Apparatus and method for non-destructive testing of structures

• US 5,633,467 A
• Filed: 12/01/1995
• Issued: 05/27/1997
• Est. Priority Date: 06/04/1993
• Status: Expired due to Fees

• Current Assignee: Pure Technologies Limited (Xylem, Inc.)
• Original Assignee: Pure Technologies US Incorporated (Xylem, Inc.)
• Inventors: Paulson, Peter O.
• Primary Examiner(s): Chilcot, Richard
• Assistant Examiner(s): Noori, Max H.
• Application Number:
  US08/556,936
• Time in Patent Office: 543 Days
• Field of Search: 73/760, 73/763, 73/786, 73/788, 73/800, 356/35.5
• US Class Current: 73/800
• CPC Class Codes: G01B 11/161 by interferometric means
• CPC Class Codes: G01B 5/30 for measuring the deformation in a solid, e.g. mechanical strain gauge

Abstract

A method and apparatus for non-destructive testing of the load bearing characteristics of a structure are disclosed. An interferometer is supported by a beam which is supported away from the surface of the structure to be tested. The interferometer is used to measure a quantity which varies with the distance between the interferometer and a reflecting means supported on the location to be tested. The reflecting means is supported in such a manner as to move responsively with deformations to the said location, and is typically attached to a probe which is urged against the said location. Preferably a force is applied or varied near the location to be tested and comparisons are made over time or as the said force varies. Such a system does not damage the structure, and does not require complicated equipment or processing.

Claims

1. A system for non-destructive testing of the load bearing characteristics of a structure, said system comprising:

an apparatus having a member (21) supported away from the surface (11) of the structure (10) to be tested by one or more supports (22,

     24) in contact with the structure;

measuring means (30) adapted to measure a quantity which varies with distance between the surface of the structure and a point on the said member remote from any of the said supports, said measuring means including

an interferometer (32);

reflecting means (34) which move responsively with deformations of the said surface;

said reflecting means and said interferometer together define at least one external optical path which varies with said quantity;

a probe (36) urged against the area of the structure to be tested, said probe supported so as to allow said probe to move responsively with deformations of the said area, wherein said reflecting means is attached to said probe, the probe being supported by said member by means of a low friction arrangement selected from the group consisting of;

bushings within a housing attached to said member;

a bendable arm attached to said member;

a flexible spring steel (70) attached to said member; and

a pair of pivot arms (78,

     79) pivotally connected to said probe, said pivot arms pivotally connected to a second member (75) rigidly connected to said support member; and

,

means (40) for both applying a force on the structure and varying repetitively said force in a predetermined manner, at a location near the area to be tested.

2. The system as defined in claim 1 wherein said probe is urged against the structure by means of the weight of said probe.

3. The system as defined in claim 1 further comprising a spring wherein said probe is urged against the structure by means of said spring.

4. The system as defined in claim 1 wherein said reflecting means comprises a retroreflecting prism.

5. The system as defined in claim 1 wherein said member is cantilevered from a single support.

6. The system as defined in claim 1 wherein said member is supported by at least three supports.

7. The system as defined in claim 1 wherein said measuring means is supported by said member.

8. A system for non-destructive testing of the load bearing characteristics of a structure, said system comprising:

an apparatus having a member (21) supported away from the surface (11 ) of the structure (10) to be tested by one or more supports (22,

     24) in contact with the structure;

measuring means (30) adapted to measure a quantity which varies with distance between the surface of the structure and a point on the said member remote from any of the said supports, said measuring means including

an interferometer (32);

reflecting means (34) which move responsively with deformations of the said surface;

said reflecting means and said interferometer together define at least one external optical path which varies with said quantity;

a probe (36) urged against the area of the structure to be tested, said probe supported so as to allow said probe to move responsively with deformations of the said area, wherein said reflecting means is attached to said probe, the probe being supported by said member by means of a low friction arrangement of circumferentially spaced races of circulating ball bearings (38a, 38b) within a housing (31) attached to said member and,

means (40) for both applying a force on the structure and varying repetitively said force in a predetermined manner, at a location near the area to be tested.

9. The system as defined in claim 8 wherein said probe is urged against the structure by means of the weight of said probe.

10. The system as defined in claim 8 further comprising a spring wherein said probe is urged against the structure by means of said spring.

11. The system as defined in claim 8 wherein said reflecting means comprises a retroreflecting prism.

12. The system as defined in claim 8 wherein said member is cantilevered from a single support.

13. The system as defined in claim 8 wherein said member is supported by at least three supports.

14. The system as defined in claim 8 wherein said measuring means is supported by said member.

15. A system for non-destructive testing of the load bearing characteristics of a structure, said system comprising:

an apparatus having a member (21) supported away from the surface (11 ) of the structure (10) to be tested by one or more supports (22,

     24) in contact with the structure and measuring means (30) adapted to measure a quantity which varies with distance between the surface of the structure and a point on the said member remote from any of the said supports; and

,

means (40) for both applying a force on the structure and varying repetitively said force in a predetermined manner, at a location near the area to be tested, wherein the means for applying a force includes means (58) for oscillating a mass and means (45) for transmitting the force to the surface of the structure and said means for oscillating a mass including;

a mass (62) slidably mounted on at least one column (64,

     65) and having a centre of gravity;

a motor (48) for rotating a shaft;

means (50, 52, 54, 56,

     58) for converting the rotary motion of said shaft into reciprocating linear motion;

the centre of gravity of the said mass being located directly over the said means for transmitting the forces generated by the said moving mass.

16. The system as defined in claim 15 wherein said reflecting means comprises a retroreflecting prism.

17. A system for non-destructive testing of the load bearing characteristics of a structure, said system comprising:

an apparatus having a member (21) supported away from the surface (11) of the structure (10) to be tested by one or more supports (22,

     24) in contact with the structure;

measuring means (30) adapted to measure a quantity which varies with distance between the surface of the structure and a point on the said member remote from any of the said supports, said measuring means including

an interferometer (32);

reflecting means (34) which move responsively with deformations of the said surface, said reflecting means comprising a retroreflecting prism;

said reflecting means and said interferometer together define at least one external optical path which varies with said quantity

a probe (36) urged against the area of the structure to be tested, said probe supported so as to allow said probe to move responsively with deformations of the said area, the reflecting means being attached to said probe; and

,

means (40) for both applying a force on the structure and varying repetitively said force in a predetermined manner, at a location near the area to be tested.

18. The system as defined in claim 17 wherein said member is cantilevered from a single support.

19. The system as defined in claim 17 wherein said member is supported by at least three supports.

20. The system as defined in claim 17 wherein said measuring means is supported by said member.

21. The system as defined in claim 17 wherein the portion (37) of said probe which is urged against said structure is pointed.

22. The system as defined in claim 17 wherein the probe is supported by said member by means of a low friction arrangement.

23. The system as defined in claim 22 wherein said low friction arrangement is selected from the group consisting of:

bushings within a housing attached to said member;

a bendable arm attached to said member;

a flexible spring steel (70) attached to said member;

a pair of pivot arms (78,

     79) pivotally connected to said probe, said pivot arms pivotally connected to a second member (75) rigidly connected to said support member;

or

circumferentially spaced races of circulating ball bearings (38a, 38b) within a housing (31) attached to said member.

24. A method for non-destructive testing of structures by measuring deformations to portions of a structure, said method comprising the steps of:

applying a static load to a location of a structure (10) to be tested;

replacing the load with a beam (21) suspended above the location to be tested, said beam supported by one or more supports (22,

     24) resting on the structure remote from the location to be tested in such a manner so as to transmit to the said beam movements of the said structure proximate to the said supports;

measuring repeatedly a quantity which varies with the distance between a portion of the said beam remote from the said supports and the said location to be tested as the location recovers the measuring step comprising;

supporting reflecting means (34) which moves responsively with deformations to the location to be tested;

utilizing an interferometer (32), in conjunction with said reflecting means, to measure the said quantity.

25. The method as defined in claim 24 further comprising the step of comparing said measurements of deformation over time or as the static load applied to the structure varies.

26. A method for non-destructive testing of structures by measuring deformations to portions of a structure, said method comprising the steps of:

applying a static load to a location of a structure (10) to be tested;

replacing the load with a beam (21) suspended above the location to be tested, said beam supported by one or more supports (22,

     24) resting on the structure remote from the location to be tested in such a manner so as to transmit to the said beam movements of the said structure proximate to the said supports;

measuring repeatedly a quantity which varies with the distance between a portion of the said beam remote from the said supports and the said location to be tested as the location recovers; and

,

comparing said measurements of deformation over time or as the static load applied to the structure varies.

27. The method as defined in claim 26 wherein the said measuring step comprises:

supporting reflecting means (34) which moves responsively with deformations to the location to be tested;

utilizing an interferometer (32), in conjunction with said reflecting means, to measure the said quantity.

28. A system for non-destructive testing of the load bearing characteristics of a structure, said system comprising:

an apparatus having a member (21) supported away from the surface (11) of the structure (10) to be tested by being cantilevered from a single support in contact with the structure and measuring means (30) adapted to measure a quantity which varies with distance between the surface of the structure and a point on the said member remote from the said support, the measuring means including;

an interferometer (32);

reflecting means (34) which move responsively with deformations of the said surface;

said reflecting means and said interferometer together define at least one external optical path which varies with said quantity;

means (40) for both applying a force on the structure and varying repetitively said force in a predetermined manner, at a location near the area to be tested.

29. The system as defined in claim 28 wherein the apparatus further includes a probe (36) urged against the area of the structure to be tested, said probe supported so as to allow said probe to move responsively with deformations of the said area, wherein said reflecting means is attached to said probe.

30. The system as defined in claim 28 wherein the probe is supported by said member by means of a low friction arrangement.

31. The system as defined in claim 30 wherein said low friction arrangement is selected from the group consisting of:

bushings within a housing attached to said member;

a bendable arm attached to said member;

a flexible spring steel (70) attached to said member;

a pair of pivot arms (78,

     79) pivotally connected to said probe, said pivot arms pivotally connected to a second member (75) rigidly connected to said support member;

or

circumferentially spaced races of circulating ball bearings (38a, 38b) within a housing (31) attached to said member.

32. The system as defined in claim 28 wherein said reflecting means comprises a retroreflecting prism.

33. A system for non-destructive testing of the load bearing characteristics of a structure, said system comprising:

an apparatus having a member (21) supported away from the surface (11) of the structure (10) to be tested by at least three supports (22,

     24) in contact with the structure and measuring means (30) adapted to measure a quantity which varies with distance between the surface of the structure and a point on the said member remote from any of the said supports, the measuring means including;

an interferometer (32);

reflecting means (34) which move responsively with deformations of the said surface;

said reflecting means and said interferometer together define at least one external optical path which varies with said quantity;

means (40) for both applying a force on the structure and varying repetitively said force in a predetermined manner, at a location near the area to be tested.

34. The system as defined in claim 33 wherein the apparatus further includes a probe (36) urged against the area of the structure to be tested, said probe supported so as to allow said probe to move responsively with deformations of the said area, wherein said reflecting means is attached to said probe.

35. The system as defined in claim 33 wherein the probe is supported by said member by means of a low friction arrangement.

36. The system as defined in claim 35 wherein said low friction arrangement is selected from the group consisting of:

bushings within a housing attached to said member;

a bendable arm attached to said member;

a flexible spring steel (70) attached to said member;

a pair of pivot arms (78,

     79) pivotally connected to said probe, said pivot arms pivotally connected to a second member (75) rigidly connected to said support member;

or

circumferentially spaced races of circulating ball bearings (38a, 38b) within a housing (31) attached to said member.

37. The system as defined in claim 33 wherein said reflecting means comprises a retroreflecting prism.

38. A system for non-destructive testing of the load bearing characteristics of a structure, said system comprising:

an apparatus having a member (21) supported away from the surface (11) of the structure (10) to be tested by one or more supports (22,

     24) in contact with the structure and measuring means (30) supported by said member and adapted to measure a quantity which varies with distance between the surface of the structure and a point on the said member remote from any of the said supports, the measuring means including;

an interferometer (32);

reflecting means (34) which move responsively with deformations of the said surface;

said reflecting means and said interferometer together define at least one external optical path which varies with said quantity;

means (40) for both applying a force on the structure and varying repetitively said force in a predetermined manner, at a location near the area to be tested.

39. The system as defined in claim 38 wherein the apparatus further includes a probe (36) urged against the area of the structure to be tested, said probe supported so as to allow said probe to move responsively with deformations of the said area, wherein said reflecting means is attached to said probe.

40. The system as defined in claim 38 wherein the probe is supported by said member by means of a low friction arrangement.

41. The system as defined in claim 40 wherein said low friction arrangement is selected from the group consisting of:

bushings within a housing attached to said member;

a bendable arm attached to said member;

a flexible spring steel (70) attached to said member;

a pair of pivot arms (78,

     79) pivotally connected to said probe, said pivot arms pivotally connected to a second member (75) rigidly connected to said support member;

or

circumferentially spaced races of circulating ball bearings (38a, 38b) within a housing (31) attached to said member.

42. The system as defined in claim 38 wherein said reflecting means comprises a retroreflecting prism.