Following on from our first blog where we discuss how we modelled a scrum machine, as part of our rugby inspired competition with seller MECAD in this blog we'll take a look at analysing our scrum machine with SOLIDWORKS Simulation.
SIMULATION METHOD AND TIPS
After creating the mode (see more in our first blog
) we wanted to run an initial static simulation to ensure the frame will withstand the forces applied by the players and find out how the design performs with and without the cross brace.
Automatically Convert Toolbox Parts to Connectors
The first great feature we can utilize to save some time is the option to convert toolbox parts to bolt connectors this allows us to enter torque values, strength data and our required factor of safety. We can also test a range of materials or different types of connector if required. Another benefit of these connectors is the run time will be reduced and we don’t need to set up any extra contact sets.
Replace Custom Connectors
We will also replace these custom pins with a pin connector from the simulation library. This is again to aid run times but also so we can review the forces passing through any one of these pins to ensure they are safe.
Utilize Shell Elements
Because there are some large flat plates on this model, we want to ensure shell elements are used for these, using this type of element will help out study to run as smoothly as posible. These can be manually defined or if the model uses sheet metal SOLIDWORKS will convert to this element type automatically. This will massively reduce the computation time by reducing the number of elements in the study and it should aid convergence. Another benefit of shells is it allow us to quickly change the thickness of the plates directly from the simulation should we need to optimise this.
Remove Non-Structural Components
Next step is to remove anything non-structural from the model so in this case the pads will be removed. This is partly due to the nonlinear nature of the foam that will be in the pad. But also, because we wouldn’t expect them to make much difference to the end result and having them in the study would require significant amount of mesh elements.
Fixing the Model
Next we can add a virtual wall to represent the unit sitting on the floor.
Now the local interactions have been set up the next step is too fix the model in place. In this case we decided because the model is symmetrical and we are assuming symmetrical forces to be applied we can use the SOLIDWORKS symmetry fixtures. This helps to stabilise the model and majorly increases run time by cutting the mesh in half!
How Much Force does a Scrum Put Out?
The next step before running the study is to set up the loading so first gravity can be quickly applied. And from a quick google search we can find roughly what the maximum force a rugby pack can put into a scrum:
We can apply this load to be distributed across each pad. We can then mesh and run the model. When viewing the result we can then display the full model as well. To start let's review the results with no cross brace, the visuals here are exaggerated so that we can see how the model behaves, the actual displacement is very small.
Stress - No Cross Brace
Displacement - No Cross Brace
Factor of Safety - No Cross Brace
From these plots we can see the model is below yield which is great and deflection is around 8mm which isn’t too bad at all! However, our factor of safety is a little lower than we would like so let’s see if we can stiffen the design and improve this. Just in case Manu Tuilagi shows up for training!
Improving our Results
So in this next study we have added some support braces. We have added these in a new configuration so we can quickly copy the previous study, switch the configuration, add the connections and rerun the study
Stress - With Cross Brace
Displacement - With Cross Brace
Factor of Safety - With Cross Brace
From these results we can see the maximum displacement is reduced from 8mm to 2.4mm! I expect this is largely due to some of the stress being relocated away from the corner sections. However, this does increase stress in other areas so it could also be worth adding additional reinforcements there if we wanted to take this a step further. However this design is now satisfactory as it achieves our desired factor of safety with a minimum of 2.17, This means that even if the forwards output double the amount of force we expect the design would be strong enough to not yield.
MORE RUGBY LIONS
Want to take a look at how we created the scrum machine, check out our first blog here.
Alternatively to take a look at MECAD's design head over to their blog here
Next week's competition is going to focus around the design of a rugby kicking tee, so check back for some more modelling tips and a look into SOLIDWORKS Plastics Simulations. Keep your fingers crossed for the Lions this weekend!