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.