Application of Interface Reduction Methods to Rotordynamic Casing Models

Abstract As the use of digital twins for the purpose of structural health monitoring increases, so does the demand for high-quality models. In the area of rotating machines, this means that the casing must also be taken into account. These are often geometrically complex assemblies that require the use of finite element models. The models are then reduced in size by established reduction methods like the Craig–Bampton (CB) reduction in order to keep the solution time, e.g., for a forced response analysis as low as possible. In case of nonlinear contact forces, e.g., friction in bolted joints, a secondary reduction step has to be applied. Here, three different interface reduction (IR) methods are investigated and used for a rotor–casing assembly including frictional damping. The necessary basics and terms are presented. The performance of the methods is evaluated for a linear model on substructure and assembly level and for a nonlinear model on the assembly level. The implementation of the interface reduction within the harmonic balance method (HBM) is presented and tested for different unbalance excitation cases.