Method for analyzing structures having deformable rigid elements

• US 5,777,236 A
• Filed: 04/03/1997
• Issued: 07/07/1998
• Est. Priority Date: 10/01/1996
• Status: Expired due to Term

• Current Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Original Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Inventors: Walls, William T.
• Primary Examiner(s): Dombroske, George M.
• Assistant Examiner(s): Noori, Max H.
• Application Number:
  US08/832,311
• Time in Patent Office: 460 Days
• Field of Search: 73/760, 73/786, 73/787, 73/788, 73/789, 73/583, 73/588
• US Class Current: 73/786
• CPC Class Codes: G01M 5/00 Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings G01M9/00 takes precedence
• CPC Class Codes: G01M 5/0016 of aircraft wings or blades

Abstract

A method of analyzing a structure containing a rigid body. The method defines a set of displacement factors to be imposed on a structure model. The method is used for calculating structure stress defining equations including a load vector representing externally applied forces on the structure model. The method modifies the load vector to compensate for rigid body deformation and evaluates stresses on the structure model from data generated from the structure stress defining equations.

Claims

1. A method for analyzing a structure having a deformable rigid element, the method comprising the steps of:

defining a set of displacement factors to be imposed on a structure model;

calculating a set of structure stress defining equations based on said set of displacement factors, wherein said structure stress defining equations include;

provision for calculating a load vector representing externally applied forces applied to the structure model;

provision for inputting a value of a known magnitude of rigid element deformation experienced by said structure before said load vector is applied;

provision for modifying the load vector to compensate for said known magnitude of rigid element deformation experienced by said structure before calculating stresses on the structure model resulting from said load vector;

applying the set of displacement factors to the structure stress defining equations;

outputting data generated from said step of applying the set of displacement factors to the structure stress defining equations;

evaluating stresses on the structure model; and

wherein said structure stress defining equations include a formula;

space="preserve" listing-type="equation">{u.sub.m }= R.sub.m !.sup.-1 {δ

.sub.G }+ G.sub.m !{u.sub.n }(4)

where;

R_m !^-1 is the inverse of a partition of a dependent multi-point constraint co-efficient matrix;

{δ

_G } is a user defined displacement term;

R_n !=is the partition of the multi-point constraint coefficient matrix; and

{u_n } is an independent set of displacements.

2. The method of claim 1, wherein the step of modifying said load vector comprises the step of introducing an expansion co-efficient into the load vector.

3. The method of claim 1, wherein said step of modifying said set of structures stress defining equations comprises the step of modifying said set of structure stress defining equations to compensate for a mechanical expansion of the rigid element.

4. The method of claim 1, wherein said step of modifying said set of structure stress defining equations comprises the step of modifying said equations to compensate for hydraulic expansion of the rigid element.

5. A method for analyzing a structure having a deformable rigid element, said method comprising the steps of:

defining a set of displacement factors to be imposed on a structure model;

calculating a set of structure stress defining equations based on said set of displacement factors to account for the deformation of said rigid element, wherein said structure stress defining equations include the steps of accounting for a known magnitude of deformation of the rigid element, and calculating a load vector representing externally applied forces applied to the structure model;

applying a set of displacement factors to the structure stress defining equations;

evaluating stresses on the structure model; and

wherein said structure stress defining equations include the formula;

space="preserve" listing-type="equation">{u.sub.m }= R.sub.m !.sup.-1 {δ

.sub.G }+ G.sub.m !{u.sub.n }(4)

where;

R_m !^-1 is the inverse of a partition of a dependent multipoint constraint co-efficient matrix;

{δ

_G } is a user defined displacement term;

R_n !=is the partition of the multi-point constraint coefficient matrix; and

{u_n } is an independent set of displacements.

6. The method of claim 5, further comprising the step of:

outputting data generated from said step of applying the set of displacement factors to the structure stress defining equations prior to said step of evaluating stresses on the structure model.

7. The method of claim 5, further comprising the step of modifying said load vector to compensate for expansion of the rigid element.

8. The method of claim 7, further comprising the step of modifying said load vector by introducing an expansion co-efficient into the load vector.

9. The method of claim 5, further comprising the step of modifying said set of structure stress defining equations to compensate for mechanical expansion of said rigid element.

10. The method of claim 5, further comprising the step of modifying said set of structure stress defining equations to compensate for hydraulic expansion of the rigid element.

11. A method for analyzing a structure having a deformable rigid element, said method comprising the steps of:

defining a set of displacement factors to be imposed on a structure model;

providing a data input for inputting said displacement factors to a processor;

using a memory to store a plurality of structure stress defining equations based on said set of displacement factors;

providing said structure stress defining equations with a provision for defining a set of displacement factors to be imposed on a structure model, a provision for calculating a load vector representing externally applied forces applied to the structure model, a provision for inputting a value of a known magnitude of deformation of said rigid element before applying said load vector to said structure model and a provision for modifying the load vector to compensate for known rigid element deformation experienced by said structure model before calculating stresses on the structure model resulting from said load vector;

using a processor to model the structure and to process said structure displacement data through said plurality of structure stress defining equations;

outputting structure displacement data generated by said processor for structural analysis and modeling; and

wherein said structure stress defining equations include the formula;

space="preserve" listing-type="equation">{u.sub.m }= R.sub.m !.sup.-1 {δ

.sub.G }+ G.sub.m !{u.sub.n }(4)

where;

R_m !^-1 is the inverse of a partition of a dependent multi-point constraint co-efficient matrix;

{δ

_G } is a user defined displacement term;

R_n !=is the partition of the multi-point constraint coefficient matrix; and

{u_n } is an independent set of displacements.

12. The method of claim 11, wherein said structure stress defining equations include the step of compensating for mechanical expansion of the rigid element.

13. The method of claim 11, wherein said structure stress defining equations comprise the step of compensating for hydraulic expansion of the rigid element.