Correlation of a discrete friction (Iwan) element and continuum approaches to predict interface sliding behavior

This paper makes quantitative comparisons between three types of models for predicting frictional interface behavior: (i) Iwan-type friction elements that describe contact in terms of discrete contact points and spring elements, (ii) analytical models based on continuum elasticity and Coulomb friction, and (iii) finite element models which incorporate a simple interface constitutive description. A simplified “fiber pullout” geometry is considered which consists of a clamped rectangular bar being pulled between friction grips. The analysis illustrates that interface slip and load transfer behavior is well described by both analytical shear models and bilinear Iwan-type elements which differentiate elastic and friction effects. Two key contribution of this work are the identification of explicit connections between discrete friction parameters (i.e. spring stiffnesses) and continuum elasticity properties, and a straightforward calibration procedure to correlate lower order models with continuum results. This represents an important step toward lower order frictional interface models that can be used to efficiently yet accurately simulate dynamic stick-slip behavior in dynamically loaded contacts.