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Hybrid Gear Performance Under Loss-of-Lubrication Conditions

Kelsen E. LaBerge (ARL), Stephen P. Berkebile (ARL), Robert F. Handschuh (NASA), Gary D. Roberts (NASA)

American Helicopter Society’s 73rd Annual ForumMay 9-11, 2017

https://ntrs.nasa.gov/search.jsp?R=20170006855 2019-02-25T03:49:28+00:00Z

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Outline

• Background• Hybrid gear design• Experimental setup• Results• Conclusions• Future work

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What is a hybrid composite gear?• Hybrid composite gear replaces the structural steel

portion of a gear with a lightweight composite material

Why hybrid gears?• Hybrid gears offer a potential to increase the power

density in drive systems. • Advanced vertical lift configurations are pushing for

multi-speed capability, requiring additional driveline components

Background

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Past Efforts

Small-Scale

3.5 inch pitch diameter hybrid gears

Large-Scale

16.5 inch pitch diameter hybrid bull gear

• One million cycle endurance test• Static torque test

• One million cycle endurance test at 3300 hp

• Operational testing at 5000 hp• Static torque test on the web

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What about operation under adverse

conditions?

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Hybrid Gear Design

Outer composite layers

Outer composite layers

Adhesive film

Adhesive film

Inner composite layers

Machined gear

Triaxial Braid Architecture

12k ±60bias yarns

2X12kaxial yarns

• T700S-50C standard modulus fiber • Prepreg / compression molding approach for flat web element • ACG MTM45-1 resin with MTA241 film adhesive

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History

• Gears were reground to correct distortion caused by the curing process – Resulted in increased backlash

• Endurance test (10,000 RPM, 490 in-lb) completed to 109 cycles• Two hybrid gears used, no damage detected after endurance test

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Procedure• Green Run at 10,000 RPM and

210 in-lb for at least 1 hour• Increase torque to 520 in-lb• At thermal equilibrium turn off

oil supply pump and cap supply line

• Continue test until failure

Experimental Setup

Contact Fatigue Test Rig at NASA Glenn Research Center

Right TC

Left TC

Out-of-Mesh TC

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Run Time (min)

0 0.5 1 1.5 2 2.5 3

Tem

pera

ture

(F)

150

300

450

600

Out of Mesh Left Gear Right Gear

Results - Baseline

Steel Driving Steel (Unshrouded)

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Results - Experiment 1

Hybrid Driving Hybrid

• After shutdown loss-of-torque was verified

• Visual inspection showed that the hub had rotated with respect to the teeth on the left gear

0 2.5 5

Tem

pera

ture

(F)

200

300

400

500

Run Time (min)

50 100 150 200 250

Out of Mesh Left Gear Right Gear

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Results - Experiment 1

Gap

Crushed composite

Disassembled left gear

Approximate location of interlock pattern

Modified right gear

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Experiment 2

Left Gear Thermocouple

Right Gear Thermocouple

Out-of-Mesh Thermocouple

(not shown)

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Results - Experiment 2

0 2.5 5

Torq

ue

(in-lb

s)

400

600

800

50 100 150

(N-m

)

50

70

90

0 2.5 5

Tem

pera

ture

(F)

200

300

400

500

Run Time (min)

50 100 150

Out of Mesh Left Gear Right Gear

Stop 2Stop 1

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Results - Experiment 2

0 2.5 5

Torq

ue

(in-lb

s)

400

600

800

50 100 150

(N-m

)

50

70

90

0 2.5 5

Tem

pera

ture

(F)

200

300

400

500

Run Time (min)

50 100 150

Out of Mesh Left Gear Right Gear

Stop 2Stop 1

Stop 1• Torque transfer verified• Black lines documented on teeth• Restarted experiment dry and

reapplied load

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Results - Experiment 2

0 2.5 5

Torq

ue

(in-lb

s)

400

600

800

50 100 150

(N-m

)

50

70

90

0 2.5 5

Tem

pera

ture

(F)

200

300

400

500

Run Time (min)

50 100 150

Out of Mesh Left Gear Right Gear

Stop 2Stop 1

Stop 2• Torque transfer verified• Gears photographed• Restarted experiment

dry and reapplied load

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Results - Experiment 2

0 2.5 5

Torq

ue

(in-lb

s)

400

600

800

50 100 150

(N-m

)

50

70

90

0 2.5 5

Tem

pera

ture

(F)

200

300

400

500

Run Time (min)

50 100 150

Out of Mesh Left Gear Right Gear

Stop 2Stop 1

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What is the source of the black substance on the gear teeth?

• Samples collected• Gear teeth• Gearbox• Uncured prepreg• Thin film adhesive

• Analyzed using energy dispersive spectroscopy for elemental characterization

Post-test Analysis

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EDS Analysis

Gear Tooth Surface Sample Gearbox Residue Sample

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EDS Analysis

Epoxy on Prepreg Thin Film Adhesive

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• The mechanical interlock design in a hybrid gear is important during an oil-out event

• The pinned interlock pattern was shown to better withstand this type of event

• At increased temperatures, softened polymer at the gear mesh may act as a lubricant or sulfur-containing lubricant additive

Conclusions

The effects of material degradation on hybrid gear design for oil-out conditions needs further investigation

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• Isolate source of performance increase• Increased backlash• Polymer lubricant

• Can polymer flow phenomenon be used to increase survivability of steel gears during an oil-out event?

Future Work

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Questions?

Acknowledgements:• A&P Technology – Provided hybrid gears

used for this project as part of a NASA SBIR

• Roger Tuck – Technician support• ARL’s Weapons and Materials Research

Directorate – EDS