Investigation Of Color Evaluation And Modeling Based On Yarn-dyed Fabrics With Warp And Weft Yarns In Different Color Depths

The color appearance of yarn-dyed fabrics is usually variable and unpredictable due to the various colors of yarns and weaving structures.The dyed yarn may be discarded once its color doesn’t qualify for the requirement.That usually happens since the yarn is dyed before weaving and it is colored in one batch that has a color depth difference.Therefore,it is important to evaluate and predict finally color of these yarn-dyed fabrics to avoid waste of yarns and reduce cost.In this study,in order to reuse the disqualified dyed yarns,the correlation of color depths between dyed yarn and yarn-dyed fabric was investigated.Besides,the correlation between visual evaluation and instrumental measurement based on these yarn-dyed fabrics was also investigated.Finally,a correlation model between visual evaluation,instrument measurement and color depth of warp and weft yarns of yarn-dyed fabrics was established to explore the possibility that the color appearance of the fabric woven from dyed-yarns disqualified in color depths met the requirements.In the first part,yarn-dyed fabric woven from warp and weft yarns dyed by the same dye and in the same color depth(the same depth fabric)was used as the target yarn-dyed fabrics.Colored yarns dyed by the same dye in different color depths(different depths fabric)were prepared to imitate the colored yarns disqualified in color depths.The correlation of color depths between dyed yarn and yarn-dyed fabric was investigated.And the color prediction models of the same depth fabric and different depths fabric were established.The apparent color depth was used as a measurement index to explore the possibility that the color appearance of the fabric woven from dyed-yarns disqualified in color depths met the requirements.It was found that for a plain fabric with 1: 1 structure,when the homochromy index(K)of warp yarn to weft yarn was 0.81-1.24,different depths fabrics had the same color prediction model as the same depth fabrics.And,it was indicated that when the homochromy index of warp and weft yarns within this range,different depths fabrics had the same color appearance as the same depth fabrics.In the second part,the influence of light sources on visual evaluation and the correlation between visual color difference and measured color difference of yarn-dyed fabric samples was analyzed based on the color difference and statistical related parameters obtained from the visual experiments and instrument measurements.Also,a best color difference formula was selected to describe the color difference of yarn-dyed fabrics.In the meantime,the human visual perception for color difference and acceptance tolerance as well as the tolerance range were investigated by combining the homochromy index and color difference of the yarn-dyed fabrics.The results showed that light sources for observers have a slight influence on visual assessment.Color-difference formula CIE2000(2:1:1)was the best among all the formulae discussed with 0.65 and 1.08 color tolerance for perceptibility and acceptability,respectively.In addition,during visual assessment,when the homochromy index K was between 0.80-1.25 for warp yarns and weft yarns,the color difference between the same depth fabric and different depths fabric was all in the color tolerance for perceptibility;When the homochromy index K was between 0.73-1.37 for warp yarns and weft yarns,the color difference between the same depth fabric and different depths fabric was all in the color tolerance for acceptability.Therefore,once the K value was confirmed based on the color requirements,warp and weft yarns with color difference between the K value could be woven to the yarn-dyed fabric,and this fabric can also meet the manufacturing requirement.In the third part,the color prediction model of yarn-dyed fabric woven from warp and weft with different color depths was built by taking the color depth(K/S value)as the measurement index and the homochromy index K as the segment basis.And this model was used in the practice for color prediction and homochromy judgment in the form of an interface program based on the Matlab App program development.The color of the dyed fabric was obtained from the warp and weft yarn colors and the homochromy index,and evaluated according to the color quality requirements to see whether the color of this yarn-dyed fabric meets the requirements.In addition,it was found that for a plain fabric with 1:1 structure woven from different linear density yarns,or yarn-dyed fabrics with different woven structure,the yarn-dyed fabrics woven with unqualified deyd yarns can also have the same color as target fabrics(the color difference was small or the probability of acceptance was high).Therefore,the corresponding model can be established according to the method provided in this thesis to determine the fluctuation range of the color depth of warp and weft yarns.It could contribute to save cost by reusing the disqualified dyed yarns during the weaving manufacturing process.