front impact exerts an offset eccentricity between the center of gravity at the bumper and the center of gravity of the subframe attachment. This offset eccentricity can result in a substantial external applied bending at the center of gravity of the front rail section, which can be a large percentage of the bending capacity of the front rail section. Thus, this external applied bending takes away from the section capability to manage the normal buckling and folding stresses due to axial collapse of the horn section of the lower frame rail member. This eccentricity of the frame configuration can result in a premature downward bending of the horn section at the onset of any axial crash.
One approach to resolving this package and loading constraint problem is to reinforcethe rearward half or third of the horn section rail length closest to subframe attachment, at lower side of the section where buckling stresses are highest, resulting in a corresponding increase in the bending capacity of the horn section. Typically, this reinforcement is provided in the form of a vertically oriented flange extending downwardly from the horn section. While this reinforcing flange solution does achieve the desired increase in bending capacity in the horn section of the lower frame rail member, the increased bending capacity penalizes the crushability of the horn section over which this solution is implemented. As a result, the horn section can only effectively crush along the forward half or so of the length of the horn section projecting forwardly of the lower frame rail