Heat treatable aluminium alloys are widely used in modern car bodies to achieve lightweight cars. Compared to steel, aluminium alloys are more sensitive to creep behaviour under high elastic stresses, since their melting point of about 600 \'03C is much lower. In order to predict permanent deformations of outer shell panels due to thermal stresses in drying processes and ensure highest quality standards regarding appearance to the customer, interdependencies with production process history must be evaluated. In this work, stress relaxation of the aluminium alloy AA6016 in initially T4 temper has been examined within the elastic regime with focus on the dependency of plastic pre-strain during primary creep phase. As a result, pre-strain becomes more important the higher the temperature was set. Hence, the former production process history of aluminium sheet metal parts must be taken into account when viscoelastic deformations are investigated. Based on the test results a pre-strain dependent material model for finite element simulations is pointed out, which can be used for novel deformation analyses of car bodies in automotive paint drying processes that contain aluminium parts out of AA6016
Modern car-bodies consist of different types of metals in order to gain the best crash performance at minimal weight. After the press and body shop, the bodies in white run through several paint drying processes, where also alloys of the 6xxx series become heat-treated. Consequently, the different thermal expansion behaviour of joined aluminium-steel components leads to high bending stress conditions within the car body structure while they heat up to 200 °C. In order to describe the process deformations numerical simulations were developed, where appropriate material models are necessary. Especially aluminium alloys with a melting point of about 600 °C can exhibit viscoplastic behaviour at 200 °C under stress. In this work, creep characteristics of the aluminium alloy AA6016 are investigated using a bending test. Based on these results an adequate model for finite element (FE-) simulations of creep strains is pointed out, which can be used for novel analyses of the whole car body in the automotive e-coat drying process.
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