Super Bowl 51 is just around the corner, and research about preventing concussions and improving helmets is back in the news.
At the point of impact, helmets undergo great stress and large deformations during a very short amount of time. Understanding a helmet’s behavior is critical to designing a safe helmet; however, it involves extremely time consuming and cost prohibitive research, including the creation of prototypes of helmets and investing significant resources in a slow-motion camera to record the behavior.
In today’s engineering world, there are tools to streamline the helmet research and design process.
To reduce the number of testing iterations, a simulation is conducted using finite element analysis (FEA) and by running a nonlinear dynamic analysis. The force, or impact load, is applied for a very small amount of time to simulate an external load like a ball, bullet, or another helmet hitting the helmet. By using impact load we can get a detailed understanding of how the helmet reacts in a very short duration of time just after impact. (Appropriate material selections are made and other restraints are defined to complete the setup of the analysis.)
The animation shown below represents a very small amount of time that has been slowed down so we can carefully analyze it. It shows the point of impact deforming a large amount due to the load and stresses that propagate to the rest of the helmet, like a wave causing deformations.
This wave propagation is dependent on the magnitude of the load, material, internal geometry, and the external shape of the helmet.
Simulating such behavior beforehand helps researchers to understand the effects of different shapes or different combinations and uses of material. Loads from different angles can also be simulated, so only the worst-case scenario can be taken to the physical testing stage. We can also calculate the stress and displacement distribution for each design and make changes to help ensure greater protection of the wearer of the helmet even before a prototype is manufactured or tested.
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So, there are tremendous benefits to simulating the loads on a helmet and reducing the number of prototypes required for destructive testing.
But why stop here?
We can take this to the next level by linking the simulation results with 3D printing for functional prototyping. The deformed shape with the overlaid color map for stress or deformation can be extracted at very tiny time intervals after the simulated impact. The worst case can then be sent to the full-color Stratasys J750 printer and appropriate color selections can be made. A few hours later, we have a full-size deformed model of a helmet.
The printed helmet can also be used for actual measurements, and form, fit and function for different sizes of heads, equipping researchers with important information in a cost-effective and quick manner—all before testing an actual prototype. These data help engineers make important design changes to the geometry or material composition to help ensure greater protection for the wearer of the helmet.
The above-mentioned workflow can be extended to other impact applications or testing that needs a slow-motion camera. Common examples are car bumpers and sports equipment such as tennis racquets and baseball bats.
If you have further questions or other ideas for applications of interest, please provide your comments below.
Manufacturing applications engineer Arvind Krishnan works at GoEngineer, focusing on finite element analysis and 3D printing. He completed his master's degree in mechanical engineering at North Carolina State University with a thesis in Using Michell Truss Principles to find an Optimal Structure Suitable for Additive Manufacturing. Arvind enjoys playing tennis, badminton, racquetball, chess, and soccer; he is also passionate about hiking and cooking.