Experimental and Numerical Analysis on Bendability of Magnesium Sheets (Masterarbeit)


Wrought magnesium alloys have emerged as promising candidates for highly loaded structural components in the automobile industry due to its low density and high specific strength. Magnesium and its alloys also have a number of undesirable properties including weak wear resistance, high chemical reactivity and poor creep resistance. However, these properties may also be an advantage in the field of biodegradable implant materials. In this work, the bendability behaviour of a third-generation magnesium alloy AZ31 (‘e-form’), are explored both experimentally and computationally. Three-point bending tests are conducted using an existing tailor-made device. The onset of failure is characterized as a function of sheet orientation with respect to its axes of orthotropy and the distance between the two supports. The test results in terms of load-displacement records are compared with respective results obtained from Finite element simulators: ABAQUS and Zset software. Uniaxial tensile tests are conducted along different orientations for characterizing the mechanical behaviour of the material being used. Experimental results from three-point bending, confirm significantly different plastic deformation behaviour from that of the simulations. In order to calibrate the material model, identification of material parameters was accomplished with the experimental data based on an optimization (error minimization) procedure. A constitutive relation based on two interacting plastic potentials is probed with particular emphasis on tension-compression asymmetry, which evolves during bending. A yield function originally proposed by Cazacu, Plunkett and Barlat in 2006, was extended by coupling it with the hardening evolution, which leads to a good representation of the mechanical behaviour.
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