Papers by Keyword: R-Value

Abstract: The scope of the paper is to understand the compliance of the prescriptive requirement of Energy Conservation Building Code, 2007, ECBC-2007. It also reveals information of product and application that comfortably exceed the thermal requirement while maintaining high standard of Fire-safety and acoustic values. The environmental objective is also met by the product/application and that helps to satisfy requirement of project’s Green certification.

Abstract: The r-value is defined as the ratio of the width strain to the thickness strain under uniaxial tensile loading. The r-value can be defined for each grain in polycrystalline metal during plastic deformation. It was pointed out that r-value of a grain affects the surface roughening of polycrystalline metal, and hence also affects the formability of thin sheet metal. On the other hand, it was shown that by using a rate-type constitutive relation for crystal slips the effect of the number of active slip systems on the yield curves is clarified. In the present paper, the relation between r-value of a grain and its operating slip systems in polycrystalline metals is studied.

Abstract: Electro-deposited pure iron has a very sharp and isotropic <111>//ND fiber texture and a needle shaped grain elongated in the ND. This pure iron exhibits an r-value of over 7, and it is difficult to explain such a high r-value only from the texture. Specific {110} plane slips, which are perpendicular to the sheet surface, exclusively act in this material and this limitation of the active slip system is the main mechanism behind the extraordinarily high r-value. Thus, tensile deformation by this slip system doesn’t require a decrease in thickness. In this study, the mechanism of this slip system limitation is investigated. Because both the {110} slip plane and grain boundary are perpendicular to the sheet surface, the slip plane can easily connect with adjacent grains. This good continuity of slip plane with adjacent grain may have an influence on the choice of slip system.

Abstract: The r–value is defined as the ratio of the width strain to the thickness strain under the uniaxial tensile test of the sheet metal. Based on r-value of grains, a model of plastic deformation of polycrystalline metal and surface roughening after plastic deformation was proposed in the previous paper. Meanwhile, Marciniak and Kuczynski proposed the so-called M-K model which give the analytical estimation of the formability of sheet metal under biaxial stretching considering a certain irregularity of the thickness of the sheet metal. Yamaguchi et al showed that the experimentally measured surface roughness may correspond to the surface irregularity suggested in the M-K model. In the present paper, the formability of sheet metal under biaxial stretching is analyzed based on the previous analysis of surface roughening caused by the difference of the r-value in the sheet metal.

Abstract: C-Mn-Cr-Mo dual phase steel was piloted in laboratory. OM, SEM, tensile tests and XRD were used to characterize the microstructures, mechanical properties and to determine the texture. The results indicate that when annealed at 860 °C, the tensile strength of the tested steel is 440 MPa, elongation and r value exceed 35% and 1.4, respectively. With the temperature increases from 820°C to 860°C, the average grain size of ferrite increases and ferrite trends to be uniform gradually, therefore, the r value increase gradually. When the temperature is higher than 860°C, bainite forming results in reducing of r value. Al could weaken the tendency of heterogeneous deformation and modified the annealing texture by refining hot-rolling grain size. Mo-based carbides existed in hot-rolled sheet developed {111} texture in the stage of ferrite recrystallization, then re-dissolved in intercritial annealing stage so as to improve hardenability.

Abstract: Deep drawing dual phase steel was designed and trial-produced in the laboratory. The microstructure and recrystallization texture was studied using OM,TEM and XRD techniques. The results show that texture components typically in DP steels are γ (<111>//ND) and α (<110>//RD) fibers, which is partly attributed to the precipitation of Mo-based carbides in hot-rolled plate. Besides, {554}<225> and {332}<113> texture components are also founded in deep drawing DP steels, which are beneficial to improvement of drawability. With the increasing of annealing temperature, the tensile strength and elongation of DP steels are increased and decreased, respectively, and the r value is reduced slightly.

Abstract: Formability and mechanical properties of metal sheets are related to on their textures. It has been studied to improve the formability and change the texture of the AA 3003 Al alloy sheets after asymmetric rolling. Asymmetrically rolled Al sheets are shown the high intensity of the distorted cube texture, {001}, distorted rotated cube texture, {001}, weak γ-fiber, ND//, {123}, {120} and {120} components. After the asymmetrically rolled AA 3003 Al alloy sheets, the plastic strain ratios of the asymmetrically rolled Al alloy sheets were about 1.7 times higher than those of the initial Al sheets. The variation of plastic strain ratios of the asymmetrically rolled Al alloy sheets could be related to the change of texture components through asymmetrical rolling in AA 3003 Al sheet.

Abstract: Texture of Al alloy is affected to the formability and mechanical properties. In this paper, it was studied that the change of texture and formability of AA 1050 Al alloy sheets which were asymmetrically rolled. Asymmetrically rolled Al sheets showed that the distorted rotated cube texture, {001}, γ-fiber, ND// and {120} and {120} components were increased. The change of texture components after the asymmetrical rolling could be affected to the variation of plastic strain ratios of the asymmetrically rolled AA 1050 Al alloy sheets.

Abstract: The texture, microstructure, plastic strain ratio r value, elongation, strain hardening index n, the value of cupping test I_E, and the correlation between r value and the other formability indices of two automotive aluminum alloys sheet 6016 and 6181, and commercial pure aluminum sheet were investigated. The results showed that the recrystallization textures of three aluminum alloys sheet are similar to each other, which mainly contain cube component. However, the r and n value, elongation, and I_E of three aluminum alloys sheet are different from each other evidently, and there is no correlation between texture and r value, and the other formability indices except the n value. The large quantity of second-phase particles in the aluminum alloy matrix has very important effect on both the r value and the formability of aluminum alloy sheet.

Abstract: Electro-deposited pure iron has a quite sharp and isotropic <111>//ND fiber texture and a needle-shaped grain elongated in ND. This pure iron shows an r-value exceeding 7, which is difficult to explain from the texture alone. In this study the deformation behavior of electro-deposited pure iron was investigated to reveal the mechanism behind the extremely high r-value. The post-deformation surface slip lines indicated that the particular <110> plane slips, which are perpendicular to ND, exclusively act in the specimen. The tensile deformation caused by this slip system does not require any decrease in thickness, hence the extraordinary high r-value is mainly attributable to this limitation of the active slip system. Presumably, the needle-shaped microstructure affected the limitation of the slip system.