Roof strength performance improvement enablers

Before 2009, rollover in vehicle accidents had not been significantly studied not only because its rate is lower than other types of accidents but also because it had been easy to meet the rollover regulation, the FMVSS 216 Roof Crush Resistance target. The regulation only requires that the strength-to-weight ratio (SWR) be 1.5, i.e., it was acceptable when the roof could withstand a force of only 1.5 times the vehicle??s weight. In other words, rollover is not considered an important safety factor. However, presently, the situation has completely changed. Rollover is now considered a key safety factor. Recently, the number of rollover incidences has been increasing, reaching as much as the number of front, side and rear accidents. Furthermore, the IIHS has begun to require that the roof must withstand a force of 4.0 times the vehicle??s weight, a more severe restriction than FMVSS. To satisfy this requirement, many manufacturers, universities and institutes are studying the topic. This paper focuses on changing the body structure to minimize injury to the occupant when rollover occurs and help rollover safety performance become excellent. This paper draws on a simple analysis that is based on general factors: changes in the material, the addition of welds and additional reinforcements. The best result will be determined, as described by this paper.