Ultrasonic testing method

• US 5,804,730 A
• Filed: 10/10/1995
• Issued: 09/08/1998
• Est. Priority Date: 10/10/1995
• Status: Expired due to Fees

• Current Assignee: Sikroski & Pfannenstiel Innovative Non-Destructive Examinations, Inc.
• Original Assignee: Sikroski & Pfannenstiel Innovative Non-Destructive Examinations, Inc.
• Inventors: Sikorski, Steven L., Pfannenstiel, Richard A.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US08/541,444
• Time in Patent Office: 1,064 Days
• Field of Search: 73/618, 73/622, 73/620, 73/627, 73/629, 73/624
• US Class Current: 73/622
• CPC Class Codes: G01N 2291/015 Attenuation, scattering
• CPC Class Codes: G01N 2291/02854 Length, thickness
• 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 2291/056 Angular incidence, angular propagation
• CPC Class Codes: G01N 2291/2675 Seam, butt welding
• CPC Class Codes: G01N 29/043 in the interior, e.g. by shear waves
• CPC Class Codes: G01N 29/2487 Directing probes, e.g. angle probes directing arrangements G01N29/221

Abstract

A single operation, multi-task, non-destructive testing technique of ultrasonic examination for defect detection, analysis and sizing. The technique utilizes the same angle, mode of propagation, calibration, set-up, and scanning patterns, for all materials, thickness of materials, and configuration of components for which it is applicable. The technique is used to detect, analyze and size planar flaws, such as fatigue cracks, which are connected to the surface opposite that from which the ultrasound is propagated. The technique relies on the fact that specular reflections received from flaws that have penetration into materials will return to the transducer before reflections which are associated with geometric features of the surface to which the flaw is connected. It also relies on the properties of the longitudinal mode of sound propagation at a 65-75 degree angle resulting in reduced specular reflections from opposite wall geometric reflectors such as weld roots and counterbores.

Claims

1. A method of ultrasonically inspecting a selected portion of a metal object having an accessible surface and an opposite surface for flaws using a transducer including an ultrasonic transmitter and receiver where the transducer is moved longitudinally toward and away from said selected portion and laterally essentially parallel to the selected portion, to detect and size flaws in said selected portion and an instrument for recording returned ultrasonic pulse signals received by said receiver where the ultrasonic signals are transmitted in the longitudinal mode within an envelope having a central axis which forms a selected angle with a line perpendicular to a surface of said piece, comprising the steps of

a) determining a reference position on said object in the selected portion on the opposite surface thereof,

b) determining a first scanning position on said accessible surface of said object for transmitting an envelope of pulses with the axis thereof directed toward said reference position whereby the points where the envelope of transmitted pulses will intersect said opposite surface on either side of said reference position and define a first longitudinal distance between said points,

c) positioning said transducer at said first scanning position and moving said transducer on said accessible surface of said object laterally while transmitting ultrasonic signals into said object with the axis of said envelope directed at said reference position,

d) noting on said instrument as indicative of a flaw the first reflected pulse of a reflection of said transmitted signals and noting the location thereof,

e) positioning said transducer on said accessible surface so as to detect a first indicated flaw and moving said transducer laterally to size the length of said a first indicated flaw,

f) moving said transducer longitudinally on said accessible surface to size the through wall extent of said a first indicated flaw

g) repeating steps e) and f) for each indicated flaw, and

h) recording the position, length and through wall extent of each detected flaw.

2. The method of claim 1 including the further steps of determining one or more additional scanning positions for transmitting ultrasonic signals into said object at the selected angle such that the envelope of pulses transmitted from said one or more additional positions will intersect said opposite surface at points which define one or more longitudinal distances which is essentially a continuation of said first longitudinal distance with minimal overlap of said first and said one or more additional longitudinal distances, whereby said first and said one or more longitudinal distances define on said opposite surface essentially completely additive longitudinal distances which is a continuous length to be inspected and longitudinally encompasses said selected portion, positioning said transducer at each of said one or more scanning positions and moving said transducer laterally while transmitting ultrasonic signals into said object, and repeating steps d), e) f), g) and h) for each determined one or more additional scanning position.

3. The method of claim 1 wherein said positions, lengths and through wall extents are recorded in electronic memory.

4. The method of claim 1 wherein a person performing said moving steps or an associate performs said recording.

5. The method of claim 1 where said selected angle is in the range of sixty-five to seventy-five degrees.

6. The method of claim 2 wherein said determined scanning positions are all on one side of said reference position.

7. The method of claim 2 wherein said determined scanning positions are on both sides of said reference position.

8. The method of claim 1 wherein said instrument is an oscilloscope and said oscilloscope has a distance scale calibrated to a multiple of the thickness of said object.

9. The method of claim 1 where said transducer is oscillated back and forth approximately 15°

during step c).

10. A method of inspecting a selected portion of a pipe comprising two sections of butt welded pipe having an outer wall surface and an interior wall surface for flaws using a transducer comprising an ultrasonic transmitter and a receiver and an oscilloscope for displaying received reflected signals where the ultrasonic signals are transmitted by said transmitter in the longitudinal mode within an envelope having a central axis which forms an angle of 65 to 75 degrees with a line perpendicular to the axis of said pipe, comprising the steps of

a) determining a reference position on said pipe on the interior surface at the center of said weld,

b) determining a scanning position on said outer surface for transmitting an envelope of pulses with the axis thereof directed toward said reference position whereby the envelope of transmitted signals will intersect said interior surface at points on either side of said weld center and define a first longitudinal distance between said points,

c) positioning said transducer at said first scanning position and moving said transducer laterally of said pipe axis on said outer surface of said pipe while transmitting ultrasonic signals into said pipe with the axis of said envelope directed at said weld center line,

d) noting on said oscilloscope as indicative of a flaw the first reflected pulse of a reflection of said transmitted signals and noting the position thereof,

e) positioning said transducer on said outer surface so as to detect a first indicated flaw and moving said transducer laterally of said pipe on the outer surface while transmitting ultrasonic signals to size the length of said a first indicated flaw,

f) moving said transducer longitudinally on said outer surface while transmitting ultrasonic signals to size the through wall extent of said a first indicated flaw,

g) repeating steps e) and f) for each indicated flaw, and

h) recording the position, length and through wall extent of each detected flaw.

11. The method of claim 10, including the further steps of determining one or more additional scanning positions for transmitting ultrasonic signals into said pipe at the selected angle such that the envelope of pulses transmitted from said one or more additional positions will intersect said inner surface at points which define one or more longitudinal distances which is essentially a continuation of said first longitudinal distance with minimal overlap of said first and said one or more additional longitudinal distances, whereby said first and said one or more longitudinal distances define on said inner surface essentially completely additive longitudinal distances which is a continuous length to be inspected and longitudinally encompasses said selected portion, positioning said transducer at each of said one or more scanning positions and moving said transducer laterally while transmitting ultrasonic signals into said object, and repeating steps d), e), f), g) and h) for each determined one or more additional scanning position.

12. The method of claim 10 wherein said positions, sizes and said through wall extents are recorded in electronic memory.

13. The method of claim 10 wherein a person performing said moving steps or an associate performs said recording.

14. The method of claim 11 wherein said determined scanning positions are all on one side of said reference line.

15. The method of claim 11 wherein said determined scanning positions are on both sides of said reference position.

16. The method of claim 10 wherein said instrument is an oscilloscope and has a distance scale calibrated to a multiple of the thickness of the wall of said pipe.

17. The method of claim 10 where said transducer is oscillated back and forth approximately 15°

during said step c).

18. A method of inspecting a section of pipe comprising two sections of butt welded pipe having outer and inner surfaces in the vicinity of the weld for the detection of planar flaws connected to said inner surface using a transducer including an ultrasonic signal transmitter and a receiver and an instrument for recording returned ultrasonic signals received by said receiver where the ultrasonic signals are transmitted in the longitudinal mode within an envelope having a central axis which forms a selected angle with the longitudinal axis of said pipe, comprising the steps of

a) determining the center of the weld on the inner surface of said pipe,

b) determining a scanning position on the outer surface of said pipe for transmitting an envelope of pulse at the selected angle with the axis thereof directed toward said weld center on the inner surface of said pipe whereby the points where the envelope will intersect said inner surface at points on either side of said weld center and define a first longitudinal distance between said points on said inner surface,

c) positioning said transducer at said scanning position and moving said transducer on said outer surface laterally of said pipe while transmitting ultrasonic signals into said pipe with the axis of the transmitted envelope directed at said weld center,

d) noting on said instrument as indicative of a flaw the first reflected pulse of a reflection of said transmitted signals and noting the location thereof,

e) positioning said transducer on said outer surface so as to detect a first indicated flaw and moving the transducer laterally of said pipe longitudinal axis to size the length of said a first indicated flaw,

f) moving said transducer longitudinally on said outer surface to determine a connection of said a first indicated flaw to said inner surface and to size the through wall extent of said a first indicated flaw,

g) repeating steps e) and f) for each indicated flaw, and

h) recording the position, length and through wall extent of each detected flaw.

19. The method of claim 18 wherein said instrument is an oscilloscope having a distance axis which is calibrated to a multiple of the thickness of said pipe.

20. The method of claim 18 wherein said positions, said lengths, and said through wall extents are recorded in electronic memory.

21. The method of claim 18 wherein a person performing said moving steps or an associate performs said recording.

22. The method of claim 18 where said transducer is oscillated back and forth approximately 15°

during said step c).

23. The method of claim 18 including the further steps of determining one or more additional scanning positions for transmitting into said pipe at the selected angle such that the envelope of signals transmitted from said one or more additional positions will intersect said inner surface at points which define one or more longitudinal distances which is essentially a continuation of said first longitudinal distance with minimal overlap of said first and said one or more additional longitudinal distances, whereby said first and said one or more longitudinal distances define on said inner surface essentially completely additive longitudinal distances which is a continuous length to be inspected and longitudinally encompasses said weld, and repeating steps c) through h) for each determined one or more additional scanning positions.

24. The method of claim 23 wherein all scanning positions are on one side of said weld.

25. The method of claim 23 wherein said scanning positions are on both sides of said weld.