Topology Optimization of Gear                                                            Web using OptiStruct             ...
Overview• Background• Introduction• Problem Setup• Results• Conclusion
Background• A framework has been developed to study and optimize rotorcraft drive  systems
Background• One of the biggest problems a designer is faced with is understanding  what fidelity of analysis is required t...
Introduction• Gear web and non-standard gear  designs can produce up to 30%  weight saving.• Gear webs have been designed ...
Introduction                                                                                     σb*= f(x)weight          ...
Problem Setup             Parameter   Symbol   Unit   Baseline               Design 2Power                      P      HP ...
Problem Setup• Radioss run for calibrating load    •   Gear model brought in from CATIA    •   Load for FEA application wa...
Problem Setup – Topology Optimization•   Components       •      Gear Teeth (blue)       •      Design Area (red)       • ...
Problem Setup – Topology Optimization                                 Objective: min : F ( x)  Volumedesign              ...
Problem Setup – Topology Optimization• σdesign< 20ksi• Cyclic Pattern, plane normal to axis of the gear, node (0,0,1.2) an...
Problem Setup – Topology Optimization• Optimized result only maintains structural integrity within design area• Optimized ...
Problem Setup – Topology OptimizationBending Region                                 Objective: min : F ( x)  Volumedesign...
Problem Setup – Topology Optimization• Optimization Responses   •   Volume – Design region   •   σb - Tooth bending stress...
Problem Setup – Initial Results                                  N = 23                                  Cyclic instances ...
Problem Setup – Initial Results                                  N = 24                                  Cyclic instances ...
Problem Setup – Further Refinement• Uniform gear web is desired for manufacturing and operation purposes• Increase number ...
Results - Baseline                     N = 23                     Cyclic instances = 184
Results – Design 2                     N = 24                     Cyclic instances = 96
Results                 Baseline                                        Design 2                            Baseline      ...
Conclusion• Topology Optimization was used to estimate material removal in the  gear web.• For a gear designed to carry a ...
Questions            THANK YOU               Sylvester Ashok             sylvester_ashok@gatech.edu                Fabian ...
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A Method to Integrate Drive System Design - Georgia tech

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Modern aerospace systems are highly complex and expensive; the US Army is the main procurer of rotorcraft in the world and has not developed a completely new airframe in some time. High development and procurement cost have instead driven the US Army to rely on constant upgrades to its ever aging fleet. These upgrades alter the performance and geometry of the systems dramatically, in order to better optimize the vehicle and aid in the design of new rotorcraft an integrated design tool was developed that enhances the overall system based on certain performance and manufacturing criteria and redesigns the system to the optimal configuration.
The objective of this study is to improve gear design for specific applications through Finite Element Analysis (FEA). A gear web (thin rimmed) is created in gears to improve strength to weight ratio of a given gear. The process, known as excess material removal, is done in this study through HyperWorks OptiStruct’s topology optimization tool.

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A Method to Integrate Drive System Design - Georgia tech

  1. 1. Topology Optimization of Gear Web using OptiStruct Sylvester Ashok and Fabian Zender Integrated Product Lifecycle Engineering Laboratory Daniel Guggenheim School of Aerospace Engineering Georgia Institute of TechnologyContent in this presentation may not be duplicated, copied, or reproduced, without the permission of the authors or Altair
  2. 2. Overview• Background• Introduction• Problem Setup• Results• Conclusion
  3. 3. Background• A framework has been developed to study and optimize rotorcraft drive systems
  4. 4. Background• One of the biggest problems a designer is faced with is understanding what fidelity of analysis is required to obtain the detail of information needed.• The balance between fidelity and detail at different stages of the design life-cycle, among different disciplines, is one of the keenly researched topics in MDAO.• Weight saving is critical in aerospace applications • How should topology optimization be treated in drive system design?
  5. 5. Introduction• Gear web and non-standard gear designs can produce up to 30% weight saving.• Gear webs have been designed in detailed stages through bench tests so far.• Topology Optimization is a method that can be used to study this using FEA.
  6. 6. Introduction σb*= f(x)weight Design B weight Design A Design A Design B σb * σb * x x Analytical sizing result Topology optimization result Since the design space is discrete, if after topology optimization, design B weighs less than design A, topology optimization cannot be considered a design refinement, instead must be used to select the optimum design.
  7. 7. Problem Setup Parameter Symbol Unit Baseline Design 2Power P HP 700RPM - RPM 5000Gear ratio mg - 3.3Diametral pitch Pd in-1 6Face width F in 2.4Pressure angle φ deg 20Material - - AISI 9310Number of teeth Np - 23 24Tangential load Pt lbf 4616.7 4424.4Radial load Pn lbf 1680.4 1610.3Bending Stress (AGMA) σb psi 35000 32951Weight W lb 7.233 7.885
  8. 8. Problem Setup• Radioss run for calibrating load • Gear model brought in from CATIA • Load for FEA application was calibrated to obtain analytical bending stress value
  9. 9. Problem Setup – Topology Optimization• Components • Gear Teeth (blue) • Design Area (red) • Shafthole (blue)• Mesh Setup • Shafthole and Design Area: Edge Deviation, 75 elements per edge • Gear Teeth: QI Optimize, element size 0.06 • 3D Solid Map, size 0.06• Load Setup • Load was distributed across a single line of nodes at pitch circle • Inside of Shafthole constrained for 6 DoF• Calibrated Load Parameter Symbol Unit Baseline Design 2Tangential load Pt lbf 6463.4 6194.2Radial load Pn lbf 2352.6 2254.4
  10. 10. Problem Setup – Topology Optimization Objective: min : F ( x)  Volumedesign Subject to: x  X  x  R n | gi ( x)  0, i  1,..., m Where, g1 ( x)  ( f   design )   * g 2 ( x)  manufacturing constraint (draw) g3 ( x)  manufacturing constraint (cyclic and symmetry) Design Non-design
  11. 11. Problem Setup – Topology Optimization• σdesign< 20ksi• Cyclic Pattern, plane normal to axis of the gear, node (0,0,1.2) and node (0,0,0). Instances = multiple of teeth • Ensure cyclic symmetry since single tooth loading is simulated• Split Draw Constraint, draw direction given by line through center of gear (0,0,1.2) and center of front face (0,0,0) • Ensure symmetry through the thickness for simpler manufacturing and ease of assembly
  12. 12. Problem Setup – Topology Optimization• Optimized result only maintains structural integrity within design area• Optimized result would lead to increased bending stress in gear teeth
  13. 13. Problem Setup – Topology OptimizationBending Region Objective: min : F ( x)  Volumedesign Subject to: x  X  x  R n | gi ( x)  0, i  1,..., m Where, g1 ( x)  ( f   design )   * g 2 ( x)   b   b * g3 ( x)  manufacturing constraint (draw) g 4 ( x)  manufacturing constraint (cyclic and symmetry)Design Non-design
  14. 14. Problem Setup – Topology Optimization• Optimization Responses • Volume – Design region • σb - Tooth bending stress• Optimization Constraint • σb < 35ksi• Optimization Objective • Minimize volume (design region)• Design Variable Constraints • σdesign < 20ksi • Cyclic constraint (number of instances = number of teeth) • Split draw constraint
  15. 15. Problem Setup – Initial Results N = 23 Cyclic instances = 23
  16. 16. Problem Setup – Initial Results N = 24 Cyclic instances = 24
  17. 17. Problem Setup – Further Refinement• Uniform gear web is desired for manufacturing and operation purposes• Increase number of instance = i * number of teeth, i = 1,2,3…..n • Number of instances for Baseline: 8 * number of teeth = 184 • Number of instances for Design 2: 4 * number of teeth = 96 • Eliminates holes through thickness
  18. 18. Results - Baseline N = 23 Cyclic instances = 184
  19. 19. Results – Design 2 N = 24 Cyclic instances = 96
  20. 20. Results Baseline Design 2 Baseline Design 2 Weight Before After % Difference Before After % Difference Gear Teeth 3.777 3.777 - 3.972 3.972 - Web 3.243 2.674 18% 3.691 2.731 26% Shaft 0.213 0.213 - 0.222 0.222 - Total 7.233 6.664 8% 7.885 6.925 12%
  21. 21. Conclusion• Topology Optimization was used to estimate material removal in the gear web.• For a gear designed to carry a specific torque, 12% weight saving was obtained.• An overdesigned gear does not translate to a lighter gear, post-topology optimization, based on preliminary studies.• Further work is required to understand feature manipulation, application for helical gears, and implementation of stiffness criteria.
  22. 22. Questions THANK YOU Sylvester Ashok sylvester_ashok@gatech.edu Fabian Zender fzender@gatech.edu

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