Aircraft industry

Multi-layered riveted joint inspection

An INDETEC ndt ADPF probe has been developed for the inspection of the complex multi-layered riveted structures. Especially,  it was developed for the inspection of  spar flange of Blanik L13 sailplane. The main advantage of the probe includes its high detection sensitivity to short-length cracks under the rivet heads in the third layer. Generally, probe is very effective for crack detection in multi-layered structures.

 

Signal evaluation:

The phase and amplitude change of the EC signal is the basic principle for evaluating the signal. If there is a crack under the rivet head, or if the crack has already propagated into an area outside the rivet head, the phase and amplitude change, and the signal is fully deformed compared to the no-crack signal. The basic eddy current responses are shown in figures below.

   

       Phase and amlplitude change                       Cracks under the rivet head                       Cracks propagated outside the rivet head

 

EC signal evaluation in Y-t display:

 

The minimal detectable crack size a90/95 is approximately 4 mm from the rivet shank edge with 90% probability at a 95% confidence interval in meeting all inspection parameters.

Reference:

Aerospace Research and Test Establishment, Prague (VZLÚ, a.s.)

[1] BOHACOVA, Marie. Methodology of short fatigue crack detection by the eddy current method in a multi-layered metal aircraft structure. Engineering Failure Analysis [online]. 2013, vol. 35, s. 597-608 [cit. 2014-09-11]. DOI: 10.1016/j.engfailanal.2013.06.009.

Available from: http://www.sciencedirect.com/science/article/pii/S1350630713002094

 

Inspection of composite structures

Our new eddy current probe is determined for these type of composite material:

Type of Discontinuities: Artificial flaw (notch, hole), delamination,v wave, missing bundles, cracks, fractures,vcarbon fiber breaking, detection of fiber orientation

Eddy current responses to selected discontinuities:

1) Carbon fiber texture

EC signal - wave EC signal - notch

2) Carbon fiber prepreg

EC signal - delamination

3) Carbon fiber reinforced plastic CFRP

EC signal - defect

 

 

Bolt-hole eddy current inspection (fastener inspection)

Fastener holes are generally given greater scrutiny, as they are often locations of crack initiation and propagation due to load transfer and stress concentration. The fidelity of BHEC inspections is greatly dependent on the quality and cleanliness of the hole.

The basic equipment for BHEC inspection contains:

   

 

Eddy current signals - aluminium alloy structure

    EC signal without crack                                   EC signal of a crack