Abstract:

Objective The technological structure of weft-knitted two-side transfer fabric is complex and changeable, and the existing system is difficult to intuitively display the structural characteristics of the fabric during design and development. A multilayer mass-spring structure model suitable for weft-knitted two-side transfer fabric is proposed to simulate the structure of weft-knitted two-side transfer fabric.

Method Firstly, the geometric structure models of looping, tucking and transfering are established, and then the structural characteristics of weft-knitted two-side transfer fabric are analyzed. Based on the conventional mass-spring model, the multilayer mass-spring model is constructed. Then the final position of the multilevel mass-spring model is solved by Newton's second law and Velocity-Verlet numerical integration method. Finally, an algorithm flow of weft-knitted two-side transfer fabric structure simulation is proposed.

Results An ideal loop model is established for the basic unit of weft-knitted two-side transfer fabric, including looping, tucking and transferring. According to the documents and the actual fabric characteristics, the relevant parameter relationships of the ideal looping model are as follows: w₁=4w₂=1.3w₃=2w₄,h₁=0.4h₂=1.2h₃. According to the different types of loops, the parameter values of each type value point will change. By adjusting the model parameters of the looping, the loop models of the tucking structure and the transferring structure are obtained. Among them, the model parameter T of the transferring coil is the sum of the total width of the loop w1 and the distance between the vertical lines of the positive and negative adjacent loop. The actual shape of the loop in the weft-knitted two-side transfer fabric were designed and woven, the position of the loop in the fabric loop shifting, and the structural features of looping, tucking and transferring in the fabric is analyzed. At the same time, the force of the adjacent loops in the fabric changes, causing the deformation of the surrounding loops. The multillayer mass-spring structure model is established and the appropriate numerical integration method is selected to solve the dynamic equation, and the loop structure deformation of weft-knitted two-side transfer fabric is analyzed. Finally, the simulation algorithm flow of weft-knitted two-side transfer fabric is put forward to determined the final position of each particle in the multi-layer spring-mass model, combined with the loop structure model of weft-knitted two-side transfer fabric, it realizes the structure simulation of weft-knitted two-side transfer fabric using Visual Studio, and the simulated fabric pattern is clear, with obvious concave-convex effect.

Conclusion In this paper, according to the loop structure characteristics of weft-knitted two-side transfer fabric, three eight-point loop geometric structure models of looping, tucking and transferring are fitted by NURBS curve. Based on the analysis of the structural characteristics of weft-knitted two-side transfer fabric, a multilayer mass-spring structure model reflecting the connection of loops in series in three-dimensional space is constructed on the basis of the conventional spring-mass model. According to Newton's second law, the force analysis of the multil ayer mass-spring structure model is carried out, the Velocity-Verlet numerical integration method is adopted to solve the dynamic equation, and through collision detection, the phenomenon of unreasonable string between loops in the structure simulation of weft-knitted two-side transfer fabric is effectively prevented. The structure simulation of weft-knitted two-side transfer fabric is realized by using the model and the applied method.

Key words: weft knitting, two-side transfer fabric, mass-spring model, structural simulation, stitch geometric structure model