Author Contributions
Conceptualization, A.N., O.H., H.S. and H.K.; methodology, A.N. and J.D.; software, A.N.; investigation, A.N. and J.D.; resources, O.H., H.S. and H.K.; writing—original draft preparation, A.N.; writing—review and editing, J.D., O.H., H.S., H.K.; visualization, A.N.; supervision, O.H., H.S., H.K.; project administration, O.H.; funding acquisition, O.H., H.S., H.K. All authors have read and agreed to the published version of the manuscript.
Figure 1.
Manufacturing process of the hot-bent uniaxial specimen: (a) taper of the planar twin-roll cast magnesium sheets; (b) hot-bent process; (c) assembly for mechanical testing with the clamping jaws, the anti-buckling device, the extensometer, and the hot-bent uniaxial specimen.
Figure 2.
Hot-bent uniaxial specimen: (a) Geometry details of the hot-bent uniaxial specimen and (b) the test setup for quasi-static and cyclic tests.
Figure 3.
Verification of the hot-bent uniaxial specimen: (a) normal stress field of a FEM analysis of a quarter model of the hot-bent specimen; (b) plot of the stress over the path ; (c) plot of the stress over the path ; (d) strain field , measured with DIC, of the hot-bent specimen with marked gauge area at an extensometer strain .
Figure 4.
EBSD orientation maps with a view in the ND: (a) the as-received material with a scanning step of ; (b) the hot-bent material of the tension layer; (c) the compression layer. The scanning step of the EBSD maps of the hot-bent material from the tension layer and the compression layer is and , respectively.
Figure 5.
(0002) Pole figures: (a) from the as-received material; (b) the hot-bent material of the tension layer; (c) the hot-bent material of the compression layer. The data for the pole figure is obtained by an EBSD measurement with a scan size of × (TD × RD).
Figure 6.
EBSD measurement to detect tension twins: (a) EBSD orientation map with view in ND from the hot-bent material of the compression layer with a scanning step of ; (b) band contrast with detected tension twins (misorientation angle (86.3 ± 5)°, marked with blue color.
Figure 7.
Schmid factor maps for basal slip (a) from the as-received material with respect to a possible load in RD and (b) TD; (c) of the hot-bent material from the tension layer with respect to a possible load in RD and (d) TD; (e) of the hot-bent material from the compression layer with respect to a possible load in RD and (f) TD.
Figure 8.
Engineering stress–strain curves from strain-controlled uniaxial tests with the as-received and the hot-bent material in RD and TD: (a) engineering stress strain curves of the uniaxial tension tests; (b) engineering stress strain curves of the uniaxial compression tests.
Figure 9.
Strain field of a hot-bent uniaxial specimen with an extensometer strain measured with DIC. The BTG, the anti-buckling device, and the extensometer are marked. The length scale starts at the beginning of the transition radius.
Figure 10.
3D and 2D -- fatigue diagrams including the results from the fatigue tests of the hot-bent specimen, the regression surface (green color), and the two 2-times error planes (red color). For the fatigue diagrams, the mean effective strain amplitude is used.
Figure 11.
3D and 2D -- fatigue diagrams including the results from the fatigue tests of the as-received specimen, the regression surface (green color), and the two 2-times error planes (red color). For the fatigue diagrams, the mean effective strain amplitude is used.
Figure 12.
3D and 2D -- fatigue diagrams including the results from the fatigue tests of the hot-bent and as-received specimens, the regression surface (green color), and the two 2-times error planes (red color). For the fatigue diagrams, the mean effective strain amplitude is used.
Table 1.
Chemical composition of the AZ31B sheet metal in weight percent (
) [
26].
Mg | Al | Zn | Mn | Cu | Si | Fe | Ni | Ca | Other Impurities |
---|
balance | 2.75 | 1.08 | 0.368 | 0.00262 | 0.0187 | 0.00282 | 0.00038 | 0.00041 | <0.004 |
Table 2.
Results of the strain-controlled tension test, in which the strain at the outer radius and inner radius in the gauge area are measured with strain gauges to determine the superimposed bending stress .
(%) | (MPa) | (%) | (%) | (MPa) |
---|
0.100 | 41.1 | 0.100 | 0.0900 | 2.05 |
0.200 | 82.1 | 0.210 | 0.180 | 6.16 |
0.300 | 123 | 0.320 | 0.290 | 6.16 |
Table 3.
Results of the yield stresses and the Young’s moduli E from the uniaxial tension and compression tests. These tests are carried out with the as-received and the hot-bent material in RD and TD.
| Uniaxial Tension Tests | Uniaxial Compression Tests |
---|
ID | (MPa) | (MPa) | (MPa) | (MPa) |
hot-bent, RD | 177.1 | 41,067 | 128.3 | 40,862 |
as-received, RD | 178.1 | 42,673 | 122.8 | 43,880 |
hot-bent, TD | 142.5 | 38,945 | 124.9 | 38,422 |
as-received, TD | 150.6 | 42,034 | 116.4 | 42,879 |
Table 4.
Applied extensometer strain amplitude , extensometer strain ratio , test frequency f, highly strained volume , mean effective strain amplitude , and the numbers of cycles to failure of the strain-controlled cyclic tests. The tests are performed on the hot-bent specimens.
Specimen ID | (%) | (−) | f (Hz) | (mm3) | (%) | (−) |
---|
UG12-060 | 0.35 | −1 | 1 | 132 | 0.344 | 14,377 |
UG12-061 | 0.35 | −1 | 1 | 523 | 0.334 | 15,075 |
UG12-062 | 0.45 | −1 | 0.5 | 43.0 | 0.469 | 2890 |
UG12-063 | 0.45 | −1 | 0.5 | 23.3 | 0.470 | 4619 |
UG12-065 | 0.55 | −1 | 0.2 | 24.4 | 0.595 | 807 |
UG12-071 | 0.55 | −1 | 0.2 | 81.7 | 0.532 | 1645 |
UG12-067 | 0.8 | −1 | 0.1 | 46.5 | 0.885 | 435 |
UG12-072 | 0.8 | −1 | 0.1 | 16.0 | 0.822 | 535 |
UG12-068 | 1.2 | −1 | 0.1 | 32.2 | 1.21 | 163 |
UG12-070 | 1.2 | −1 | 0.1 | 4.99 | 1.15 | 224 |
Table 5.
Determined material values , , and for the hot-bent material, the as-received material, and the combination of the hot-bent and as-received material. In addition, the coefficient of determination is given to estimate the quality of the regression.
Specimens | (%) | (−) | (−) | (−) |
---|
hot-bent | 6.13 | −0.310 | −0.0189 | 0.968 |
as-received | 6.30 | −0.279 | −0.0460 | 0.942 |
hot-bent & as-received | 4.94 | −0.266 | −0.0231 | 0.944 |