Characterization of twist of fancy yarns using wavelet analysis of sensor signal

Yarn twist variations may cause stripes in the direction of weft yarns or local defects on a fabric surface. Since fast Fourier transform and time analysis cannot directly detect local frequency variations of yarn signal and defect sensors are designed to detect the diameter decreases without considering frequency analysis, no data associated with twist-related frequency changes can be obtained when inspecting Chenille yarn (Cy) defects. This study proposes the prediction of twist level ( T) and twist variations ( ΔT) of Cy whose twist changes in accordance with the spatial period of pile density by using wavelet analysis, allowing localized frequency variations to be obtained. Complex-valued Paul wavelet was used to determine the ΔT of signals with small frequency fluctuations, while Morlet wavelet was addressed for signals with high frequency change. The relation of the signal frequency to the pile yarn density and, correspondingly, twist was modeled by equations. To prevent discontinuities in wavelet cross-spectrum (WCS), the twist simulation signal was generated by equalizing twist oscillation amplitudes without changing their phase. To compare ideal twist to the local twist, another simulation signal demonstrating the ideal twist at sample-specific frequency was generated. The WCS of the simulation signals allowing the segmentation of variation intervals was used for determining ΔT and yarn portions, where the twist is compatible with ideal twist, by establishing correlation between scales and twists. For yarn samples with various T and ΔT types, the T and ΔT results obtained by the proposed wavelet-based algorithm showed the mean absolute relative percentage errors of 1.617% and 37.062%, respectively.

Investigation of tensile strength and elongation properties of chenille upholstery fabrics including recycling polyester yarns

Every day, millions of plastic and polyethylene terephthalate bottles are being thrown away by people. This leads not only to the reduction of landfills and increase in environmental problems but also to pollution of marine and oceans that affect the lives of many living things. Therefore, recycling of waste polyethylene terephthalate bottles with recycling technologies has great environmental importance. In this study, recycled polyester yarns obtained by recycling waste polyethylene terephthalate bottles and standard polyester yarns were used in staple forms, as well as binder and pile yarns of the chenille yarn structure. In this context, 16 different chenille yarns were produced and the production parameters such as rotor speed, spindle speed, and pile density are kept constant by selecting the appropriate values. Then, these chenille yarns were used as weft to produce upholstery fabrics. Tensile strength and elongation tests were applied to the upholstery fabrics, and the results were evaluated statistically. As a result of the tensile strength tests and statistical analyses, it is concluded that the weft breaking strength of all types of woven fabrics, which have 100% recycled polyester in the structures of chenille yarns as weft, is slightly decreased compared to other types, but this decrease is not statistically significant. The use of recycled polyester yarns in the structures of chenille yarns, which are widely used in the upholstery sector, will be beneficial in producing more sustainable and eco-friendly fabrics.

A Theoretical Approach to Twist Design of Chenille Yarn

This study examines the twist design of chenille yarns from theoretical consideration. Four kind of chenille yarns were selected for practice validation. The results indicate that there was little deviation between the twist under theoretical approach and the actual tested values; linear density of centre yarn and pile yarn, pile yarn density have significant effects on the twist design of chenille yarns.