I could see where the inner band of the first LPT nozzle stage could contact the IPT blades at the TE root, perhaps initiating blade failure. This would seem to be in conflict with the failure sequence in the powerplant report
I'm puzzled by the words (my bold) in the quote above.
Do you have a link to the section of the report that you refer?
Typically it is only in a final report which may contain an analyis where critical details are explained and supported.
My read so far is that a local (oil fire) overheat occurred sufficient to release the IPT disk from the compressor load at the drive arm.
This overheat may include only the innermost portions of the turbine disk.
Does the referenced report detail any estimates of disk body material strength from Bore to rim of the disk?.
If not then the strength of the disk may have been only marginally impacted by the oil fire.
Regardless of the answer to my question, the released disk from its drive arm is an important detail in its progression. If it was only completely released in the tangential direction (torque loss only) then it may not have permitted the free disk from moving aft into the aft nozzle vane clusters.
Whether the disk moves aft or not, it would still free wheel up in speed at a very rapid rate while remaining centered about the engine centerline. The tendancy is for it to seek restraint both upon the remaining drive arm/shaft pieces as well as its still intact blade tips against the outer case structure.
The time between the separation from its drive arm and burst would be dependant on several factors
1) the average material strength and average temperature in the compartment (local strength losses due to a localized fire would not be significant as the disk stretches and redistributes its strain)
2) The residual pressure trace across the turbine blades vs time
3) any loss of turbine blades in this stage
Rubbing friction itself against the aft nozzle vanes and between the blade tips and case would be negligible in such an event.
Likewise any false bearing between the blade roots and the aft nozzles would be negligible.
I haven't seen any factual information that suggests that blade to vane contact would be expected in the airfolis for this design.
In the end it's a F=MA over time that assess how far aft the rotor might have moved vs the speed vs time of the free wheeling disk under a decreasing gas load.
If any of the above has been convered already in a report I would be pleased to read it.
Meanwhile I am quite happy with the recommendations provided by this investigation todate (Fault analysis vs quailty control at the manufacturers)