考虑温度因素的钢-橡胶墨辊挤压接触动力学特性及其微尺度间隙内油墨的流动

There are multiple ink rollers in the inking system of printing machine, hard and soft ink rollers arrange alternately and in the state of pressing contact. The material of hard roller is usually steel or plastic, and soft roller is steel core covered by a layer of rubber. Ink is transferred by the pressing contact of rollers, and thickness of the ink layer in the pressing contact area is in the micro-scale. Rubber layer of the soft roller deforms largely by pressing contact, and the viscoelasticity of rubber makes it has the phenomenon of deformation hysteresis in the process of pressing contact rolling, then its temperature rises because of mechanical loss. There are coupling relationship among dynamics characteristics of rollers, mechanical loss characteristics of rubber, flow characteristics of micro-scale ink, and temperature characteristics of the coupling structure of rollers and ink. By analysis of temperature increasing due to mechanical loss of rubber in the process of pressing contact rolling, dynamics characteristics of ink rollers considering temperature will be researched. By analysis of velocity slipping of viscoelastic ink flowing in the micro-scale channel between steel – rubber rollers, temperature increasing because of viscous dissipation of ink fluid, and heat transferring characteristics of ink fluid, ink flow characteristics considering temperature will be researched. At last, by fluid – solid –heat coupling analysis, dynamics characteristics of steel – rubber rollers with micro – scale fluid layer and flow characteristics of ink considering temperature, and temperature characteristics of the coupling structure of rollers and ink, will be researched. Research results will provide foundation for temperature control and printing color quality control in the printing process, and broaden current research of dynamics and micro fluid.

印刷机输墨系统中存在多个软硬相间排列的墨辊，其中硬辊为碳素钢辊或塑料辊，软辊是在金属辊芯外包覆橡胶层。通过两辊挤压接触传递油墨，挤压接触区油墨层厚度在微尺度范畴。软辊的橡胶层在挤压接触时会发生较大变形，而橡胶的粘弹特性使其在滚动挤压接触过程中会有形变滞后引起的力学损耗生热。墨辊结构的动力学特性、橡胶的力学损耗特性、微尺度油墨的流动特性、墨辊-油墨耦合结构的温度特性间具有很强的耦合关系。通过分析挤压接触过程中橡胶的力学损耗生热，研究考虑温度因素的墨辊动力学特性；通过分析粘弹性油墨流体在钢-橡胶构成的微尺度间隙内的速度滑移、粘性耗散及热交换特性等，研究考虑温度因素的油墨流动特性；最后通过流-固-热耦合分析，研究考虑温度因素的墨辊-油墨结构的动力学特性、油墨流动特性，及墨辊-油墨耦合结构的温度特性。研究成果可以为印刷过程温度控制及色彩质量控制提供理论依据，同时拓展当前的动力学研究及微流体研究。

胶印机输墨系统通过钢-橡胶辊间的挤压接触旋转以实现油墨在两辊构成的微尺度间隙内的流动。在油墨传递与流动过程中，软质橡胶辊的变形、微尺度油墨的流动特性以及油墨黏性剪切和橡胶黏弹滞后产生的温度升高具有很强的耦合关系。本项目主要研究内容：(1)开发了钢-橡胶墨辊对滚试验台，能够实现辊间接触压力、挤压区温度、油墨层厚度、软辊变形、两辊转速的测量。（2）考虑速度滑移研究油墨在微尺度间隙内的流动特性。当滑移速度与油墨速度方向相同时，油墨流速、墨层厚度比不考虑滑移时更大；当滑移速度与油墨速度方向相反时，油墨流速、墨层厚度比不考虑滑移时更小。不同黏度区间的油墨黏度对滑移速度的影响不同，滑移速度随通道尺度减小而增加。（3）分析油墨流体的黏性耗散生热。通道尺度的减小、油墨黏度的增大均导致黏性耗散增强，但过小的通道尺度会强化油墨与外界的换热效果。（4）采用单向解耦和热结构耦合方法分析橡胶墨辊黏弹滞后生热。建立了考虑温度因素的橡胶材料超弹-黏弹本构模型，分析发现橡胶层厚度的减小、橡胶硬度的增大均会导致黏弹滞后生热增加。（5）分析温度因素对钢-橡胶墨辊挤压接触动力学特性的影响。对经典圆柱体赫兹接触理论进行了多因素修正，得到能综合考虑橡胶材料特性、工况条件、温度因素的瞬时钢-橡胶辊接触特性；结构温度随两辊转速和辊间结合力增大而增大，温度升高导致压深变形、接触宽度增加，最大接触压力、橡胶辊接触应力下降。（6）对墨辊-油墨结构进行流-固-热耦合分析。用弹簧单元和阻尼单元等效油墨和橡胶的黏弹特性，建立墨辊-油墨结构的简化动力学模型；考虑橡胶材料的温敏和黏弹特性，修正线接触弹流润滑理论中的压力公式、膜厚公式，获得更精确的油墨层厚度和压力分布。本项目研究可为胶印过程中温度和墨量的精准控制提供理论依据。 . 项目成果包括钢-橡胶辊对滚实验平台1套；论文13篇；软件著作权3个；专利5个；培养研究生10名。