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1

Multi-core and many-core SPMD parallel algorithms for construction of basins of attraction

Silveira Marcos, Gonçalves Paulo J.P., Balthazar José M.

Journal of Theoretical and Applied Mechanics

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2019

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Vol. 57 nr 4

1067--1079

EN

Construction of basins of attraction, used for the analysis of nonlinear dynamical systems which present multistability, are computationaly very expensive. Because of the long runtime needed, in many cases, the construction of basins does not have any practical use. Numerical time integration is currently the bottleneck of algorithms used for the construction of such basins. The integrations related to each set of initial conditions are independent of each other. The assignment of each integration to a separate thread seems very attractive, and parallel algorithms which use this approach to construct the basins are presented here. Two versions are considered, one for multi-core and another for many-core architectures, both based on a SPMD approach. The algorithm is tested on three systems, the classic nonlinear Duffing system, a non-ideal system exhibiting the Sommerfeld effect and an immunodynamic system. The results for all examples demonstrate the versatility of the proposed parallel algorithm, showing that the multi-core parallel algorithm using MPI has nearly an ideal speedup and efficiency.

2

Dynamical jump attenuation in a non-ideal system through a magnetorheological damper

Piccirillo V., Tusset A. M., Balthazar J. M.

Journal of Theoretical and Applied Mechanics

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2014

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Vol. 52 nr 3

595--604

EN

This paper is concerned with the Sommerfeld effect (Jump phenomena) attenuation in an non-ideal mechanical oscillator connected with an unbalanced motor excitation with a limited power supply (non-ideal system) using a magnetorheological damper (MRD). The dynamical response of systems with MRD presents different behavior due to their nonlinear characteristic. MRD nonlinear response is associated with adaptive dissipation related to their hysteretic behavior. The Bouc-Wen mathematical model is used to represent the MRD behavior. Numerical simulations show different aspects about the Sommerfeld effect, illustrating the influence of the different electric current applied in the MRD to control the force developed by this damper.

3

Influence of ideal and non-ideal excitation sources on the dynamics of a nonlinear vibro-impact system

Moraes F. H., Pontes B. R. (jr), Silveira M., Balthazar J. M., Brasil R. M. L. R. F.

Journal of Theoretical and Applied Mechanics

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2013

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Vol. 51 nr 3

763--774

EN

The objective of the present work is to analyze the dynamics of a vibro-impact system consisting of two blocks of different mass coupled by a spring with two stages. Two different types of excitation sources for the system are used in the analysis: the first is an ideal excitation in form of a harmonic force, and the second is a non-ideal excitation in form of a DC electric motor with limited power supply which has an unbalanced rotor. The control parameter for both situations is the excitation frequency of the system. The analysis includes time histories of displacements and velocities, phase portraits and diagrams of the displacement and frequency, used to show the Sommerfeld effect. For certain values of the parameters of the system, the motion is chaotic. The mathematical model of the system is used to obtain an insight to the global dynamics of the vibro-impact system. The model with a non-ideal excitation is more realistic, complete and complex than the model with the ideal excitation.

4

On a nonlinear and chaotic non-ideal vibrating system with shape memory alloy (SMA)

Piccirillo V., Balthazar J. M., Pontes B. R. Jr., Felix J. L. P.

Journal of Theoretical and Applied Mechanics

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2008

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Vol. 46 nr 3

597-620

EN

In this paper, we present nonlinear dynamic behaviour of a system which consists of a mass connected to a rigid support by a shape memory alloy (SMA) element and a damper. In order to disturb the system, a DC motor with limited power supply is connected to the mass, causing an interaction between the vibrating structure and the energy source. The SMA element is characterised using a one-dimensional phenomenological constitutive model, based on the classical Devonshire theory. We analyse the non-ideal system in form of two coupled nonlinear differential equations. Some interesting nonlinear phenomena as the Sommerfeld effect and nonlinear resonance including periodic, chaotic and hyperchaotic regime are presented.

PL

W pracy przedstawiono opis dynamiki nieliniowego układu złożonego z masy połączonej ze sztywnym podłożem za pośrednictwem elementu z pamięcią kształtu i tłu- mikiem. W celu realizacji wymuszenia w układzie zastosowano silnik prądu stałego z ograniczonym poborem mocy, który pobudza do ruchu masę, tworząc w ten sposób sprzężenie mechaniczne pomiędzy układem drgającym a źródłem energii. Element z pamięcią kształtu opisano za pomocą jednowymiarowego modelu fenomenologicznego opartego na teorii Devenshire’a. Przeanalizowano rozważany nieidealny układ opisany dwoma sprzężonymi nieliniowymi równaniami ruchu. Zaobserwowano i opisano interesujące zjawiska nieliniowe w postaci efektu Sommerfelda i nieliniowego rezonansu w zakresie drgań okresowych, chaotycznych i hiperchaotycznych.

5

Auto-Balancing of Rotors with a Rigid Bearing

Sperling L., Ryzhik B., Duckstein H., Grobel K. H.

Machine Dynamics Problems

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2004

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Vol. 28, No. 2

45-64

EN

The paper presents a study of automatic balancing of rotors with a fixed point, for example rotors with a rigid bearing. In such rotor systems permitting only tilting oscillations, similarly to the case of the Laval rotor, the full compensation of unbalance is possible by balancing in only one plane. We consider a rotor equipped with an auto-balancing device consisting of a circular track with two moving balls. The investigations include derivation and analysis of existence and stability conditions for synchronous motions, an analysis of non-synchronous biharmonic motions near the critical speed, and a discussion on the influence of the gyroscopic terms, particularly a new type of Sommerfeld effect. The results are confirmed and complemented by computer simulations.