Experimental Modal Analysis of Geometrically Nonlinear Structures by Using Response-Controlled Stepped-Sine Testing

2022-01-01
Karaağaçlı, Taylan
Özgüven, Hasan Nevzat
© 2022, The Society for Experimental Mechanics, Inc.The everlasting competition in the industry to achieve higher performance in aircraft, satellites, and wind turbines encourages lightweight design more than ever, which eventually gives birth to more flexible engineering structures exhibiting large deformations in operational conditions. Accordingly, continuously distributed geometrical nonlinearity resulting from large deformations is currently an important design consideration. Being guided with this motivation, this paper investigates the performance of a recently developed promising nonlinear experimental modal analysis method on a clamped-clamped beam structure which exhibits geometrical nonlinearity continuously distributed throughout the entire structure. The method is based on response-controlled stepped-sine testing (RCT) where the displacement amplitude of the excitation point is kept constant during the frequency sweep. In this study, the nonlinear beam structure is instrumented with multiple accelerometers at several different locations along its length and is excited at a single point. Tests are conducted at energy levels where no internal resonance occurs, yet the beam structure exhibits strong stiffening nonlinearity which results in jump phenomenon in the case of classical constant-force sine testing. Nonlinear modal parameters are experimentally identified as functions of modal amplitude by applying standard linear modal identification methods to quasi-linear frequency response functions (FRFs) measured with RCT. Validation of the identified modal parameters is accomplished by comparing the constant-force FRFs synthesized using the identified modal parameters with the ones obtained from constant force testing and also with the ones extracted from the harmonic force surface (HFS).
39th IMAC, A Conference and Exposition on Structural Dynamics, 2021

Suggestions

Active control of the tip vortex: an experimental investigation on the performance characteristics of a model turbine
Anik, E.; Abdulrahim, A.; Ostovan, Y.; Mercan, B.; Uzol, Oğuz (2014-06-20)
This study is part of an on-going experimental research campaign that focuses on the active control of the tip leakage/vortex characteristics of a model horizontal axis wind turbine rotor using tip injection. This paper presents both baseline (no-injection) data as well as data with tip injection, concentrating on the effects of tip injection on power and thrust variations with the Tip Speed Ratio (TSR). The experiments are conducted by placing a specially designed 3-bladed model wind turbine rotor at the e...
Analysis of a wind turbine foundation on stiff clay with analytical and 3D finite element methods
Yaşar, Baki Eren; Huvaj Sarıhan, Nejan; Department of Civil Engineering (2019)
Optimum design of onshore wind turbine foundations have been a topic of interest in geotechnical engineering in recent decades. However, the literature is lacking a systematic methodology for the design of onshore wind turbine foundations with three-dimensional finite element method (3D FEM) and a practical study evaluating the factors affecting the foundation design. The goals of this study are (i) to present a comprehensive design procedure by summarizing the literature, (ii) to investigate the key issues...
Development of a high fidelity finite element model of a wind turbine blade via modal testing
Amer, Chadi; Şahin, Melin; Department of Aerospace Engineering (2015)
The design of an optimised horizontal axis 5-meter-long wind turbine rotor blade, is a research and development project, in order to fulfil the requirements of high efficiency torque-from-wind production. For this purpose, a research study is presented here, by investigating the structural characteristics of a composite wind turbine blade via finite element modelling and experimental modal analysis. At first, modal tests are performed by using various sensor-actuator pair combinations. After that the geomet...
Experimental Study of a TLP Offshore Floating Wind Turbine
Oğuz, Elif; Clelland, David; İncecik, Atilla; Dai, Saishuai; López, Juan Amate; Sánchez, Gustavo (null; 2016-07-18)
Tank testing in a wind and wave environment is a key part of the design process for the development of an offshore floating wind turbine. The current paper describes an extensive experiment campaign carried out at the Kelvin Hydrodynamics Laboratory at the University of Strathclyde to determine the hydrodynamic performance of the Iberdrola TLPWIND offshore floating wind turbine with the NREL 5MW reference turbine over a range of environmental conditions. Tests were carried out for 70m water depth and the de...
Analysis and verification of a pyroshock test system
Küçükbayram, Anıl İsmail; Özer, Mehmet Bülent; Department of Mechanical Engineering (2021-2-03)
In the aerospace industry, systems, subsystems, and units are exposed toexplosive events during their lifecycle. Any explosive event creates shock in the structure, and it propagates until it is damped. This shock wave may be hazardous for some electronic and optical components. It may damage a component and cause failure in the equipment. For this reason, satellite equipmenthas tobe qualifiedto withstand all static and dynamic loads encountered during launch and operational life. Thus, one of ...
Citation Formats
T. Karaağaçlı and H. N. Özgüven, “Experimental Modal Analysis of Geometrically Nonlinear Structures by Using Response-Controlled Stepped-Sine Testing,” presented at the 39th IMAC, A Conference and Exposition on Structural Dynamics, 2021, Virtual, Online, 2022, Accessed: 00, 2022. [Online]. Available: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85120523760&origin=inward.