundreds of My after accretion Enceladus was an appropriate body for an origin of life. I continue consideration of the hypothesis that Enceladus was a cradle of life in the Solar System. I found that simple organisms could be ejected in icy grains into the space by volcanic jets or by meteoroid impacts. Several mechanisms could be responsible for later transport of the grains to the early Earth and other terrestrial planets. Eventually I suggest that Enceladus is the most appropriate body for a cradle of life in the Solar System.
2
Content available Experimental and numerical three-point bending test for sandwich beams
Czechowski L., Jankowski J., Kotełko M.
Journal of KONES
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2017
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Vol. 24, No. 3
53--62
EN
The article deals with an experimental investigation of mechanical properties of sandwich beams obtained from bending tests. The tested specimens consisted of foam or honeycomb core and face sheets made of aluminium alloys, plywood or composite material. The face sheets and the core were bonded with glue material. Beams of different dimensions, namely beam width, as well as core and face sheets thickness, were tested. Three point bending tests were carried out, which mid span deflections of the beam versus applied force were recorded. Experimental test results were compared with simulations on the basis of finite element method. The full, non-linear analysis, taking into account large displacements and using contact elements was performed. The obtained results are presented in loaddeflection diagrams. Some conclusions concerning ultimate loads and failure behaviour of tested beams made of different materials have been derived.
3
Content available The formation of single-channel and multiple-channel rivers on large slopes
Misiura K., Czechowski L., Witek P., Bendiukova A.
Geological Quarterly
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2016
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Vol. 60, No. 4
981--989
EN
We investigated the formation of different types of rivers depending on slope, total discharge, and grain size. Calculations were performed using numerical package CCHE2D, developed by the National Center for Computational Hydroscience and Engineering. The model is based on the Navier-Stokes equations for depth-integrated two-dimensional turbulent flow and the three-dimensional convection-diffusion equation of sediment transport. For each model we use the same river geometry, suspended load concentration, and bedload transport rate. We distinguish three types of rivers using two methods for classification (single-channel, multiple-channels and transitional). We found that the trend line for transitional rivers is an increasing function of Q in space (Q, d) and that for large S the number of multichannel rivers decreases.
4
Content available Modelling of small river deltas : the dependence of morphology on grain size and discharge
Witek P., Czechowski L., Misiura K.
Geological Quarterly
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2016
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Vol. 60, No. 4
975--980
EN
We studied the dependence of the morphology of small river deltas on the grain size, the total discharge, and the slope of the deposits. We use Computational Fluid Dynamics (CFD) methods of numerical modelling. For all models we used the same initial geometry of the river valley and a portion of the lake. Our simulations show the expected dependence of the shape of our simulated small deltas on the grain size. Moreover, we find that the final type of delta could be characterized by the average slope in the region close to the delta front.
5
Content available remote Early Thermal History of Rhea: The Role of Serpentinization and Liquid State Convection
Czechowski L., Łosiak A.
Acta Geophysica
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2016
|
Vol. 64, no. 6
2677--2716
EN
Early thermal history of Rhea is investigated. The role of the following parameters of the model is investigated: time of beginning of accretion, tini, duration of accretion, tac, viscosity of ice close to the melting point, η0, activation energy in the formula for viscosity, E, thermal conductivity of silicate component, ksil, ammonia content, XNH3, and energy of serpentinization, cserp. We found that tini and tac are crucial for evolution. All other parameters are also important, but no dramatic differences are found for realistic values. The process of differentiation is also investigated. It is found that liquid state convection could delay the differentiation for hundreds of My. The results are confronted with observational data from Cassini spacecraft. It is possible that differentiation is fully completed but the density of formed core is close to the mean density. If this interpretation is correct, then Rhea could have accreted any time before 3-4 My after formation of CAI.
6
Numeryczna analiza stanu naprężenia nadbudowy podłogi kompozytowej do zastosowania w pojazdach dostawczych
Czechowski L., Kotełko M., Jankowski M.
Przegląd Mechaniczny
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2015
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nr 5
21--26
PL
Prezentowana praca zawiera modele trójwymiarowe oraz wyniki analizy stanu naprężenia w nadbudowie podłogi kompozytowej-aluminiowej, mocowanej do konstrukcji samochodu dostawczego za pomocą śrub. Nadbudowana konstrukcja w zależności od przeznaczenia jest tak projektowana, aby była możliwość zamocowania siedzeń do przewozu osób z łatwą regulacją, a jednocześnie został spełniony warunek wytrzymałościowy i przemieszczeniowy wynikający z wymogów normatywnych dla tego typu pojazdów. Materiały zastosowane w symulacji części podzespołów są kompozytami wzmocnionymi włóknem szklanym z matrycą żywiczną, a w symulacji elementów prowadzących i suwających są stopem aluminium, natomiast stelaż siedzenia wykonany został ze stali o podwyższonej wytrzymałości. W analizie numerycznej wykorzystano elementy bryłowe, belkowe oraz elementy wiążące RBE3. Celem symulacji było odwzorowanie rzeczywistych warunków wyrywania siedzenia z prowadnic pod obciążeniem statycznym. Problem rozwiązano, stosując oprogramowanie MSC Patran/Nastran.
EN
The present work includes tree-dimensional models and analysis results of the stress state in the composite-aluminum floor superstructure, fixed to the vehicle structure by means of boIts. The superstructure, depending on its purpose, was designed to make mounting of easy regulation passenger seats possible and with fulfiling the strength and displacement terms concerning, normative requirements. The materials used in the simulation are composite reinforced with glass fibers in the epoxy matrix and aluminum for sliding parts. The structure of the seat is made of a high-strength Steel. In numerical simulation, the solid elements, the beam elements and the connection elements RBE3 were implemented. The main purpose of the simulation was to conduct numerical calculation of pulling seats from the floor structure under the static loading close to real conditions. The problem by means of MSC FEA software was solved.
7
Content available Study of dynamic buckling of FG plate due to heat flux pulse
Czechowski L.
International Journal of Applied Mechanics and Engineering
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2015
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Vol. 20, no. 1
19--31
EN
The paper deals with a FEM analysis of dynamic buckling of functionally graded clamped plates under heat flux loading with huge power. The materials of structures as well as their properties are varying in each layer across the plate thickness formulated by the power law distribution. The heat flux was applied evenly to the whole ceramic surface. The analysis was developed in the ANSYS 14.5 software. The duration of the heat flux loading equal to a period of natural fundamental flexural vibrations of given structures was taken into consideration. To implement large deflections of structures, the Green-Lagrange nonlinear-displacement equations and the incremental Newton-Raphson algorithm were applied. An evaluation of the dynamic response of structures was carried out on basis of the Budiansky-Hutchinson criterion. The studies were conducted for different volume fraction distributions and different shapes of the heat flux loading. The computation results of the heat flux versus maximal plate deflection are shown and discussed.
8
Content available Numerical modelling of rivers on Earth and Titan
Misiura K., Czechowski L.
Geological Quarterly
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2015
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Vol. 59, No. 3
565--580
EN
The differences in the evolution of rivers on Earth and on Titan are investigated. Dynamical analysis of the rivers was performed using a numerical package CCHE2D developed by the National Center for Computational Hydroscience and Engineering, University of Mississippi. The model is based on the Navier-Stokes equations for depth-integrated two-dimensional turbulent flow and the three-dimensional convection-diffusion equation of sediment transport. The model enables investigation of the evolution of rivers as a function of total discharge and other parameters of the river. Series of short (from one to several hours) and long (up to 67 days) simulations were performed. We have found that three different liquid hydrocarbons considered for Titan’s rivers give similar velocity fields. It was also found that the suspended load is the main means of transport in Titan’s rivers, while in terrestrial ones, for the same discharge, the bedload could be of the same order as suspended load. Moreover, we suppose that for specific boundary conditions, the evolution of rivers on the Earth promotes the development of braided rivers, while for the same conditions evolution on Titan favours regular meandering rivers
9
Content available remote Comparison of Early Evolutions of Mimas and Enceladus
Czechowski L., Witek P.
Acta Geophysica
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2015
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Vol. 63, no. 3
900--921
EN
Thermal history of Mimas and Enceladus is investigated from the beginning of accretion to 400 Myr. The numerical model of convection combined with the parameterized theory is used. The following heat sources are included: short lived and long lived radioactive isotopes, accretion, serpentinization, and phase changes. The heat transfer processes are: conduction, solid state convection, and liquid state convection. We find that temperature of Mimas’ interior was significantly lower than that of Enceladus. If Mimas accreted 1.8 Myr after CAI then the internal melting and differentiation did not occur at all. Comparison of thermal models of Mimas and Enceladus indicates that conditions favorable for the start of tidal heating lasted for a short time (~107 yr) in Mimas and for ~108 yr in Enceladus. This could explain the Mimas-Enceladus paradox. In fact, in view of the chronology based on cometary impact rate, one cannot discard a possibility that also Mimas was for some time active and it has the interior differentiated on porous core and icy mantle.
10
Statyczne i dynamiczne wyboczenie prostokątnych płyt funkcjonalnie gradientowych przy obciążeniach cieplnych
Czechowski L., Kowal-Michalska K.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
|
2013
|
z. 101
23--24
PL
Materiały funkcjonalnie gradientowe (FGM), po raz pierwszy wprowadzone w 1984 r., stały się bardzo popularne w badaniach naukowych i zastosowaniach inżynierskich. Typowy FGM jest dwufazowym (zwykle metal-ceramika), heterogenicznym kompozytem, których wzajemna zawartość zmienia się w sposób ciągły. Wysoka odporność na temperatury (ceramika) i dobre właściwości mechaniczne (metal) sprawiają, że konstrukcje wykonane z FGM są stosowane jako osłony w otoczeniu wysokich temperatur. Wyboczenie FG płyt pod wpływem ustalonych w czasie obciążeń cieplnych było, w ostatnich kilku latach, przedmiotem wielu prac. Problem dynamicznego wyboczenia cienkościennych, gradientowych konstrukcji poddanych impulsowemu przyrostowi temperatury wydaje się być ważny inżynierskiego punktu widzenia.
11
Content available remote Dynamic Response of Viscoplastic Thin-Walled Griders in Torsion
Czechowski L.
Mechanics and Mechanical Engineering
|
2013
|
Vol. 17, nr 1
7--16
EN
This work deals with an analysis of isotropic or orthotropic girders subjected to transient dynamic loads. The duration of dynamic loading was assumed to be equal to a period of the natural fundamental flexural vibrations of a structure under analysis. Numerical calculations were performed with the finite element method using ANSYS ® 11.0 software. The results of computations were presented as maximum angle of the rotation of the girder in a function of the dynamic load factor, DLF (the ratio of pulse loading amplitude to static critical load). In study it has been taken into account apart from the elastic–plastic range of material with isotropic hardening as well as the strain rate effect described by Perzyna model.
12
Content available Numerical simulation of energy absorption in polyurethane foams under impact
Jankowski M., Czechowski L., Kotełko M.
Journal of KONES
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2012
|
Vol. 19, No. 4
245-252
EN
Selection of proper mechanical characteristics of the padding material of the head rest, namely polyurethane foam, is particularly important in the design process of the vehicle seat head restraint. In the paper the code of numerical simulation of flexible polyurethane foam absorber response against impact of a rigid body (passenger's head) is presented. The code is based on the lump mass method. Basics of the numerical algorithm based on this method are presented. Material constitutive model of flexible polyurethane foam (FPF) derived on the basis of former experimental tests and used in the algorithm is described. Comparative results of numerical simulations together with results of experiments carried out on drop hammer rig with flat impact or are shown. The results are presented on diagrams of deceleration versus time. Also comparative Finite Element simulations are carried out. The FE simulation was performed using the implicit analysis, taking into account the multi-linear, hyper-elastic material model and large strain (non-linear geometric relations). The influence of damping coefficient on the deceleration characteristics was investigated. Some final conclusions concerning the applicability of the numerical code based on the lump mass method, as well as its advantages in comparison with the FE software are derived.
13
Content available Analysis of thin - walled girders subjected to a pulse torsional torque
Czechowski L., Kubiak T.
Journal of KONES
|
2012
|
Vol. 19, No. 1
51-61
EN
Thin-walled structures, which are primarily meant for static load service conditions may be subjected to transient dynamic loads, which may in turn lead to a more dangerous state of stress in the structure. These transient overloads as compared to steady state (static) loads may deteriorate the mechanical properties of the structural member or lead to its failure. Therefore, analysis of dynamically loaded structures, or the answer to the question at what dynamic loading relative to static loading the structures may be serviceable, is a valid and pertinent issue. This paper deals with thinwalled iso- and/or orthotropic box girders subjected to a pulsed torsional moment causing restrained torsion. Numerical calculations were conducted by means of the ANSYSŽ software, a computer suite applying the finite element method [12]. The results were presented in the form of displacement maps and diagrams determining the maximum angle of rotation or deflection of the girder wall as a function of the dynamic load factor, DLF (the ratio of pulse loading amplitude to static critical load).
14
Content available Experimental Tests of a Property of Composite Material Assigned for Ballistic Products
Czechowski L., Jankowski J., Kubiak T.
Fibres & Textiles in Eastern Europe
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2012
|
Vol. 20, no. 3 (92)
61--66
EN
An empirical investigation of a selected static property of a composite is presented in this paper. For the purpose of studying the quality and property of multilayer composite material assigned for manufacturing some ballistic products, the following were conducted: tensile test, hardness test, bending test and delamination test. Before the tests were carried out, procedures were created for each of them. Selected results of the tests performed are shown and discussed.
PL
W niniejszej publikacji przedstawiono sposób przeprowadzania badań eksperymentalnych mających na celu wyznaczanie właściwości wytrzymałościowych materiałów kompozytowych stosowanych na osłony balistyczne. W pracy omówiono próby rozciągania, twardości, zginanie i rozwarstwienia, dla których przygotowano procedury badawcze. Przedstawione i omówione wyniki badań eksperymentalnych mogą posłużyć przy projektowaniu osłon balistycznych.
15
Content available remote Thermal history and large scale differentiation of the Saturn’s satellite Rhea
Czechowski L.
Acta Geophysica
|
2012
|
Vol. 60, no. 4
1192-1212
EN
Thermal history of Rhea from the beginning of accretion is investigated. We developed a numerical model of convection combined with the parameterized theory. Large scale melting of the satellite’s matter and gravitational differentiation of silicates from ices are included. The results are confronted with observational data from Cassini spacecraft that indicate minor differentiation of the satellite’s interior. We suggest that partial differentiation of the satellite’s interior is accompanied (or followed) by the process of light fraction uprising to the surface. The calculation indicates that the partial differentiation of the matter of the satellite’s interior is possible only for narrow range of parameters. In particular, we found that the time from the formation of CAI (calciumaluminum rich inclusions in chondrites) to the end of accretion of Rhea is in the range of 3-4 My.
16
Content available Numeryczna analiza procesu hartowania w piecu rurowym z zimną komorą chłodzenia
Pokrzywa M., Niewiedzielski R., Kula P., Atraszkiewicz R., Lipa S., Czechowski L., Jankowski J., Wajman T., Sobczak K.
Postępy Nauki i Techniki
|
2011
|
nr 8
59-67
PL
W artykule przedstawiono zagadnienie wymiany ciepła pomiędzy stalowym wsadem poddanym uprzednio obróbce cieplno-chemicznej (nawęglanie próżniowe) a przepływającym gazem pod wysokim ciśnieniem. Problem naukowy rozwiązano wykorzystując stworzony w środowisku Delphi, specjalnie dla tego typu zagadnień, zewnętrzny program nadrzędny, umożliwiający połączenie oprogramowania opartego na metodzie objętości skończonej - ANSYS CFX 12.0 i metodzie elementów skończonych - ANSYS 12.0. Do programu zaimplementowane zostały dwa modele: przepływowy i termiczny. Stworzony program pozwala na analizę tempa chłodzenia w każdym punkcie objętości i optymalizację procesu chłodzenia z intensywnie i turbulentnie przepływającym gazem. Dla poprawnego zdefiniowania i modelowania zjawiska wymiany ciepła pomiędzy wsadem a medium chłodzącym stworzono bazę danych materiałowych, obejmującą wielkości fizyczne pozwalające stworzyć model numeryczny uwzględniający przemiany fazowe z tzw. ciepłem utajonym oraz wpływ szybkości chłodzenia na zmiany zachodzące w strukturze detalu. Przy tworzeniu baz materiałowych posłużono się programem JMatPro.
EN
The following work presents the issue of heat transfer between the steel charge after vacuum carburizing process and gas which intensively flows through. The external managing program has been created in Delphi environment to solve the scientific research problem, which connect the Finite Volume Method - ANSYS CFX 12.0 with Finite Element Method - ANSYS 12.0. To the program there were implemented two models: flow and thermal. Created program allows to analyze cooling rate at each point of the volume and optimize the cooling process with gas intensively and turbulently flowing through. For the correct definition and modeling of the phenomenon of the heat transfer between the steel charge and cooling gas, the database of material properties was created, which includes physical quantities that allow to create a numerical model taking into account the so-called phase transitions with latent heat and the influence of the cooling rate to changes in the structure of the detail. Thanks to JMatPro4 program, the application of different material properties database of material properties could be applied.
17
Content available remote Stan naprężenia w elastomerze zawierającym cząstki ferromagnetyczne w polu magnetycznym
Boczkowska A., Jaroniek M., Czechowski L., Niezgoda T.
Mechanik
|
2010
|
R. 83, nr 7
470-474
PL
Przedstawiono wyniki analizy modelowania metodą elementów skończonych oraz badań metodą elastooptyki magnetoreologicznego elastomeru w obecności pola magnetycznego. Celem przeprowadzonych symulacji numerycznych i badań eksperymentalnych było uzyskanie wiedzy o wzajemnym oddziaływaniu elastomeru i kulek żelaza (wyznaczenie wartości odkształcenia i naprężenia) oraz zdobycie doświadczenia niezbędnego do modelowania takich oddziaływań na poziomie mikrostruktury w rzeczywistym elastomerze zawierającym cząstki żelaza o wymiarach mikronowych.
EN
Analysis results of the FEM models and the magnetorheologic photoelasticity tests of elastomer materials exposed to magnetic fields.
18
Content available remote Modelowanie procesu hartowania
Czechowski L., Jankowski J., Kubiak T.
Mechanik
|
2010
|
R. 83, nr 7
484-486
PL
Przedstawiono wyniki badań, które są następstwem wstępnych analiz i - w efekcie końcowym - mają służyć do optymalizacji procesu hartowania (doboru odpowiednich parametrów nagrzewania i chłodzenia w piecu hartowniczym - krzywa opisująca szybkość chłodzenia) w taki sposób, aby otrzymać strukturę martenzytyczną na odpowiedniej głębokości oraz jak najmniejsze odkształcenia lub odkształcenia równomierne, powodujące że zostanie zachowany kształt detalu.
EN
Presented are primary conclusions of the research tests intended for optimization of the quench hardening process (identification of suitable criteria for proper selection of the heating and cooling parameters and cooling rate curve) in order to arrive at the martensite structure reaching the desired depth and also at the minimum possible distortion or else a uniform distortion preventing deformation of the part.
19
Content available remote Failure analysis of an energy absorber subjected to pressure pulse
Czechowski L., Jankowski J.
Mechanics and Mechanical Engineering
|
2010
|
Vol. 14, nr 2
193-199
EN
In the paper, an influence of the amplitude of pulse loading and the thickness of susceptible parts taking over the pressure pulse on the absorber operation is investigated. The presented absorber consists of six truncated conical shells covered with a thin plate. Elements of the absorber are made of an isotropic material with a bilinear strain-stress curve. A nonlinear contact problem for the triangular loading pulse was solved with the ANSYS code.
20
Content available Analysis of magnetic field effect on ferromagnetic spheres embedded in elastomer pattern
Boczkowska A., Czechowski L., Jaroniek M., Niezgoda T.
Journal of Theoretical and Applied Mechanics
|
2010
|
Vol. 48 nr 3
659-676
EN
The results of modelling of the magnetorheological elastomers (MREs) microstructure using Finite Elements Method (FEM) are shown. MREs are solids analogous to magnetorheological fluids consisting of carbonyl-iron particles and a soft elastomer matrix. Fabrication of MREs is performed in an external constant magnetic field. Due to the presence of this field, the ferromagnetic particles tend to arrange themselves into elongated chains according to the magnetic field lines. FEM analysis of the MREs microstructure takes into account two cases: magnetic power and elastic vectors as well as their interactions between the components of the composite. The paper describes spatial ordering of the particles based on their interactions with the magnetic field. Two phenomena were taken into account: the force of a magnetic field and the local magnetic dipoles. Both fields have been modelled for a circular conductor with electrical current.
PL
W pracy przedstawiono wyniki modelowania mikrostruktury magnetoreologicznych elastomerów (MRE) z wykorzystaniem metody elementów skończonych (MES). MRE są odpowiednikami w stanie stałym cieczy magnetoreologicznych, złożonymi z cząstek żelaza karbonylkowego i miękkiej osnowy elastomerowej.Wytwarzanie MRE prowadzone jest w stałym polu magnetycznym. Pod wpływem pola cząstki ferromagnetyczne układają się w łańcuchy wzdłuż linii pola magnetycznego, tworząc strukturę kolumnową. W analizie MES mikrostruktury MRE rozpatrzono siły magnetyczne i sprężystości oraz ich wzajemne oddziaływania pomiędzy składnikami kompozytu. Przedstawiono przestrzenne rozmieszczenie cząstek w oparciu o ich oddziaływania w polu magnetycznym. W rozważaniach wzięto pod uwagę rozkład pola magnetycznego i momenty dipolowe cząstek. W obu przypadkach pole było zamodelowane dla kołowego przewodnika prądu elektrycznego.
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