A number of amphiphilic N-isopropylacrylamide (NIPAAm) oligomers and polymers with a S-1-dodecyl-Sʹ-trithiocarbonate (DTC) and an amino terminal group were prepared using RAFT polymerization: DTC-NIPAAm 13-NH 3 Cl (1), DTC-NIPAAm 61-NH 3 Cl (2), DTC-NIPAAm 78-NH 3 Cl (3), DTC-NIPAAm 119-NH 3 Cl (4). and DTC-NIPAAm 274-NH 3 Cl (5). Aqueous solutions of 1-5 became cloudy upon heating at pH 10, while 1-4 did not exhibit thermosensitivity at pH 7.0, instead forming stable rods and vesicles in aqueous solution. Nanorods and nanosquares were obtained from metal cyanide complexes of 1 and 2, both of which had low degrees of polymerization, and aqueous solutions of these nanocomposites became cloudy at pH 7.0. The electrostatic interactions between the amine segments and the anionic metal cyanide complexes as well as the low degree of polymerization in the vicinity of approximately 100 were both found to have a significant role in the morphology and thermoresponsiveness of the hybrids. These hybrid NIPAAm oligomer/metal cyanide complexes may allow the design of flexible, functional supramolecular systems in aqueous solutions.
In this study, the effect of the material anisotropies of hot-rolled high-strength steel sheet on localized deformation behavior in hole expansion test has been investigated experimentally. First, the hole expansion test with the circular hole has been conducted to investigate the effect of anisotropies of material properties on the localized deformation behavior around the hole edge. Next, the hole expansion test with the oval hole has been conducted to investigate the effect of the major axis direction of the oval hole on the localized deformation behavior around the hole edge. As a result, it was clarified that the effect of anisotropies of r-value and n-value on the localized deformation behavior is strong, especially the anisotropy of n-value.
In this study, the circular hole expansion process of high-strength steel sheet is numerically simulated using FE analysis with Hill48 quadratic, Gotoh’s fourth order, Yld2000-2d and Yoshida’s sixth order polynomial yield function. The effects of anisotropic yield functions on local reduction of thickness are evaluated. The thickness distribution around the circular hole edge at just before necking depends on the initial hole diameter. When the initial hole diameter is relative large, the simulation results give almost same thickness distribution among different yield functions. While the initial hole is relative small, individual characteristics of yield function becomes clear and the sixth order yield function gives the best prediction.
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