Modelling tangential friction considering contact pressure distribution of rough surfaces

Frictional interfaces play an important role on the dynamic response of jointed structures. To accurately predict the dynamics of jointed structures, the phenomenological Iwan-type models, which consist of many spring-slider elements in parallel or series, are often used to describe interface frictional behavior. In this paper, a novel tangential friction modelling approach based on the framework of Iwan model is proposed. Specifically, the density function of slider critical slip force, which is vital to deduce the final form of Iwan model, is determined by a new method. The method is based on the real rough surface and contact pressure results due to rough contact are introduced to derive the form of Iwan model. This provides a physical method to derive the density function of slider critical slip force, while in the past the density function is usually assumed artificially without a clear physical meaning. In the proposed method, twofold Weibull mixture model is used to represent the contact pressure distribution of actual rough surfaces. Following this, the corresponding Iwan density function is derived based on the local Coulomb friction. Then substituting Iwan density function into Iwan model, the explicit relationship be-tween the tangential force and the relative displacement is deduced. The proposed modelling approach is applied to sphere-on-sphere contact and the comparison between the simulation and theoretical results shows perfect agreement. Then, the proposed modelling approach is validated against published experimental results for a flat-on-flat contact and a bolted joint. Compared to the classic Iwan model, the proposed model can better match the experimental results at the transition from microslip to macroslip. This study considers the influence of real rough contact characteristics on tangential friction behavior and provides a new tangential friction model deriving method.