On the completeness of interface descriptions and the consistency of blocked forces obtained in-situ

Meggitt, JWR; Moorhouse, AT

Abstract

Blocked forces can be used to describe, independently, the operational characteristics of a vibratory source. Their use
within a computational model avoids the need to represent explicitly the complex mechanisms that lead to vibratory
excitation. To obtain and apply an experimental blocked force with confidence it is important that likely sources of
error are known, and measures of their severity are available. In this paper we introduce the notions of completeness
and consistency, and detail their role in the introduction of systematic errors in a blocked force characterisation. Their
mathematical origins are described and criteria to quantify their severity are proposed; the Interface Completeness
Criterion (ICC), and the Measurement Consistency Criterion (MCC). These are illustrated through numerical and
experimental examples. Completeness is related to the interface description adopted in a source characterisation
(i.e. the number of degrees of freedom used). The ICC represents the quality of an interface description and can
be quantified from in-situ measurements, i.e without having to remove the source from its assembly. Consistency
is related to the underlying dynamics shared by active and passive quantities (whether measured or modelled). The
issue of consistency is more general, completeness being a special case, and so a single criterion is hard to formulate.
When an inconsistency arises between the blocked force of a vibration source and its corresponding free interface
frequency response function matrix, the MCC provides a quantitative indication of its severity. Importantly, many of
the concepts discussed apply equally in the context of experimental dynamic sub-structuring.

• Journal Article Type: Article
• Acceptance Date: Mar 25, 2020
• Online Publication Date: May 5, 2020
• Publication Date: Nov 1, 2020
• Deposit Date: Mar 25, 2020
• Publicly Available Date: May 14, 2020
• Journal: Mechanical Systems and Signal Processing
• Print ISSN: 0888-3270
• Publisher: Elsevier
• Volume: 145
• Pages: 106850
• DOI: https://doi.org/10.1016/j.ymssp.2020.106850
• Publisher URL: https://doi.org/10.1016/j.ymssp.2020.106850
• Related Public URLs: https://www-sciencedirect-com.salford.idm.oclc.org/journal/mechanical-systems-and-signal-processing
• Additional Information: Funders : Engineering and Physical Sciences Research Council (EPSRC); Projects : EMBED; Grant Number: EP/P005489/1