Characterization of Angle Dependent Color Travel of Printed Multi-Color Effect Pigment on Different Color Substrates
Color-travel pigments, which exhibit much more extensive color change as well provide angle-dependent optical effect can be used in many industrial products. In present paper the multi-color effect pigment printed on three different foils with different background color (black, silver and transparent) was investigated. The pigment was based on synthetically produced transparent silicon dioxide platelets coated with titanium dioxide. CIEL*a*b* values and reflection of prints were measured by multi-angle spectrophotometer at constant illumination at an angle of 45o and different viewing angles (-15o, 15°, 25o, 45o, 75o and 110o) were used. The measurements of printed multi-color pigment showed that CIEL*a*b* color coordinates varied to great extents, depending on detection angles as well on color of the printing substrate. The study revealed that pigmnet printed on black background obtained significant change in color. The study has also shown that when viewing angle increases, the reflection curves decreases.
The Effect of Spectrophotometer Geometry on the Measured Colors for Textile Samples with Different Textures
Spectrophotometers are usually built based on one of these two kinds of geometry; d/8 (diffuse/8) and 45/0. Considering that measured or observed colors depend on the illuminating and viewing conditions, the 45/0 spectrophotometer geometry or d/8 geometry affects the results. In addition, the sample characteristics such as gloss or texture can also influence the measuring results. Therefore, the effect of geometry will be affected by the characteristics of the sample. In this paper, the effect of spectrophotometer geometry on the result of color measurement is investigated for textile samples with different types of texture. In addition, the effect of texture on the measured colors was compared for two geometries. To this end, 63 polyester samples contained of 9 color centers each of them has 7 different types of texture were used. The spectral reflectance data of the fabrics were measured using two spectrophotometers with different geometry; d/8 and 45/0. Other parameters of the two measuring systems such as the aperture size, laboratory conditions, the sample's direction in front of the spectrophotometer and the number of specimen's layers were equal. The measured values of two instruments were compared. It was shown that the spectrophotometer geometry influences the color coordinates of the samples. The d/8 spectrophotometer with include mode usually gives larger lightness values. C* and H* values are affected by the type of spectrophotometer and this effect is dependent on the color center of the sample. In another part of the present study, the color change via the texture difference was evaluated for each of the two geometries, and the obtained results were compared with each other. It was found that the surface texture of the sample influences the measured color from 0.4 to about 4.8 CIEDE2000 (1:1:1) unit for both two types of the spectrophotometer. Moreover, as same as d/8 geometry, the color change via the texture which is measured by 45/0 shows no acceptable correlation with visual assessments.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME