Location

Williamsburg, VA

Start Date

1-1-1988 12:00 AM

Description

The accurate in-situ measurement of part dimensions during fabrication is of much interest to the manufacturing industry, especially for untended manufacturing. The goal of this work is to apply non-contacting ultrasonic techniques to the precise thickness measurement, during machining, of metal parts of rotation having a nominal wall thickness of 1.5 mm. The desired accuracy is ±.0025 mm at all points on the approximately 200 mm diameter steel shells, where part access is restricted to one side at a time for the measurement. In a feasibility study, dimensional information using eddy current techniques was overwhelmed by conductivity variations in the 304-stainless steel samples [1]. The approach here is to precisely measure ultrasonic echo transit times, and calulate part dimensions, knowing the material sound speed. To that end, feasibility results on flat disk specimens possessing a wide range of grain sizes representative of the shell’s variable metallurgy are reported here. Factors affecting ultrasonic dimensional precision including grain size, texture, sample temperature and surface roughness are discussed, with an emphasis on precision limitations due to finite grain sizes in thin parts. Both longitudinal (10 to 30 MHz) and shear (3 MHz) wave measurements were made, the latter using electromagnetic acoustic transducers (EMATS).

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

7B

Chapter

Chapter 7: Characterization of Materials

Section

Process Control

Pages

1563-1572

DOI

10.1007/978-1-4613-0979-6_83

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Precision Ultrasonic Thickness Measurements of Thin Steel Disks

Williamsburg, VA

The accurate in-situ measurement of part dimensions during fabrication is of much interest to the manufacturing industry, especially for untended manufacturing. The goal of this work is to apply non-contacting ultrasonic techniques to the precise thickness measurement, during machining, of metal parts of rotation having a nominal wall thickness of 1.5 mm. The desired accuracy is ±.0025 mm at all points on the approximately 200 mm diameter steel shells, where part access is restricted to one side at a time for the measurement. In a feasibility study, dimensional information using eddy current techniques was overwhelmed by conductivity variations in the 304-stainless steel samples [1]. The approach here is to precisely measure ultrasonic echo transit times, and calulate part dimensions, knowing the material sound speed. To that end, feasibility results on flat disk specimens possessing a wide range of grain sizes representative of the shell’s variable metallurgy are reported here. Factors affecting ultrasonic dimensional precision including grain size, texture, sample temperature and surface roughness are discussed, with an emphasis on precision limitations due to finite grain sizes in thin parts. Both longitudinal (10 to 30 MHz) and shear (3 MHz) wave measurements were made, the latter using electromagnetic acoustic transducers (EMATS).