Risk-based design and maintenance systems and methods

• US 7,840,376 B2
• Filed: 03/20/2008
• Issued: 11/23/2010
• Est. Priority Date: 03/20/2008
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Torng, Yi Tony
• Primary Examiner(s): Charioui; Mohamed
• Application Number:
  US12/052,256
• Publication Number:
  US 20090240468A1
• Time in Patent Office: 978 Days
• Field of Search: 702/35, 702/59, 702/98, 702/99, 702/138, 702176-185, 702/193, 244/100.R, 703/2
• US Class Current: 702/177
• CPC Class Codes: G06Q 10/06 Resources, workflows, human or project management; Enterprise or organisation planning; Enterprise or organisation modelling

Abstract

A method for determining an optimal inspection schedule for a structure is described. The method includes determining a crack size distribution table for the structure, determining a plurality of risk values, each risk value for a different estimated usage hours of the structure and based on said crack size distribution table, estimating a first inspection interval based on a predetermined risk value threshold, and determining a second inspection interval based on analyzing the rate of increase of risk value and probability of detection of a crack in said first inspection interval.

Claims

1. A computer-based method for determining an optimal inspection schedule for a structure, said method comprising:

determining a crack size distribution table for the structure by a computer using the location and inspection data;

determining a plurality of risk values for the structure by the computer, each risk value for a different estimated usage hours of the structure and based on said crack size distribution table;

estimating, by the computer, a first inspection interval based on a predetermined risk value threshold input into the user interface; and

determining, by the computer, a second inspection interval based on analyzing the rate of increase of risk value and probability of detection of a crack in said first inspection interval.

2. A computer-based method according to claim 1 wherein estimating a first inspection interval comprises determining a risk associated with postponing inspection of the structure for a period of time.

3. A computer-based method according to claim 2 further comprising:

evaluating whether the risk associated with postponing inspection of the structure is smaller than the predetermined risk value threshold; and

if the risk is smaller, changing the current accumulated usage hours and yearly usage hours associated with an inspection interval, and repeating the determination of the first inspection interval until a larger risk, substantially close to the predetermined risk value threshold, is found.

4. A computer-based method according to claim 3 further comprising estimating the hours of structure usage until the first inspection is required.

5. A computer-based method according to claim 1 wherein determining a plurality of risk values comprises:

defining input data for a first analysis; and

evaluating risk at the current accumulated hours of structure usage.

6. A computer-based method according to claim 5 further comprising:

evaluating risk at the current accumulated hours of structure usage plus or minus one to ten years of structure usage hours; and

verifying the risk increases monotonically over the range of risk evaluation data.

7. A computer-based method according to claim 1 wherein determining a plurality of risk values comprises utilizing a crack growth analysis and an updated crack size distribution to compute a single flight probability of fracture.

8. A computer-based method according to claim 7 further comprising:

computing a probability of detection (POD);

computing missed cracks distribution in the structure;

updating the crack size distribution with the computed POD; and

computing an updated single flight probability of fracture (SFPOF) and an updated usage interval probability of failure (UIPOF).

9. A computer-based method according to claim 1 further comprising identifying all critical locations on the structure where an inspection is required.

10. A computer-based method according to claim 1 wherein determining a second inspection interval comprises modifying the second inspection interval until all risks associated with postponing inspection of the structure before a probability of detection (POD) inspection are less than the predetermined risk value threshold.

11. A computer programmed to assess risk associated with a structural inspection schedule for a flight platform, said computer programmed to:

utilize input data to evaluate a probability of fracture risk at the current accumulated hours of usage, and the probability of fracture risks for the current accumulated hours of usage plus or minus a range of usages;

verify, over the usage range, that the probability of fracture risks increases monotonically;

determine a risk associated with postponing, for a period of time, the inspection described by a structural maintenance plan, the determined risk based on a period of postponement that corresponds with the probability of fracture risk for a specific level of usage;

evaluate if the determined risk is less than a risk requirement defined in the structural maintenance plan; and

estimate the hours of usage for the flight platform until the first inspection, which is when the risk is within a defined threshold of, but less than, the risk requirement.

12. A computer according to claim 11 wherein to utilize input data to evaluate a probability of fracture risk, said computer is programmed to utilize crack growth analysis data and data relating to an updated crack size distribution in the computation of a single flight probability of fracture (SFPOF).

13. A computer according to claim 11 wherein said computer is programmed to:

evaluate whether the risk associated with postponing inspection of the structure is smaller than the risk requirement defined in the structural maintenance plan; and

change the current accumulated usage hours and yearly usage hours associated with an inspection interval until a larger risk, substantially close to the predetermined risk value threshold, is found.

14. A computer according to claim 11, wherein to determine a risk associated with postponing the inspection described by a structural maintenance plan, said computer is programmed to:

compute a probability of detection (POD);

compute missed cracks distribution in the structure;

update the crack size distribution with the computed POD; and

compute an updated single flight probability of fracture (SFPOF) and an updated usage interval probability of failure (UIPOF).

15. A computer according to claim 11 wherein said computer is programmed to produce a single flight probability of failure (SFPOF) for each near term inspection that is identified in a force structural maintenance plan.

16. A computer-based method for assessing a risk associated with a structural inspection schedule for a flight platform, said method comprising:

evaluating, based on data input into a computer, a probability of fracture risk at the current accumulated hours of usage, and the probability of fracture risks for the current accumulated hours plus or minus a range of usage hours;

verifying, based on computer generated results, and over the range of usage hours, that the probability of fracture risks increases monotonically;

determining, by the computer, a risk associated with postponing, for a period of time, the inspection described by a structural maintenance plan, the determined risk based on a period of postponement that corresponds with the probability of fracture risk for a specific usage hour;

evaluating, by the computer, if the determined risk is less than a risk requirement defined in the structural maintenance plan; and

estimating, by the computer, the hours of usage for the flight platform until the first inspection is needed, which is when the risk is within a defined threshold of, but less than, the risk requirement.

17. A computer-based method according to claim 16 further comprising utilizing crack growth analysis data and data relating to an updated crack size distribution to compute a single flight probability of fracture (SFPOF).

18. A computer-based method according to claim 16 further comprising:

evaluating whether the risk associated with postponing inspection of the structure is smaller than the risk requirement defined in the structural maintenance plan; and

changing the current accumulated usage hours and yearly usage hours associated with an inspection interval until a larger risk, substantially close to the predetermined risk value threshold, is found.

19. A computer-based method according to claim 16, wherein determining a risk associated with postponing the inspection described by a structural maintenance plan comprises:

computing a probability of detection (POD);

computing a missed cracks distribution in the structure;

updating the crack size distribution with the computed POD; and

computing an updated single flight probability of fracture (SFPOF) and an updated usage interval probability of failure (UIPOF).

20. A computer-based method according to claim 16 further comprising producing a single flight probability of failure (SFPOF) for each near term inspection that is identified in a force structural maintenance plan.