STRESSES INDUCED BY RANDOM LOADING

• US 20120239358A1
• Filed: 03/08/2012
• Published: 09/20/2012
• Est. Priority Date: 03/16/2011
• Status: Active Grant

• Current Assignee: Airbus Operations Limited (Airbus SE)
• Original Assignee: Airbus Operations Limited (Airbus SE)
• Inventors: YIU, Hoi
• Granted Patent: US 9,449,123 B2
• Time in Patent Office: Days
• US Class Current: 703/2
• CPC Class Codes: G01M 7/00 Vibration-testing of structures; Shock-testing of structures G01M9/00 takes precedence
• CPC Class Codes: G01M 7/022 Vibration control arrangements, e.g. for generating random vibrations
• CPC Class Codes: G01N 2203/0073 Fatigue
• CPC Class Codes: G01N 3/00 Investigating strength properties of solid materials by application of mechanical stress
• CPC Class Codes: G06F 30/23 using finite element methods [FEM] or finite difference methods [FDM]

Abstract

A computer-implemented method of modelling a root-mean-square stress in a structure induced by a random load. The method comprises determining a modal correction factor based on data representing the eigensolution for the structure in free vibration. The modal correction factor characterises the proportion of the random load, which is attributable to the root-mean-square response of the structure. Once the modal correction factor has been calculated, it is applied to data representing a stress in the structure due to a forced vibration to thereby determine the root-mean-square stress induced by the random load.

Claims

1. A computer-implemented method of modelling a root-mean-square stress in a structure induced by a random load, the method comprising:

determining a modal correction factor based on data representing the eigensolution for the structure in free vibration, the modal correction factor characterising the proportion of the random load which is attributable to the root-mean-square response of the structure; and

applying the modal correction factor to data representing a stress in the structure due to a forced vibration to thereby determine the root-mean-square stress induced by the random load.

2. A computer-implemented method of modelling a root-mean-square stress in a structure according to claim 1, wherein the method further comprises determining the eigensolution using a finite element method modal analysis.

3. A computer-implemented method of modelling a root-mean-square stress in a structure according to claim 1, wherein the random load is characterised by a power spectral density.

4. A computer-implemented method of modelling a root-mean-square stress in a structure according to claim 1, wherein, for a particular location in the structure, the stress due to the forced vibration is determined as being proportional to a corresponding modal stress in free vibration.

5. A computer-implemented method of modelling a root-mean-square stress in a structure according to claim 4, wherein, for a particular location in the structure, the ratio of the stress in the structure due to the forced vibration and the corresponding modal stress in free vibration is determined using the Miles equation:

6. A computer-implemented method of modelling a root-mean-square stress in a structure according to claim 1, wherein the modal correction factor is calculated as:

7. A computer-implemented method of modelling a root-mean-square stress in a structure according to claim 1, further comprising displaying, using a visual display device, the root-mean-square stresses determined for a plurality of locations in the structure for inspection by a user.

8. A computer-implemented method of modelling a root-mean-square stress in a structure according to claim 1, wherein the random load is an acoustic pressure.

9. A computer-implemented method of modelling a root-mean-square stress in a structure according to claim 8, wherein the acoustic pressure is characterised as:

10. A computer program product comprising a non-transitory computer-readable storage medium having computer readable instructions stored thereon, the computer readable instructions being executable by a computerised device to cause the computerised device to perform a method of modelling a root-mean-square stress in a structure induced by a random load, the method comprising:

determining a modal correction factor based on data representing the eigensolution for the structure in free vibration, the modal correction factor characterising the proportion of the random load which is attributable to the root-mean-square response of the structure; and

applying the modal correction factor to data representing a stress in the structure due to a forced vibration to thereby determine the root-mean-square stress induced by the random load.

11. A computer program product according to claim 10, wherein the method further comprises determining the eigensolution using a finite element method modal analysis.

12. A computer program product according to claim 10, wherein the random load is characterised by a power spectral density.

13. A computer program product according to claim 10, wherein, for a particular location in the structure, the stress due to the forced vibration is determined as being proportional to a corresponding modal stress in free vibration.

14. A computer program product according to claim 13, wherein, for a particular location in the structure, the ratio of the stress in the structure due to the forced vibration and the corresponding modal stress in free vibration is determined using the Miles equation:

15. A computer program product according to claim 10, wherein the modal correction factor is calculated as:

16. A computer program product according to claim 10, further comprising displaying, using a visual display device, the root-mean-square stresses determined for a plurality of locations in the structure for inspection by a user.

17. A computer program product according to claim 10, wherein the random load is an acoustic pressure.

18. A computer program product according to claim 17, wherein the acoustic pressure is characterised as:

19. A computer apparatus for modelling a root-mean-square stress in a structure induced by a random load, the apparatus comprising a processor configured to:

determine a modal correction factor based on data representing the eigensolution for the structure in free vibration, the modal correction factor characterising the proportion of the random load which is attributable to the root-mean-square response of the structure; and

apply the modal correction factor to data representing a stress in the structure due to a forced vibration to thereby determine the root-mean-square stress induced by the random load.

20-21. -21. (canceled)