Introduction of line contact in frequency-based substructuring process using measured rotational degrees of freedom

Abstract

The theory of frequency-based substructuring enables us to combine the dynamical behavior of multiple subsystems into the common response of the whole system. Subsystem's properties can be numerically or experimentally obtained in the form of frequency response functions. Response models are then coupled together taking into account a connectivity conditions. However, when one is dealing with a statically indeterminate multi-point connections such as flanges connected over several bolts, it is difficult to properly define a model in the numerical environment. In order to obtain real contact conditions a few methods like virtual point transformation and multi-point connection were proposed in recent years. Since an indirect approach of obtaining rotational motion struggle to accurately define local dynamic characteristics i.e. antiresonances, it also rely on assumption of rigid interface. In this paper we are introducing an alternative approach, where all six degrees of freedom are experimentally obtained with aim to directly address local joint flexibility in the substructuring process. This procedure represent an alternative to the method that removes the effects of a flexible fixture, however here it is done directly by measuring contact dynamic without the need of additional fixture block. Rotational responses are directly obtained using rotational accelerometer that enable us to gather all six degrees of freedom in each experimental point. Consequently, contact can be fully defined with less measurement points where several of them with only translational responses are required in other methods for reconstruction of rotational motion.