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Machines
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Nonlinear Dynamics of Mechanical Systems and Machines
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Nonlinear Dynamics of Mechanical Systems and Machines

A special issue of Machines (ISSN 2075-1702). This special issue belongs to the section "Machine Design and Theory".

Deadline for manuscript submissions: closed (30 November 2024) | Viewed by 2295

Special Issue Editor

Dr. Aurelien Grolet

E-Mail Website
Guest Editor
Maître de Conférence, Arts et Métiers, Lille, France
Interests: non-linear dynamics; vibration

Special Issue Information

Dear Colleagues,

This Special Issue aims to explore the nonlinear dynamics of mechanical systems and machines, with a special emphasis on experimental investigation. Various fields are considered, such as model reduction, nonlinearity identification, vibration reduction, special nonlinear effects (localization, energy transfer, instabilities, etc.), with applications in the various fields of mechanical systems. Studies on simple nonlinear models representing nonlinear phenomena occurring in industrial machines are also welcome. In all cases, it is important that all studies include experimental measurements either to compare to numerical simulations, to demonstrate the effectiveness of a particular nonlinear device, or simply to point out a peculiar effect that is due to nonlinearity.

Dr. Aurelien Grolet
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Machines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • non-linear dynamics
  • model reduction
  • nonlinear identification
  • vibration reduction
  • localisation
  • energy transfer
  • bifurcation
  • experimental measurements of nonlinear phenomenon
  • engineering nonlinearities

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Further information on MDPI's Special Issue policies can be found here.

Published Papers (2 papers)

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Research

18 pages, 7285 KiB  
Article
Nonlinear Dynamics of Whirling Rotor with Asymmetrically Supported Snubber Ring
by Heba Hamed El-Mongy, Tamer Ahmed El-Sayed, Vahid Vaziri and Marian Wiercigroch
Machines 2024, 12(12), 897; https://doi.org/10.3390/machines12120897 - 6 Dec 2024
Cited by 1 | Viewed by 816
Abstract
Rotor–stator whirling is a critical malfunction frequently encountered in rotating machinery, often resulting in severe damages. This study investigates the nonlinear dynamics of a whirling rotor interacting with a snubber ring through numerical simulations that account for the stiffness asymmetries of the snubber [...] Read more.
Rotor–stator whirling is a critical malfunction frequently encountered in rotating machinery, often resulting in severe damages. This study investigates the nonlinear dynamics of a whirling rotor interacting with a snubber ring through numerical simulations that account for the stiffness asymmetries of the snubber ring. A two-degrees-of-freedom (DOF) model is employed to analyse the contact interactions that occurred between the rotor and the snubber ring, assuming a linear elastic contact model. The analysis also incorporates the static offset between the centers of the rotor and the snubber ring. The dynamic behaviour of the whirling system is characterised by pronounced nonlinearity due to transitions between contact and non-contact states. The model is first validated against our prior theoretical and experimental studies. The nonlinear responses of the rotor are analysed to evaluate the effects of stator asymmetry through various techniques, including time-domain waveforms, frequency spectra, rotor orbits, and bifurcation diagrams. Furthermore, the influence of varying system parameters, such as rotational speed and the damping ratio, both with and without stator asymmetry, are systematically analysed. The results demonstrate that the rubbing response is highly sensitive to small variations in system parameters, with stator asymmetry significantly affecting system behaviour, even at low asymmetry levels. Direct stiffness asymmetry is shown to have a more pronounced effect than cross-coupling stiffness. The system exhibits a range of dynamics, including periodic, quasi-periodic, and chaotic responses, with regions of periodic orbits coexisting with chaotic ones. Complex phenomena such as period doubling, period halving, and jump bifurcations are identified, alongside quasi-periodic and period doubling routes to chaos. These findings contribute to a deeper understanding of the nonlinear phenomena associated with rotor–stator whirling and provide valuable insights into the unique characteristics of rubbing faults, which could facilitate fault diagnosis. Full article
(This article belongs to the Special Issue Nonlinear Dynamics of Mechanical Systems and Machines)
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22 pages, 9204 KiB  
Article
Analysis of the Nonlinear Complex Response of Cracked Blades at Variable Rotational Speeds
by Bo Shao, Chenguang Fan, Shunguo Fu and Jin Zeng
Machines 2024, 12(10), 725; https://doi.org/10.3390/machines12100725 - 14 Oct 2024
Viewed by 1063
Abstract
The operation of an aero-engine involves various non-stationary processes of acceleration and deceleration, with rotational speed varying in response to changing working conditions to meet different power requirements. To investigate the nonlinear dynamic behaviour of cracked blades under variable rotational speed conditions, this [...] Read more.
The operation of an aero-engine involves various non-stationary processes of acceleration and deceleration, with rotational speed varying in response to changing working conditions to meet different power requirements. To investigate the nonlinear dynamic behaviour of cracked blades under variable rotational speed conditions, this study constructed a rotating blade model with edge-penetrating cracks and proposes a component modal synthesis method that accounts for time-varying rotational speed. The nonlinear response behaviours of cracked blades were examined under three distinct operating conditions: spinless, steady speed, and non-constant speed. The findings indicated a competitive relationship between the effects of rotational speed fluctuations and unbalanced excitation on crack nonlinearity. Variations in rotational speed dominated when rotational speed perturbation was minimal; conversely, aerodynamic forces dominated when the effects of rotational speed were pronounced. An increase in rotational speed perturbation enhanced the super-harmonic nonlinearity induced by cracks, elevated the nonlinear damage index (NDI), and accentuated the crack breathing effect. As the perturbation coefficient increased, the super-harmonic nonlinearity of the crack intensified, resulting in a more complex vibration form and phase diagram. Full article
(This article belongs to the Special Issue Nonlinear Dynamics of Mechanical Systems and Machines)
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