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# Axial Load Distribution in a Jet Engine Spline Coupling PowerPoint PPT Presentation

Axial Load Distribution in a Jet Engine Spline Coupling. Justin McGrath. Master of Engineering Project Rensselaer Polytechnic Institute Hartford, CT. Spline Coupling Background. Elongated gear teeth Used in high torque applications

Axial Load Distribution in a Jet Engine Spline Coupling

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## Axial Load Distribution in a Jet Engine Spline Coupling

Justin McGrath

Master of Engineering Project

Rensselaer Polytechnic Institute

Hartford, CT

### Spline Coupling Background

• Elongated gear teeth

• Used in high torque applications

• Used in jet engines to transfer torque from disks to shafts

• The pressure faces of the teeth distribute the load

### Spline Coupling Schematic

• Spline Couplings used in several Pratt & Whitney Engines:

• F-119

• F-135

• PW4000

• PW2000

• PW6000

### Challenges in Spline Design

• Even distribution of the torque load on the pressure face of the spline teeth

• Uneven loading causes premature wear and reduces the life of the coupling system

• Designers must understand the load behavior of the coupling system to make changes that will even the load

• This project looks into analyzing axial load distribution in a representative spline coupling

### Theoretical Methodology

• Derived equation of axial load distribution using Tatur’s method:

p(x) – axial load at the root fillet radius

L – Contact length of the coupling system

c – effective tooth height

R – pitch radius

N – Number of teeth

T – tau, the applied torque

α – constant of integration

### Finite Element Methodology

• Create 3D model of the coupling system:

• Import Geometry into ANSYS & apply loads:

### Finite Element Methodology

• Load data is extracted from the finite element model and compared to the theoretical equation:

### Results

Both methods show the load peaking at either end of the contact length

The theoretical solution predicts a higher maximum load

### Discussion

• The theoretical solution predicts higher loads because:

• Tatur’s Method assumes 100 % transfer of load with no deflection

• FE model shows only about 75% of the load is transferred

• The other 25% is used in bending the teeth, and torsionally deflecting the coupling system

### Discussion

• Both methods converge when looking at a normalized plot

This confirms that the boundary conditions used in the FE model agree with the theoretical boundary conditions

### Conclusion

• The theoretical equation is the more conservative method in analyzing axial load distribution in a spline coupling system as it predicts higher maximum & average loads

• The theoretical equation is also a much faster method

• The Finite Element solution more accurately predicts the load that will be seen during engine operation, but it is a time consuming apporach

• The Finite Element model shows that all else being equal there is more capability in the coupling system when compared to the theorecitcal approach

### Back Up Slides

Analytical Calculations

Finite Element Calculations

### Back Up Slides

Table 1 – Material Properties of 3D Spline Coupling Model

### Back Up Slides

Table 2 – Geometric Properties of 3D Spline Coupling Model