Shape FinderChapter EightANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape FinderChapter OverviewIn this chapter, using the Shape Finder in Design Simulation will be covered.In Design Simulation, performing shape optimization is based on a linear static structural analysis.It is assumed that the user has already covered Chapter 4 Linear Static Structural Analysis prior to this section.The capabilities described in this section are generally applicable to ANSYS DesignSpace Entra licenses and above.Some options discussed in this chapter may require more advanced licenses, but these are noted accordingly.Other type of analyses are covered in their respective chapters.February 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape FinderBasics of Shape OptimizationRequesting the Shape Finder performs shape or topological optimizationShape Finder is an optimization problem, where the energy of structural compliance is minimized based on a volume reduction constraintAnother way to view this is that the Shape Finder tries to obtain the best stiffness to volume ratio. The Shape Finder tries to find areas where material can be removed without adversely affecting the strength of the overall structure.The Shape Finder is based on a single static structural environmentThe Shape Finder cannot be used for multiple environmentsThe Shape Finder currently cannot be used for modal, heat transfer, or other analysesAlthough based on a single static structural analysis, because it is an optimization, many iterations will be performed internally, so it can be computationally expense.February 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape FinderBasics of Shape OptimizationIn the example below, a simple assembly has supports and a bolt load. The Shape Finder allows the user to determine where material may be removed for the given loading condition, if weight reduction was sought.Shape optimization is useful for conceptual designs or performing weight-reduction on existing designsModel shown is from a sample Inventor assembly.February 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape FinderA. Shape Optimization ProcedureThe shape optimization procedure is very similar to performing a linear static analysis, so not all steps will be covered in detail. The steps in yellow italics are specific to shape optimization analyses.Attach GeometryAssign Material PropertiesDefine Contact Regions (if applicable)Define Mesh Controls (optional)Insert Loads and SupportsRequest Shape Finder ResultsSet Shape Finder OptionsSolve the ModelReview ResultsFebruary 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder Geometry and Material PropertiesUnlike linear static analyses, only solid bodies can be used for shape optimizationLine or surface bodies cannot be used with the Shape FinderFor material properties, Youngs Modulus and Poissons Ratio are requiredIf acceleration (and other inertial loads) are present, mass density is also requiredIf thermal loading is present, coefficient of thermal expansion and thermal conductivity are also requiredFebruary 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder Contact RegionsAny type of face-to-face contact may be included with Shape FinderBecause shape optimization requires multiple iterations, if nonlinear contact is present, the overall solution will take longerSince line and surface bodies are not supported in Shape Finder, edge contact and spot welds cannot be used.February 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder Mesh ControlsThe density of the mesh affects the fidelity of the solutionAs with other analyses, this is also true for shape optimization. A finer mesh will be computationally more expensive, but the areas where material can be removed will be much more clearly defined, as shown in the example below:Model shown is from a sample Unigraphics assembly.February 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder Loads and SupportsAny loads and supports may be used with the Shape FinderBecause the Shape Finder tries to minimize volume and maximize stiffness based on the loads and supports, the loads and supports are very important and will influence the results.The Shape Finder will generally keep material where loads are present and where supports are reacting to the load.Different load and support conditions will create different load paths, so the Shape Finder results will differ.The Compression Only support is nonlinear. Because Shape Finder is an optimization problem, a nonlinear support may increase solution time considerably.Thermal loads may also be used (if supported by license).However, note that the Shape Finder results may be unintuitive in cases where thermal strains are large. In these situations, it may be advisable to run two environments, one with and another without thermal loads to compare the differences.February 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder Requesting ResultsFor shape optimization, only the Shape Finder results are validUnder the Solution branch, the Shape Finder result(s) can be requestedNo other type of result can be requested. If a stress analysis is desired, duplicate the Environment branch, then request displacement and stress/strain results.For Shape Finder, simply specify the target reduction amount (default is 20% reduction)Note that too much reduction of material will result in a truss-like structureFebruary 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder Solution OptionsThe solution branch provides details on the type of analysis being performedFor a shape optimization, none of the options in the Details view of the Solution branch usually need to be changed.“Solver Type” or “Weak Springs” can be changed, if needed, per the guidelines in Chapter 4 for static structural analyses.“Large Deflection” is not applicable to shape optimization.The “Analysis Type” will display “Shape” for the case of shapeoptimization. If thermal loads arealso present, then “Thermal Shape”will be shown. Note that this refersto a thermal-stress analysis, not apurely thermal analysis.February 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder Solution OptionsFor the Shape Finder, the following is performed internally:The Shape Finder procedure corresponds to topological optimization in ANSYS.In Design Simulation, only a single stress analysis is supported (whereas in ANSYS, modal analysis and multiple load cases are supported)If thermal loads are present, a thermal analysis is performed first.A thermal analysis is only performed once, at the start of the simulation. This means that the thermal loading does not account for redistribution of temperatures due to changes in shapeFebruary 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder Solution OptionsFor bodies that results are scoped to (see next Chapter), these elements will have element type 1 as SOLID95.18x elements, such as SOLID186 and 187 are not used.SOLID92 is not used. If only tetrahedral elements exist, SOLID95 is used in degenerate tetrahedral form.All other solid elements (as well as surface effect, contact, or spring elements) will have element types greater than 1. In topological optimization in ANSYS, only material for element type 1 is removed.Support of other non-solid elements, such as SURF154, CONTA174, TARGE170, and COMBIN14 in topological optimization is undocumented.February 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder Solution OptionsThe TOxxxx family of topological optimization commands are not used. Instead, the older, undocumented TOPxxx commands are used, although the functionality is very similarTOPDEF defines the problem statementSimilar to TOCOMP, TOVARTOPDEF,vol_reduction,load_case, accuracy:where vol_reduction is percent volume reduction, based on input in Details window. Other arguments are internally specifiedTOPEXE runs the topological solutionSimilar to TOEXETOLOOP or TOPITER are not used. A *DO loop is used internally loop through multiple topological iterationsBesides the output file (solve.out), a summary of the last shape optimization run can be found in the “compliance.out” ASCII file located in the Solver working directory.February 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder Solving the ModelAfter setting up the model, one can perform the shape optimization just like any other analysis by selecting the Solve button.A shape optimization is several times more computationally expensive than a single static analysis on the same model because many iterations are required.The Worksheet tab of the Solution branch provides detailed solution output, including how many shape optimization loops have been performed.February 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder Reviewing ResultsAfter solution is complete, the Shape Finder results can be viewedAs indicated in the legend, orange denotes material which can be removed, and beige is marginalThe details view compares the original and final mass of the structure (including the marginal material)February 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder Reviewing ResultsAnimations are also quite helpful in visualizing where material could be removed and what the resulting shape may look like.February 2, 2004Inventory #0020108-ANSYS Workbench - SimulationANSYS Workbench - SimulationTraining ManualShape Finder B. Workshop 8Workshop 8 Shape FinderGoal:Use the shape optimization tool to indicate potential geometry changes that will result in a 40% reduction in the mass of the model shown below.February 2, 2004Inventory #0020108-