Service-type creep-fatigue experiments with cruciform specimens and modelling of deformation

Advanced material models for the application to component life prediction require multiaxial experiments. A biaxial testing system for cruciform test pieces has been established in order to provide data for creep, creep-fatigue and thermomechanical fatigue (TMF) experiments. For this purpose a cruciform specimen was developed with the aid of Finite element calculation and the specimen design was optimised for tension and compression load. The testing system is suitable for strain (displacement) and load control mode. A key feature deals with the opportunity to perform thermomechanical experiments. Further, a constitutive material model is introduced which is implemented as a user subroutine for Finite element applications. The constitutive material model of type Chaboche considers both isotropic as well as kinematic hardening and isotropic damage. Identification of material parameters is achieved by a combination of Neural networks and subsequent Nelder–Mead Method.