Generalised round-trip identity—For the determination of structural dynamic properties at locations inaccessible or too distant for direct measurement. (27th October 2021)

• Record Type: Journal Article
• Authors: Wienen, K.; Sturm, M.; Moorhouse, A.T.; Meggitt, J.W.R.
• Is Part Of: Journal of sound and vibration. Volume 511(2021)
• Publication Date: 2021-10-27
• Subjects: Frequency response function -- Experimental structural dynamics -- Transfer path analysis -- Virtual acoustic prototyping -- In-situ blocked force -- System identification; Sound -- Periodicals; Vibration -- Periodicals; Son -- Périodiques; Vibration -- Périodiques; Sound; Vibration; Periodicals; Electronic journals; 620.205
• DOI: 10.1016/j.jsv.2021.116325
• Languages: English
• ISSNs: 0022-460X

Abstract

Abstract: In noise and vibration engineering, a structure's passive dynamic properties are often quantified by frequency response functions (FRFs). This paper focuses on acquiring FRFs from experimental tests, considering both, translational (x, y, z) and rotational (e.g. moments around these axes) terms. In practical applications, test structures may not allow FRFs to be measured directly due to the impracticality of applying a controlled excitation in a particular direction (e.g. in-plane), the inability to measure rotational dynamics (e.g. moment excitation), insufficient signal-to-noise ratio (SNR) between excitation and response degrees of freedom, or simply due to restricted access. Methods exist to resolve some of the mentioned issues using indirect experimental techniques, such as the round-trip identity. However, these methods are limited to cases in which the driving-point FRFs are sought-after. The present paper extends previous work into a more generalised formulation of the round-trip identity feasible for reconstructing driving-point and transfer mobilities from in-situ measurements conducted in coupled assemblies. By using the round-trip identity, the excitation of moments and/or inaccessible points is avoided altogether and instead replaced by a number of applied forces remote to the points of interest. Manipulation of this round-trip identity yields a formulation for long distance transfer FRFs, expressed in terms of multiple shorter transfer path elements, which are less prone to insufficient SNR. These practical applications of the generalised round-trip concept are experimentally validated for multi-input multi-output assemblies.