A Reduced Iwan Model That Includes Pinning for Bolted Joint Mechanics

Bolted joints are prevalent in most assembled structures; however, predictive models for their behavior do not exist. Calibrated models, such as the Iwan model, are able to predict the response of a jointed structure over a range of excitations once calibrated at a nominal load. The Iwan model, though, is not widely adopted due to the high computational expense of implementation. To address this, an analytical solution of the Iwan model is derived under the hypothesis that for an arbitrary load reversal, there is a new disSandia National Laboratories1, Albuquerque, NM, USA William Marsh Rice University, Houston, TX, USA 1: Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporations, for the U.S. Department of Energy’s National Nuclear Security Administration under Contract DE-AC0494AL85000. E-mail: [email protected] tribution of dry friction elements, which are now stuck, that approximately resemble a scaled version of the original distribution of dry friction elements. The dry friction elements internal to the Iwan model do not have a uniform set of parameters and are described by a distribution of parameters, i.e. which internal dry friction elements are stuck or slipping at a given load, that ultimately governs the behavior of the joint as it transitions from microslip to macroslip. This hypothesis allows the model to require no information from previous loading cycles. Additionally, the model is extended to include the pinning behavior inherent in a bolted joint. Modifications of the resulting framework are discussed to highlight how the constitutive model for friction can be changed (in the case of an Iwan-Stribeck formulation) or how the distribution of dry friction elements can be changed (as is the case for the Iwan plasticity model). The Reduced Iwan Plus Pinning (RIPP) model is then applied to the Brake-Reuß beam in order to discuss methods to deduce model parameters from experimental data.