Abstract:

Objective This study investigates the evolution of the stress-strain field during the continuous open-width printing and dyeing of weft knitted fabrics, which are highly susceptible to tension fluctuations, width shrinkage, and buckling. Given the unique mechanical properties of knitted fabrics, conventional tension control models and equipment designs often fail to meet the requirements for low tension and small deformation processing. This research focuses on developing a finite element dynamic model to accurately simulate the spatiotemporal evolution of stress-strain field during continuous processing, providing theoretical support for designing equipment and low-tension control models.
Method A macroscopic constitutive model for weft knitted fabrics was developed using the small parameter perturbation method to derive the elastic tensor, which was further determined for the material through finite element calculations. A coupled rigid-flexible finite element dynamic model was developed to simulate the continuous processing of knitted fabrics, including interactions with rollers. The model was validated through the finite element dynamic simulation and experimental results. The analysis covers tension distribution, deformation behavior, and the relationship between roller configurations and fabric morphology changes.
Results The results indicate that tension distribution in the width direction of the fabric is uneven during processing. The edge areas experience higher and more stable tension, while the central areas exhibit alternating width-wise stress patterns, leading to buckling. Widthwise shrinkage is primarily controlled by active rollers, where larger wrap angles can reduce shrinkage significantly. In contrast, passive rollers and idle zones have a minimal impact on shrinkage but considerably affect the duration of tension fluctuations due to their inertia. Furthermore, the application of passive rollers with variable damping properties improves the stability of tension transmission, preventing excessive fluctuations that could affect fabric quality. The study shows that active rollers and their wrap angles of fabric can significantly enhance tension uniformity and reduce morphological issues. Shortening the idle zone length and optimizing the roller surface curvature are effective measures to alleviate stress distribution imbalances and reduce the happening of wrinkle. By the finite element dynamic simulation and experiment, it shows that combination of mechanical adjustments and advanced control strategies will contribute to a more uniform tension distribution across the fabric width and effectively mitigates the risk of widthwise shrinkage and central buckling. These improvements are crucial for ensuring higher product quality and reducing defects during processing. Overall, the research provides a reliable foundation for future equipment design and tension control model enhancements aimed at accommodating the unique mechanical characteristics of knitted fabrics in continuous printing and dyeing systems.
Conclusion The study comprehensively reveals the spatiotemporal evolution of stress-strain field during open width printing and dyeing process. The findings emphasize that optimizing roller configurations, such as increasing active rollers, adjusting wrap angles, and employing variable damping passive rollers, can improve tension uniformity and reduce shrinkage and buckling. These measures enhance system stability and product quality. Future research will focus on refining the simulation model to predict post-winding fabric morphology more accurately and expanding experimental validation to ensure the broader applicability of the proposed control strategies. The study provides valuable theoretical guidance for designing advanced equipment and control systems tailored to the unique characteristics of knitted fabrics.

Key words: knitted fabric, tension control, stress-strain field, deformation, rigid-flexible coupling, open width printing and dyeing, width shrinkage