Improvement in formability and geometrical accuracy of incrementally formed AA1050 sheets by microstructure and texture reformation through preheating, and their FEA and experimental validation

摘要

The work involves finite element analysis (FEA) and experimental investigation of formability and geometrical accuracy prevailing in single point incremental forming (SPIF) process. Preheating at different temperatures was performed in order to reform microstructures (grain size) and texture (spatial grain orientation distribution) of AA1050 sheet. Preheating led to removal and rearrangements of defects in the crystal structure in comparison with the distorted structures present in cold-worked commercial aluminum sheets. Preheating at higher temperatures resulted in coarser grains with preferential texture and increased area fraction of homogenously oriented grains. Numerical simulation of SPIF process has been done to predict the effect of preheating on von Mises stresses, forming load, wall thickness distribution and geometrical accuracy of formed parts. For the purpose, Johnson-Cook models' parameters were evaluated by mechanical characterization of the samples with varying microstructural and texture arrangements resulted due to variations in preheating temperatures. FEA of the process revealed that preheating of the sheets resulted in reduced forming load, uniform wall thickness distribution and improved geometrical accuracy. The results were further validated by experiments and compared to the original samples with fine and randomly orientated grains.