High strain rate and high temperature behaviour of metallic materials for jet engine turbine containment

Abstract
This work presents a study on the mechanical characterisation of the materials involved in air jet engine turbines. The final objective is to analyse the phenomenon of a turbine blade off failure, to verify the requirements of the case containment. The materials in the turbine are under high temperatures, ranging from 400C to 800C and when the fail of the blade occurs if impacts against the case, reaching strain rates up to 10³ s ^{- 1}. To obtain the behaviour of the materials, testing at high strain rate and high temperature at one time is necessary. The experimental set-up used was a split Hopkinson pressure bar, with a high temperature furnace adapted. The bars used on the device were high strength nickel alloys with a cooling system to decrease the temperature of the measurement devices. The effect of wave dispersion due to the temperature gradient has been also studied to correct the measurements if necessary. The material tested has been the FV535 stainless steel used on the case. The full stress-strain curves at different temperatures and at strain rates up to 10³ s^-1 have been obtained. The experimental results show a marked influence of the strain rate and the temperature that cannot be neglected. The Johnson-Cook material model has been used to fit the results of the material tests.