For a light duty truck, the frame is a structural system and it must go through a series of proving ground events to meet fatigue performance requirement. Nowadays, in order to meet stringent CAFE standards, auto manufacturers are seeking to keep the vehicle weight as light as possible. The weight reduction on the frame is a challenging task as it still needs to maintain the strength, safety, and durability fatigue performance.
CAE fatigue simulation is widely used in frame design before the physical proving ground tests are performed. A typical frame durability fatigue analysis includes both the base metal fatigue analysis and seam weld fatigue analysis. Usually the gauges of the frame components are dictated by the seam weld fatigue performance so opportunities for weight reduction may exist in areas away from the welds. One method to reduce frame weight is to cut lightening holes in the areas that have little impact on the frame fatigue performance. In this paper, the authors propose a new methodology to systematically identify the locations of these non-critical areas, in which slots or holes can be added while the frame still maintains good durability performances.
A light duty truck frame is used to demonstrate the efficiency of this process. Through this approach, authors were able to reduce 3% to 5% of weight on components of a well-designed frame without compromising the frame durability fatigue performance.