Methods and systems for analyzing structural test data

• US 20060069521A1
• Filed: 09/30/2004
• Published: 03/30/2006
• Est. Priority Date: 09/30/2004
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Sermersheim, Jeffrey S., Meyer, Eric S., Fields, Scott S., Knopp, Kenneth L.
• Granted Patent: US 7,171,314 B2
• Time in Patent Office: Days
• US Class Current: 702/42
• CPC Class Codes: G01M 5/0025 of elongated objects, e.g. pipes, masts, towers or railways G01M5/0058 takes precedence
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 7/025 Measuring arrangements
• CPC Class Codes: G01N 2203/0073 Fatigue
• CPC Class Codes: G01N 2203/0244 Tests performed "in situ" or after "in situ" use

Abstract

Systems and methods for analyzing structural test data are disclosed. In one embodiment, a method includes applying a sequence of loads to a test article, receiving raw test data indicative of the applied loads from at least one sensor operatively associated with the test article, receiving predicted test data indicative of the predicted loads on the test article, filtering out invalid test data, cycle counting to pair loads in the test data, performing a first fatigue damage computation based on the raw test data, performing a second fatigue damage computation based on the predicted test data, and comparing the first and second fatigue damage computations. The filtering, cycle counting, and performing of the first and second fatigue damage computations, and the comparison of the first and second fatigue damage computations, may be performed simultaneously using a spreadsheet program.

Claims

1. A method of analyzing structural test data, comprising:

applying a sequence of loads to a test article;

receiving raw test data indicative of the applied loads from at least one sensor operatively associated with the test article;

receiving predicted test data indicative of a predicted loads on the test article;

performing a filter to eliminate invalid data from the applied and predicted loads;

performing a cycle counting operation to pair peak and valley loads;

performing a first fatigue damage computation based on the raw test data;

performing a second fatigue damage computation based on the predicted test data; and

comparing the first and second fatigue damage computations.

2. The method of claim 1, wherein at least one of performing a first fatigue damage computation and performing a second fatigue damage computation includes performing a crack initiation computation.

3. The method of claim 1, wherein performing a first fatigue damage computation comprises performing a crack initiation computation.

4. The method of claim 3, wherein performing a crack initiation computation includes calculating notch stress and strain based on the raw test data indicative of the applied load and an elastic K_T.

5. The method of claim 4, wherein calculating notch stress and strain includes calculating notch stress and strain based on a nominally elastic Neuber'"'"'s Equation.

6. The method of claim 4, wherein performing a crack initiation computation includes correcting a calculated notch strain for load cycle stress ratio effects.

7. The method of claim 6, wherein correcting a calculated notch strain for load cycle stress ratio effects includes correcting a calculated notch strain for load cycle stress ratio effects using a Smith, Watson, and Topper equivalent stress equation.

8. The method of claim 3, wherein performing a crack initiation computation includes calculating at least one of a damage and a failure criteria.

9. The method of claim 8, wherein calculating at least one of a damage and a failure criteria includes performing a summation of the calculated damage associated with continued load cycling using a Palmgren and Miner'"'"'s Rule.

10. The method of claim 8, wherein calculating at least one of a damage and a failure criteria includes assuming a crack initiation occurs when a total damage is greater than or equal to 1.0.

11. The method of claim 1, wherein comparing the first and second fatigue damage computations includes comparing a first damage summation associated with a first continued load cycling with a second damage summation associated with a second continued load cycling.

12. The method of claim 1, wherein performing a first fatigue damage computation includes performing a first fatigue damage computation simultaneously with performing a second fatigue damage computation.

13. The method of claim 1, wherein performing a first fatigue damage computation simultaneously with performing a second fatigue damage computation includes simultaneously performing the first and second fatigue damage computations using a spreadsheet program.

14. The method of claim 1, wherein at least one of performing a first fatigue damage computation and performing a second fatigue damage computation includes performing a respective damage computation using a spreadsheet program.

15. The method of claim 1, wherein comparing the first and second fatigue damage computations includes comparing the first and second fatigue damage computations simultaneously with at least one of performing a first fatigue damage computation and performing a second fatigue damage computation using a spreadsheet program.

16. The method of claim 1, wherein performing a cycle counting operation to pair peak and valley loads includes performing a rainflow cycle counting operation to pair peak and valley loads.

17. The method of claim 1, wherein the following portions are performed simultaneously:

performing a filter to eliminate invalid data from the applied and predicted loads;

performing a cycle counting operation to pair peak and valley loads;

performing a first fatigue damage computation based on the raw test data; and

performing a second fatigue damage computation based on the predicted test data.

18. The method of claim 1, wherein the following portions are performed simultaneously:

applying a sequence of loads to a test article;

receiving raw test data indicative of the applied loads from at least one sensor operatively associated with the test article;

receiving predicted test data indicative of a predicted loads on the test article;

performing a filter to eliminate invalid data from the applied and predicted loads;

performing a cycle counting operation to pair peak and valley loads;

performing a first fatigue damage computation based on the raw test data; and

performing a second fatigue damage computation based on the predicted test data.

19. A computer program product for analyzing structural test data, comprising:

a first portion adapted to receive raw test data indicative of applied loads from at least one sensor operatively associated with a test article;

a second portion adapted to receive predicted test data indicative of predicted loads on the test article;

a third portion adapted to perform a filter to remove invalid test data from the applied test data and the predicted test data;

a fourth portion adapted to perform a cycle counting operation on the applied test data and the predicted test data;

a fifth portion adapted to perform a first fatigue damage computation based on the raw test data;

a sixth portion adapted to perform a second fatigue damage computation based on the predicted test data; and

a seventh portion adapted to compare the first and second fatigue damage computations.

20. The computer program product of claim 19, wherein at least one of the fifth portion and the sixth portion is further adapted to perform a crack initiation computation.

21. The computer program product of claim 19, wherein the fifth portion is further adapted to perform a crack initiation computation.

22. The computer program product of claim 19, wherein the fifth portion is further adapted to calculate notch stress and strain based on the raw test data indicative of the applied load and an elastic K_T.

23. The computer program product of claim 22, wherein the fifth portion is further adapted to calculate notch stress and strain based on a nominally elastic Neuber'"'"'s Equation.

24. The computer program product of claim 22, wherein the fifth portion is further adapted to correct a calculated notch strain for load cycle stress ratio effects.

25. The computer program product of claim 24, wherein the fifth portion is further adapted to correct a calculated notch strain for load cycle stress ratio effects using a Smith, Watson, and Topper equivalent stress equation.

26. The computer program product of claim 21, wherein the fifth portion is further adapted to perform a crack initiation computation including calculating at least one of a damage and a failure criteria.

27. The computer program product of claim 26, wherein the fifth portion is further adapted to perform a summation of the calculated damage associated with continued load cycling using a Palmgren and Miner'"'"'s Rule.

28. The computer program product of claim 26, wherein the fifth portion is further adapted to assume a crack initiation occurs when a total damage is greater than or equal to 1.0.

29. The computer program product of claim 19, wherein the seventh portion is further adapted to compare a first damage summation associated with a first continued load cycling with a second damage summation associated with a second continued load cycling.

30. The computer program product of claim 19, wherein the fifth portion is further adapted to performing a first fatigue damage computation simultaneously with the performance of the second fatigue damage computation.

31. The computer program product of claim 30, wherein at least one of the fifth portion and the sixth portion is further adapted to simultaneously performing the first and second fatigue damage computations using a spreadsheet program, respectively.

32. The computer program product of claim 30, wherein at least one of the fifth portion and the sixth portion is further adapted to perform a respective damage computation using a spreadsheet program.

33. The computer program product of claim 19 wherein the seventh portion is further adapted to compare the first and second fatigue damage computations simultaneously with at least one of performing a first fatigue damage computation by the fifth portion and performing a second fatigue damage computation by the sixth portion using a spreadsheet program.

34. The computer program product of claim 19, wherein the fourth portion is further adapted to perform a rainflow cycle counting operation to pair peak and valley loads.

35. The computer program product of claim 19, wherein the third, fourth, fifth, and sixth portions are adapted to perform simultaneously.

36. The computer program product of claim 19, wherein the first, second, third, fourth, fifth, sixth and seventh portions are adapted to perform simultaneously.

37. A method of performing a structural test, comprising:

operatively coupling at least one sensor to a test article;

applying a sequence of loads to the test article;

receiving raw test data indicative of the applied loads from the at least one sensor;

analyzing the raw test data, including;

receiving predicted test data indicative of a predicted load on the test article;

performing a filter operation to remove invalid data including spikes a and dropouts;

performing a cycle counting operation to pair peak and valley loads in the actual and predicted test data

performing a first fatigue damage computation based on the raw test data;

performing a second fatigue damage computation based on the predicted test data; and

comparing the first and second fatigue damage computations.

38. The method of claim 37, wherein at least one of performing a first fatigue damage computation and performing a second fatigue damage computation includes performing a crack initiation computation.

39. The method of claim 38, wherein performing a crack initiation computation includes calculating notch stress and strain based on the raw test data indicative of the applied load and an elastic K_T.

40. The method of claim 38, wherein performing a crack initiation computation includes correcting a calculated notch strain for load cycle stress ratio effects.

41. The method of claim 38, wherein performing a crack initiation computation includes calculating at least one of a damage and a failure criteria.

42. The method of claim 37, wherein performing a first fatigue damage computation includes performing a first fatigue damage computation simultaneously with performing a second fatigue damage computation.

43. The method of claim 37, wherein performing a first fatigue damage computation simultaneously with performing a second fatigue damage computation includes simultaneously performing the first and second fatigue damage computations using a spreadsheet program.

44. The method of claim 37, wherein comparing the first and second fatigue damage computations includes comparing the first and second fatigue damage computations simultaneously with at least one of performing a first fatigue damage computation and performing a second fatigue damage computation using a spreadsheet program.

45. The method of claim 37, wherein performing a cycle counting operation to pair peak and valley loads includes performing a rainflow cycle counting operation to pair peak and valley loads.

46. The method of claim 37, wherein the following portions are performed simultaneously:

performing a filter to eliminate invalid data from the applied and predicted loads;

performing a cycle counting operation to pair peak and valley loads;

performing a first fatigue damage computation based on the raw test data; and

performing a second fatigue damage computation based on the predicted test data.

47. The method of claim 37, wherein the following portions are performed simultaneously:

applying a sequence of loads to a test article;

receiving raw test data indicative of the applied loads from at least one sensor operatively associated with the test article;

receiving predicted test data indicative of a predicted loads on the test article;

performing a filter to eliminate invalid data from the applied and predicted loads;

performing a cycle counting operation to pair peak and valley loads;

performing a first fatigue damage computation based on the raw test data; and

performing a second fatigue damage computation based on the predicted test data.

48. A method of analyzing structural test data, comprising:

applying a sequence of loads to a test article;

receiving raw test data indicative of the applied loads from at least one sensor operatively associated with the test article;

receiving predicted test data indicative of a predicted loads on the test article;

performing a filter operation to remove invalid loads from the raw and predicted test data;

performing a cycle counting operation to pair peak and valley loads in the raw and predicted data data;

performing a first fatigue damage computation based on the raw test data;

performing a second fatigue damage computation based on the predicted test data; and

comparing the first and second fatigue damage computations, wherein at least one of the performing of the first and second fatigue damage computations includes performing a crack initiation computation including

calculating notch stress and strain based on the raw test data indicative of the applied load and an elastic K_T;

correcting a calculated notch strain for load cycle stress ratio effects; and

calculating at least one of a damage and a failure criteria.

49. The method of claim 48, wherein calculating notch stress and strain includes calculating notch strain for load cycle stress ratio effects using a Smith, Watson, and Topper equivalent stress equation.

50. The method of claim 48, wherein correcting a calculated notch strain for load cycle stress ratio effects includes correcting a calculated notch strain for load cycle stress ratio effects using a Smith, Watson, and Topper equivalent stress equation.

51. The method of claim 48, wherein calculating at least one of a damage and a failure criteria includes performing a summation of the calculated damage associated with continued load cycling using a Palmgren and Miner'"'"'s Rule.

52. The method of claim 48, wherein calculating at least one of a damage and a failure criteria includes assuming a crack initiation occurs when a total damage is greater than or equal to 1.0.

53. The method of claim 48, wherein comparing the first and second fatigue damage computations includes comparing a first damage summation associated with a first continued load cycling with a second damage summation associated with a second continued load cycling.

54. The method of claim 48, wherein performing a first fatigue damage computation includes performing a first fatigue damage computation simultaneously with performing a second fatigue damage computation.

55. The method of claim 48, wherein performing a first fatigue damage computation simultaneously with performing a second fatigue damage computation includes simultaneously performing the first and second fatigue damage computations using a spreadsheet program.

56. The method of claim 48, wherein at least one of performing a first fatigue damage computation and performing a second fatigue damage computation includes performing a respective damage computation using a spreadsheet program.

57. The method of claim 48, wherein comparing the first and second fatigue damage computations includes comparing the first and second fatigue damage computations simultaneously with at least one of performing a first fatigue damage computation and performing a second fatigue damage computation using a spreadsheet program.

58. The method of claim 48, wherein performing a cycle counting operation to pair peak and valley loads includes performing a rainflow cycle counting operation to pair peak and valley loads.

59. The method of claim 48, wherein the following portions are performed simultaneously:

performing a filter to eliminate invalid data from the applied and predicted loads;

performing a cycle counting operation to pair peak and valley loads;

performing a first fatigue damage computation based on the raw test data; and

performing a second fatigue damage computation based on the predicted test data.

60. The method of claim 48, wherein the following portions are performed simultaneously:

applying a sequence of loads to a test article;

receiving raw test data indicative of the applied loads from at least one sensor operatively associated with the test article;

receiving predicted test data indicative of a predicted loads on the test article;

performing a filter to eliminate invalid data from the applied and predicted loads;

performing a cycle counting operation to pair peak and valley loads;

performing a first fatigue damage computation based on the raw test data; and

performing a second fatigue damage computation based on the predicted test data.