Microstructure-based modelling of rubbing in polycrystalline honeycomb structures

A microstructure-based modelling approach was used to study the deformation behaviour of polycrystalline honeycomb structures under rubbing loading. Rubbing originates from the sliding contact between sealing surfaces in a gas turbine engine. As a stationary component of the sealing system, the honeycomb structure’s role is to prevent catastrophic failure of the rotating component. Therefore, normal forces and surface deformations of the honeycomb structure need to be minimised to limit the heat input into the rotating component. To achieve a detailed representation of the honeycomb material response, the constitutive behaviour of the employed nickel-based superalloys Hastelloy X and Haynes 214 was modelled with a crystal plasticity approach, utilising a finite element framework. Uniaxial tensile tests at relevant temperatures and strain rates resembling the rubbing allowed the identification of crucial model parameters. The simulative studies based on the unit cell of the honeycomb structure revealed that the normal forces and the surface deformations are strongly affected by the microstructural features (size and orientation of the grains) and the applied deformation rate. In addition, a significant amount of residual stresses could be found for the macroscopically unstressed state after cooling and unloading.