Effect of In-plane and Surface Anisotropy of Titanium Sheet on Sheet Formability

1. 1. Influence of in-plane anisotropy on formability of titanium plate
The performance of in different directions relative to the rolling of the plate is different, so that the deformation of the cylindrical forming part becomes asymmetric, and the lugs appear on the forming part. The appearance of the lugs, in addition to making the shape of the shaped part not conform to the requirements (belonging to the conformability category), is also detrimental to the allowable deformation degree.
Obviously, the appearance of the lugs on the cylindrical forming part will inevitably make the shrinkage deformation in the direction of the cylinder unevenly distributed on the cylinder, the valleys are large, the lugs are small, and the valleys are more prone to unstable wrinkling or shearing Cut and rupture. If the deformation is evenly distributed, this kind of wrinkling or cracking could have been avoided, or at least it would only happen with a larger deformation.
The main effect of the lug on the deformation can be expressed in the direction of the lug in addition to the valley; the performance is that the material in the direction of the lug and the four corners of the die will be cracked. This is because the wool line of the lug part is wide, and the force required for further deformation must also be greater. When it is large to a certain degree, the largest force part-the fillet of the die will crack.
Of course, for non-axisymmetric parts, according to the specific conditions of the parts, the blanking orientation is properly selected, and the in-plane anisotropy is used to turn it into a favorable factor, which can sometimes increase the allowable deformation.
The influence of in-plane anisotropy on conformability is also manifested in curved parts. Due to the in-plane heterogeneity of the material, that is, the main strain direction is not always integrated with the main stress direction, the bending line is not a bending piece that is consistent with the rolling direction or transverse direction of the plate, and it appears that it should not happen intuitively. wry.
The in-plane anisotropy of titanium plates has significant adverse effects, especially in the formability. Due to the different performance in different directions, even if the forming stress is the same, different springback will occur during unloading, which will deform the shape of the formed part, and the original plane will also warp.
2. The influence of surface anisotropy on sheet formability
As mentioned above, the typical manifestation of surface anisotropy is that the force-bearing plate no longer maintains a flat surface and exhibits curvature. Obviously, placing the wool properly during forming to make the formed curvature consistent with the curvature caused by the surface anisotropy will facilitate the forming of the part and increase the allowable deformation; otherwise, the allowable deformation will be reduced. For example, the 1.5mm thick TCIM material has obvious surface anisotropy. When the round hole is flanged, if the side with a greater thickness anisotropy index is the inner surface of the flanging member, the ultimate flanging coefficient may be comparable to that when it is on the outer surface. Large 2.8%.
Due to the surface anisotropy will produce undesirable curvature changes, so in general, it has an adverse effect on conformability and shapeability.

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