In springback analysis, the deformed part must be constrained properly. In an under-constrained model it will be difficult to obtain a converged solution if it is at all possible. An over-constrained model does not necessarily help improve the convergence. In some cases, it may be more difficult to converge due to artificial compressive stress from excessive constraint. This condition can often under estimate the springback amount or distort the shape if the model is badly over-constrained.
The proper constraint should only eliminate all rigid body rotation and translation modes. A properly spaced 3-point constrain method works fine in most cases. The user, however, must exercise caution if a symmetrical boundary condition is already defined in the model. The constraint, similar to a SPC, can be added under the *INTERFACE_SPRINGBACK_SEAMLESS card. The constraints will be added automatically at the beginning of the springback analysis.
the model needed to be constrained properly, properly constrains should be able to make sure that there is no rigid body rotation and translations.