Apparatus for Measuring Stresses on Rotating Blades and Methods Thereof

• US 20090145242A1
• Filed: 12/11/2007
• Published: 06/11/2009
• Est. Priority Date: 12/11/2007
• Status: Abandoned Application

• Current Assignee: Hamilton Beach Brands Incorporated (Hamilton Beach Brands Holding Co.)
• Original Assignee: Hamilton Beach Brands Incorporated (Hamilton Beach Brands Holding Co.)
• Inventors: Branson, Ben H. III, Hanes, Adam, Pryor, Ernest B. JR.
• Application Number:
  US11/954,005
• Publication Number:
  US 20090145242A1
• Time in Patent Office: Days
• US Class Current: 73/856
• CPC Class Codes: G01L 5/009 Force sensors associated with material gripping devices
• CPC Class Codes: G01N 2203/0073 Fatigue

Abstract

A strain gauge apparatus for measuring stresses on a rotating blade includes a strain gauge assembly, a shaft connectable to the rotating blade, a slip ring connected to the shaft, and a sleeve for covering lead wires routed along the shaft from the strain gauge and connected to the slip ring. The present invention also relates to a method of determining the fatigue life of a rotating blade.

Claims

1. A strain gauge apparatus for measuring stresses on a rotating blade comprising:

a strain gauge assembly that includes;

a strain gauge for measuring strain on a rotating blade, and

lead wires connected to the strain gauge;

a shaft connected to the rotating blade; and

a slip ring connected to the shaft and the lead wires.

2. The strain gauge apparatus of claim 1, wherein the strain gauge is secured to the rotating blade.

3. The strain gauge apparatus of claim 1, wherein the strain gauge is covered.

4. The strain gauge apparatus of claim 1, further comprising a sleeve covering at least a portion of the lead wires.

5. The strain gauge apparatus of claim 4, wherein the sleeve is an annular sleeve or a flexible wrap.

6. The strain gauge apparatus of claim 1, further comprising a data acquisition system in communication with the strain gauge.

7. The strain gauge apparatus of claim 1, wherein the rotating blade is a blender blade, a food processing blade, a mixing blade, a turbine blade, a propeller blade, or a cutting blade.

8. A strain gauge apparatus for measuring stresses on a blender blade mounted within a blender, comprising:

a strain gauge secured to a blender blade;

a shaft connected to the blender blade and extending through an upper portion of the blender;

lead wires connected to the strain gauge and routed along the shaft; and

a slip ring connected to the lead wires and the shaft at the upper portion of the blender.

9. The strain gauge apparatus of claim 8, further comprising a mounting structure engaged with the blender and the slip ring to secure the slip ring relative to the blender.

10. The strain gauge apparatus of claim 8, wherein the slip ring has a stationary portion and a rotating portion, the strain gauge apparatus further comprising:

a blender lid;

a mounting structure secured to the lid and the stationary portion; and

wherein the shaft is secured to the rotating portion.

11. The strain gauge apparatus of claim 8, further comprising a data acquisition system in communication with the strain gauge.

12. The strain gauge apparatus of claim 8, further comprising a sleeve covering at least a portion of the lead wires.

13. A method of measuring stresses on a rotating blade comprising the steps of:

securing a strain gauge having lead wires on a rotating blade mounted to a blade shaft;

connecting a shaft to the blade shaft for rotation therewith;

connecting a slip ring having slip ring wires to the shaft;

routing the lead wires along the shaft and connecting the lead wires to the slip ring; and

connecting the slip ring wires to a data acquisition system.

14. The method of claim 13, further comprising the step of covering the strain gauge with a coating.

15. The method of claim 13, further comprising the step of covering the lead wires.

16. A method of determining the fatigue life of a rotating blade comprising the steps of:

obtaining raw stress data on a rotating blade under actual use conditions;

converting the raw stress data into a first data set;

obtaining simulated stress data on the rotating blade under simulated use conditions;

converting the simulated stress data into a second data set; and

evaluating the first and second data sets to determine the fatigue life of the rotating blade.

17. The method of claim 16, wherein the step of converting the raw stress data comprises the steps of:

reducing the raw stress data to a rainflow histogram;

normalizing the rainflow histogram to an equivalent zero mean stress data set; and

grouping counts for common zero mean stress data ranges of the normalized equivalent zero mean stress data set.

18. The method of claim 16, wherein the second data set is a stress versus number of cycles to failure curve.

19. The method of claim 16, wherein the fatigue life is determined by applying the Palmgren-Miner linear damage hypothesis to the first and second data sets.

20. The method of claim 16, wherein the step of obtaining raw stress data comprises the steps of:

instrumenting the rotating blade with a strain gauge apparatus;

stressing the rotating blade under actual use conditions; and

measuring the stresses on the stressed rotating blade.

21. A method of evaluating rotating blades comprising the steps of:

obtaining raw stress data on a rotating blade under actual use conditions;

converting the raw stress data into a first data set;

obtaining simulated stress data on the rotating blade under simulated use conditions;

converting the simulated stress data into a second data set;

evaluating the first and second data sets to determine the fatigue life of the rotating blade; and

comparing the fatigue life to a predetermined fatigue life value.

22. The method of claim 21, wherein the step of converting the raw stress data comprises the steps of:

reducing the raw stress data to a rainflow histogram;

normalizing the rainflow histogram to an equivalent zero mean stress data set; and

grouping counts for common zero mean stress data ranges of the normalized equivalent zero mean stress data set.

23. The method of claim 21, wherein the second data set is a stress versus number of cycles to failure curve.

24. The method of claim 21, wherein the fatigue life is determined by applying the Palmgren-Miner linear damage hypothesis to the first and second data sets.

25. The method of claim 21, wherein the step of obtaining raw stress data comprises the steps of:

instrumenting the rotating blade with a strain gauge apparatus;

stressing the rotating blade under actual use conditions; and

measuring the stresses on the stressed rotating blade.