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.
OF DIFFERENT FAULTS INFLUENCE OVER OUTPUT SIGNAL FROM PULSED EDDY CURRENT TRANSDUCER
The results of applied output electromagnetic field due to interaction with electromagnetic field of eddy current that is made of the same output field in the investigation object are based on electromagnetic eddy current method. It is successfully applied to: early detection of areas with structural non-homogeneities where appearance of faults is possible, defending of very small defects and the details term exploitation has been evaluated, the degree of attrition of the surface protective layers is qualified. Redistribution of eddy currents is caused to the presence of defects in controlled items. Their changing reaction on force field and modification signal transducer is done. The aim of this work is to investigate the influence of different faults over output signal from pulsed eddy current transducer based on a model that is made in Mag Net 7.4. The results from this investigation can be applied in nondestructive testing.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.