Analysis of shape defects during flexible roll forming of steel/aluminum double-layered blanks
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ORIGINAL RESEARCH
Analysis of shape defects during flexible roll forming of steel/aluminum double-layered blanks Young Yun Woo 1 & Il Yeong Oh 1 & Tae Woo Hwang 1 & Young Hoon Moon 1 Received: 25 February 2019 / Accepted: 8 August 2019 # Springer-Verlag France SAS, part of Springer Nature 2019
Abstract Flexible roll forming is an advanced sheet-metal-forming process that allows the production of parts with variable cross-sections. Double-layered blanks can have enhanced properties such as a high stiffness-to-weight ratio and high corrosion resistivity when combined with suitable materials. However, in the flexible-roll-forming process of double-layered blanks, additional shape defects and interface delamination can occur owing to their inhomogeneous mechanical properties compared with those of single-layered blanks. In this study, investigations on shape defects generated during the flexible-roll-forming process of steel/ aluminum double-layered blanks were performed. Shape defects such as web-warping, wrinkling, and delamination at the interface were investigated on three different blanks with trapezoidal, convex, and concave shapes. The results show that the process-induced longitudinal strains significantly affect the occurrence of shape defects. Moreover, the longitudinal strains strongly depend on the blank shapes, their stacking order, and mechanical properties of the constituent layers. Keywords Double-layered blank . Flexible roll forming . Web-warping . Web warping . Wrinkling
Introduction Roll forming is widely applied in many industries such as the automotive industry, ship construction, and aerospace engineering to reduce the material weight without degrading the performance. In conventional roll forming processes, the blank is incrementally transformed into a target profile by bending it continuously with a series of forming rolls [1, 2]. This process exhibits high productivity, high product quality, and low costs [3, 4]. However, the conventional roll forming process can only manufacture parts with constant cross-sections. In many cases, parts with variable cross-sections are required to reduce the weight and increase the functionality [5–7]. To overcome the limitations of the conventional roll forming process, flexible roll forming has been developed. The forming rolls in the flexible-roll-forming process can move both axially and rotationally along a variable roll trajectory, thus realizing variable cross-sections [8]. In flexible roll forming, the metal blank is bent, and the flange is * Young Hoon Moon [email protected] 1
School of Mechanical Engineering, Pusan National University, 30 Jangjeon dong, Geumjeonggu, Busan 609-735, Republic of Korea
longitudinally stretched or compressed. If the required longitudinal deformation in the flange is insufficient, shape defects will occur. To date, many studies have been carried out on shape defects in conventional and flexible-roll-forming processes [9–12]. The most frequent defects occurring in a flexible-rollforming process are web-warping and wrin
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