Case Studies

simulation@rand.com | RandSIM.com | 888.483.0674 D2H Advanced Technologies: Simulating Safety at Olympic Speed up the development cycle to market and builds confidence in understanding how the physical parts will perform, whilst reducing product development costs. Given the explicit nature of the analyses, D2H relied on Ansys LS-Dyna to predict helmet crashworthiness under all high-speed impact scenarios. Not only were these simulations used to gain insight, but it was also imperative that the simulation predictions correlated closely to reality. According to James, "Its fundamental that the simulation correlates back to physical testing to gain confidence in your development work. There's a well-known saying—that rubbish in = rubbish out!" The Solution Due to a long-standing strategic partnership with Rand SIM, D2H was able to determine the most effective analysis approach given the project requirements and get started quickly with the right tool, Ansys LS-Dyna, without delays or upfront licensing complexity. With Ansys LS-DYNA, the D2H team had access to different material models, like the Fu Chang model, that are well suited for materials like polystyrene foam where energy absorption and elastic rebound are critical. These features were important for designing a safe, compliant helmet, since the composite shell spreads the forces across a polystyrene foam core that surrounds the head and manages acceleration to that part of the body. To meet the regulatory requirements, it was also critical to test the helmet materials at different temperatures, since polystyrene performs very differently based on atmospheric conditions. The team needed to simulate product performance under temperatures ranging from -20 degrees Celsius to 38 degrees Celsius alongside artificial ageing and water absorption environmental conditions. Prior to simulating full helmet model studies, D2H first correlated small- scale foam and composite simulations to material characterization testing. "The data from material testing was converted to stress-strain data which was then interpreted by the Ansys LS-DYNA material model used. I was surprised by how well the solver interpreted the material data and made it efficient to correlate the two, even at different temperatures," James said. The confidence in material modelling combined with the explicit dynamic's capabilities of Ansys LS-Dyna allowed D2H to quickly assess the impact various composite laminates and helmet core designs would have on helmet stability and safety across the entire range of possible impact scenarios. "The client was pleased with the speed at which we were able to run through different cases, environmental conditions, helmet positions and anvil types. We were able to do 30+ runs over a period of a couple of days," James noted. These analyses provided rapid insight into which environmental conditions presented the greatest challenges, enabling the team to concentrate their efforts on the highest priority concerns. In response, D2H quickly vetted different iterations of the polystyrene core, shape and various design features to uncover the most effective solution.

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