seal evaluation using ansys workbench evaluation using ansys workbench hua wang, li jun zeng trw...

Seal Evaluation Using ANSYS WorkBench

Hua Wang, Li Jun ZengTRW Automotive

Content• Introduction

• Materials Model– Stress / Strain nonlinearity

– Thermal expansion

• Analyses and Results– Axial symmetric 2D O‐ring seal evaluation

– 3D seal groove evaluation

• Summary and limitation

Seal Evaluation Using ANSYS WorkBench 2Oct. 30, 2012

Introduction

• TRW was first‐to‐market in 2001 with its Electric Park Brake (EPB) on a mass production vehicle. Today, there are more than 15million TRW EPB calipers on road worldwide.

• Comparing to traditional mechanical parking brake, EPB reduces drag and saves weight, allows for greater freedom of vehicle interior design and packaging, enhances vehicle safety and driver comfort.

Oct. 30, 2012 Seal Evaluation Using ANSYS WorkBench 3

http://trw.com/braking_systems/electric_park_brakehttp://trw.com/braking_systems/electric_park_brakehttp://trw.com/braking_systems/electric_park_brake

http://trw.com/braking_systems/electric_park_brake





Introduction

• Robust sealing of electric motor case is critical for EPB application in different environments. Improper sealing may allow moisture into the actuator case chamber, which can cause corrosion and lead to other function failures.

• The EPB actuator case under study is made from fiber filled plastic, which is bolted on to a foundation housing made of aluminum. The O‐ring rubber seal is in‐between the plastic case and aluminum base.

Seal Evaluation Using ANSYS WorkBench 4

CAE Livonia

Oct. 30, 2012

Plastic

Rubber

Aluminum

Introduction

• To evaluate whether the actuator case to foundation housing interface has a robust seal, CAE analyses were conducted using ANSYS Workbench:

– Include thermal and mechanic non‐linear material properties of rubber, plastics, and aluminum.

– 2D axial‐symmetric model for rubber seal evaluation.

– 3D model for seal groove deformation evaluation.

– Two different Electric Parking Brake (EPB) systems were evaluated• Design A – baseline

• Design B – new design

5

CAE Livonia

5Seal Evaluation Using ANSYS WorkBenchOct. 30, 2012

Material Model• Plastic (Actuator Case)

– PPS 40% GF (Baseline Design A)

– PBT 30% GF (Design B)

• Both PPS & PBT have stress strain curves corresponding to different temperatures.

• Parallel thermal expansion:– PPS 40% GF: Coefficient of linear thermal

expansion (Parallel): 2.6E‐05/°C– PBT 30% GF: Coefficient of linear thermal

expansion (Parallel): 2.5E‐05/°C• Transverse thermal expansion:

– Unknown

Notes:PBT (Polybutylene terephthalate)PPS (Polyphenylene Sulfide)GF Glass Fiber

Seal Evaluation Using ANSYS WorkBench 6

PPS 40% GF

PBT 30% GF

Oct. 30, 2012

Material Model

• Cast Aluminum (Foundation) – Nonlinear stress‐strain curve

– Coefficient of linear thermal expansion: 2.35E‐05/°C

• Hyperelastic (O‐ring)– Ogden 2nd order model

– Coefficient of linear thermal expansion: 8.5E‐05/°C

Seal Evaluation Using ANSYS WorkBench 7Oct. 30, 2012

2D Axial Symmetry Model

8Seal Evaluation Using ANSYS WorkBench

Design A Design B

Oct. 30, 2012

• 5‐Step Analyses:

1) O‐ring installation (stretch) (Ref. temperature: 22°C)

2) Actuator installation (squeeze) (Ref. temperature: 22°C)

3) Temperature drops to: ‐30°C

4) Temperature rises to: 23°C


2D – Axial Symmetry ModelDesign A (Baseline)



2D – Axial Symmetry ModelDesign B (New Design)

Design A and Design B / Contact Pressure


Outside

Inside

Bottom

22°C

‐30°C

23°C

150°C

Oct. 30, 2012

Design A and Design B / Contact Force

12

Outside

Inside

Bottom

22°C

‐30°C

23°C

150°C


Effects of Friction


Friction Coefficient: 0.15 Friction Coefficient: 0.01

Summary


• The o‐ring seals three surfaces in groove: inner, outer and bottom interface between actuator and caliper.

• The seal pressure and contact force change with temperature; it decreases as temperature drops, and increases as temperature rises.

• The Design B has better sealing than baseline, as it showed higher seal pressure (bottom side) or high contact force (inside and outside).

• The bottom interface seal pressure still holds as friction diminishes.

Oct. 30, 2012

3D Model ‐ Seal Groove Deformation


• 4‐Step Analyses:

1) Apply bolt pretension (Ref. temperature: 22°C)

2) Temperature drops to: ‐30°C



Design A Design B

Oct. 30, 2012

Dimension of Groove Height

Seal Evaluation Using ANSYS WorkBench [16]

Path location in Caliper 2.55 mm

Groove Height

Design A

Path location in Actuator

2.55 mmGroove Height

Path location in Caliper

Path location in Actuator Design B

• The dimension change of groove height is evaluated along two perimeters.• Path of actuator location

• Path of caliper location

Oct. 30, 2012

Change of Groove Height (µm) / Lower Temperature


Bolt 1

0°

180°

90°

270°

Bolt 2

Design BDesign A

0°

Bolt 1180°

Bolt 2270°

90°

Oct. 30, 2012

Change of Groove Height (µm) / High Temperature

[18]

position ‐ A

position ‐ B

position ‐ A

position ‐ B

Seal Evaluation Using ANSYS WorkBench

Design A

0°

Bolt 1180°

Bolt 2270°

90°

Bolt 1

0°

180°

90°

270°

Bolt 2

Oct. 30, 2012

Design A / Groove Path / Actuator Radial Def. (µm)


Bolt 2Bolt 1

0°

Bolt 1

180°

Bolt 2270°

90°

Oct. 30, 2012

Design A / Groove Path / Caliper Radial Def. (µm)


Bolt 2

0°

Bolt 1

180°

Bolt 2270°

90°

Oct. 30, 2012

Design B / Groove Path / Actuator Radial Def. (µm)


Bolt 1Bolt 2

Bolt 1

0°

180°

90°270°

Bolt 2

Oct. 30, 2012

Design B / Groove Path / Caliper Radial Def. (µm)


Bolt 2

Bolt 1

0°

180°

90°270°

Bolt 2

Oct. 30, 2012

Summary • The seal groove deformation is within 40μm over the temperature range for both designs: – Maximum groove height change of design A: ‐16 µm at ‐30°C, 38 µm at 150°C

– Maximum groove height change of design B: 20 µm at ‐30°C, 14 µm at 150°C

• When temperature drops, Design A shows decreased groove height.

• When temperature rises, Design B shows less groove height expansion.

• Design B seal groove height deforms more uniformly comparing to the baseline design.

Seal Evaluation Using ANSYS WorkBench [23]Oct. 30, 2012

Conclusion / Limitation• Using ANSYS Workbench, seal evaluation was performed on two different EPB designs:

– 2D axial‐symmetric model for rubber seal evaluation.– 3D model for seal groove deformation evaluation.

• Design B shows better sealing behave Overall.– Higher sealing pressure/force.– Less groove deformation at high temperatures.

• Plastic material with fiber filler has different thermal expansion in parallel and normal direction. Normal direction generally has higher thermal expansion than parallel direction. Only parallel direction is taken into account during this analysis.

Seal Evaluation Using ANSYS WorkBench [24]Oct. 30, 2012

seal evaluation using ansys workbench evaluation using ansys workbench hua wang, li jun zeng trw...

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