Investigating plastic deformation around a reheat-crack in a 316H austenitic stainless steel weldment by misorientation mapping

Rahul Unnikrishnan, Shirley M. Northover, Hedieh Jazaeri, P. John Bouchard
2016 Procedia Structural Integrity  
During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation
more » ... mmercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data. Abstract Creep degradation in austenitic stainless steels is associated with nucleation and growth of cavities that can link up to form micro-and macrocracks, usually along grain boundaries. A reheat crack found near a header nozzle weld removed from a nuclear power station has been examined using both electron backscatter diffraction (EBSD) and hardness mapping. The EBSD studies revealed higher levels of lattice misorientation towards the weld region where the crack initiated with strain particularly concentrated at grain boundaries. The pattern of deformation shown by the EBSD measurements was confirmed by the hardness survey. Abstract Creep degradation in austenitic stainless steels is associated with nucleation and growth of cavities that can link up to form micro-and macrocracks, usually along grain boundaries. A reheat crack found near a header nozzle weld removed from a nuclear power station has been examined using both electron backscatter diffraction (EBSD) and hardness mapping. The EBSD studies revealed higher levels of lattice misorientation towards the weld region where the crack initiated with strain particularly concentrated at grain boundaries. The pattern of deformation shown by the EBSD measurements was confirmed by the hardness survey.
doi:10.1016/j.prostr.2016.06.436 fatcat:iyxc7j7yufdutccfpopezaxe3m