Browsing by Subject "Forming"
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Item The construction and use of physics-based plasticity models and forming-limit diagrams to predict elevated temperature forming of three magnesium alloy sheet materials(2013-08) Antoniswamy, Aravindha Raja; Taleff, Eric M.Magnesium (Mg) alloy sheets possess several key properties that make them attractive as lightweight replacements for heavier ferrous and non-ferrous alloy sheets. However, Mg alloys need to be formed at elevated temperatures to overcome their limited room-temperature formabilities. For example, commercial forming is presently conducted at 450°C. Deformation behavior of the most commonly used wrought Mg alloy, AZ31B-H24, and two potentially competitive materials, AZ31B-HR and ZEK100 alloy sheets, with weaker crystallographic textures, are studied in uniaxial tension at 450°C and lower temperatures. The underlying physics of deformation including the operating deformation mechanisms, grain growth, normal and planar anisotropy, and strain hardening are used to construct material constitutive models capable of predicting forming for all three Mg alloy sheets at 450°C and 350°C. The material models constructed are implemented in finite-element-method (FEM) simulations and validated using biaxial bulge forming, an independent testing method. Forming limit diagrams are presented for the AZ31B-H24 and ZEK100 alloy sheets at temperatures from 450°C down to 250°C. The results suggest that forming processes at temperatures lower than 450°C are potentially viable for manufacturing complex Mg components.Item Physics-based material constitutive models for the simulation of high-temperature forming of magnesium alloy AZ31(2012-08) Carpenter, Alexander James; Taleff, Eric M.; Bourell, David L.; Kovar, Desiderio; Seepersad, Carolyn C.; Engelhardt, Michael D.Magnesium sheet alloys, such as wrought AZ31, have material properties that make them an attractive option for use in automotive and aircraft components. However, the low ductility of magnesium alloys at room temperature necessitates the use of high-temperature forming to manufacture complex components. Finite-element-method (FEM) simulations can assist in determining the optimum processing parameters for high-temperature forming, but only if an accurate material constitutive model is used. New material constitutive models describing the deformation behavior of AZ31 sheet at 450°C are proposed. These models account for both active deformation mechanisms at this temperature: grain-boundary-sliding creep and five-power dislocation-climb creep. Phenomena affecting these deformation mechanisms, such as material anisotropy and grain growth, are also investigated. This physics-based approach represents an improvement over previous material models, which require nonphysical parameters and can only predict forming for a limited range of conditions. Tensile tests are conducted to obtain data used in fitting constitutive models. New models are used in FEM simulations of both tensile tests and biaxial gas-pressure bulge tests. Simulation results are compared to experimental data for validation and determination of model accuracy.Item The tensile behavior of AA6013 at room temperature and 240 °C(2021-12-07) Fascitelli, Dominic Gianni; Taleff, Eric M.Automotive manufacturers are pursuing technologies, such as lightweighting, that improve vehicle fuel-efficiency and reduce emissions. High-strength aluminum alloys might provide performance equal to the current ultra-high-strength steels while decreasing vehicle weight. High-strength 6xxx-series aluminum alloys, such as AA6013, are candidates for lightweighting structural components of vehicles because of their high strength-to-weight ratios compared to steel. In the peak-aged condition, these alloys often lack the ductility necessary to form complex part geometries at room temperature. Forming at elevated temperatures increases the ductility but can reduce strength. Retrogression forming and reaging (RFRA) is a relatively new technology for warm forming parts in high-strength aluminum alloys and then recovering strength to equal the peak-aged condition. Previous studies on aluminum alloy AA6013 performed by Rader et al. demonstrated a significant response to retrogression and reaging. New data for AA6013 are presented from tension tests at room temperature and 240 °C, an appropriate temperature for retrogression of this alloy. The effects of different heat treatments on room temperature properties are investigated. The effects of temperature and time at temperature on plastic deformation are investigated using experiments at 240 °C. Retrogression from the T6 temper reduced room-temperature strength by 3.5%, but subsequent reaging restored strength to within 2% of the original T6 temper. At 240 °C, the yield stress was 25 to 30% lower and elongations after rupture were 42% higher than at room temperature for the T6 temper. Stress relaxation at 240 °C decreased stress by 32 to 43% at a fixed elongation within approximately three minutes. These results suggest that RFRA could be viable for forming complex components in AA6013-T6