Frontal Offset Crash: Smart Structure Solution

Abstract

Abstract The majority of real world frontal collisions involve partial overlap of the vehicle front. Excessive, intrusion is usually generated on the impacted side subjecting occupants to higher contact injury risk compared with full frontal collision. The problem encountered by the front end design engineer is to address conflicting requirements of keeping the G-level in the full frontal crash within its permitted values, and minimizing intrusions in offset crash. Traditional solutions to this problem focus on the use of three forked and cross members to ensure continuity of the load path into the passenger compartment. The ideal structure for offset crash is to stiffen the impacted side of the structure, and transfer part of the load to the non-impacted side to even out the load on both sides. Smart hydraulic structure is proposed to meet these ideal requirements. Sample hydraulic “Smart Structures” were designed and tested for feasibility of crash under high-pressure and high-speed impact conditions. This research is attempting to find a solution to the design trade off faced by the designer for offset crash. A novel system of “Smart Structures” is introduced to support the function of the existing passive structure. The proposed “Smart Structures” consist of two independently controlled hydraulic cylinders integrated with the front-end rails. A ten-degrees of freedom, two-dimensional spring-mass-damper simulation model has been developed to study the dynamics of crash between two vehicles in head-on collisions. The model inputs mass, speed of both colliding vehicles, overlap ratio and deformation characteristics of both passive and “smart” structures. The model assumes that the two colliding structures geometrically interact with each other. Full simulations of various scenarios of offset crashes were investigated using “Smart Structures” integrated with the front rail members. Deployable “Smart Structures” have not been considered in this paper as this scenario was covered in previous publication (9). “Smart Structures” proved superior to the traditional passive structures by absorbing more energy for the same crush zone distance, stiffening the impacted side and stiffening the structure at high-speed impacts. The results are reduced intrusion for offset crashes while maintaining the permitted G-level in both full and offset crashes.