Papers by Keyword: Hot Band

Abstract: The distribution of temperature on the rubbing surface is an important factor influencing the lifetime of a brake disc. With a copper-base sintered brake pad and a forge steel disc, up-to-brake experiments have been conducted on a full-scale test bench at a highest speed of 200 Km/h and a maximum braking force of 22.5 KN. The temperature distributions on brake disc surface have been acquired by an infrared thermal camera, and the contact pressure on the contact surface of the friction pair has been calculated by the finite element software ABAQUS. The results show that the area and thermal gradient of the hot bands increase with the increase of braking speed and braking force. The hot bands occur in priority at the radial location of r=200 mm and r=300 mm, and move radially in the braking process. The finite element modelling calculation indicates that the distribution of the contact pressure on the disc surface in radial direction is in a "U"-shape. The maximum contact pressure occur at the radial locations of r=200 mm and r=300 mm, and the minimum contact pressure occur in the vicinity of the mean radius of the disc. The conformity of contact pressure distributions with the practical temperature evolutions indicates that the non-uniform distribution of the contact pressure is the factor resulting in the appearance of hot bands on the disc surface.

Abstract: Optical absorption of orthorhombic and hexagonal manganites RMnO3 (R= Pr3+, Gd3+, Sm3+, Eu3+, Ho3+, Tm3+, Er3+, and Yb3+) were studied in polarized light in the near- and mid-infrared range for the temperature range 80 - 300 K. Several spectral features associated with 4f-4f transitions of R3+ ions were found in the transparency window of RMnO3. Anisotropy of the absorption spectra in the range of multiplet 4f-4f transitions and changes in populations of the multiplet levels with temperature were observed.

Abstract: Non oriented electrical steels are soft magnetic materials used in the core of electrical motors. No preferential anisotropy of the electrical texture in the rolling plane is desired. Nowadays these special steels are mainly alloyed with Si, Al and some additives to improve the magnetic properties and to reach a good of formability. For (Si, Al)-concentrations higher than 2 wt.% the α- γ-α phase transformation is suppressed, resulting in a bcc crystalline structure from liquidus to room temperature. These electrical steels, which will be discussed in the paper, exhibit the lowest values of the magnetic losses. Hot rolling of FeSi electrical steels has been found to be one of the fundamental steps in producing these materials with optimum properties. The resulting properties, as well known, are determined by the type of magnetic textures and the structural inhomogeneities. Electron Backscattered Diffraction (EBSD) is a reliable tool for microstructural and texture characterization of different materials. Two compositions of electrical steel are studied by optical microscopy and EBSD, with special attention paid to characterize the grain morphology and its texture through thickness.