Minimizing the effect of bending on ultrasonic measurements in a load-bearing member

• US 6,009,759 A
• Filed: 05/02/1997
• Issued: 01/04/2000
• Est. Priority Date: 05/03/1996
• Status: Expired due to Fees

• Current Assignee: Progress Bank
• Original Assignee: Ultrafast, Inc.
• Inventors: Kibblewhite, Ian E., Vecchio, Christopher J.
• Primary Examiner(s): Brock, Michael
• Assistant Examiner(s): FAYYAZ, NASHMIYA SAQIB
• Application Number:
  US08/850,139
• Time in Patent Office: 977 Days
• Field of Search: 73/761, 73/597, 73/599, 73/627, 73/629
• US Class Current: 73/761
• CPC Class Codes: F16B 31/02 for indicating the attainment of a particular tensile load or limiting tensile load apparatus for, or method of, determining value of torque or twisting moment for tightening a nut or other member similarly stressed G01L5/24
• CPC Class Codes: G01L 5/246 using acoustic waves
• CPC Class Codes: G01N 2291/02827 Elastic parameters, strength or force

Abstract

A load-indicating device including a load-bearing member adapted to deform when stressed. Ultrasonic waves are directed into one end of the load-bearing member and ultrasonic echoes are received at the same end by ultrasonic wave transmitting and receiving equipment. In one embodiment, ultrasonic waves are transmitted and received using an ultrasonic transducer disposed on either the head or the opposite end of the load-bearing member. The head, the end, the shank or a combination thereof are contoured to reduce the influence of geometric variations and asymmetrical stress in the load-bearing member on the ultrasonic measurement. A method is also provided, which encompasses a model, by which preferred geometries of the contoured surfaces of the load-bearing member can be designed. Also provided are a method of making a load-bearing member including contouring at least one end of a load-bearing member, or the shank to reduce the influence of geometric variations and asymmetrical stress in the load-bearing member on ultrasonic measurement, and a method of identifying a contour on a load-bearing member that will provide accurate and reliable ultrasonic load measurements.

Claims

1. A method of making a load-indicating member comprising the steps of:

providing a load-bearing member subjected to deformation when stressed such that one portion thereof moves relative to another portion thereof, said load-bearing member having a first end, a second end, and a predetermined length;

contouring at least a portion of at least one of said first and second ends of said load-bearing member to reduce the influence of geometric variations and asymmetrical stress in said load-bearing member on ultrasonic measurement, said contour approximating a sphere and having a radius of curvature of approximately 25 to 70 percent of the length of said member; and

providing means for transmitting ultrasonic waves through said load-bearing member and receiving ultrasonic echoes, said ultrasonic wave transmitting and receiving means disposed at an end of said load-bearing member.

2. The method according to claim 1, wherein said contour is convex.

3. The method according to claim 1, wherein said contour receives each of said ultrasonic waves directly from said ultrasonic wave transmitting and receiving means and reflects each of said ultrasonic echoes directly back to said ultrasonic wave transmitting and receiving means.

6. The method according to claim 1, wherein said ultrasonic wave transmitting and receiving means is a transducer selected from the group consisting of piezoelectric and electromagnetic transducers.

7. The method according to claim 1, wherein said ultrasonic wave transmitting and receiving means is a laser.

4. A load-indicating device comprising:

a load-bearing member adapted to deform when stressed and having a first end, a second threaded end, and a predetermined length, wherein at least a portion of said second threaded end is contoured to reduce the influence of geometric variations and asymmetrical stress in said load-bearing member on ultrasonic measurement;

wherein said contour is approximately spherical and convex, and has a radius of curvature of approximately 30 to 60 percent of the length of said member; and

means for transmitting ultrasonic waves through said load-bearing member and receiving ultrasonic echoes, said ultrasonic wave transmitting and receiving means disposed at said first end of said load-bearing member.

5. The device according to claim 4, wherein said ultrasonic wave transmitting and receiving means is a transducer selected from the group consisting of piezoelectric and electromagnetic transducers.

8. A load-indicating device comprising:

a load-bearing member adapted to deform when stressed and having a first end, a second end, and a predetermined length, wherein at least a portion of at least one of said first and second ends of said load-bearing member is contoured to reduce the influence of geometric variations and asymmetrical stress in said load-bearing member on ultrasonic measurement, said contour approximating a sphere and having a radius of curvature of approximately 25 to 70 percent of the length of said member; and

means for transmitting ultrasonic waves through said load-bearing member and receiving ultrasonic echoes, said ultrasonic wave transmitting and receiving means disposed at an end of said load-bearing member.

9. The method according to claim 8, wherein said contour is convex.

10. The device according to claim 8, wherein said contour receives each of said ultrasonic waves directly from said ultrasonic wave transmitting and receiving means and reflects each of said ultrasonic echoes directly back to said ultrasonic wave transmitting and receiving means.

11. The device according to claim 8, wherein said load-bearing member is selected from the group consisting of a fastener, a bolt, a stud and a rivet.

12. The device according to claim 8, wherein said first end of said load bearing member has a recess, said recess having an internal surface and said internal surface is contoured over a portion thereof.

13. The device according to claim 8, wherein said end opposite said contoured end is flat, and said ultrasonic wave transmitting and receiving means is adjacent said flat end.

14. The device according to claim 8, wherein said ultrasonic wave transmitting and receiving means is a transducer selected from the group consisting of piezoelectric and electromagnetic transducers.

15. The device according to claim 14, wherein said selected transducer is permanently attached to one of said first and second ends of said load-bearing member.

16. The device according to claim 14, wherein said selected transducer is removably attached to one of said first and second ends of said load bearing member.

17. The device according to claim 8, wherein said ultrasonic wave transmitting and receiving means is a laser.

18. The device according to claim 8, wherein both said first end and said second end of said load bearing member are contoured.

19. The device according to claim 18, wherein said first end contour has a first radius of curvature and said second end contour has a second radius of curvature, and

wherein a sum of said first radius of curvature and said second radius of curvature is approximately equal to the length of said load-bearing member.

20. The device according to claim 18, wherein said first end contour has a radius of curvature of approximately 25 to 70 percent of the length of said member and said second end contour has a radius of curvature of approximately 25 to 70 percent of the length of said member.

21. The device according to claim 13 wherein said contour has a radius of curvature of approximately 30 to 70 percent of the length of said member.