Lightweighting an automotive fuel tank through formability analysis

Abstract

For lightweighting automotive sheet metal parts, it is important to use the right grade/material with the minimum possible initial blank thickness in the forming processes. Fuel tank is one of the most critical sheet metal parts in automobiles due to its complex shape and large depth. In this work, a simulation-based approach has been employed to study the feasibility of lightweighting an automotive fuel tank (for two wheelers) by reducing blank thickness and changing steel grade. Formability analysis has been carried out using numerical simulations of a 0.8 mm thick sheet of Extra Deep Drawing (EDD) steel which is being used to manufacture the fuel tanks. Simulations have been performed to find out the minimum initial sheet thickness which can be formed successfully without failure or excessive thinning. From the predictions of formability, thinning, and strain distributions in the formed parts, it has been found that the weight of the part can be reduced by 12.5% by reducing the initial thickness from 0.80 to 0.70 mm. To reduce the thickness further, simulations have also been carried out by changing the grade from EDD steel to Interstitial Free (IF) steel which has superior drawability than EDD steel. It has been found that the blank thickness can be further reduced to 0.65 mm in the case of IF steel which is expected to result in 19.0% reduction in the weight of the component. The predictions have been validated by the actual press trials in the industry with reduced sheet thickness. The predicted strain distribution and thinning in the formed parts have also been validated with the experimental press trails. In addition to the weight reduction, the proposed change in thickness and grade would lead to a reduction of 16.5% and 4.0%, respectively, in the raw material cost of the fuel tank.