A novel method for the identification of a model for the nonlinear characteristic of a bolted lap-joint

Joints are the main source of nonlinearity and energy dissipation in large assembled structures which could be otherwise considered as linear. Consequently, modeling and parameter identification of joints play a significant role in any successful design and finite element (FE) modeling of structures. In the present research, an identification procedure is proposed for the modeling of the nonlinear behavior of a bolted joint. The main emphasis are placed on the simplicity of the experimental procedures involved as well as ease of incorporation of the identified model in the FE model of the structure. Using the concept of the optimum equivalent linear frequency response function, structure was excited by two levels of random force, at two bolt preload levels, and then the eigen values of the nonlinear structure and the inverse eigen-sensitivity identification technique are used, in order to identify the nonlinear properties of bolted joints. The results of implementing the method are promising and indicative of the fact that, in contrast to static Iwan’s model of a bolted joint, the equivalent dynamic characteristics of a bolted joint may be frequency dependent, as the different modes will affect the interface zone of the jointed structures in a different manner.