How do I complete a Buckling study in SOLIDWORKS Simulation Professional? Every study in SOLIDWORKS Simulation follows the same 6 general steps. You can read more about these steps here: Six Steps To Your Simulation Study. Buckling studies are no different.
Let us cover the basics first. The purpose of a linear bucking study in SOLIDWORKS SIMULATION Professional is to find the load factor at which a structure will lose its compressive stiffness and collapse, causing failure. This is accomplished by calculating the natural frequencies of the model and finding the load factor at which the natural frequency becomes zero. As a result, bucking analysis is very closely related to frequency analysis. See my colleague’s blog on frequency analysis here for more information.
Before a bucking study is created, it is recommended that we verify the results of a basic static structural load first. This will ensure that the model is not failing due to material yielding before even attempting a buckling analysis. We will use the example of a folding chair, and apply a 350 pound static load to the seat. Results of the static study are below:
The max stress in the model is well below yielding everywhere, so we can assume the model will not fail due to material yielding.
A buckling analysis starts the same as other study types. Choose ‘New Study’ from the command manager and select ‘Buckling’.
Once the study is created, first go into the study properties to tell SOLIDWORKS Simulation how many buckling “modes” to solve for.
In this case, I chose to solve for the first 5 buckling modes. These modes will tell us at which load factors, the first 5 resonant frequencies become zero, indicating structural buckling.
Next, make sure that materials, contacts, and fixtures are properly defined on the model. I copied them over from the static analysis to make sure the loading scenario is the same for both. For more information on these subjects see the previous How do I blog here.
Now that the boundary conditions are complete all that is left to do is mesh and run the model. The results come out as amplitude plots.
The units of these plots need not really concern the average user, the main use of these plots is to discern the buckling mode shape. See the mode shape below:
The bucking mode indicates how the structure would behave if the buckling load factor were met. To determine a list of these load factors, simply right click the Results folder and select “List Buckling Factor of Safety.”
Notice that the first buckling load is negative. This is normal and happens from time to time. All that it means is the structure will exhibit that mode of bucking if the applied load was reversed and multiplied by that value. In this case, it is unlikely we will have 350 pounds * 149 pulling UP on the chair, so it can be safely ignored. See below for a chart from the SOLIDWORKS Simulation Professional training manual that clarifies what the ranges of buckling factors mean.
The next buckling load factor is 81.5. This means that if my applied load were 81.5 times higher, the structure would buckle as in the animation. I would exceed the yield strength of the material long before I reached this load, so I can assume buckling is of no concern for this design!
I hope that this blog gave you insight into the workflow and capabilities of buckling analyses in SOLIDWORKS Simulation Professional. This blog has an accompanying video under the same title. Check out the Computer Aided Technology video page for more information and subscribe.
Matthew Sherak, CSWE-Simulation
Simulation Product Specialist, Application Engineer
Computer Aided Technology, Inc.