Dynamic parameter estimation of bolted assemblies

In this paper, a parameter estimation model for identifying bolted assemblies is proposed using frequency response functions (FRFs). A dynamic model of structures with fixed joints is developed by taking into consideration the contact stiffness, contact damping and bolt preload which influences the dynamic behaviour of structures. The stiffness of any mechanical structure as well as the amount of damping and the presence of nonlinearities are mainly determined by the bolted joints. The dynamic model can accurately reflect the dynamic characteristics of the joints. Based on the state space representation of a multi mass-spring-damper system, a parameter identification models are proposed in order to identify the dynamic model parameters of the joints using experimentally obtained test data of the whole structure including the joints. The dynamic tests reveal the influence of the bolt pretension on the FRFs, contributing to changes both in frequency and amplitude. The effectiveness and accuracy of the FEM dynamic model have also been validated through experimental results. The development of the model assures a theoretical base for the dynamic modelling of bolted assemblies, e. g. being part of machine tool structures.