Estimation of Rotational Frequency Response Function of Structures

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In this study, a measurement method of rotational FRF using a rigid T-block was presented. A feasibility study using a beam structure was conducted last year. The followings are the contents of this year study.1. Improvement of accuracy and expansion of applicabilityEffect of random noise on rotational FRF measurement is investigated. The estimation approach in order to improve the accuracy is presented. The advanced approach is also examined, in which the elastic vibration of the T-block is considered to expand the applicable frequency range. By these investigations the applicable frequency range is expanded up to 1,000 Hz whereas the range is originally covered up to 500 Hz.2. Application to an industrial structureThe presented FRF estimation method is applied to an automobile sub-frame structure. The validity is confirmed by comparing estimated FRF with the FEM prediction. Structural Dynamics Modification is carried out to the sub-frame by using the rotational FRFs. Applicability to the real industrial structure is confirmed.3. Summary of the StudyThe flow of the experimental modal analysis in which the rotational DOFs are taken into account is presented. It is shown that the experimental modal analysis becomes more useful and predictable in the presented scheme.