Analyzing and modeling of short-time dynamic yarn handling processes through the example of high-performance warp knitting

• Applicants: Professor Dr.-Ing. Michael Beitelschmidt; Professor Dr.-Ing. Chokri Cherif
• Subject Area: Lightweight Construction, Textile Technology ; Mechanics
• Term: since 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 394705170

In the textile industry, there have been two major developments in recent years aimed at increasing the production, structural variability and quality of textiles. These comprise the increase in performance of textile machines by higher machine speeds and wider working widths, which leads to more cost-effective production of textile goods, as well as the production of high-precision, requirement-oriented and high-performance technical products from yarn materials such as glass, carbon, aramid and staple fiber yarns. The determination of interactions and dependencies between the different yarn materials, process parameters and the required yarn guiding elements is imperative for a significant improvement and thus homogenization of the yarn run. Hence, the objective of the 1st funding period was to research and model short-term dynamic yarn processing using the example of high-performance warp knitting. The yarn running processes have been evaluated by simulation and measurement methods including extremely short-term dynamic stress scenarios, such as transverse accelerations with resulting transverse and longitudinal vibrations and the associated damping phenomena. In addition, dynamic alternating stresses as a result of the discontinuous stitch formation process and superimposed operating speed-dependent natural vibrations of the working elements in the warp knitting machines were of fundamental importance for the surface formation process. The in-depth analysis of these factors built the basis for the development of a comprehensive yarn running model for individual warp yarns in the high-performance warp knitting machine. The aim of the 2nd funding period is the spatially and time-resolved analysis and modelling of the dynamic behavior of the warp yarns in the complete warp yarn sheet. Additionally, their interactions with each other over the entire working width, the influencing parameters of material, knitted fabric weave, working width, production speed and transient operating cases (machine start, stop) are taken into account. A second objective is the description and development of new yarn tension compensation mechanisms to compensate for the different, highly dynamically doubly alternating yarn tension stresses on each warp yarn within one machine revolution for material-independent utilization of the machine speed of 4400 rpm and, in perspective, increases up to 7000 rpm. A third objective is the modelling of the warp knitting process, the prediction of the pattern-dependent quality and force-elongation properties of the warp knit taking into account non-linearities and hysteresis effects of the materials, elongation rate-dependent characteristic values (friction, force-elongation behavior, damping and edge effects) and the derivation of start setting parameters of the warp knitting machine for a fast pattern change.

• DFG Programme: Research Grants