Extension of the tip excitation technique to the rotational compliance measurement of curved structures

The present paper presents an extension of the so-called tip excitation technique for measuring the rotational compliance of curved structures. On the basis of the original form of the technique, developed for attached plane structures, the technique is improved to take into account the presence of the in-plane vibration and the rigid motion. Two derivatives of the technique are developed: the first one using two accelerometers allows a more accurate indication of rotational response, thus providing a good accuracy in middle frequency range; the second one using double excitation effectively eliminates the in-plane force excitation, thus providing an excellent measurement accuracy at both low and middle frequencies. Numerical simulations using finite element modeling are performed to analyze different parameters affecting the performance of the technique. Experimental validations are then reported. It is shown that the technique is successfully extended to curved structures while retaining the advantages of the original version of the method in terms of its simplicity and its capacity for mass loading compensations.