Ultrasonic stress measurement using the critically refracted longitudinal (LCR) ultrasonic technique

• US 6,477,473 B2
• Filed: 07/03/2001
• Issued: 11/05/2002
• Est. Priority Date: 07/30/1998
• Status: Expired due to Fees

• Current Assignee: Don E. Bray
• Original Assignee: Don E. Bray
• Inventors: Bray, Don E.
• Primary Examiner(s): Hilten, John S.
• Assistant Examiner(s): PRETLOW, DEMETRIUS R
• Application Number:
  US09/898,218
• Publication Number:
  US 20010049587A1
• Time in Patent Office: 490 Days
• Field of Search: 702/39, 702/42, 702/35, 702/59, 702/171, 702/185, 702/54, 735/97, 735/79, 736/40, 736/42, 737/88, 738/41, 738/665, 734/321, 736/32, 738/620-1-8, 738/19, 737/66
• US Class Current: 702/42
• CPC Class Codes: G01L 1/255 using acoustic waves, or acoustic emission G01L1/10 and G01L1/16 take precedence
• CPC Class Codes: G01N 2291/02827 Elastic parameters, strength or force
• CPC Class Codes: G01N 2291/103 one emitter, two or more receivers
• CPC Class Codes: G01N 2291/2623 Rails; Railroads
• CPC Class Codes: G01N 2291/2693 Rotor or turbine parts
• CPC Class Codes: G01N 29/07 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 29/227 related to high pressure, tension or stress conditions

Abstract

The latent stress in a material can be measured using critically refracted longitudinal ultrasonic technique. The system uses a frame to hold a hydraulic piston. The piston is used to apply an adjustable force against the probes. A signal is initiated by a first transducer. The signal is angled against the piece under test so as to create a critically refracted wave along the piece. The delay time to receive the wave at a first and second probe is measured. The delay time correlates to a stress in the piece.

Claims

1. A method for measuring the internal stress in a material comprising the steps of:

(a) applying a transducer probe in physical contact with the material;

(b) applying at least one receiving probe in physical contact with the material;

(c) applying a contact force at an interface between said probes and the material, comprising the steps of placing a variable force ram in physical contact with said probes, attaching a load frame to said variable force ram, and securing said load frame to the material;

(d) transmitting a critically refracted longitudinal wave through the material from the transducer probe to the at least one receiving probe; and

(e) calculating the internal stress of the material as a function of a travel time from the transducer probe to the at least one receiving probe of the longitudinal wave through the material.

2. The method of claim 1 wherein the force of step (c) is applied equally against said probes.

3. The method of claim 1 wherein the step of securing said load frame to the material comprises attaching at least one magnet to said load frame.

4. The method of claim 1 further comprising the step of measuring the temperature of the material.

5. The method of claim 4 wherein step (e) further comprises:

calculating the internal stress of the material as a function of the temperature of the material.

6. A method for measuring the internal stress in a material comprising the steps of:

(a) placing a first and a second receiving probes in forced contact with the material;

(b) applying a contact force at an interface between said probes and the material, comprising the steps of placing a variable force ram in physical contact with said probes, attaching a load frame to said variable force ram, and securing said load frame to the material;

(c) transmitting a critically refracted longitudinal ultrasonic wave through the material;

(d) measuring the wave at the receiving probes; and

(e) calculating the internal stress of the material as a function of a travel time of the longitudinal wave between said probes through the material.

7. The method of claim 6 wherein the forced contact comprises applying an equal contact force to both said probes.

8. The method of claim 6 wherein the step of securing said load frame to the material comprises attaching at least one magnet to said load frame.

9. The method of claim 6 wherein the step of securing said load frame to the material comprises using a mechanical constraint.

10. The method of claim 6 wherein the step of securing said load frame to the material comprises using a vacuum constraint.