Aviation Safety

As part of the European research program "Clean Sky for Aviation" Fraunhofer ITWM has developed an integrated and fully automated solution for the surface inspection and measurement of BLISKs (Bladed Integrated Disk) together with the partners Hexagon Metrology (Wetzlar) and Hexagon Technology Center (Heerbrugg, Switzerland).

AMI4Blisk – Automated Measurement and Inspection System for Bladed Disks

Inspection of the surface of a BLISK (Bladed Integrated Disk) with two cameras and one light source
© Photo ITWM

Inspection of the surface of a BLISK (Bladed Integrated Disk) with two cameras and one light source

An important component in todays aero-engines are the turbines, so called BLISKs (short for bladed disks). Because of current high quality standards in air traffic safety, those BLISKs need to be checked visually and manually for defects by specialists for several hours. The discovered defects then are measured down to micrometer scale to obtain a quantitative description. In the european research program »Clean Sky«the Fraunhofer ITWM in corporation with Hexagon Technology Center (Heerbrugg, Schweiz) developed an intregrated and fully automated solution for the surface inspection and measurement of BLISKs. In this project we wanted to further improve safety in aviation.

First the geometry of the BLISK has to be measured with a Coordinate Measurement Machine (CMM). This is done by Hexagon in Wetzlar. In combination with the CAD-Model, this step provides all information about the actual shape and geometry of the BLISK and gives us information about possible deviations from desired values.

 

 

A challenge for image processing: Exact positioning of the defects in a 3D coordinate system.
© Photo ITWM

A challenge for image processing: Exact positioning of the defects in a 3D coordinate system.

Challenges of Defect Inspection

Task of the Fraunhofer ITWM was to develop a solution in a second step. The surface of the BLISK is scanned up to 100% by several cameras and investigated for defects. Location and defect type (e.g. crack, point of impact) of potential surface defects are stored for further analyses. This task contains some obstacles: One was to find and develop the best illumination system to make every defect type visible on a BLISK. Due to the variety of defects, a combination of several illumination methods was needed. Another challenge was the complex free-form surface of the BLISK that makes it even harder to track it with lighting and cameras such that every part of the surface could be scanned. Additionally, cameras and parts of the illumination had to be small and light so that a CMM can hold and move them. Last but not least, for a robust detection of defects complex algorithms have to be developed that do not need many samples to find all defects automatically.

Surface Inspection of one BLISK.
© Photo ITWM

Surface Inspection of one BLISK.

Classify and Measure Defects

In a third step, the found defects were classified and measured down to micrometer scale. Therefore, a new sensor for defect measurement and defect classification was developed, done by Hexagon in Heerbrugg. From the results of step two, a measuring program has been generated. The potential defect locations, gained from step two, build the data base for this task. These measurements produce a quantitative description of all potential defects. For defects in question an additional inspection needs to be done manually by specialists.

 

Partners:

  • Hexagon Metrology GmbH, 2012-2015

 

Further Contacts:

  • Clean Sky - SAGE – Sustainable And Green Engines
  • MTU Aero Engines – Industry Partner