AHSS Application in Roof Strength

Rollover crash is one of the important fatal crash modes in highway accidents. To protect occupant safety, the National Highway Traffic Safety Administration (NHTSA) has proposed a higher roof strength requirement in the upcoming new federal regulation. Meanwhile fuel efficiency and environmental friendliness demands that the safety cage design should have the minimum weight while providing the sufficient roof crush strength. These requirements pose a challenge to automotive design engineers.

In this paper, Advanced High Strength Steels (AHSS) are introduced as an enabler to support this challenging task. The advantages of different types of AHSS for vehicle crashworthiness are presented. The criteria to select materials to improve the roof crush performance are discussed in detail. A new steel design concept using AHSS with tensile strength ranging from 590 to 980 MPa is introduced to illustrate how steels of different strength levels were used in the design FEA simulations demonstrated that the AHSS design was capable of meeting the proposed more stringent roof crush requirement. However, a holistic approach must be taken when steels of high strength are used, including optimized use of steel strength, strength and formability compromise, part geometry modification, adopting appropriate manufacturing processes, such as roll forming, and innovative design.