TOPOLOGICAL, SIZE AND SHAPE OPTIMIZATION OF AN UNDERWING PYLON SPIGOT

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TOPOLOGICAL, SIZE AND SHAPE OPTIMIZATION OF AN UNDERWING PYLON SPIGOT

  1. 1. TOPOLOGICAL, SIZE AND SHAPEOPTIMIZATION OF AN UNDERWINGPYLON SPIGOTPrepared by: M. Basaglia (Alenia Aermacchi), S. BoniCerri (Alenia Aermacchi), G. Turinetti (Altair)
  2. 2. SPIGOT OPTIMIZATION Topological, Size and Shape Optimization of an Underwing Pylon Spigot•Aircraft pylons have the function of supporting external payloads and areinstalled under the wing and / or the fuselage. Pylons that are being developedin Alenia Aermacchi will be installed on M-346 new advanced training aircraft.•Inside the pylon, the structure called spigot or, in some cases, pivot is a highlystressed structure made of high resistant steel and is the component thattransfers the concentrated loads coming from the carried mass to the wing orfuselage structure.•The design activity started from the available space envelope, from theinterfaces that were defined as non-design zones and the sizing loads (a set of26 load cases). The application has been performed using OptiStruct.•Two subsequent optimizations have been conducted: the first one followed atopological approach, the second one was set as a shape optimization. 2
  3. 3. SPIGOT OPTIMIZATION 3
  4. 4. SPIGOT OPTIMIZATION RBE3 area for the WING/SPIGOT interface force application. Applied force - upper node RBE3 area for the WING/SPIGOT interface force application. Applied force - lower node CELAS - X, Y, Z direction 4Spigot constrained to the ground (conservative approach) through celas elements
  5. 5. SPIGOT OPTIMIZATION Stress - max principal 5
  6. 6. SPIGOT OPTIMIZATIONPresent spigot configuration Weight = 4.352 kg 6
  7. 7. SPIGOT OPTIMIZATION Starting volume 26 load cases Non design areaNon design area 7
  8. 8. SPIGOT OPTIMIZATIONMain advantage of topological optimization is to easily check how thestructure is designed by the optimization tool in relation to somedifferent design and manufacturing strategies (objective, responses andconstraints).First optimization iterations are developed with the objective ofminimum weight compliance referred to all load conditions (with thesame weight equal to 1).Constraints: mass fraction, minimum dimension, stress level, planes ofsymmetry, direction of machining. 8
  9. 9. SPIGOT OPTIMIZATIONResponses: Weight compliance, mass fraction Constraint: mass fraction ≤ 0.25 Objective: MIN weight compliance 9
  10. 10. SPIGOT OPTIMIZATION Responses: Weight compliance, mass fraction Constraint: mass fraction ≤ 0.25Manufacturing constraints: XZ plane of symmetry, mindim in the whole design space Objective: MIN weight compliance 10
  11. 11. SPIGOT OPTIMIZATION Responses: Weight compliance, mass fraction Constraint: mass fraction ≤ 0.25Manufacturing constraints: YZ and XZ planes of symmetry, mindim in the whole design space 11 Objective: MIN weight compliance
  12. 12. SPIGOT OPTIMIZATION Responses: Weight compliance, mass fraction, stressConstraint: mass fraction ≤ 0.25, maximum principal stress<1000MPa in the ‘non design’ area Manufacturing constraints: XZ plane of symmetry, mindim in the whole design space 1 draw direction (Z) 12 Objective: MIN weight compliance
  13. 13. SPIGOT OPTIMIZATION Responses: Weight compliance, mass fraction, stressConstraint: mass fraction ≤ 0.25, maximum principal stress<1000MPa in the ‘non design’ areaManufacturing constraints: XZ plane of symmetry, mindim in the whole design space, 2 design spaces in order to define draw directions (X, Z) 13 Objective: Min weight compliance
  14. 14. SPIGOT OPTIMIZATION Responses: Weight compliance, mass fraction, maximum stress Constraint: mass fraction ≤ 0.25 Constraint: stress in the critical area (highlighted in the above figure) ≤ 1000 MPaManufacturing constraints: XZ plane of symmetry, mindim in the whole design space, 1 draw direction (Z) 14 Objective: MIN weight compliance
  15. 15. SPIGOT OPTIMIZATION Response: Mass, displacementConstraint: Displacement constraint on the top of the Spigot extracted from the starting configuration.Manufacturing constraints: XZ plane of symmetry, mindim in the whole design space, 1 draw direction (Z) 15 Objective: MIN mass
  16. 16. SPIGOT OPTIMIZATION Shape optimization phaseSide flange thickness Spigot base radius (dense Mesh) Side cutout size Lower hole diameterSpigot conicity Lower transverse stiffener thickness 16
  17. 17. SPIGOT OPTIMIZATIONOptimization problem definition:Objective = Minimize MassConstraints =• Stress ≤ Sigma max• Bolt forces ≤ F max In the above figure, the highlighted areas represent a dense mesh zone, where the stress response is checked. The mass growth is due to the approximation coming from the topological optimization and the redesigning of new CAD with some violation of stress constraint. 17
  18. 18. SPIGOT OPTIMIZATION The above figure shows the contours of shape changes, where the red area represents the biggest parameter reduction.Spigot final configuration 18
  19. 19. SPIGOT OPTIMIZATION Configuration and mass evolution Present weight Weight at the beginning of Weight at the end of the shape the shape optimization optimization FEM weight = 4.360 kg FEM weight = 4.028 kg FEM weight = 4.138 kg CAD weight = 4.352 Kg CAD weight = 4.015 Kg CAD extimated weight = 4.125 KgThe weight reduction between the starting configuration and the configuration at the last optimization is of 5% 19
  20. 20. SPIGOT OPTIMIZATION Conclusions•The topological optimization phase gave the evidence of thepossibility of saving weight removing material in some areas,compared to the traditional design, in a way that with a standardsizing approach is difficult to imagine.•The shape optimization permitted to refine the previouslyidentified design.•An interesting weight reduction (for this kind of structure) of 5%has been obtained. 20
  21. 21. SPIGOT OPTIMIZATION Q&AThank you for your attention 21

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