Extending modal testing technology for model validation of engineering structures with sparse nonlinearities: A first case study. (1st February 2017)

• Record Type: Journal Article
• Authors: delli Carri, Arnaldo; Weekes, B.; Di Maio, Dario; Ewins, D.J.
• Is Part Of: Mechanical systems and signal processing. Volume 84:Part B(2017)
• Page Start: 97
• Page End: 115
• Publication Date: 2017-02-01
• Subjects: Modal testing -- Nonlinear structures -- Model upgrading -- Model updating -- Model validation; Structural dynamics -- Periodicals; Vibration -- Periodicals; Constructions -- Dynamique -- Périodiques; Vibration -- Périodiques; Structural dynamics; Vibration; Periodicals; 621
• DOI: 10.1016/j.ymssp.2016.04.012
• Languages: English
• ISSNs: 0888-3270

Abstract

Abstract: Modal testing is widely used today as a means of validating theoretical (Finite Element) models for the dynamic analysis of engineering structures, prior to these models being used for optimisation of product design. Current model validation methodology is confined to linear models and is primarily concerned with (i) correcting inaccurate model parameters and (ii) ensuring that sufficient elements are included for these cases, using measured data. Basic experience is that this works quite well, largely because the weaknesses in the models are relatively sparse and, as a result, are usually identifiable and correctable. The current state-of-the-art in linear model validation has contributed to an awareness that residual errors in FE models are increasingly the consequence of some unrepresented nonlinearity in the structure. In these cases, additional, higher order parameters are required to improve the model so that it can represent the nonlinear behaviour. This is opposed to the current practice of simply refining the mesh. Again, these nonlinear features are generally localised, and are often associated with joints. We seek to provide a procedure for extending existing modal testing to enable these nonlinear elements to be addressed using current nonlinear identification methods directed at detection, characterisation, location and then quantification – in order to enhance the elements in an FE model as necessary to describe nonlinear dynamic behaviour. Emphasis is placed on the outcome of these extended methods to relate specifically to the physical behaviour of the relevant components of the structure, rather than to the nonlinear response characteristics that are the result of their presence. Highlights: Outlined a pragmatic and data-driven approach to the modal testing of nonlinear structures. Studied a reference test-structure (Wing-Pylon) following the mentioned approach. Addressed the identification of the nonlinear elements that act over the Underlying Linear Model. Augmented (Upgrade) and corrected (Update) the ULM, accommodating those elements. Checked the validity of the upgraded model across structural modifications.