Incorporating Boundary Nonlinearity into Structural Vibration Problems

This paper presents a methodology for accurately incorporating the nonlinearity of boundary conditions (BCs) into the mode shapes, natural frequencies, and dynamic behaviour of analytical beam models. Such models have received renewed interest in recent years as a result of their successful implemen...

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Main Authors: Alex J. Elliott, Andrea Cammarano
Format: Article
Language:English
Published: MDPI AG 2024-10-01
Series:Vibration
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Online Access:https://www.mdpi.com/2571-631X/7/4/50
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author Alex J. Elliott
Andrea Cammarano
author_facet Alex J. Elliott
Andrea Cammarano
author_sort Alex J. Elliott
collection DOAJ
description This paper presents a methodology for accurately incorporating the nonlinearity of boundary conditions (BCs) into the mode shapes, natural frequencies, and dynamic behaviour of analytical beam models. Such models have received renewed interest in recent years as a result of their successful implementation in state-of-the-art multiphysics problems. To address the need for this boundary nonlinearity to be more completely captured in the equations of motion, a nonlinear algebra expansion of the classical linear approach for developing solvability conditions for natural frequencies and mode shapes is presented. The method is applicable to any BC that can be accurately represented in polynomial form, either explicitly or through the application of a Taylor expansion; this is the only assumption made in removing the need for the use of analytical approximations of the dynamics themselves. By reducing the BCs of the beam to a system of polynomials, it is possible to utilise the tensor resultant to develop these solvability conditions analogous to the conditions placed on the matrix determinant in linear, classical cases. The approach is first derived for a general set of nonlinear BCs before being applied to two example systems to investigate the importance of including nonlinear tip behaviour in the BCs to accurately predict the system response. In the first, a theoretical, symmetric system, in which a beam is supported by nonlinear springs, is used to explore both the applicability of the methodology and the improvements it can make to the accuracy of the model. Then, the more practical example of a cantilever beam with repulsive magnetic interaction at the tip is used to more explicitly assess the importance of properly incorporating boundary nonlinearity into multiphysics problems.
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spelling doaj-art-c9d474e846e84566866a3b6e7b6c78c92024-12-27T14:58:47ZengMDPI AGVibration2571-631X2024-10-017494996910.3390/vibration7040050Incorporating Boundary Nonlinearity into Structural Vibration ProblemsAlex J. Elliott0Andrea Cammarano1Faculty of Engineering and Applied Sciences, Cranfield University, Cranfield MK43 0AL, UKSchool of Engineering, University of Southampton, Southampton SO16 7QF, UKThis paper presents a methodology for accurately incorporating the nonlinearity of boundary conditions (BCs) into the mode shapes, natural frequencies, and dynamic behaviour of analytical beam models. Such models have received renewed interest in recent years as a result of their successful implementation in state-of-the-art multiphysics problems. To address the need for this boundary nonlinearity to be more completely captured in the equations of motion, a nonlinear algebra expansion of the classical linear approach for developing solvability conditions for natural frequencies and mode shapes is presented. The method is applicable to any BC that can be accurately represented in polynomial form, either explicitly or through the application of a Taylor expansion; this is the only assumption made in removing the need for the use of analytical approximations of the dynamics themselves. By reducing the BCs of the beam to a system of polynomials, it is possible to utilise the tensor resultant to develop these solvability conditions analogous to the conditions placed on the matrix determinant in linear, classical cases. The approach is first derived for a general set of nonlinear BCs before being applied to two example systems to investigate the importance of including nonlinear tip behaviour in the BCs to accurately predict the system response. In the first, a theoretical, symmetric system, in which a beam is supported by nonlinear springs, is used to explore both the applicability of the methodology and the improvements it can make to the accuracy of the model. Then, the more practical example of a cantilever beam with repulsive magnetic interaction at the tip is used to more explicitly assess the importance of properly incorporating boundary nonlinearity into multiphysics problems.https://www.mdpi.com/2571-631X/7/4/50nonlinear vibrationsGalerkin methodfinite element analysisnonlinear boundary conditions
spellingShingle Alex J. Elliott
Andrea Cammarano
Incorporating Boundary Nonlinearity into Structural Vibration Problems
Vibration
nonlinear vibrations
Galerkin method
finite element analysis
nonlinear boundary conditions
title Incorporating Boundary Nonlinearity into Structural Vibration Problems
title_full Incorporating Boundary Nonlinearity into Structural Vibration Problems
title_fullStr Incorporating Boundary Nonlinearity into Structural Vibration Problems
title_full_unstemmed Incorporating Boundary Nonlinearity into Structural Vibration Problems
title_short Incorporating Boundary Nonlinearity into Structural Vibration Problems
title_sort incorporating boundary nonlinearity into structural vibration problems
topic nonlinear vibrations
Galerkin method
finite element analysis
nonlinear boundary conditions
url https://www.mdpi.com/2571-631X/7/4/50
work_keys_str_mv AT alexjelliott incorporatingboundarynonlinearityintostructuralvibrationproblems
AT andreacammarano incorporatingboundarynonlinearityintostructuralvibrationproblems