A typical aeroengine is made of many assemblies such as multiple stages of turbine and compressor blades, combustor section, fan section to name a few. These assemblies have many components connected by mechanical joints. These joints create interfaces which are subjected to various static and dynamic loads causing vibration during operation. In the turbomachinery field, the components are designed pushing structural envelopes for performance and efficiency. Hence, during the design phase, accurate prediction of operational vibration levels is critical. The cyclic and rotational nature of the components lead to high modal density and avoiding the resonances in the operating frequency range is next to impossible. Hence, the ideal option is to control the peak vibration levels. The crucial contacts such as bladed disk shroud contacts, blade-root joints and under-platform dampers are designed carefully to provide friction damping by allowing micro-sliding at these contacts. However, the contact interfaces introduce nonlinearity due to friction and inturn affect the dynamic response. The current linear solvers are not sufficient any more, as the results lead to great simplification and do not reflect realistic scenarios. Hence, robust nonlinear solvers considering friction contacts are necessary.

The micro-sliding at the contacts naturally leads to fretting wear. Fretting wear over a large number of cycles leads to high cycle fatigue (HCF), which is a dominant failure mode of turbomachinery components during operation. In addition, the partial or full sliding at the contacts leads to energy dissipation. This energy dissipation accumulated over a number of cycles leads to loss of material and alters the contact conditions. These new contact conditions affect the contact preload and alter the dynamic response, sometimes crossing over vibration amplitude limits. Especially, the blade tip shroud contacts are designed to provide structural rigidity, sealing and low vibration amplitudes and are assembled with a certain prestress. The fretting wear and reducing preload conditions can change the dynamic behaviour of the blade. In extremities, the blade can act as a free standing cantilever beam leading to