FEA SIMULATION IMPROVES HELMET SAFETY

THE PROJECT

Easton, one of the world’s leading manufacturer of baseball and softball equipment decided to implement numerical simulations within its helmet design process. The ultimate goal was to better evaluate how changes to a helmet’s design could impact its compliance to NOCSAE normalized ball impact test requirements on material failure as well as Severity Index (SI score; injury criterion) and avoid costly design iteration through failed laboratory tests. A second objective was to reduce and target the required physical tests based on extensive use of virtual testing early in the design process.

Before carrying out numerical simulations within its product development workflow, Easton’s design team had to create an initial concept, produce a series of prototypes, conduct physical peripheral ball impact tests on the prototypes, assess the damage, modify the concepts, and retest all over again. This process is costly and time-consuming in order to achieve optimal results.

The customer, along with experts from Creaform Engineering, implemented a brand-new workflow—using numerical simulations—in order to accelerate the helmet testing process. From the sketches given by the customer, our advanced surface modeling team designed all the initial Class A surfaces and the thickness of the shell based on our knowledge in this matter. Once this first design was completed, our numerical simulation team used the finite element method (FEM) to perform more than 100 virtual ball impact tests to map both peak strain and SI scores versus the impact location. It allowed the members of the team to identify the critical regions of the helmet and uniformize the performance levels even before the first mold being designed.

A round of simulations and concept iterations aligned the advanced surfacing team on the modifications that needed to be made to the shell design. The team had to ensure that the helmet’s thickness variations were optimized to facilitate the molding process and ensure that the end product featured the performance levels that were required by the NOCSAE standards.
Thanks to this new FEM-based design process, Easton and Creaform Engineering were able to accelerate the project’s time to market as the number of physical tests on prototypes was substantially reduced as well as inspection timelines and costs.

Services provided

• Advanced Class A surfacing
• Detailed 3D mesh of the NOCSAE headform and calibration of a numerical headform using experimental data
• Detailed 3D mesh of the helmet shell and foam padding for accurate representation of strength and stiffness
• Establishment of a specific method for helmet vs head positioning and foam preload.
• Automation of more than 100 virtual impact locations with mappings of peak strain and SI scores
• Iterations with the numerical model in order to ensure compliance of all critical locations

Technical challenges

• Ensure that the numerically simulated headform precisely corresponded to its mechanical counterpart to accurately predict the SI score
• Properly correlate the FEM, following initial tests, to guarantee an accurate SI score and material failure prediction
• Automate a simulation sequence of 116 virtual ball impact tests for a single design iteration
• Develop advanced mappings of the peak strains and SI scores to identify performance and worst testing conditions

GALLERY