Correlation of the Federal Motor Vehicle Safety Standard 225 (FMVSS225) Requirement of an Automotive Seat System Using LS-DYNA

The National Highway Traffic Safety Administration (NHTSA) has issued a final rule for a new safety standard related to child seats and their anchorage systems in vehicles. FMVSS 225 – Child Restraint Anchorage Systems (CRAS) requires that motor vehicle manufacturers provide a new method for installing child restraints that are standardized and independent of the vehicle seat belt. The requirements for CRAS can ensure their proper location and strength for the effective securing of child-occupants in an automotive seat system. There are four pull tests for FMVSS 225 - forward pull with top tether, forward pull without top tether, lateral pull to the right, and lateral pull to the left. The tests are performed by applying a specified load to the child seat anchorage system using Static Force Application Devices (SFAD), mandated by NHTSA. The regulation requires that the displacement of the load application point on the SFAD, along the horizontal plane, should be less than 125 mm and there should not be any structural separation [1][2]. LSDYNA is widely used for the “quasi-static” simulation of the automotive seat systems and plays a key role in improving design and saving cost. Due to the dynamic effects in quasi-static simulations, correlating the displacement for FMVSS 225 using LSDYNA becomes a challenge. At Lear Corporation’s test lab, physical tests were conducted on number of different seats and the results were correlated by simulating the tests in LSDYNA. Based on the knowledge and data collected over a period of 3 years, the authors have established a methodology to simulate FMVSS 225 and correlate accurately with the physical test.