Blades under test

Villaroche, France-based SNECMA is using Cedip Infrared Systems’ Silver 450M IR camera for the remote non-contact fatigue testing of its engine turbine blades.

SNECMA designs, develops and produces engines for civil and military aircraft, launch vehicles and satellites.

To improve the design of its aero-engines, engineers at SNECMA sought to better understand the behaviour of differently treated engine turbine blades when subjected to extreme vibration testing.
To simulate vibration conditions, engineers mounted a turbine blade on a fixed, rigid support and subjected it to powerful pulsated air blasts considerably in excess of what would be encountered in an aero-engine even in extreme use. Crack propagation was induced by gradually increased the frequency of the intense air blasts to the resonant frequency of the turbine blade.

Using a Silver 450M thermal IR camera, SNECMA engineers were then able to pinpoint the exact stress limit of a range of differently treated turbine blades as the appearance of a crack is proceeded by a localised heating effect. 

During crack propagation the temperature at this point rises by several hundreds of degrees.  However as the point is very small and the crack propagation process very fast (a few milliseconds) this places great demands on the IR camera in terms of the need for excellent spatial definition, high frame frequency and large dynamic range (ambient to 800°C).

The Silver 450M is specifically designed for users of IR technology who want to perform thermal imaging at fast frame rates with a high sensitivity and accuracy. The Silver 450M’s 320 x 240 pixel format InSb detector delivers a 400Hz full frame rate while maintaining good linearity and high sensitivity.

Offering a sub-array windowing mode with integration time adjustable in 1µs increments and smart external triggering capability the Silver 450M is able to synchronise image capture to even the most transient events.

Incorporating an integral optical front end, SNECMA engineers were able to precisely focus on microscopic areas of turbine blades then, using a bayonet mounting, quickly change the lens to adapt the field of view for turbine blades of different sizes.

Transferring images at a full 14-bit dynamic range via a CAMLINK interface to a remote PC enabled engineers to record a complete 15 minute experiment with remarkable thermal discrimination from ambient to 800 °C.

Using additional functionality within the Silver 450M camera software, SNECMA were able to integrate IR data with readings from strain guages also installed on the turbine blades under test.