Vibration suppression using tuneable flexures acting as vibration absorbers

Vibration suppression is an area of engineering that is vital for the development of manufacturing of low stiffness structures. A diversity of passive, active and semi-active vibration control techniques exist in the literature, many of them focused on the tool or the workpiece, while little attention has been paid into the dissipation capabilities of the fixtures. In this paper, the vibration attenuation capabilities of tuneable flexures are presented, proving the ability of beam-shaped supports to mitigate the vibration induced by the manufacturing process (e.g. machining loads) to the workpiece. The proposed modelling approach puts a solid theoretical basis on how to construct flexures tuned in such a way to allow their natural frequency to match the frequency of excitation, thus absorbing the energy from the workpiece and keeping it at low vibration levels. By means of a multiple-degree-of-freedom (MDOF) model and considering the system as three different bodies with springs and dampers, the dynamic behaviour of the system is examined theoretically starting from the geometry and material of the flexures on which the fixturing system is based. This is further validated with finite element analysis (FEA) as well as experimental results showing a low discrepancy between the models on the prediction of the resonant frequencies of up to a 0.6%. The importance of understanding the critical clamping load for the locking of the contact surfaces is also presented, as it is indispensable for the proper functioning of the flexures-based fixturing system. Finally, the vibration suppression capability of the flexures at the targeted frequency is experimentally validated and proved to substantially reduce (ca. 90%) the vibration response of the workpiece when compared with the non-suppressed frequencies. The proposed model represents an avenue to address the inverse problem for the design of a fixture with vibration absorption capabilities, depending on the manufacturing process parameters, the workpiece and the chatter that needs to be suppressed.