Non-Contact MEMS-Sensor Array Inspection of Composites and Metallic Parts Using Lamb Waves
article
Composite materials are becoming more popular in the aerospace industry, because of their
physical properties. In quality assurance and in-service inspection, there is a need for fast,
non-contact, high-quality, non-destructive inspection techniques. The most common
approach is to perform the inspection using water-coupled high-frequency transducers.
Full wavefield techniques are promising to replace the conventional inspection approach.
However, these are currently performed by a laser vibrometer setup, which has drawbacks.
As an alternative, a low-cost micro-electro-mechanical system (MEMS) sensor array and
dedicated processing scheme are presented enabling fast inspection of large samples.
This inspection approach uses a piezoelectric actuator to excite the composite or metallic
part with Lamb waves. An array of MEMS sensors records the energy that radiates into
the surrounding air. A dedicated processing scheme will translate the measured wavefield
into a thickness map of the inspected part. For composite parts, the material’s anisotropy
needs to be taken into account for accurate thickness mapping. In principle, all relevant
defects show up as local thickness reductions. The results in this paper are obtained with
a MEMS-sensor array of 128 elements capable of detecting ultrasound up to 250 kHz at
a typical stand-off distance of 100 mm. Defects up to 6 mm in diameter could be detected
in thick panels, and defects as small as 2.5 mm could be detected in thin panels. A fullsize
fuselage experiment shows that the method is also suited for fast inspection of large inspection
areas
physical properties. In quality assurance and in-service inspection, there is a need for fast,
non-contact, high-quality, non-destructive inspection techniques. The most common
approach is to perform the inspection using water-coupled high-frequency transducers.
Full wavefield techniques are promising to replace the conventional inspection approach.
However, these are currently performed by a laser vibrometer setup, which has drawbacks.
As an alternative, a low-cost micro-electro-mechanical system (MEMS) sensor array and
dedicated processing scheme are presented enabling fast inspection of large samples.
This inspection approach uses a piezoelectric actuator to excite the composite or metallic
part with Lamb waves. An array of MEMS sensors records the energy that radiates into
the surrounding air. A dedicated processing scheme will translate the measured wavefield
into a thickness map of the inspected part. For composite parts, the material’s anisotropy
needs to be taken into account for accurate thickness mapping. In principle, all relevant
defects show up as local thickness reductions. The results in this paper are obtained with
a MEMS-sensor array of 128 elements capable of detecting ultrasound up to 250 kHz at
a typical stand-off distance of 100 mm. Defects up to 6 mm in diameter could be detected
in thick panels, and defects as small as 2.5 mm could be detected in thin panels. A fullsize
fuselage experiment shows that the method is also suited for fast inspection of large inspection
areas
TNO Identifier
985378
Source
Journal of Nondestructive Evaluation Diagnostics and Prognostics of Engineering Systems, 6