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چكيده انگليسي :

Isfahan University of Technology Investigation into the Warp Knitted Loop Geometry using a Mechanical Model Marzieh Javadi Toghchi Email address m javaditoghchi@tx iut ac ir Department of Textile Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor s Name and Email address Dr Saeed Ajeli sajeli@cc iut ac irAbstractDetermining the loop form is the key issue in the knitting technology The loop form and its dimensionalproperties are very important to predict the knitting dimensional characteristics and some of its properties suchas tensile behavior and drape The shape of knitting loop is predicted by Elastica shape in the most previous studies The loop has 3D shape inthe warp knitted fabric so a 3D model of loop could provide a better explanation of loop geometry In this project the finite element modeling with Non linear geometry and static Riks analysis for an elastic rodwas employed to estimate the 2D and 3D Elastica shapes under post buckling condition A 3D Elastica formswhen two equal moments in opposite directions are employed in addition to a pair of balancing forces The casestudy is in ill condition and the Riks method is useful for unstable cases and can speed up convergence in ill conditioned cases without any instability In fact the modified Riks method is chosen because the straight rodexceeds the critical pressure load and post buckling occurs The 3D beam element type is chosen for this caseand material is assumed perfectly elastic and homogeneous The circular cross section about 5mm in diameter isutilized A Beam element type is chosen due to small ratio of cross section radius to the rod length Then a photo of a buckled elastic rod is taken by a digital camera and this Elastica shape is assumed as defaultdata in finite element software The static method with nonlinear geometry is used for this analysis in ABAQUSsoftware since time has no significant effect on the solution and large rotation is applied Static method that isimplicit accurate and limited to simple issues without complex contacts is used in this study A twisted shape of Elastica was investigated through applying a pair of equal unbalancing twisted torques to theends of a 2D Elastica shape using finite element analysis In fact the torques s make the 2D Elastica shape twistinto z direction which is similar to a warp knit loop The Elastica shape turns on 3D path and the axial of the rodis rotated and out of plane deformation happens as a result of applying torsion torques The experimental aspectratios for basic and twisted Elastica shapes are obtained and compared with those of theoretical ones Thetheoretical and experimental results were in good agreement Therefore this shape of Elastica could beconsidered suitable for warp knitted loop definition The obtained loop can be used in the warp knitted fabricmodels under external or internal forces and yarn friction extension and compression effects could be taken intoconsideration in future Abaqus models The FEM is an appropriate method in this study because the usage of the loop modeling results in the warp knitted fabric models under different conditions In this study a single bar warp knitted fabric is simulatedunder low strain condition and 3D model of loop is used as the overlap of this simulated fabric The DynamicExplicit method is used and the model results are compared with the real fabric results at low strains The modelresult corresponds well with that of experimental Key wordsFinite element method warp knitted loop twist and buckling 3D Elastica loop geometry

جوادي طوقچي، مرضيه

بررسي هندسه حلقه بافت حلقوي تاري به كمك يك مدل مكانيكي

روش اجزاء محدود , كمانش و پيچش , الاستيكاي سه بعدي