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Stretching a circular blank over a circular domed punch is modelled using the ABAQUS finite element code. Hemispherical, elliptical and flat-bottomed punches are investigated as well as the effect of strain hardening, friction, blank diameter, blankholder pressure and die radius. The results are illustrated using forming limit and other diagrams and summarized in a table that illustrates how strain in the different regions of the blank can be controlled and redistributed.

Stress and strain distributions developed in a tube during the tube bending operation is important in estimating the limit bending radii, springback and structural properties of the tube. In this paper, A new strain distribution model for tube bending, considering stretching, circumferential strain and cross section flattening, is presented. The axial, circumferential, thickness and effective strains on the outer surface, inner surface and mid-surface of a bending tube were calculated from grid measurement, and are shown in different ways. Thickness strain was also obtained from thickness measurement. Comparison is made among the results from measurement and modeling and a very good agreement is obtained between the new model and the measurement.