Study On The Computer-aided Design And Simulation Of Warp Knitted Plush Fabric

Having a large proportion of warp-knitted fabrics,the plush fabrics are widely used in home textiles,fashion materials and automobile decorations.The recent development of electronically driven technology and piezo jacquard technology makes more advanced patterning possibilities for plush fabrics,which offers consumers more access to high-grade and customized plush products.Because of this higher requirement,a more advanced and efficient design approach is needed,which usually refers to a computer-aided design(CAD)system.Therefore,this work firstly conducted a further research on basic knitting principle and jacquard technology of warp-knitted plush fabrics which were then represented with mathematic matrixes.Afterwards,a simulation approach was proposed based on study on loops structures and visualization method of piles.Then with this approach,a CAD system was developed for designing and simulating warp-knitted plush fabrics,which has powerful functions of design and simulation to enhance development competitiveness and improve the informatization.A study was done on knitting theory of plush products on machines with single-needle bar and double-needle bars to conclude the formation method of jacquard plush effect.By employing mathematic matrixes to describe the information of threading cycle,lapping movement and jacquard bitmap,this work concluded an algorithm for judging plush areas and non-plush areas and then built the basic CAD design model as a basis for further fabric simulation.The loops modeling process included defining geometric key points,drawing loops path and generating 3D loops.After analyzing the geometrical features of interlaced loops in a fabric,a stitched loop modeling method was presented,in which it was divided into four segments including the loop arc,loop arms,loop feet and the underlap.For the inlay structure,it was divided into two parts,the underlap and the underlap arc.Geometries of loops were positioned by key spacial points and their z coordinates were set according to their spatial arrangement from the side view.To simulate deformation behavior of loops in a fabric,a mass-spring model was built and the elastane force on massless springs was analyzed for calculating shifts of loops particles and final position when balanced.This physically simulation method received a more realistic result.After balanced positions of loops particles achieved,a Cardinal spline curve was used to form yarn path through particles and key geometric points based on specific geometric parameters.Merits of the Cardinal spline curve were concluded by being compared with approximate spline curves.Moreover,the effect from geometric parameters on spline curves formation was also analyzed.With the yarn path formed,a sweeping method was proposed for generating 3D loop surface.This method constructed tangent rotating recursion frames along the path curve and rotated these frames according to the tangents of the path curve.Tangent rotating recursion frames efficiently solved possible faults when sweeping by a sharp angle.For simulating 3D plush appearance,a method was proposed based on multi-layer slices.According to piles geometries in a fabric,this work formed section slices and axis slices of piles and then presented their generation in geometry shader.The selection of different slices was based on the observation in order to eliminate visual interstice when observation is parallel to the slice plane.To make the simulation of random piles more realistic,fractal noises was taken and a mapping algorithm was given between the textured noises and the lean angles of piles.When rendering textured slices of piles,this work generated shadow effect with multi-layers and used percentage closer filter approach to antialias the shadow of simulated piles for enhancing the sense of spatial reality.The simulation was implemented in a pixel shader on the basis of a lighting model with shade.Based on the researches done above,a CAD system was developed for designing and simulating warp-knitted plush fabrics by using graphical interfaces of GDI and DirectX in Visual Studio environment.This system has visually interactive design interfaces of threading,lapping and jacquard patterns.It also has function windows for defining parameters of threading,lapping,techniques and yarn configurations.It can be conveniently used for designing jacquard plush fabrics on both single-needle bed and double-needle bed machines.Efficiency and practicability of the simulation method was proved by comparing simulation results and real knitted fabrics.The CAD system in this work can help designers efficiently develop new products and moreover,with the exported simulation images,it can also offer references for realizing 3D virtual display of plush garments.