Working With Imported Geometry: Common Complications for FEA Analysis

1. Working With Imported Geometry: Common Complications for FEA Analysis • Discussion of common complications in finite element analysis (FEA) • Thin walled elements • Extreme aspect ratios, such as I-beams • Contact conditions that change during analysis

2. Section 1 Module 8 Page 1 Working With Imported Geometry Common Complications with FEA Overview • Usually, geometry imported into FEA can be automatically meshed with the default mesh options with no issues. • Sometimes there are complications with meshing, especially when one dimension is extremely large compared to the other two. • Sometimes, small features also complicate a mesh and distort local elements. • In assemblies, objects sometimes move relative to each other and come into contact after analysis, also causing difficulties.

3. Section 1 Module 8 Page 2 Working With Imported Geometry Common Complications with FEA Example • I-beams are an example of long, slender objects with small cross-sectional areas. • I-beams are both thin-walled elements and have high aspect ratios. • Autodesk® Simulation Multiphysics has a built-in utility to create beams from library databases.

4. Section 1 Module 8 Page 3 Working With Imported Geometry Common Complications with FEA Defining beams within FEA • Beams can of course be modeled in CAD and imported into your FEA package, but it is difficult to refine the mesh enough to get a true output. • Alternatively, beams can be defined with Autodesk® Simulation Multiphysics, using line segments defined as beam elements and the software’s built-in beam databases. • These beams model with their cross sections and are highly accurate. • They also provide shear and moment diagrams for the user.

5. Section 1 Module 8 Page 4 Working With Imported Geometry Common Complications with FEASmall features • For a small feature on a large object, it can be difficult to get the mesh density needed on the small feature. To resolve try: • Locally refining the mesh • Switching to tetrahedral elements, or a mixture of tetrahedrons and bricks • Suppressing small features in areas of low stress • Redesigning to eliminate or reduce the severity of the small feature

6. Section 1 Module 8 Page 5 Working With Imported Geometry Common Complications with FEA Contact conditions that change during analysis • When an assembly has a large range of motion, such that two objects that are initially far apart come in contact, the analysis may fail. To resolve try: • Predefining a contact between the two objects, such as “Surface” • Limiting the range of motion with boundary conditions • Removing some components from the assembly and just importing the loading that would occur

7. Section 1 Module 8 Page 6 Working With Imported Geometry Common Complications with FEA Thin-walled features • When an object has one dimension that can be described as its “thickness”, the user may have trouble meshing the geometry. To resolve try: • Using the midplane geometry to treat the geometry as surfaces, inputting the thickness as a parameter • Modeling as plate elements • Using CAD to model as surfaces Solidworks® beam as plate and midplane

8. Section 1 Module 8 Page 7 Working With Imported Geometry Common Complications with FEA Summary • Discussion of common complications in finite element analysis (FEA) • Thin walled elements • Extreme aspect ratios, such as I-beams • Contact conditions that change during analysis • The video will demonstrate modeling an I-beam in Autodesk® Simulation Multiphysics and discuss some of the common complications that can occur with finite element analysis.