基于交织点改进弹簧-质点模型的纬编针织物动态变形模拟

Dynamic deformation simulation of weft knitted fabrics based on improved mass-spring model at interlacing points

为了对不同线圈单元组成的纬编针织物进行动态变形模拟,从而预设织物结构形态和加速面料设计流程。首先通过建立三维结构模型,获得了线圈中心线型值点和交织点之间的关系,并基于交织点改进传统弹簧-质点模型,得到了与纬编针织物适配度更高的变形模型,然后以交织点为桥梁关联结构模型和变形模型,通过NURBS曲线反算原理绘制线圈中心线路径,采用力学求解方法不断更新织物形态变化,使用计算机工具展现了关联模型的动态模拟过程,并举例展示了不同织物组织的变形模拟效果。模拟效果表明,建立的三维结构模型具有合理性与真实性,改进的弹簧-质点模型具有极高的适配性,基于交织点关联两者为后续模拟提供了支撑,采用NURBS曲线并通过力学求解等方法实现纬编针织物的三维动态模拟具有可行性。

Objective Because of the diversity of loop unit combination,the threading relationship and the pulling effect between different loops,weft knitted fabric structure are prone to deformation,thus achieving a rich fabric appearance.In order to dynamically simulate the deformation process of weft knitted fabric composed of different basic loop structure units,the overall structure of the fabric was controlled and the details of the loop structure were described,so as to further reduce production cost,speed up production efficiency and improve production quality.Method Interlacing pointsin the fabrics were represented by a three-dimensional structure model of the loop,as an improvement to the traditional mass-spring model.In order to associate the loop structure model and the mass-spring model with the interlacing point as the link,Non-uniform rational B-splines(NURBS)curves were to simulate the loop centerline,and the mass position through internal force analysis and dynamic solution were constantly updated through.Finally,computer tools were adopted to show the dynamic simulation effect of the associated model.Results The three-dimensional structure model of the loop and weft plain knitted fabric was established,involving the interlacing pointsand the type value points,as well as the loop distance,loop height and loop thickness.On this basis,the relationship between the type value pointsof the loop centerline and the interlacing pointswere obtained,and the three-dimensional structure model of other loops and composite fabrics through deformation were also achieved.The mass-spring model unit more suitable for the loop structure unit was established,and the improved mass-spring model was formed.On this basis,the mass-spring model of the corresponding fabric was obtained by changing and adjusting the model unit according to the change of the loop type.The connection between the loop structure model and the mass-spring model was established by using the interlacing point as the link,and the loop centerline used to describe the geometric path of the loop structure model was generated by fitting based on the principle of NURBS curve inverse calculation problem,as well as the mass positions in the mass-spring system were constantly updated through internal force analysis and dynamic solution.The dynamic deformation simulation of weft knitted fabric was achieved by using computer tools.An example was given to show the simulation effect of the associated model.As well as an example,the simulation effectsof fabric deformation including multiple different types of loops were shown.Conclusion The loop structure model and mass-spring model of weft knitted fabric were established based on the interlacing point,and the relationship between them was created.The loop centerline simulated by NURBS curve was basically consistent with the geometric structure of the fabric.After reasonable internal force analysis and dynamic solution,the mass positions in the mass-spring model system were constantly updated.The dynamic simulation process of weft knitted fabric was realized.