Average grain size evaluation using scattering-induced attenuation of coda waves.

Area of Science:

• Materials Science
• Non-destructive Testing
• Acoustics

Background:

• Grain size is critical for polycrystalline metal mechanical properties.
• Conventional methods for grain size evaluation are often time-consuming and require extensive scanning.
• A need exists for rapid, non-destructive methods for average grain size determination.

Purpose of the Study:

• To propose a novel method for rapid average grain size evaluation using ultrasonic coda waves.
• To develop a model correlating ultrasonic wave attenuation with grain size.
• To validate the method's accuracy and robustness on various metal components.

Main Methods:

• Utilizing ultrasonic coda waves for material inspection.
• Developing a piecewise energy attenuation function to determine effective attenuation coefficient.
• Constructing a power-law model to link attenuation coefficient with average grain size.
• Performing ultrasonic testing on nickel-based superalloy specimens and a turbine disk.

Main Results:

• The proposed method enables rapid average grain size evaluation from a single inspection point.
• A power-law model effectively correlates coda wave attenuation with average grain size.
• Validation on superalloy plates and a turbine disk specimen demonstrated reliability.
• The method achieved a maximum relative error of less than 20% in grain size estimation.

Conclusions:

• The ultrasonic coda wave method provides a fast and accurate approach for average grain size evaluation.
• This technique offers advantages over conventional point-by-point scanning methods.
• The method is robust and applicable to complex geometries and non-uniform microstructures.