Abstract
Stretch forming process is primarily used for generating curved structures from sheet metals such as car body panels or aircraft fuselage panels. Although there are large number of studies about stretch forming, these investigations focus mainly on flat sheet metals. However, various parts especially in the automotive industry, such as passenger car fenders are first preformed to a profile and afterwards stretch formed to generate desired final geometry. Moreover, as a consequence of weight reduction activities, these fender parts are usually made of ultra-high strength steels (UHSS) in the last two years. In the current study, stretch forming characteristics of an open profile made of martensitic UHSS (MS1500) are investigated using finite elements method (FEM). Used geometry was an asymmetrical hat profile which was preformed using roll forming prior to stretch forming. Mechanical properties of the material used is characterized using tensile test and modeled using Swift isotropic strain hardening rule. Strain and stress distribution along the bend section, geometry and springback in the final part as well as forming force have been investigated using finite element (FE) simulations. A twist has been observed in the final product along its longitudinal axis. To validate the FE results, experiments have been conducted. Twist problem is also detected in the manufactured samples. The amount of springback in produced part was similar to the experiments. It is found that FE simulations can model stretch forming process of open profiles accurately.
Highlights
Due to the tightening in green-house-gas emission regulations, the demand for light-weight parts especially in automotive industry has been continuously rising in the last two decades [1]
Stretch forming process of an open profile made of ultra-high strength steels (UHSS) MS1500 steel is investigated using finite element simulation and experiments
finite element (FE) simulations proved the feasibility of the process
Summary
Due to the tightening in green-house-gas emission regulations, the demand for light-weight parts especially in automotive industry has been continuously rising in the last two decades [1]. Due to its high efficiency, this process is preferred in the manufacturing of open and closed profile type geometries. Stretch forming is a process where flat sheet panels are formed under tensile stresses using a punch and axial gripper system [5]. It is majorly used in automotive, aerospace and shipbuilding industry to manufacture large curved parts. To increase the pedestrian safety, ends of these parts are curved Such a geometry can be efficiently manufactured using roll forming and stretch forming combination. The paper at hand aims at investigating and validating the stretch forming process of an open profile using FEA and experiments
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