Geometrical features

The final shape of the flange is another important factor to compare the feasibility of both processes. The geometrical feature of flanges obtained in tests with a 61 mm pre cut hole diameter and a 8 m

rpm are analysed.

Figure 5.7 details both specimens before they were processed. They were cut along the meridional direc

scanned using the scanner model 3D Geomagic Capture to

shape and thickness evolution.

Figure 5.7 Flanged specimens with a pre cut hole with a diameter of 61 mm and 8 mm

⁄ , ̅⁄ and 3

evolution, the results concluded that single enhancement in formability

quantified at approximately 40% in terms of relative flange heigh approximately 30% in terms of relative thickness reduction ( improvement does not manifest when using traditional

flangeability, which reflects the fact that this parameter does not reproduce the mechanism of failure in hole flanging by SPIF.

5.4. Geometrical features

The final shape of the flange is another important factor to compare the feasibility of both processes. The geometrical feature of flanges obtained in tests with a 61 mm pre cut hole diameter and a 8 m

rpm are analysed.

details both specimens before they were processed. They were cut along the meridional direction of the flange and polished. The flange profiles were

using the scanner model 3D Geomagic Capture to

shape and thickness evolution.

Flanged specimens with a pre cut hole with a diameter of 61 mm and 8 mm tool radius by SPIF at 0 rpm (a) and press working (b)

and LFR versus evolution, the results concluded that single

enhancement in formability regarding the press working, which quantified at approximately 40% in terms of relative flange heigh approximately 30% in terms of relative thickness reduction ( improvement does not manifest when using traditional

flangeability, which reflects the fact that this parameter does not reproduce the failure in hole flanging by SPIF.

Geometrical features

The final shape of the flange is another important factor to compare the feasibility of both processes. The geometrical feature of flanges obtained in tests with a 61 mm pre cut hole diameter and a 8 mm tool radius for press working and SPIF at 0

details both specimens before they were processed. They were cut tion of the flange and polished. The flange profiles were

using the scanner model 3D Geomagic Capture to

shape and thickness evolution.

Flanged specimens with a pre cut hole with a diameter of 61 mm and 8 mm tool radius by SPIF at 0 rpm (a) and press working (b)

versus HER are visualized. Comparing their evolution, the results concluded that single-stage SPIF exhibits a significant

regarding the press working, which quantified at approximately 40% in terms of relative flange heigh approximately 30% in terms of relative thickness reduction ( improvement does not manifest when using traditional

flangeability, which reflects the fact that this parameter does not reproduce the failure in hole flanging by SPIF.

Geometrical features

The final shape of the flange is another important factor to compare the feasibility of both processes. The geometrical feature of flanges obtained in tests with a 61 m tool radius for press working and SPIF at 0

details both specimens before they were processed. They were cut tion of the flange and polished. The flange profiles were

using the scanner model 3D Geomagic Capture to

Flanged specimens with a pre cut hole with a diameter of 61 mm and 8 mm tool radius by SPIF at 0 rpm (a) and press working (b)

are visualized. Comparing their stage SPIF exhibits a significant regarding the press working, which is approximately quantified at approximately 40% in terms of relative flange height (

approximately 30% in terms of relative thickness reduction ( ̅

improvement does not manifest when using traditional LFR as a measure of flangeability, which reflects the fact that this parameter does not reproduce the

The final shape of the flange is another important factor to compare the feasibility of both processes. The geometrical feature of flanges obtained in tests with a 61 m tool radius for press working and SPIF at 0

details both specimens before they were processed. They were cut tion of the flange and polished. The flange profiles were

using the scanner model 3D Geomagic Capture to measure their local

Flanged specimens with a pre cut hole with a diameter of 61 mm and 8 mm tool radius by SPIF at 0 rpm (a) and press working (b)

are visualized. Comparing their stage SPIF exhibits a significant is approximately

t (ℎ⁄ ) and

̅ ₃

⁄ ). This as a measure of flangeability, which reflects the fact that this parameter does not reproduce the

The final shape of the flange is another important factor to compare the feasibility of both processes. The geometrical feature of flanges obtained in tests with a 61 m tool radius for press working and SPIF at 0

details both specimens before they were processed. They were cut tion of the flange and polished. The flange profiles were measure their local

Figure 5.8 displays the flange profile of both specimens. The continuous red line represents the theoretical internal profile of the flange. The distortion is visible in both cases. In the SPIF case, the flange accurately reproduce the theoretical shape at the base and shows a slight inward distortion at the wall. This wall distortion is primarily attributed to the springback of the flange but can also be influenced by the tool deflexion that is exhibited to a certain extent in this process. In the case of press working, although distortion of the wall is similar or even seems to improve regarding the incremental case, the flange shows an important springback at the base. This springback is directly related to the blank-holder force and clamping condition during the tests. This distortion may be improved by increasing the blank-holder force and modifying the clamping system. However, this analysis is beyond the scope of this study, which was originally focused on the comparative evaluation of the formability between both hole flanging processes.

Figure 5.8 Comparison of flange profile from specimens with a 61mm pre cut hole diameter and 8 mm tool radius by SPIF at 0 rpm (left) and press working (right)

The thickness distribution versus the flange height in both tests are shown in Figure 5.9. As discussed in section 0, the thickness distribution in the incremental flange is considerably more irregular than that in press working, as a result of the high strain gradient exhibited in the meridional direction in this process (see Figure 5.2). The large thickness reduction obtained around the middle of the flange is also observed.

According to the Figure 5.9, the local and incremental deformation induced in the single-stage SPIF can intensively stretch the material, which enables higher and thinner flanges for a given HER parameter. Conversely, the conventional hole flanging process provides shorter but thicker (more robust) flanges for an identical specimen. Thus, the practical application and service requirements of the flange will determine the more suitable process in each case.

process to improve the material distribution during a flanging operation. As highlighted by several researchers (Morales-Palma et al.,2017, Skjoedt et al., 2008, 2010, Verbert et al.,2008, Duflou et al.,2010, Liu et al.,2014), multi-stage

strategies are able to control the excessive thinning and can improve the dimensional accuracy of the flange. However, apart from an increase in the process complexity, the main drawback is the notable increase in process time as the number of stages (steps) increases.

Figure 5.9 Comparison of flange height and thickness for specimens with a 61mm pre cut hole diameter and 8 mm tool radius by SPIF at 0 rpm and press working