## 4 Results
### Formability Properties  
Once the model was fitted, it was used as a virtual lab for the realization of several \"experiments\" with the aim of determining the formability properties of the LT and HT bainitic steels. The r-value is calculated, as explained in Section 3.7, using uniaxial tension virtual experiments performed at \(15^{\circ}\) intervals in directions parallel to the sheet plane, between RD and TD. The calculated r-values for each angle \(\alpha\) with respect to RD for different strain levels are shown in Figure 6. The figure also shows the corresponding stress levels. For both materials, these stress levels are very similar for all directions. Only a small decrease around \(30^{\circ}\) and a similar increase at \(75^{\circ}\) are observed, slightly more pronounced in the case of the HT material. The trend is the same independently of the applied strain. When looking at the r-values, the anisotropy is more significant for the LT material, where clear peak and valley are distinguished at \(15-30^{\circ}\) and \(75^{\circ}\), respectively. The behavior of the HT material is quite different, with r-values increasing as the loading direction approaches TD. Since there are no large variations in stress and r-value levels depending on loading direction, it can be concluded that the anisotropy of the material is low. Nevertheless, although subtle, the observed differences will have an important impact. Figure 5: Fitting of experimental tensile curves corresponding to quasi-static experiments in the rolling and transversal directions (**bottom row**) and at high strain rate in the rolling direction (**top row**). The combined \(R^{2}\) value is 0.944. The fitted parameters are listed in Table 4.  
A different set of simulations was performed in which biaxial conditions were imposed, with the goal of calculating yield surfaces and forming limit curves. First, using the uniaxial tests in the RD and TD directions, the \(\theta_{0}\) and \(\theta_{00}\) values were calculated using (23), then simulations were run at regular intervals between both angles. The measured stress levels in directions parallel to RD and TD were then calculated for equal values of plastic work in all the simulations. The isoline obtained for each different value of plastic work corresponds to the projection of the yield surface of the material on the sheet plane for those loading conditions and plastic work value. Obtained yield surfaces corresponding to plastic work levels for specific values of plastic strain during uniaxial tensile deformation along RD, for two different stain rates, are shown in Figure 7. In the figure, both the yield stress and the strain rate direction at that point, indicated by a small vector, can be seen. At the studied strain rates, both materials initially show a response close to the [PERSON] criterion at the beginning of plastic deformation. However, as the plastic work increases, the yield surface changes to adopt a shape closer to the one given by [PERSON]'s criterion. Comparing the yield surfaces of both materials (the results of the other material are represented in each graph using a light grey color), it is seen that this difference is slightly more pronounced for the case of the LT material along TD, while it is more pronounced for the HT material in the direction parallel to RD. Nevertheless, it can be concluded that the response of both materials is very similar. The same trends are observed at quasi-static and high strain rates, but the stress levels are obviously higher at higher strain rates due to the strain rate hardening effect. Finally, the results of simulations under biaxial conditions were also used for the calculation of forming limit curves, following the process described in Section 3.7.