Bypassing the Repeatability Issue in Nonlinear Experimental Modal Analysis of Jointed Structures by using the RCT-HFS Framework

Date

2023-2-13

Author

Özgüven, Hasan Nevzat
Gürbüz, M. Fatih
Karaağaçlı, Taylan

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Mechanical joints, which are indispensable for almost all mechanical systems, are often an important source of nonlinearity due to frictional, backlash and/or preload effects. Recent studies have shown that the contact pressure distribution at bolted joint interfaces is the key parameter that governs joint friction and, therefore, the nonlinear damping mechanism in these systems. The problem is that this pressure distribution is susceptible to several different factors: bolt preload, bolt tightening order, surface roughness, surface flatness, and misalignments during the assembly process. These issues lead to considerable variability and repeatability problems in the nonlinear dynamics of jointed structures. Consequently, the accurate identification of nonlinear damping in jointed structures is still a challenging task. The combined use of the response controlled stepped-sine testing (RCT) and the harmonic force surface concept (HFS) constitutes a framework that determines frequency response curves from the same measurement in two different ways; either by directly measuring them or by synthesizing them from the identified nonlinear modal parameters. Since any possible discrepancy of the frequency response curves obtained from the same measurement cannot be attributed to the repeatability issue, the RCT-HFS framework validates the accuracy of the identified nonlinear modal parameters in a sense bypassing the repeatability problem. In this study, this novel feature of the RCT-HFS framework is used in identifying and validating the accuracy of the modal model of a benchmark beam with a bolted lap joint.

Subject Keywords

Joint nonlinearity, Friction nonlinearity, Response-controlled stepped-sine testing, Harmonic force surface, Repeatability

URI

https://hdl.handle.net/11511/105230

Collections

Department of Mechanical Engineering, Conference / Seminar