Process design for flexible T-profile-rolling of tailored thickness stringers with different cross sections

Abstract

Abstract A new process, called flexible T-profile-rolling, is being developed to produce T-profiles with variable thickness distribution in longitudinal direction by flexible rolling. These tailored thicknesses allow for load-adapted and weight-optimised design of stringer profiles for aircrafts. The new process can replace the chemical milling currently used in the production of stringers and enables a more environmentally friendly and resource-saving production of the thickness changes. In order to achieve uniform thicknesses in the web and flange of the T-profile, a new rolling stand with rolls inclined against the T-profile and varying roll radii was developed. However, the varying roll radii cause different longitudinal strains in the profile cross-section due to the varied contact areas between the roll and the rolling stock, resulting in unwanted profile bowing. This bowing depends on the profile dimensions, as the adjacent roll radii vary over the profile cross-sections. This paper demonstrates the effects of profile dimensions on deflection through numerical investigations with different web heights, flange widths and thickness reductions. A straightening method is presented to obtain straight profiles as a function of the profile dimensions. The results show that this process can produce almost straight T-profiles with variable thicknesses for different cross section dimensions.