Wind tunnel balance and method of use

Patent metadata

Field	Value
Publication number	US-10267708-B2
Application number	US-201715598766-A
Country	US
Kind code	B2
Filing date	May 18, 2017
Priority date	May 18, 2017
Publication date	Apr 23, 2019
Grant date	Apr 23, 2019

Abstract

A balance has a balance centerline and an axial force measurement section having a longitudinal slot partially dividing the axial force measurement section into a first part and a second part longitudinally overlapping each other and interconnected by corner flexure groups. The axial force measurement section has an axial force measurement beam located approximately midway between the corner flexure groups. The axial force measurement beam has strain gages for determining axial force on the model. Each corner flexure group includes flexures each having a first flexure root and a second flexure root respectively joined to the first part and the second part. The flexures each have a flexure midpoint between the first and second flexure roots, and a flexure thickness that is tapered along the flexure length from each of the first and second flexure roots to a reduced thickness proximate the flexure midpoint.

First claim

What is claimed is:

1. An internal balance for a wind tunnel model, comprising:
a balance body having a balance centerline and including an instrumentation portion extending axially between a model interface portion for supporting a wind tunnel model, and a sting interface portion for coupling to a sting of a wind tunnel;
the instrumentation portion including an axial force measurement section and at least one moment/force measurement section having strain gages for determining at least one of moments and lateral forces on the model;
the axial force measurement section including a longitudinal slot having opposing slot ends and partially dividing the axial force measurement section into a first part and a second part longitudinally overlapping each other and interconnected by a corner flexure group at each of the slot ends on each of opposing lateral sides of the balance centerline;
the axial force measurement section having an axial force measurement beam located at a balance longitudinal center approximately midway between the corner flexure groups, the axial force measurement beam having a measurement beam first end and a measurement beam second end respectively coupled to the first part and the second part and having strain gages for determining axial force on the model; and
each corner flexure group including a plurality of spaced parallel flexures each having a flexure length extending between a first flexure root and a second flexure root respectively joined to the first part and the second part, the flexures each having a flexure midpoint between the first and second flexure roots and having a flexure thickness that is tapered along the flexure length from each of the first and second flexure roots to a reduced thickness proximate the flexure midpoint.

2. The balance of claim 1 , wherein:
the flexure thickness is tapered in a manner such that stress in the flexure is approximately constant along the flexure length.

3. The balance of claim 1 , wherein:
the flexure thickness of each flexure in a corner flexure group is uniquely tapered according to an anticipated load to be borne by the flexure.

4. The balance of claim 1 , wherein:
the flexures in each corner flexure group have the same flexure thickness and the same taper.

5. The balance of claim 1 , wherein:
in each corner flexure group, the flexure nearest the balance longitudinal center has a flexure thickness that is less than the corresponding flexure thickness at the same flexure lengthwise location in each of the remaining flexures in the corner flexure group.

6. The balance of claim 1 , wherein:
the strain gages of the at least one moment/force measurement section is configured to determine lateral forces and moments on the model including a normal force, a side force, a pitching moment, a rolling moment, and a yawing moment; and
the flexure thickness is tapered in a manner such that stress in the flexure is approximately constant along the flexure length when the normal force, the side force, the pitching moment, the rolling moment, the yawing moment, and the axial force are simultaneously applied to the balance.

7. The balance of claim 1 , wherein:
the balance body includes a vertical slot at each corner flexure group, the vertical slot having an inboard slot wall and an outboard slot wall respectively defining a laterally inboard side of the flexures in the corner flexure group and a side wall of an interior portion of the first part or the second part, the interior portion located between a pair of the corner flexure groups respectively on opposing lateral sides of the balance centerline;
the inboard slot wall and the outboard slot wall at each corner flexure group terminating at a slot base fillet, the inboard slot wall transitioning to the slot base fillet at a fillet tangent point; and
at least one flexure in at least one corner flexure group includes a flexure fillet at an intersection of the first flexure root or the second flexure root respectively with the first part or the second part, the fillet tangent point being aligned with a lowermost portion of the flexure fillet.

8. The balance of claim 1 , wherein:
the balance body includes a plurality of cross-sectional transition areas, each cross-sectional transition area being a location of a change in a cross-sectional shape or size of the balance body; and
at least one of the cross-sectional transition areas has a non-constant-radius fillet in which a profile of the non-constant-radius fillet when viewed in transverse cross section is a non-radius or is comprised of multiple radii.

9. The balance of claim 8 , wherein:
the non-constant-radius fillet in at least one of the cross-sectional transition areas is one of an elliptical fillet and a streamline fillet.

10. The balance of claim 8 , wherein at least one of the following cross-sectional transition areas has a non-constant-radius fillet:
an intersection of at least one of the first flexure root and the second flexure root respectively with the first part or the second part;
a transition from the longitudinal slot to a shovel slot separating the first part from the second part;
a transition from the instrumentation portion to at least one of the model interface portion and the sting interface portion;
an intersection of a relief cut with a wall of an interior portion of the first part or the second part;
an inside corner of a measurement beam vertical cutout defining the axial force measurement beam; and
an inside corner of a measurement beam vertical slot defining the axial force measurement beam.

11. An internal balance for a wind tunnel model, comprising:
a balance body having a balance centerline and an instrumentation portion having an axial force measurement section and at least one moment/force measurement section, the axial force measurement section including a longitudinal slot having opposing slot ends and partially dividing the axial force measurement section into a first part and a second part longitudinally overlapping each other and interconnected by a corner flexure group at each of the slot ends on each of opposing lateral sides of the balance centerline, each corner flexure group including a plurality of spaced parallel flexures each having a flexure length extending between a first flexure root and a second flexure root respectively joined to the first part and the second part;
the axial force measurement section having an axial force measurement beam located approximately midway between the corner flexure groups and having a measurement beam first end and a measurement beam second end respectively coupled to the first part and the second part;
the balance body including a vertical slot at each corner flexure group, the vertical slot having an inboard slot wall and an outboard slot wall respectively defining a laterally inboard side of the flexures in the corner flexure group and a side wall of an interior portion of the first part or the second part, the interior portion located between a pair of the corner flexure groups respectively on opposing lateral sides of the balance centerline;
the inboard slot wall and the outboard slot wall at each corner flexure group terminating at a slot base fillet, the inboard slot wall transitioning to the slot base fillet at a fillet tangent point; and
at least one flexure in at least one corner flexure group includes a flexure fillet at an intersection of the first flexure root or the second flexure root respectively with the first part or the second part, the fillet tangent point being aligned with a lowermost portion of the flexure fillet.

12. A method of measuring loads on a model in a wind tunnel, comprising:

Assignees

• Boeing Co

Inventors

• Skube Seth
• Bennett Henry

Classifications

• B64F5/60

  Testing or inspecting aircraft components or systems · CPC title

• G01M9/062 Primary

  Wind tunnel balances; Holding devices combined with measuring arrangements · CPC title

• G01M9/04

  Details · CPC title

• G01M17/00

  Testing of vehicles (testing fluid tightness G01M3/00; testing elastic properties of bodies or chassis, e.g. torsion-testing, G01M5/00; testing alignment of vehicle headlight devices G01M11/06; testing of engines G01M15/00) · CPC title