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In face of the need of the production of new materials for the automotive industry with better performance allied to the concern with environmental issues, aiming to reduce the consumption of fossil fuels, emerged from the decade of 1990, the advanced high-strength steels (AHSS), which reconcile a small sheet thickness and high mechanical resistanc...
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... steels advanced high-resistance (HSS) are widely used today as automotive structural components to improve the energy absorption of mechanical impact (crashworthiness) without the addition of weight to the bodyshell (YAMANO AND IWAYA, 2005). Figure 1 illustrates the evolution regarding the resistance of mentioned steels of high resistance. ...
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... 9. Bauschinger effect and hysteresis circuit Source: Dieter (1981) In the work of Tarigopula et al. (2008), it is possible to view the typical mechanical behavior of dual phase and interstitial free steels with respect to the effect Bauschinger. The comparison between these two steels is shown in Figure 10. It is observed that only for the biphasic steel, the path of reverse deformation follows the lowest levels with relation to steel IF due to effect Bauschinger. ...
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... 7 shows the main models of fold normally used by the industry in the manufacture of parts and components and also by researchers for reproduction and study of the effect springback. Among the models of bending presented in previous pictures, in this present work, was used to bending in the air or bending of three points in the air -Air Bending test, whose schematic representation is shown in Figure 11 (a). In this same figure in (b), are represented the surfaces of the sheet metal after the bending, being that the external surface refers to the portion of the sample, the compressed bottom surface refers to the portion of the sample and on the gripped the middle region of the thickness is neutral axis. . ...
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... Metal Forming (2016) In accordance with Altan (2003), the magnitude of springback is defined by the difference of angles before and after springback, as schematically illustrated in Figure 12. ...
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... electrons are scattered over a trajectory that form a pair of cones, whose intersection with the CCD sensor fluorescent screen form the pair of lines of Kikuchi, as can be observed in Figure 16. These lines are closely related to the sample crystallography, making possible its analysis. ...
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... the ferrite core needs to be deformed considerably more around the rigid martensite to accommodate the deformation applied macroscopically. As is shown in Figure 17 (a), the curvature of the crystalline reticulum is not concentrated in sharp lines, but spreads out on the whole grain. This suggests that dislocations that are associated with this curvature lead to a kind of tempering that is not so strongly isotropic, since the dissipation of the tension by crystalline lattice will depend on the increase of the tangle of disagreements formed by fragmentation of martensite and curvature of ferritic grain. ...
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... suggests that dislocations that are associated with this curvature lead to a kind of tempering that is not so strongly isotropic, since the dissipation of the tension by crystalline lattice will depend on the increase of the tangle of disagreements formed by fragmentation of martensite and curvature of ferritic grain. This contrasts with the remarks made to the steel IF (Figure 17 (b)) to show the absence of any structure aligned or structure of steel bands in DP. In the steel IF, this banding can be responsible for the appearance of cross effect. ...
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... is believed that all systems of slip this material will be affected by the disagreements that are present and thus give rise to a tempering dependent on the tangle or density of dislocations, known as forest hardening, since in DP does not occur the cross effect. Figure 17. Maps of contrast of misorientation maximized (MMC). ...
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... determination of the chemical composition of these materials was executed in the Laboratoire Génie of Production -LGP/ENIT using optical emission spectrometer equipment FOUNDRY-MASTER Xpert, OXFORD Instruments ( Figure 19). ...
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... materials were sectioned in the same sufficient dimensions to the mechanical bending test, i.e., 80 mm x 30 mm and each one of them was placed on the UV light emitter present on equipment and the measurement was automatically performed, being that the percentage by mass of chemical elements present was provided by software coupled to spectrometer. Figure 19. Optical emission spectrometer FOUNDRY-MASTER Xpert, OXFORD Instruments, used to determine the chemical composition of the materials studied in LGP/ENIT Source: Author's own production ...
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... sectioning, small samples cut were submitted to a hot mounting. It was used a embutidora Arotec manufacturer, brand price 30mi, at the Laboratory of Metallography DMT -FEG ( Figure 21). In the LGP -ENIT, was used hot mounting machine CitoPress-1 model, manufactured by STRUERS ( Figure 22). ...
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... test was carried out in a universal test machine INSTRON brand in LGP -ENIT ( Figure 31). Figure 32 shows the device mounted to the sheet metal forming of three points bending in air coupled to a dial indicator gauge to measure the stiffness constant die and allow the reliability of experimental and theoretical subsequently (by simulation with finite elements). ...
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... compositions of the steels obtained in optical emission spectrometer ARC_IF180 ARC_IF200 ARC_BH220 PEUG_IF200 ARC_LC200 PEUG_P220 PEUG_BH220 ARC_DP600 Docol_DL800 ARC_DP780 In Table 3, RT refers to the limit of resistance to traction, LE refers to yield strength, ε% refers to the percentage of elongation, and refers to the elasticity module or Young and Ur refers to the module of resiliency. It is noted in figure 41 that the last 3 steels, biphasic (ARC_DP600, DP780_ARC and Docol_DL800), which have the largest percentages by weight of carbon if compared to the other studied steels (Table 2) Therefore, the greater the resistance of these steels, the greater the module of resiliency and lower the rate of elongation. . Yield strength and tensile strength values with the standard deviation for each one of the 10 studied steels ...
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... Author's own production Figure 50. Comparison between the precision obtained by the LaserLevel application and the respective measurements by ImageJ in Excel platform Figure 51. The Force (kN) x displacement (mm) curve for the Air bending at 30° in steel ARC_BH220 ...
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... average values with their respective standard deviations are presented in Table 7. Table 7. Average degree of misorientation before and after Air bending for steels corresponding to the 2° and 3° sets Figure 103. Occurrence of coincidence sites to the ARC_DP780 steel Source: Author's own production ...
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... and the angles of rotation of misalignment between the two cubic crystalline networks that gave origin to the new lattice between them are 60° and 50,5° respectively. Comparing the biphasic steels (Figures 102 and 103) with the ferrite single-phase steels it is noticed that the presence of martensite in biphasic steels was not able to change the type of site of coincidence, since both for biphasic steels as for steels of single phase, the sites are the same, only varying the intensity of occurrence of each one of them. ...
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... figure 104 shows the average values for the diameter of the grains of all material analyzed. Note that the first three steels (ARC_DP780, Docol_DL800 and ARC_DP600), which represent the 3° set of steels, are those which have the lowest grain sizes. ...
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... regard to the diameter of the grains, in the region of the external surface before air bending, the maximum value reaches 20 µm and falls by half, approximately 10 µm for the region along the thickness before air bending and back to increase to 15 µm after air bending, for this same region. Figure 104. The average diameter of the grains with their respective standard deviation values for steels analyzed before and after air bending in their respective surfaces Source: Author's own production ...
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... air bending After air bending Figure 105. Misorientation of grains in function of the grain size for ARC_LC200 steel. ...
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... of grains in function of the grain size for ARC_LC200 steel. In (a) and (b): region of the external surface and the region along the thickness, respectively before air bending and in (c): the region along the thickness after air bending Figure 106. Misorientation of grains in function of the grain size for PEUG_P220 steel. ...
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... of grains in function of the grain size for PEUG_P220 steel. In (a) and (b): region of the external surface and the region along the thickness, respectively before air bending and in (c): the region along the thickness after air bending Figure 107. Misorientation of grains in function of the grain size for PEUG_BH220 steel. ...
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... of grains in function of the grain size for PEUG_BH220 steel. In (a) and (b): region of the external surface and the region along the thickness, respectively before air bending and in (c): the region along the thickness after air bending Figure 108. Misorientation of grains in function of the grain size for Docol_DL800 steel. ...
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... of grains in function of the grain size for Docol_DL800 steel. In (a) and (b): region of the external surface and the region along the thickness, respectively before air bending and in (c): the region along the thickness after air bending Figure 109. Misorientation of grains in function of the grain size for ARC_DP780 steel. ...
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... between the scatter graphics (degree of misorientation x diameter of grains) and the graphics of the fractions When comparing the graphics present in Figures 105 to 109 with the graphics of Figures 110 to 114, it is noted that there is a correlation between them. ...
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... between the scatter graphics (degree of misorientation x diameter of grains) and the graphics of the fractions When comparing the graphics present in Figures 105 to 109 with the graphics of Figures 110 to 114, it is noted that there is a correlation between them. ...
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... the PEUG_BH220 steel presented a degree of springback intermediary and in turn this material presents a predominance of sub-structured fraction. Based on the Figures 115 and 116, it is noticed that there is a predominance of recrystallized fraction in the region of the external surface and a predominance of fraction deformed in the region along the thickness in materials before air bending. ...
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... the basis of the Figure 116, it is important to note that the region suffers more with the lamination process during the manufacture of steel, is the region along the thickness, since only in this region there is a predominance of deformed fraction. ...
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... after air bending, the sub-structured fraction is predominant for the 5 material analyzed, as to note in Figure 117. 118, 119 and 120 show the analysis of fractions for each one of the sets of steels grouped according to the degree of springback. ...
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... Figure 118 shows the fractions of the structures of the grains for steels of 1° set, and in this case the analysis was performed only before air bending. There is a large difference in percentage of each one of the three fractions for each one of the 2 cases (region of the external surface and the region along the thickness). ...
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... it is possible to say that a same material when subjected to a mechanical stress, the mechanical response of this material in the region of the external surface is different than the mechanical response in the region along the thickness, once that in each of these areas there is an imbalance of the percentages of the fractions, causing grain are prepared in very distinct crystallographic orientations among themselves. Parto of these conclusions can be applied to steels of 2° set ( Figure 119). ...
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... the previous sets, the steels belonging to 3° set ( Figure 120), do not present a very great imbalance between the percentages of fractions for each region analyzed. It is observed the presence, however small, of all fractions in the two regions analyzed. ...
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... to apply a tension in these materials, the mechanical response expected when the tension travels by the external surface is not very different from the mechanical response expected when the same tension reaches the region along the thickness, once that the percentages of the fractions of its regions are not very different between themselves. Figure 119. Structure of grain to the steels of 2° set. ...
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... to the Figure 121, both materials have a tension increase with the increase of the deformation, thus characterizing the hardening. The difference occurs later when in case (a), after having been exceeded stage of flow, the direction of loading is reversed and the material deformed becomes flow on reverse deformation, showing an increase of mechanical resistance with the plastic deformation, since the tension of module σ 1 is greater than σ 0 , being that this type of hardening is classified as isotropic. ...
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... plasticity both for the initial loading as for reverse is controlled by different mechanisms, having as a result the hardening of kinematic type, observed the following for steels of 3° set (WU, 2002). Figure 121. Stress-strain curves to illustrate the types of hardening in materials subjected to reverse deformation. ...
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