Harnessing the power of topology studies in SOLIDWORKS Simulation: Part 1

Topology studies, available in SOLIDWORKS Simulation Professional and SOLIDWORKS Simulation Premium, are a highly effective way for design engineers to create lightweight, optimized parts. Topology studies can be used to explore a variety of design iterations to satisfy an optimization goal, subject to a set of geometric constraints.

Topology studies start with a maximum design space which represents the maximum allowable size for the component. The topology optimization then seeks a new distribution of material, within the boundaries of the maximum allowable geometry, considering all the external loads, fixtures, and manufacturing constraints.

A variety of optimization goals are available to the user, including best stiffness to weight ratio, minimum mass or minimum displacement of a component.

Let us explore the various steps needed set up a topology study in SOLIDWORKS Simulation Professional or SOLIDWORKS Simulation Premium using the example of a simple bracket.

Step 1: Create a baseline design

Prior to initiating a topology study, first create a baseline design for the component. The baseline design is what the designer would conceive as a good initial concept, in the absence of advanced FEA tools.

The baseline design in this example is shown below. It consists of an 8mm thick, 80mm x 60mm baseplate, two 8mm thick tangs with 10mm diameter through holes, and four M8 clearance holes on the corners of the baseplate. The tangs are pinned to a male clevis which is delivering the load to the bracket. The bracket is made from 316L stainless steel. It could be machined or fabricated. It weighs 432 grams.

Step 2: Perform a linear static analysis on the baseline design

Once the baseline design is established, run a linear static stud. This is recommended because the user should first establish correct setup of the fixtures and loads. The user should also validate that the baseline design is generally fit-for-purpose, with acceptable stress levels and factors of safety, before attempting the topology study. Topology studies are computationally intensive and time consuming and you don’t want to find that your model is not properly restrained or causes some other kind of error when you are running the topology study. You are much better off troubleshooting the basic setup of your model with a linear static study.

In this example I have applied a ‘Fixed Geometry’ fixture to the four M8 holes. The applied load is a 10,000 N bearing load in both the positive Z and negative Y directions to the two holes of the tangs. The setup is shown below.

A plot of von Mises stress on the bracket is shown below. 316L stainless steel has a yield strength of 170 MPa. The red ‘hot spots’ in proximity to the upper bolt holes are stress singularities that are caused by the fixture at this location, so they are not accurate and can be overlooked in this case.

Step 3: Create a maximum design space model

The goal of a topology study is to allow the solver to choose the most efficient placement of material. We want to give the solver maximum flexibility for choosing the material placement. In order to facilitate this, we need to establish a starting geometry with as much material as possible. We do this by creating a maximum design space model, where we fill in all the available space with material. In the case of this bracket example, we only save space for where the four M8 fasteners are located, where the pin is located, plus a space claim for where the male clevis that delivers the load is located. The mass of this component is 1057 grams.

We then reapply the fixtures and loads and run a linear static study of the maximum design space model to ensure everything is set-up correctly before attempting the topology optimization.

Step 4: Create topology study

We are finally ready to create our topology study. We do this by starting a new study and selecting ‘Topology Study’ from the available options.

The Simulation Tree that appears for a topology study looks similar to a linear static study with the familiar folders including ‘Parts’, ‘Connections’, ‘Fixtures’, ‘External Loads’, ‘Mesh’ and ‘Results’. We also observe two news folders that are unique to a topology study; ‘Goals and Constraints’ and ‘Manufacturing Controls’.

Before adjusting ‘Goals and Constraints’ and ‘Manufacturing Controls, we must set up loads and fixtures in the topology study in the same way as the linear static study. To save time, the loads and fixtures can be dragged and dropped from our linear static study into the topology study.

Step 5: Apply goals and constraints

If we right click on the ‘Goals and Constraints’ folder we can choose whether to optimize for best stiffness to weight ratio, minimum displacement or minimum mass. A detailed discussion about the differences between the various optimization goals can be found in the help files here:

http://help.solidworks.com/2020/english/SolidWorks/cworks/hidd_goals_constraints.htm

Clicking ‘Best Stiffness to Weight ratio’ is generally the best place to start and opens the following dialogue box.

We are offered 4 choices for constraints that can be applied to the analysis. They are a displacement constraint, a mass constraint, a frequency constraint, and a stress/factor of safety constraint.

In this case I chose a mass constraint. Recall that my baseline component has a mass of 432 grams and that my maximum design space model has a mass of 1057 grams. To achieve a meaningful (on the order of 30%) mass savings relative to my baseline design, I want my final part to weigh about 300 grams. That represents a 70% weight reduction of my maximum design space model, the starting point of the topology study.

Further explanation about the other constraints available can be found here:

http://help.solidworks.com/2020/english/SolidWorks/cworks/hidd_goals_constraints.htm

In part 2 of this blog we will complete the topology study by applying manufacturing controls, meshing, solving, post processing and then preparing the part for manufacturing.

Now go design some innovative products with the help of the comprehensive analysis tools available in SOLIDWORKS Simulation.

Alon Finkelstein
Simulation Product Specialist
Computer Aided Technology, Inc.