3.2.1 FE Modelling of the non-standard MTP Specimen
Concerning the role of geometry constraint that non-standard MTP specimen has, the complex stress state and the stress triaxiality in essence within the total effective gauge length specimen play an important role in high temperature LCF testing. Thus, it is necessary to evaluate the geometry constraint effect in order to obtain correct transferability between SSFS and non-standard small-sized specimen testing results. To overcome this, the authors have established a new methodology which links the MTP FE model with cyclic UVP constitutive model for determination of scaling factor in order to obtain more accurate applied displacement. The identified scaling factor will be accommodated into high temperature LCF and CF testing of MTP specimen for further comparison and validation.
The identification of scaling factor was simulated through MTP FE model by comparing with SSFS experimental high temperature LCF data. Fig.6a shows an example of non-standard experimental MTP LCF testing set-up. The corresponding 3D FE model, mesh and boundary conditions chosen are given in Fig.6b, while the FE model were performed using C3D8-8 node hexahedral elements. The MTP FE models were constrained in an identical way to the clamping conditions placed on the specimen during LCF testing, as shown in Fig.6a. The extensometers are equivalent to place at the shoulder regions as illustrated in Fig.6b, which is capable to measure the whole deformation including parallel gauge length and transition fillet radius regions.