| ABSTRACT: | LOW FREQUENCY-SAFT INSPECTION METHODOLOGY FOR COARSE-GRAINED
STEEL RAIL COMPONENTS (MANGANESE STEEL FROGS)
A. Diaz, E. Andersen, and T. Samuel
Battelle Northwest Division (BNWD), Richland, Washington, USA
In the rail industry, sections of high strength Manganese steel are employed at critical locations in
railroad networks. Ultrasonic inspections of Manganese steel microstructures are difficult to
inspect with conventional means, as the propagation medium is highly attenuative, coarse-
grained, anisotropic and nonhomogeneous in nature. Current inservice inspection methods are
ineffective while pre-service X-ray methods (used for full-volumetric examinations of
components prior to shipment) are time-consuming, costly, require special facilities and highly
trained personnel for safe operations, and preclude manufacturers from inspecting statistically
meaningful numbers of frogs for effective quality assurance. Inservice examinations consist of
visual inspections only and by the time a defect or flaw is visually detected, the structural
integrity of the component may already be compromised, and immediate repair or replacement is
required.
A novel ultrasonic inspection technique utilizing low frequency ultrasound (100 to 500 kHz)
combined with a synthetic aperture focusing technique (SAFT) for effective reduction of signal
clutter and noise, and extraction of important features in the data, has proven to be effective for
these coarse grained steel components.
Results from proof-of-principal tests in the laboratory demonstrate an effective means to detect
and localize reflectors introduced as a function of size and depth from the top of the frog rail.
Using non-optimal, commercially available transducers coupled with the low-frequency/SAFT
approach, preliminary evaluations were conducted to study the effects of the material
microstructure on ultrasonic propagation, sensitivity and resolution in thick section frog
components with machined side-drilled holes. Results from this study will be presented and
discussed.
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