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1
Content available Vibration properties of auxetic beam
Matuszewska A., Stręk T.
Vibrations in Physical Systems
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2018
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Vol. 29
art. no. 2018031
EN
This study presents vibration analysis for a beam with an auxetic cross-section. In order to verify damping properties of auxetic materials, the numerical results were compared with classical H-beam which has basic geometry. The response of analyzed models was considered with taking into account the Rayleigh damping of the internal material structure. Performed calculations comprise deformation of the certain beam, selected points displacement and vibration transmission loss coefficient. The analysis was carried out by means of Finite Element Method using Comsol Multiphysics software.
2
Content available Forced response of plate with viscoelastic auxetic dampers
Stręk T.
Vibrations in Physical Systems
|
2018
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Vol. 29
art. no. 2018003
EN
The example studies a forced response of plate with viscoelastic auxetic damper located at the free end of the plate. Damping elements consist of the cover layer and layer of viscoelastic material with positive or negative Poisson's ratio. Viscoelastic materials are often used for reduction of vibration (seismic or wind induced vibrations in building structures or other structures). The common feature is that the frequency of the forced vibrations is low. Calculations are made using finite element method with Comsol Multiphysics software.
3
Content available Fatigue life of polymer dental crown
Michalski J., Stręk T.
Vibrations in Physical Systems
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2018
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Vol. 29
art. no. 2018010
EN
In this article fatigue life of polymer dental crown will be analyzed. Chewing forces occurring in repetitive cycles can lead to fatigue destruction of material. To predict a number of cycles to failure finite element method can be applied and results may be used to improve the design of acrylic dental crowns. Also, the modal analysis will be performed in order to find natural frequencies of the system and prevent destruction from vibrations.
4
Content available Dynamic analysis of optimized two-phase auxetic structure
Idczak E., Stręk T.
Vibrations in Physical Systems
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2017
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Vol. 28
art. no. 2017003
EN
This paper presents a dynamic analysis of earlier optimized auxetic structure. This optimization based on the distribution of two materials in such way to obtain a minimal value of Poisson’s ratio (PR), which indicates the auxetic properties. The initial optimized shape was so-called star structure, which if is made from one material has the PR close to 0.188. After optimization with the goal function of PR-minimization, the obtained value was equal to -9.5043. Then the eigenfrequencies for the optimized structure were investigated. The calculations were carried out by means of Finite Element Method (FEM). For optimization of the value of Poisson’s ratio was used algorithm MMA (Method of Moving Asymptotes). The computing of single material properties (PR, Young’s modulus, density) for the whole shape was made by means of SIMP method (Solid Isotropic Method with Penalization).
5
Content available Computational modelling of vibrations transmission loss of auxetic lattice structure
Idczak E., Stręk T.
Vibrations in Physical Systems
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2016
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Vol. 27
123--128
EN
In this article dynamical properties of auxetic lattice structures will be analysed. Auxetic structures are materials, which have negative Poisson’s ratio and some of these have got specific dynamic properties. Their dynamic behaviour in the frequency domain will be also shown in this article. The possibility of isolation of auxetics will show the factor VTL – Vibration Transmission Loss.
6
Content available Finite element analysis of dynamic properties of thermally optimal two-phase composite structure
Nienartowicz M., Stręk T.
Vibrations in Physical Systems
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2014
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Vol. 26
203--210
EN
This paper presents modelling and a FEM analysis of dynamic properties of a thermally optimal two-phase composite structure. Simulations were provided for 2D models. At the first step, topology optimization was performed, where an internal energy was minimized. At the second step, analysis of dynamic properties was executed. Calculations allowed to determine eigenfrequencies and the mode shape of the structure. Solid isotropic material with penalization (SIMP) model was used to find the optimal solution. The optimization algorithm was based on SNOPT method and Finite Element Method.
7
Content available remote Differential evolution in system parameters identification
Stręk T., Nienartowicz M.
Vibrations in Physical Systems
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2012
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Vol. 25
373--379
EN
In this paper the Differential Evolution (DE) optimization algorithm is presented and applied in benchmark problem: minimization of Rosenbrock’s function and identification of mechanical systems parameters. DE optimization algorithm is also used in conjunction with a squared error measure to identify the optimal model parameter values of mass-spring-damper (MSD) using time series experimental data.
8
Content available remote Symplectic integrators for cascade of mass-spring system
Jopek H., Stręk T.
Vibrations in Physical Systems
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2006
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Vol. 22
155--160
9
Content available remote Influence of magnetic field on heat transfer in ferrofluid
Stręk T.
Vibrations in Physical Systems
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2006
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Vol. 22
331--336
10
Finite element analysis of influence of magnetic field on heat transfer in ferrofluid
Stręk T.
Systems : journal of transdisciplinary systems science
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2006
|
Vol. 11, nr 1
109-116
EN
The viscous, two-dimensional, incompressible and laminar time dependent heat transfer flow through a ferromagnetic fluid is considered in this paper. Flow takes place in channel between two parallel flat plates under the influence of the permanent magnet or magnetic dipole located beyond the channel. It is assumed that there is no electric field effects and the variation in the magnetic field vector that could occur within the ferrofluid is negligible. This magneto-thermo-mechanical problem is governed by dimensionless equations. Results are obtained using standard computational fluid dynamics code FEMLAB with modifications to account for the magnetic term when needed.
11
Content available remote Laminar flow in trapezoidal grooves at finite Bond numbers with shear stress at the liquid-vapor interface by the method of fundamental solutions
Jopek H., Kołodziej J. A., Stręk T.
Computer Assisted Mechanics and Engineering Sciences
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2006
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Vol. 13, No. 3
395-405
EN
The problem of determination of Poiseuille number for a steady gravitational flow of liquid in an inclined open trapezoidal groove is addressed. The solution comprises of two parts. First, for a given groove's dimension, liquid-solid contact angle, and the Bond number, the shape of the free surface is determined starting from the Young--Laplace equation. The shooting method is used for solution of a two-point boundary value problem. Then, having determined the shape of the free surface and slope the groove, the fully developed laminar flow is determined. The boundary value problem is solved using the method of fundamental solutions. Given the distribution of liquid velocity, the Poiseuille number, as a function of the other parameters of the model is analysed.
12
Thermal convection in polymer solutions numerical experiment
Stręk T.
Zeszyty Naukowe Politechniki Poznańskiej. Budowa Maszyn i Zarządzanie Produkcją
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2004
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Nr 1
113-130
EN
In thermodynamics of fluids by convective motion it is understood that a fluid flow which, apart from mechanical quantities, is characterized also by thermal and/or other fields. Dimensionless governing equations are presented for this problem. Dimensionless numbers: the Prandtl number, the Rayleigh number and the Eckert number are introduced. In this paper numerical algorithm for solution of thermal convection in polymer is presented. Rheology model used for polymer is the Carreau model of non-Newtonian fluid. Numerical solutions for convective cooling of Carreau fluid in box are presented.
PL
W termodynamice płynów ruch konwekcyjny płynu jest charakteryzowany nie tylko przez wielkości mechaniczne, ale także przez pole cieplne i inne pola. W artykule przedstawiono bezwymiarowe równania opisujące zagadnienie konwekcji termicznej. W równanich tych wykorzystano liczby bezwymiarowe: Prandtla, Rayleigh i Eckerta. Zamieszczono również algorytm numerycznego rozwiązania problemu konwekcji termicznej w polimerach z wykorzystaniem metody elementów skończonych. Model reologiczny użyty do opisu polimerów to model nienewtonowskiego pfynu Carreau. Przytoczono wyniki numerycze konwekcyjnego ochładzania płynu Carreau w kwadratowym obszarze o „nieskończonej" długości.
13
Content available remote Validated high precision solution of second order initial value problem with Taylor model
Stręk T.
Vibrations in Physical Systems
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2004
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Vol. 21
357--360
EN
The problem of reliability of computer computations is one of great concern to specialists in many areas of science and engineering. The notion of computing estimates of numerical error in computer simulations is not new. In recent years, considerable progress has been made in determining theoretical and computational techniques that aid to improve the reliability of results of simulations. An important advance in this area has been the recent discovery of methods to determine upper and lower bounds of local approximation error in any given simulation. Different from floating-point computations, interval arithmetic offers a simple mechanism to evaluate an enclosure of a function. Interval arithmetic is the arithmetic defined on sets of intervals, rather than sets of real numbers. The power of the interval arithmetic lay in implementation of interval arithmetic on computers. The fundamental problem in interval methods is computing the ranges of values of real function. The overestimation of the range of a given function by the interval arithmetic expression is strongly dependent on the arithmetic expression of the given function. The reason for this is based on the fact that interval arithmetic does not follow the same rules as the arithmetic for real numbers.
14
Content available remote Natural convection of power-law fluid
Uściłowska A., Stręk T.
Vibrations in Physical Systems
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2004
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Vol. 21
399--402
15
Content available remote Influence of uncertainties and wrapping effect reduction in linear dynamical systems by affine arithmetic
Stręk T.
Vibrations in Physical Systems
|
2004
|
Vol. 21
361--364
16
Content available remote The Lyapunov exponents for the partitioned-pipe mixer
Stręk T.
Computer Assisted Mechanics and Engineering Sciences
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2003
|
Vol. 10, No. 3
271-280
EN
This paper presents a mechanical model of the partitioned-pipe mixer (PPM) in case where pipe of the static mixer rotates with angular periodic velocity. Mixing becomes more efficient if the forcing of fluid mixing process is time periodic. Chaos in duct flows can be achieved by time modulation or by spatial changes along the duct axis. The values of Lyapunov exponents for flow in PPM are calculated.
17
Content available remote Engineering computation by artificial neural networks
Stręk T.
Vibrations in Physical Systems
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2002
|
Vol. 20
272--273
18
Content available remote Applications of QR-based algorithm to determination of fractal dimension of chaotic system
Stręk T.
Vibrations in Physical Systems
|
2002
|
Vol. 20
274--275
19
Content available remote Symulacja komputerowa mieszania dwóch płynów Carreau w prostokątnej kawernie
Stręk T.
Vibrations in Physical Systems
|
2000
|
Vol. 19
264--265
20
Content available remote The computer simulation of mixing of non-Newtonian fluid in 2-D semi-cylinder cavity
Stręk T.
Computer Assisted Mechanics and Engineering Sciences
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2000
|
Vol. 7, No. 1
1-9
EN
In this paper some results of the computer simulation of mixing of non-Newtonian fluid are presented. Numerical calculations were done for dimensionless form of the equations of motion for the Carreau fluid in incompressible and viscous flow in a two-dimensional semi-cylindrical cavity. The full Navier-Stokes equations for the Carreau fluid were written in velocity-vorticity, and next in finite difference form. The solutions were accomplished by finite time-step advancement. The mixing process was studied by tracking the motion of particles in the mixing region. The particles were represented by marked points. The mixing efficiency was quantified in terms of the average distance between the tracer particles and the centroid of the particle distribution.
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