Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Altair ® OptiStruct ® Meet Today's Complex Product Development Challenges with Award-Winning Concept Design Technology

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.  CAD import  Geometry cleanup / repair  Prepare geometry according to mesh requirements  Meshing, mesh quality checks  Material, properties (i.e. thickness)  Loads, constraints (boundary conditions)  Export of FE solver deck  Analysis  Postprocessing  Loadstep(s) But, where is the CAD data coming from? ? ?

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. But, where is the CAD data coming from? Chirurgen, die entstellte Gesichter rekonstruieren, müssen handwerklich extrem begabt sein: Fehlende Gesichtsknochen werden per Hand modelliert und an den Patienten angepasst. Eine Methode aus dem Bauwesen verspricht jetzt deutlichen Fortschritt für die plastische Chirurgie.

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Situation: ? The CAE Driven Design Process Your professor asks you the follwing: „For the given stucture I need to have a new, more innovative,and lighter solution. Material properties remain the same, however. Delivery date: If possible, yesterday …“

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. What if there are no similar or previous designs to reference? What if the similar design doesn’t scale for the new configuration? What if you don’t have experience with this type of design? What if previous designs were never optimized for weight? What if you have many load cases? What if you have limited time to make design changes? What if your engineering judgment leads you down the wrong path? … Challenges of the early design phase The CAE Driven Design Process

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.... Innovative or „old“ and well known solutions ??? In the concept phase the designer has maximum design freedom, but minimum design knowledge 80% of the product weight is determined at the concept design stage Challenges of the early design phase The CAE Driven Design Process

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Aircraft structural design and synthesis are mainly driven by: Experience and company know-how Human intuition Engineering judgment Available design tools and methods Average wing rib spacing for Boeing 7X7 series Average wing rib spacing for Airbus jets Source: [SEN04] Challenges of the early design phase The CAE Driven Design Process

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. The CAE Driven Design Process

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Definition of available package space Mesh generation, definition of loads and boundary conditions Setup of optimization problem, definition of design constraints Computation Interpretation of results CAD Design Topology Optimization – Conceptual Design The CAE Driven Design Process

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.  Penalization of intermediate density through power law  > 1.0  r      = 2 ~ 4 Density = 1 Density = 0 SIMP Method (Solid Isotropic Microstructure with Penalty for Intermediate Density, Bends ø e 1989; Zhou and Rozvany 1990) E/E0E/E0       1 1 Where K and K represent the penalized and the real stiffness matrix of an element, respectively,  is the density and  the penalization factor which is always greater than 1. Topology optimization – how does it work? (material) intermediate solutions are avoided The CAE Driven Design Process

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. The Optimization Problem Statement: Objective (What do I want?) min f(x) also min [max f(x)] Design Variables (What can I change?) X i L ≤ X i ≤ X i U i =1,2,3,…N Design Constraints (What performance targets must be met?) g j (x) ≤ 0 j = 1, 2, 3, …, M Optimization – how does it work? The CAE Driven Design Process

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Optimization Terminology Design Variables: System parameters that are varied to optimize system performance. Design Space: selected parts which are designable during optimization process. For example, material in the design space of a topology optimization Response: Measurement of system performance. Objective Function: Any response function of the system to be optimized. The response is a function of the design variables. Ex. Mass, Stress, Displacement, Moment of Inertia, Frequency, Center of Gravity, Buckling factor, and etc. Constraint Functions: Bounds on response functions of the system that need to be satisfied for the design to be acceptable. Feasible Design: One that satisfies all the constraints. Infeasible Design: One that violates one or more constraint functions. Optimum Design: Set of design variables along with the minimized (or maximized) objective function that satisfy all the constraints. The CAE Driven Design Process

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. max. dimension The CAE Driven Design Process Exercise Determine/find a „light weight“ design (i.e. with miminum mass) The max. model dimension (design space) is given i.e. your design proposal (2D with constant thickness, T= 1mm) may be smaller or may contains holes etc. Restriction: Maximum allowed opening at the tip: +/ mm Material: Steel (E, nu) F=+/- 100 N Using the max. design space, the opening at the tip is +/ mm

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. max. dimension The CAE Driven Design Process Exercise File: Clip_2D_geometry/ clip_geometry.iges for CATIA import, you may need to change the file extension to *.igs 2. Import the CAD data in CATIA 1. Think about your design proposal … 3. Build your design in CATIA (Make use of symmerty) 4. Export your design as *.iges or *.step 5. Import your design in HyperMesh (CAD data)

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. The CAE Driven Design Process Exercise File: your_design.iges / step 6. You may need to cleanup your geometry 8. Define Material, Property, SPC and Loads (Forces), Load Step 1,2, Meshing 100 N 9. Run analysis 10. Postprocessing and documentation

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. The CAE Driven Design Process Exercise File: your_design.iges / step 10. Postprocessing and documentation Element size Max. displacementVon MisesArea* Mesh type MIXED Mesh type TRIA *see next slides for more information on how to measure AREA your decision

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. HyperMesh Introduction Measure AREA Select elements

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Base design forces constraints Topology optimization - Exercise Objective: min. Mass / Volume Restrictions: max. allowable opening (displacement) at tip: uy=0.07 mm The CAE Driven Design Process

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Topology optimization process - Exercise The CAE Driven Design Process

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. uy=-0.05 mmuy=-0.07 mm Interpretation of optimization results (by 2 student designers) and re-analysis of their given design Design interpretation IDesign interpretation II Topology optimization process - Exercise The CAE Driven Design Process

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Creates h3d file: *_s1.h3d

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Use slider to adjust appropriated density value (i.e. dark blue elements disappear) Display element densities (iso-plot)

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Super impose contour plot of displacements (note that the displacement values shown refer to all elements)

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. To post-process elements above density threshold and corresponding displacements re-run the analysis Based on the last optimization run e.g. design_29, the results file will be named: _rst029_s1.h3d

Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.

What is the difference between volumfrac response and volume response? Is minimizing mass identical to minimizing volume in OptiStruct? Is there a way I can control the step size of the optimization? What is the procedure for restarting an OptiStruct job? Is it possible to obtain rib pattern information on shell models using topology optimization? How can I assign and/or change the modeweights in a subcase (load case)? How do I calculate the NORM factor for a combined compliance and frequency optimization problem? What is the difference between specifying a constraint on the designable volume and minimizing the designable volume? What is the difference between using forces and prescribed displacements? What is the initial value of material fraction at the beginning of an optimization run (iteration 0)? How can I assign material fraction to 1 at iteration 0? Can I combine various optimization types (size with shape and/or topography)? The results of Iteration 0 in an attempted topology optimization are different from the results of a run with ANALYSIS. What is wrong? How can I follow the iteration history while OptiStruct is running? Can I use stress constraints with topology or free-size optimization? Can I use buckling constraints on a topology or free-size optimization? Is there a way to debug the rigid body modes in a model? Can volume or mass be defined as a response for topography optimization? How can the same response from different loadsteps be added together? FAQ‘s