The strip comparison method, based on the serial exploration method described by Torgerson [Theory and Methods of Scaling; Wiley & Sons (1958); Chap. 7], for the development of near-threshold color difference models was presented and validated with theoretical data by the authors in a previous work. In this study, we investigate parametric effects derived from the use of the strip comparison method on chromaticity-discrimination ellipses around the red CIE color center. The results obtained led to the conclusion that the strip comparison method has little effect on the parameters of the chromaticity-discrimination ellipses determined by the pair comparison method when pairs of patches in the strips are separated by a black line 0.5 mm thick or are separated by 3 mm spacing on a white background and also correlates well with the parameters reported by other authors using the pair comparison method at the threshold.
The ceramic tile industry has become an extremely competitive sector. The entry of new Asian and South American manufacturers into the market is shifting the leadership in production and exports from the traditional clusters of Europe to China, Turkey, and Brazil. In this uncertain environment, enterprises should raise the quality and cut costs by means of new products and processes. Ceramic tiles lightened by carving of a deep back relief could give rise to a generation of new, efficient products. These tiles could be manufactured with fewer raw materials than the traditional ones, which may lead to saving of weight and energy. Additionally, a lighter final product improves working conditions on the shopfloor and at the building site. Nevertheless, lightened tiles are structurally different from traditional ones, and so is their mechanical behavior. Because tiles are constructive elements, it is necessary to know their response under typical loads and assure fulfillment of the valid standards.This paper aims at evaluating the flexural strength (R) of lightened ceramic floorings using solid three‐dimensional modelling and the finite‐element method, establishing a new formula for the application of the international standard ISO 10545 “Ceramic Tiles.” In order to achieve this objective, one reference model and 48 different relief versions were designed, which underwent a simplified computational simulation of the bending test. In accordance with the Rankine criterion, the maximal stresses of each version were calculated, as much as their distribution. Next, we correlated the results defining a new parameter called “normalized thickness,” defined as the thickness that a carved tile should have to behave as a traditional flooring under flexion. This parameter allowed the adjustment of the international standard ISO 10545 to this kind of a product, facilitating their certification and therefore their real introduction in the market. Finally, thanks to the collaboration of the company Keros Cerámica S. A., it was verified that the methodology used was appropriate.
The manufacturing of ceramic tiles is a very complex process, where a wide range of variables has an important influence in the final product. With regard to external appearance, the most of the production defects take place in the decoration station. Nevertheless, these defects are usually detected before baking, when the product is already finished, causing an important loss of effectives. Under this perspective, a mechanism able to detect the printing defects in the green parts would achieve 2 goals: on one hand, the reduction of the nonquality costs since green parts can be more easily recycled; and on the other hand, it would point out the real root cause of the failure by indicating, for instance, which ink is causing the problem. Color Prediction Models (CPM) are mathematical approaches which relate the microscopic distribution of the printed dots of a halftone image with the resulting macroscopic color. Its usage is extended in the field of the Graphic Arts, especially for calibration and fine image reproduction. However, they are barely known in the ceramic tile industry, a sector that keeps many similarities with the Graphic Arts one in terms of decorating. In this paper, we analyzed the prediction quality of 4 successful CPM (MurrayDavies, Yule-Nielsen, Neugebauer and Neugebauer Modified Yule-Nielsen) on 1 and 2 inks halftones printed on ceramic substrates, setting a comparison between them by means of linear and non-linear optimization techniques. Moreover, we proposed a value for the enigmatic"n"parameter on ceramic surfaces, which is said to model the optical dot gain phenomenon.
The ceramic tile industry faces up to a saturated market and needs to offer innovative products constantly, competitive in quality and optimal from the economic and environmental point of view. Ceramic tiles lightened by the execution of a deep back relief could be manufactured with less raw material than the traditional one, which has an effect in the saving of weight and energy. Additionally, a lighter final product improves working conditions on the shopfloor and at the building site. Nevertheless, lightened tiles are structurally different, and so is their mechanical and thermic behaviour. Because it is a constructive element it is necessary to know its response under typical loads and assure fulfilment of the valid standards. This paper aims at the objective of evaluating lightened ceramic floorings employing solid three-dimensional modelling and finite elements method (FEM), establishing an optimal definition of the back relief. In order to achieve this objective, 1 reference model and 56 different relief versions were defined, which underwent 4 structural tests. After deciding that both mass and principal stresses (Rankine criterion), were the magnitudes to consider in the study, the maximal stresses of each version for each test were calculated, as much as their distribution. Next, 4 comparison coefficients were defined and a suitability order was established. Finally, thanks to the collaboration with a ceramic company it was verified that the employed methodology was appropriate. Altogether, it has been concluded that lightened tiles could improve both raw material consumption and structural response simultaneously. A set of fundamental behaviour guidelines has been extracted and could be taken as a basis for the back relief design of any enterprise. Regardless these guidelines, this paper proposes a methodology for the geometric evaluation of floorings that could be extended to other kinds of products and design variables.
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