Minimising compliance

Aadit

Hi,

 

I am currently doing a topology optimisation on a simple cantilever beam with the objective of minimising compliance and the constraint is the volumefrac. 

 

The aim is to compare the compliance values from Hypermesh with the values obtained from MATLAB simulation (99 line SIMP code). 

 

My question is:

1) I have obtained results from both MATLAB and Hypermesh. However the the results don't seem to match. The MATLAB values are roughly twice the values obtained from hypermesh. Would anyone be able to explain why this is?

 

2) In post processing, ISO slider can be used to vary the densities. Why does Hypermesh provide a range (slider) to change the volfrac, when the volfrac was already defined in the constraint? Also why doesn't MATLAB provide a similar range? 

Crashphys

For question 1, you will need to upload both your MATLAB code and your model, at the very least your model. Implementation is likely the difference in the results. Make sure you validate both your code and model according to some kind of baseline.

 

For question 2, OptiStruct (the solver), uses the SIMP method to perform Topology Optimization. The SIMP method is costly when performing topology optimization if you use a discrete approach (that is, either 1 or 0 for element density). To overcome the issue, OS uses a relative density between 0 and 1. Given these relative densities, you as the designer will have to determine what elements you will remove and which will remain. Usually you assign a cut-off of something like anything <0.67 relative density is zero volume. The ISO slider allows you to quickly view which elements are under a certain relative density so that you can determine which is which.