Characterization of Post-Annealing Mechanical Behavior of Preformed Aluminum Alloy 5182-0

Prestrain;Anneal;Tensile Properties;Anisotropy;Forming Limit Diagram;Aluminum Alloy;Mechanical Engineering;Engineering;Mechanical Engineering

Li, JingjingShih, Albert J. ;

University of Michigan

关键词: Prestrain;    Anneal;    Tensile Properties;    Anisotropy;    Forming Limit Diagram;    Aluminum Alloy;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/89739/jingjli_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Preform annealing is a new technology for forming aluminum sheets where aluminum panels are formed by a sequence of preform stamping, annealing and final stamping. The total formability is enhanced compared to conventional one-step stamping. The post-annealing mechanical behavior is different from the as-received material; thus it is important to understand the changes in material behavior due to preforming and annealing for formability analysis, process simulation and optimization. This dissertation presents studies on the kinetic behavior of AA5182-O during static recovery and recrystallization, tensile behavior and its relationships with different pre-strain and annealing conditions, and a stress-based forming limit criterion. Microstructure and texture evolution were also investigated to help understand the mechanical property changes.Three research topics are carried out in this dissertation:1)Development of kinetic modeling of AA5182-O during static recovery and recrystallization: Two empirical models for the yield stress of post-annealed AA5182-O were developed in terms of the applied pre-strain, annealing temperature, and time. The effects of pre-strain and annealing on post-annealing elongation, total effective elongation and strain-hardening exponent were also investigated.2)Post-annealing mechanical properties and their relationships with pre-strain and annealing conditions: Tensile and anisotropic behavior subjected to different pre-strain paths, levels and annealing conditions have been characterized. Statistical methods were applied to indentify the important process variables and their influences on the post-annealing properties. 3)Stress-based forming limit criterion for preform annealing: A method to account for the preforming and annealing effects on the strain hardening behavior has been presented. With this method, the forming limit criterion in the stress space was transformed from the strain space for this two-stage forming process with annealing, where the strain information on localized necking was directly observed via the digital image correlation method. The strain-based forming limits showed the dependence on pre-straining and annealing history; however, the stress-based forming limits are independent of these processing histories, and converge to a single forming limit curve that is close to the as-received forming limit. This finding is critical to the finite element simulation of this complex forming process with local annealing.