ORIGINAL ARTICLE Thickness dependent yielding behavior and formability of AA6082-T6 alloy: experimental observation and modeling Onur Çavuşoğlu 1 & Halit İlhan Sürücü 2 & Serkan Toros 3 & Mahmut Alkan 3 Received: 5 July 2019 /Accepted: 23 December 2019 # Springer-Verlag London Ltd., part of Springer Nature 2020 Abstract This study analyzes thickness-dependent of the yielding behavior and forming limit diagrams (FLDs) of the AA6082-T6 aluminum alloy sheet. Mechanical behavior of the materials of 1 and 1.5 mm sheet thickness is observed having performed anisotropy and tensile tests at 0 ° , 15 ° , 30 ° , 45 ° , 60 ° , 75 ° , and 90 ° to the rolling direction. By using Hill-48 and Barlat-89 yield criteria, r-value and yield stress relations were defined and yield loci were obtained. Forming limit diagrams were created using experimental data and Marciniak-Kuczynski (MK) model. It was observed that increased sheet thickness also increases anisot- ropy while decreasing yield stress; yield locus was found to be smaller. The formability of the material increased as the sheet thickness increases. Keywords 6082 . Yield locus . Anisotropy . Sheet metal forming . Forming limit diagram 1 Introduction Today, lightweight vehicle manufacturing efforts in the auto- motive industry have gained great importance in the goal to reduce fuel consumption and CO 2 emissions caused by auto- mobiles. Therefore, lightweight design plays an important role in the energy economy and environmental protection [1]. In the light of these efforts made in the automotive industry, a closer look into the materials used in manufacturing shows that aluminum alloys have widespread use [2]. Aluminum alloys are preferred in the automotive industry thanks to their characteristics such as low density, formability, weldability, high corrosion resistance, and improved driving safety due to the higher strength they offer [3, 4]. Deformation conditions of material have an impact on its mechanical properties which, therefore, may modify its forming behaviors [5, 6]. With advanced computer software, it is now possible to estimate the forming behavior of materials with re- spect to their forming conditions [7]. Sheet metal forming pro- cess involves several parameters such as sheet thickness, yield stress, work hardening, strain rate sensitivity, and elasticity mod- ulus [8, 9]. These parameters affect the flow stress-strain relation and forming limit diagram [10]. The possibility of successful estimations depends on the material model and material charac- terization results used in the finite element analysis as part of the forming simulation software [11, 12]. Literature offers studies focusing on the forming behaviors of materials under varying deformation conditions. Nasiri et al. defined the yield locus in AA3104-H19 alloy sheet ma- terial forming due to heat and strain rate using three yielding functions and suggested forming limit diagrams using the M- K FLD model [13]. Naka et al. analyzed the effects of sheet thickness on the yield locus of the AZ91 magnesium alloy sheet material [14]. Abedrabbo et al. created yield locus and defined the forming limit diagrams in order to investigate the formability behavior of AA3003-H111 aluminum alloy with respect to temperature using finite element software [8, 15]. Kilpatrick et al. reported the effects of the aging process and serrated yielding of 2024 aluminum alloy on the yield locus using the Hill-48 yield model [16]. Anderson et al. defined the yielding behavior of the 7075-O aluminum alloy under pre- strain effects [17]. Lăzărescu et al. studied the effects of the use of material characterization parameters as part of yield * Onur Çavuşoğlu onurcavusoglu@gazi.edu.tr 1 Faculty of Technology, Department of Manufacturing Engineering, Gazi University, Ankara, Turkey 2 Bor Vacational School, Niğde Ömer Halisdemir University, Niğde, Turkey 3 Faculty of Engineering, Department of Mechanical Engineering, Niğde Ömer Halisdemir University, Niğde, Turkey The International Journal of Advanced Manufacturing Technology https://doi.org/10.1007/s00170-019-04878-6