Location

La Jolla, CA

Start Date

1-1-1998 12:00 AM

Description

The titanium alloys used in rotating jet engine components present interesting UT inspection challenges. They have complicated, duplex, anisotropic structures which vary on several dimensional scales [1,2]. Individual metal crystallites with typical dimensions on the order of several microns comprise the fine scale structure (microstructure). Colonies of aligned crystallites, which develop from prior beta grains during cooling, can have dimensions of several millimeters and comprise the large scale structure (macrostructure). Cylindrical billets destined for use in rotating engine components are typically inspected using 5 MHz broadband transducers, with higher frequency inspections planned. Because macrostructure dimensions often exceed the sonic wavelength, sound beams can be distorted during propagation, leading to modifications of ultrasonic signals. These modifications are of two basic types: (1) identical reflectors at the same depth but located at different sites on a specimen produce different sonic echoes due to the influence of the local macrostructure (signal fluctuation); and (2) the average signal strength is different from the value it would have in a similar fine-grained material (signal attenuation).

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

17B

Chapter

Chapter 6: Materials Characterization

Section

Materials Properties

Pages

1469-1476

DOI

10.1007/978-1-4615-5339-7_190

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Ultrasonic Signal Attenuation in Engine Titanium Alloys

La Jolla, CA

The titanium alloys used in rotating jet engine components present interesting UT inspection challenges. They have complicated, duplex, anisotropic structures which vary on several dimensional scales [1,2]. Individual metal crystallites with typical dimensions on the order of several microns comprise the fine scale structure (microstructure). Colonies of aligned crystallites, which develop from prior beta grains during cooling, can have dimensions of several millimeters and comprise the large scale structure (macrostructure). Cylindrical billets destined for use in rotating engine components are typically inspected using 5 MHz broadband transducers, with higher frequency inspections planned. Because macrostructure dimensions often exceed the sonic wavelength, sound beams can be distorted during propagation, leading to modifications of ultrasonic signals. These modifications are of two basic types: (1) identical reflectors at the same depth but located at different sites on a specimen produce different sonic echoes due to the influence of the local macrostructure (signal fluctuation); and (2) the average signal strength is different from the value it would have in a similar fine-grained material (signal attenuation).