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Process-Integrated Online Monitoring of Safety-Relevant Aluminum Airbag Pressure Vessel Components for a Combined Defect Detection and Material Property Determination by Using Contactless NDT (EMUS and EC)

: Becker, R.; Dobmann, G.; Salzburger, H.-J.

Brusey, B.; Bussiere, J.F.; Dubois, M.; Moreau, A. ; Canadian Institute of Mining, Metallurgy and Petroleum:
Advanced Sensors for Metals Processing
Quebec: Met Soc, 1999
ISBN: 0-919086-92-6
Annual Conference of Metallurgists of CIM - Gateway to the 21th Century <38, 1999, Quebec>
Fraunhofer IZFP ()
Aluminum Pressure Casting; process integration; process monitoring; safety

Airbagpressure vessels for the north-American market mainly are made by forging and by the use of steel alloys. In Europe aluminium alloys are common ant the manufacturing process is extrusion of circular blancs - made from cold rolled plates - in a form applying a 100 t press at room temperature. Then by heat treatment the strength/hardness of the material is properly adjusted and after that the pressure vessel parts have to be continuously inspected with an inspection and handling cycle time of 3 s. Inspection of the axis-symmetric parts is asked for surface breaking extrusion defects as well as for surface parallel delaminations in the bulk volume. Futhermore, the material strength is a quality characteristic that has to be nondestructively registered and documented. The inspection is performed by eddy current probes and an EMAT, of which the eddy current impedance measurements are used for surface-breaking extrusion defect detection and sizing (single frequency technique with digit al locus curve filtering) and strength characterization (3-frequency technique with digital filtering for signal-to-noise enhancement). The bulk delaminations are detected by an EMAT-resonance technique using a spiral eddy current coil and permanent mafnets for the EMA-energy transformation. The inspections are performed by singling the parts on a conveying belt, rotating two of them parallel on turntables scanning with the transducers in specially selected circular scan paths. The performance of the system is characterized by a number of 6000 parts per shift in the two time-parallel inspection lines with 3 shifts in 24 hours. The registered quality characteristics are documented by laser writing onto the surface of each part. The emphasis of the contribution is on the presentation and discussion of the safety and economical benefits by process-integrated NDT.