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Study of the Effect of Bolted Joint Damping-Stiffness Nonlinearity on Part Failures in Dynamic Environment Testing.

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Title: Study of the Effect of Bolted Joint Damping-Stiffness Nonlinearity on Part Failures in Dynamic Environment Testing.
Authors: Clark, B.1 (AUTHOR) bclark42@student.byu.edu, Allen, M. S.1 (AUTHOR) matt.allen@byu.edu, Pacini, B.2 (AUTHOR) brpacin@sandia.gov
Source: Experimental Techniques. Feb2026, Vol. 50 Issue 1, p163-174. 12p.
Subjects: Bolted joints, Damping (Mechanics), Vibration tests, Stress concentration, Frequency response, Nonlinear theories
Abstract: Bolted joints are very common in assembled structures and are a well-known source of nonlinear behavior in systems. This work explores the effect that nonlinearity can have on vibration environment testing, focusing on the nonlinear behavior that is typical to bolted structures. A single-degree-of-freedom system containing an Iwan joint is used to represent the mode of interest of a bolted structure. The nonlinearity is approximated as quasi-linear, or in other words, is characterized by amplitude-dependent natural frequency and damping ratio. The model was subjected to various environmental tests to understand how the outcomes of the test might be different for the nonlinear system as compared to a linear system. To facilitate this, a simple approach is developed that allows one to use the amplitude dependent frequency and damping to predict the behavior during an environmental test. The simulations show that the response of the nonlinear system could be significantly larger or smaller than expected if the system were linear, depending on the amplitude at which the system is driven and where the control accelerometer is located. If the environment is specified as a base acceleration, then nonlinearity in the component can cause the displacement, and thus the stress in the component, to be more than an order of magnitude larger or smaller than expected from a linear model. In contrast, if the control accelerometer monitors the mode of interest, then the target vibration levels will be obtained, yet with far different base excitation levels than would be expected if the system were linear. Because vibration-based testing requires certain vibration levels to be reached and maintained, these results may have implications for the vibration control software and the settings needed to successfully complete the test. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:Bolted joints are very common in assembled structures and are a well-known source of nonlinear behavior in systems. This work explores the effect that nonlinearity can have on vibration environment testing, focusing on the nonlinear behavior that is typical to bolted structures. A single-degree-of-freedom system containing an Iwan joint is used to represent the mode of interest of a bolted structure. The nonlinearity is approximated as quasi-linear, or in other words, is characterized by amplitude-dependent natural frequency and damping ratio. The model was subjected to various environmental tests to understand how the outcomes of the test might be different for the nonlinear system as compared to a linear system. To facilitate this, a simple approach is developed that allows one to use the amplitude dependent frequency and damping to predict the behavior during an environmental test. The simulations show that the response of the nonlinear system could be significantly larger or smaller than expected if the system were linear, depending on the amplitude at which the system is driven and where the control accelerometer is located. If the environment is specified as a base acceleration, then nonlinearity in the component can cause the displacement, and thus the stress in the component, to be more than an order of magnitude larger or smaller than expected from a linear model. In contrast, if the control accelerometer monitors the mode of interest, then the target vibration levels will be obtained, yet with far different base excitation levels than would be expected if the system were linear. Because vibration-based testing requires certain vibration levels to be reached and maintained, these results may have implications for the vibration control software and the settings needed to successfully complete the test. [ABSTRACT FROM AUTHOR]
ISSN:07328818
DOI:10.1007/s40799-025-00827-z