Nonlinear lap joint interface modeling and updating strategies for assembled structures

A comparison between two known strategies of modeling lap joint interfaces, namely, zero-thickness and thin layer interface theories and their associated updating procedures, is made. Finite element models capable of accurately representing nonlinear behavior of assembled structures with localized nonlinearities in their bolted lap joint are developed. A practical strategy is employed in updating of these structures that initially parameters describing linear behavior are updated based on the low-amplitude excitation experimental observations. In the next step, parameters representing nonlinear effects are updated using stepped-sine excitations near the structure resonance frequency. In both steps, the Particle Swarm Optimization (PSO) algorithm is used to reduce the discrepancies between experimental observations and model predictions. The identified contact interface models are validated by comparing their predictions with the experimental data not included in the updating procedure. In what concerns the updating process, the convergence rate of parameter identification in a model with zero thickness frictional contact elements was lower and more time-consuming compared to the model with thin layer interfaces.This study shows assigning appropriate material properties for the thin interface layer results in contact forces with comparable accuracy to the ones obtained by zero thickness elements with less computational efforts.