UT detection and sizing method for thin wall tubes

• US 6,772,638 B2
• Filed: 10/30/2001
• Issued: 08/10/2004
• Est. Priority Date: 10/30/2001
• Status: Expired due to Fees

• Current Assignee: Areva NP Incorporated (AES Corporation)
• Original Assignee: Framatome ANP, Inc. (AES Corporation)
• Inventors: Pop, Mihai G., Matney, Russell M., Wyatt, Joseph R. III
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US10/015,982
• Publication Number:
  US 20030079545A1
• Time in Patent Office: 1,015 Days
• Field of Search: 735/98, 736/20, 736/22, 736/00, 736/23, 736/27, 736/29
• US Class Current: 73/627
• CPC Class Codes: G01N 2291/011 Velocity or travel time
• CPC Class Codes: G01N 2291/0231 Composite or layered materials
• CPC Class Codes: G01N 2291/0421 Longitudinal waves
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 2291/0428 Mode conversion
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 2291/048 Transmission, i.e. analysed material between transmitter and receiver
• CPC Class Codes: G01N 2291/056 Angular incidence, angular propagation
• CPC Class Codes: G01N 2291/2634 cylindrical from outside
• CPC Class Codes: G01N 29/11 by measuring attenuation of acoustic waves

Abstract

A method for sizing cracks is disclosed using a combination of depth crack sizing methods to improve crack sizing accuracy for thin walled tubing and tight crack surface openings less than 0.001 inches for cracks of any depth. The tube or plate wall can consist of a single material or multiple metallic electrodeposited or otherwise intimately bonded layers of materials with different magnetic properties and the sizing method comprises known depth sizing methods such as shear wave, time of flight and the selective use of two unique depth sizing methods designated as Mode Converted Signal (MCS) and Full Skip Normalization (FSN) which provide correction factors for the known sizing methods.

Claims

1. A method of sizing surface cracks in a metal surface using sound wave measurements of propagation and reflection thereof which are initiated at an optimal degree angle to the surface comprising the steps of:

acquire sound wave data by displacing a transducer along the direction of propagation of the sound waves;

review the acquired signals for a crack tip signal;

review the acquired sound wave data for signal reflections at ½

skip, full skip and 1½

skip locations,

when ½

skip, full skip and 1½

skip reflections are detected

reviewing reflected signal data to determine if no crack tip signal was detected and that reflections are present at the ½ and

1½

skip locations;

using target motion time of flight (TOF) data to estimate the depth of the crack and correcting the TOF depth estimate for a mode converted signal (MCS) with MCS correction to size the surface crack only if no full skip reflection signal is present.

2. A method as set forth in claim 1 including the further steps of:

reviewing signal reflected data to determine if full skip signal was present in addition to the ½

skip and 1½

skip signals;

using the ratio of the 1 skip amplitude to the average of the ½

skip and 1½

skip amplitudes to size the surface crack whenever all three of the above signals are present.

3. A method as set forth in claim 2, wherein the sound waves are waves measured by an ultrasonic transducer initiated at an appropriate angle to the metal surface being tested.

4. A method as set forth in claim 3 wherein the metal surface is a composite or otherwise intimately bonded layer of metal tube or plate having a crack width less than 0.001 in.

5. A method of sizing surface cracks in a metal surface as set forth in claim 1, wherein the TOF depth estimate is the UT system depth measurement based on a conventional shear wave target motion time of flight (TOF) analysis.

6. A method as set forth in claim 5, wherein the MCS correction comprises multiplying the TOF depth estimate by a MCS correction factor.

7. A method as set forth in claim 6 wherein the metal surface is a thin wall tube and the MCS correction factor is determined experimentally and is between 1.6 and 1.9.

8. A Full Skip Normalization FSN method using the ratio of a full skip signal amplitude to the average of outer diameter skip signal amplitudes to depth size deep cracks propagating from a surface located opposite from a UT transducer comprising the steps of:

measuring a full skip signal amplitude;

measuring a series of outer diameter signal amplitudes;

averaging said series of outer diameter signal amplitudes;

forming a ratio of the measured full skip signal amplitude to the averaged series of outer diameter amplitudes; and

converting the ratio of the full skip signal amplitude to averaged outer diameter amplitudes to a remaining wall thickness using an empirically derived formula.

9. A method as set forth in claim 8 where for the given application of the thin wall tubing with thickness approximately 0.050 inches, the remaining wall thickness is obtained by the following formula: