FRF estimation on rotational degrees of freedom of structures

In conventional vibration testing, frequency response functions (FRFs) are measured only on translational degrees of freedom. This paper presents a new estimation method of rotational FRFs. In the proposed method a T-shaped block is attached to the measurement point. The block is excited by conventional impact hammer; the inner force and the response of the connection point including rotational DOFs are estimated; and finally the FRFs including rotational DOFs at the connection point of the structure is obtained. The feasibility of the method is investigated experimentally by applying it to a beam structure.