Topic
Modal testing
About: Modal testing is a research topic. Over the lifetime, 4047 publications have been published within this topic receiving 64772 citations.
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01 Jan 2005
TL;DR: In this article, it is shown that stress histories can be estimated with high accuracy by integrating measured accelerations to obtain displacement and then performing a modal decomposition of the so estimated displacements.
Abstract: In this paper it is shown that stress histories can be estimated with high accuracy by integrating measured accelerations to obtain displacement and then performing a modal decomposition of the so estimated displacements. The relation between the modal coordinate and the stress in an arbitrary point is established by a finite element model. It is shown, that when performing the modal decomposition, either experimental mode shapes or numerically estimated mode shapes can be used. However, it is important to verify that the numerical modes correspond reasonably well to the experimental modes. It is shown that the so estimated stress histories can replace strain gauge measurements in many cases, and it allows for an accurate estimation of fatigue damage. Nomenclature Φ Mode shape matrix. ∆σ Stress range. D Damage. f Natural frequency. N Number of stress cycles. q(t) Time depend modal coordinate vector. y(t) Time depend displacement vector. exp Experimental determined value. FE Numerical (finite element) determined value.
33 citations
TL;DR: In this paper, the authors investigated the coupled modes, including coupled torsional-flexural vibration and coupled longitudinal flexural vibration, for non-rotating crankshafts which are free-free suspended.
33 citations
TL;DR: In this article, a parametric study is carried out to investigate the influence on the solutions, and thus the system modal damping and frequency, of the cable geometry-elasticity parameter, cable inclination, damper position, mass ratio, frequency ratio, and damper damping ratio.
Abstract: Based on the theoretical derivations of the free vibration problem for a cable-TMD system in the companion paper, a parametric study is carried out in the present paper to investigate the influence on the solutions, and thus the system modal damping and frequency, of the cable geometry-elasticity parameter, cable inclination, damper position, mass ratio, frequency ratio, damper damping ratio, and tuning mode. Emphasis is put on the system modal damping, as this is an important index of the performance of the TMD. The features and mechanisms of energy transfer and damping redistribution from the TMD to each mode of the cable-TMD system are also investigated and discussed.
33 citations
TL;DR: In this paper, the authors focused on the experimental evaluation of uncertainty sources in modal parameter measurement, when high-energy laser pulses are used to excite the vibration of the structure.
33 citations
TL;DR: In this paper, the authors measured modal damping using strain-gauge data from an operating wind turbine and verified the method by extracting damping values from an analytically generated data set.
Abstract: The authors have measured modal damping using strain-gauge data from an operating wind turbine. This new technique for measuring modal damping is easier and less expensive than previously used methods. Auto-correlation and cross-correlation functions of the strain-gauge data have been shown to consist of decaying sinusoids which correspond to the modal frequencies and damping ratios of the wind turbine. The authors have verified the method by extracting damping values from an analytically generated data set. Actual operating response data from the DOE/Sandia 34-m Test Bed has been used to calculate modal damping ratios as a function of rotor rotation rate. This capability will allow more accurate fatigue life prediction and control.
33 citations