Buried Corrosion Detection in Multi-layer Airframe Structures
Substantial enhancements in Pulsed Eddy Current instrumentation and array probes provide a unique capability for the detection and imaging of sub-layer corrosion. The use of giant magnetoresistive (GMR) elements in an inductive array provides increased depth of sensitivity over conventional eddy-curr ent sensing coils. This paper provides an overview of newly developed instrumentation, whic h provides a portable, battery-operated platform for multi-layer corrosion dete ction in flight line or repair facilities. Demonstrated capability includes rapid inspec tion and detection of material loss in lap joints with air gaps and complex geometries. Advanced imaging capability and post-processing allows multi-layer analysis, with distinct C-scan images of up to four (4) 1-mm layers.
Characterization of Hidden Corrosion In Multilayer Aircraft Structures Using Transient Eddy-Current NDE
Previous research [1–4] has demonstrated that transient eddy-current (EC) techniques have significant advantages for the nondestructive evaluation (NDE) of hidden corrosion in multilayer aircraft structures when compared with conventional EC NDE. By sampling the time-domain response to a step or pulsed excitation using a high-speed digitiser, the probe response is effectively captured over a wide range of frequencies within a single measurement of only a few milliseconds duration, giving a very significant performance advantage over swept-frequency methods. In addition, direct measurement of the transient magnetic field (eg. using a Hall effect device), rather than the voltage induced in a pickup coil, allows transient EC NDE to probe more deeply into a multilayer structure compared to conventional EC techniques, giving improved sensitivity to deeply buried defects including hidden corrosion [1, 2, 5].
Brushite-collagen composites for bone regeneration.
Brushite-based biomaterials are of special interest in bone regeneration due to their biocompatibility and biodegradability; on the other hand, collagen is a well-known osteoconductive biomaterial. In the present study a new brushite-collagen composite biomaterial is reported. This new biomaterial was prepared by combining citric acid/collagen type I solutions with a brushite cement powder. The obtained biomaterial was a cement paste, with improved handling properties. The effect of collagen on the setting reaction of brushite cement was studied, and was found to speed up the cement setting reaction. The cement paste set into a hard ceramic material within 18.5+/-2.1min and had compressive strength similar to that of spongeous bone (48.9+/-5.9MPa in dry conditions and 12.7+/-1.5MPa in humid conditions). The combination of collagen with citric acid revealed an interesting synergistic effect on the compressive strength of the composite material. Moreover, this new biomaterial had excellent cohesion properties (ninefold better than brushite cement), and high cellular adhesion capacity (threefold higher than brushite cement). The composite biomaterial described in this study combines good handling properties, compressive strength, cohesion and cell adhesion capacity, along with the osteoconductive and biodegradable properties inherent in brushite and in collagen-based biomaterials.