端面扭动摩擦界面行为研究

发布时间：2018-06-09 21:20

本文选题：摩擦模型 + 端面扭动　；参考：《中国矿业大学》2014年硕士论文

【摘要】：本文基于弹性半无限空间理论，建立刚性平冲头作用在弹性半无限空间的端面扭动摩擦模型，利用Maple编写计算程序，获得了法向应力分布，摩擦扭矩与黏着半径、扭动角的关系。研制了一种端面扭动摩擦界面实时观测装置，开展了PMMA与45#钢端面扭动摩擦磨损测试，利用高速显微摄像仪，实时观测并逐帧分析摩擦界面的黏着区与滑移区，获得了不同载荷和扭动角下界面的实时磨损形貌与循环次数的准确动态关系。基于MC尼龙和PTFE的试验数据，从摩擦扭矩-扭动角（T-θ）曲线和稳定摩擦扭矩等方面进一步验证端面扭动摩擦模型的正确性，取得的结论如下： 1、端面扭动接触中心的法向应力最小，而在靠近平底冲头的棱角处，法向应力迅速增加，出现应力集中。剪切模量、扭动角、摩擦系数和法向力四因素综合改变黏着半径的大小，即决定了端面扭动的接触状态，它们与黏着半径成非线性关系。摩擦扭矩随黏着半径整体上呈现先增加直至近边缘处达到最大值，然后略有减小。 2、PMMA-45#钢配副的T-θ曲线随角位移幅值的增加由直线形转变为椭圆形最后变为平行四边形。相同角位移幅值下，黏着半径会随法向载荷的增大而增加。在扭动角为0.1°时，PMMA在法向载荷83N、123N和163N下的理论黏着半径都为5mm，表明扭动界面处于完全黏着状态，而实测的黏着半径分别为3.8mm、4mm和4.15mm。在扭动角为0.25°时，PMMA在法向载荷83N、123N和163N下的理论黏着半径分别为1.48mm、3.88mm和5mm，可知扭动界面处于部分滑移或黏着状态，而实测的黏着半径分别为1.88mm、3.2mm和3.4mm。在扭动角为0.5°时，PMMA在法向载荷83N、123N和163N下的理论黏着半径分别为0.074mm、0.5mm和1.2mm，而实测的黏着半径分别为0、0和0.5mm，整个界面处于完全滑移状态。实测的黏着半径与理论值较接近，即从黏着半径与扭动角的关系验证了端面扭动模型的正确性。 3、端面扭动界面损伤首先发生在接触界面边缘处，，部分滑移区表现为擦伤形貌，完全滑移区则表现为银纹损伤。随着循环次数的增加，黏/滑边界处损伤逐渐加重同时向接触中心扩散，直到循环结束，接触中心仍无损伤。在部分滑移区，黏/滑交界处出现沿周向不均匀分布的擦伤形貌，且磨痕沿周向不断生长，逐渐沿径向拓展，伴随着轻微的细纹(即银纹）损伤。在完全滑移区，银纹的波纹状特征非常明显，银纹沿径向产生，经历伸长变宽和模糊消失的过程，最后留下塑性流动的痕迹。相同载荷下，PMMA磨损体积随角位移幅值的增大而呈略微增加趋势；相同角位移幅值下，PMMA磨损体积随着法向载荷的增加而增加。 4、MC尼龙复合材料和PTFE的扭矩都随扭动角的增加急剧减小至稳定状态，端面总扭矩随摩擦系数和法向载荷的增大呈线性增加。部分滑移状态时的扭矩值高于完全滑移状态的扭矩。不同角位移下的实验扭矩与计算曲线相似，揭示了该扭动摩擦模型可近似预测弹性变形下聚合物材料的扭矩。
[Abstract]:Based on the theory of elastic semi infinite space, the friction model of the end of rigid flat punch in the elastic half infinite space is established. The relationship between the normal stress distribution, the friction torque and the adhesion radius and the twist angle is obtained by using Maple to write the calculation program. A real time observation device for the interface between the friction and the torsion is developed, and the PMMA and 4 are carried out. The friction and wear test of the 5# steel end is tested. By using a high-speed micro camera, the real time observation and analysis of the adhesion and slip areas of the friction interface are observed. The exact dynamic relationship between the real time wear morphology and the cycle times of the interface under different loads and twists is obtained. Based on the test data of MC nylon and PTFE, the friction torque twist angle (T- theta) curve is obtained. The correctness of the torsional friction model is further verified by the line and the stable friction torque. The conclusions are as follows:
1, the normal stress of the contact center is minimal, and the normal stress is increased rapidly at the angle of the flat bottom punch. The stress concentration is rapidly increased. The shear modulus, the twist angle, the friction coefficient and the normal force change the size of the adhesive radius synthetically, that is, the contact state of the torsion is determined, which is nonlinear with the adhesion radius. The friction torque increases with the adhesive radius as a whole, until the maximum value near the edge, then slightly decreases.
2, the T- theta curve of the PMMA-45# steel mating pair increases with the angular displacement from a straight line to an ellipse and turns to a parallelogram. Under the same angular displacement, the adhesion radius increases with the increase of the normal load. At the torsion angle of 0.1 degrees, the theoretical adhesion radius of PMMA at the normal load 83N, 123N and 163N is 5mm, indicating the torsion boundary. When the surface is in full adhesion, the measured adhesion radius is 3.8mm, 4mm and 4.15mm. are 0.25 degrees at the torsion angle. The theoretical adhesion radius of PMMA under the normal load 83N, 123N and 163N are 1.48mm, 3.88mm and 5mm respectively. When the torque angle is 0.5 degrees, the theoretical adhesion radius of PMMA under normal load 83N, 123N and 163N is 0.074mm, 0.5mm and 1.2mm respectively. The measured adhesion radius is 0,0 and 0.5mm, the whole interface is in the state of complete slip. The measured viscosity is close to the theoretical value, that is, the relationship between the adhesion radius and the twist angle verifies the end face twisting. The correctness of the model.
3, the surface torsion interface damage occurs first at the edge of the contact interface, and the partial slip region shows the scratch morphology, and the complete slip region shows a Silver Stripe damage. With the increase of the number of cycles, the damage of the viscous / sliding boundary is gradually increased and diffused to the contact center until the circular junction, the contact center still has no damage. In the partial slip zone, viscosity / There is an uneven distribution along the circumferential direction at the slip junction, and the grinding marks are growing along the circumference, gradually expanding along the radial direction, accompanied by slight fine lines (i.e., Silver Stripe) damage. In the complete slip zone, the ripple characteristics of the silver lines are very obvious. The silver striations are produced along the radial direction, and the process of stretching and blurring, and finally leaving plastic flow. Under the same load, the wear volume of PMMA increases slightly with the increase of the angular displacement amplitude, and the PMMA wear volume increases with the increase of the normal load.
4, the torque of MC nylon composite and PTFE decreases sharply to the stable state with the increase of the torque angle. The total torque of the end face increases linearly with the increase of the friction coefficient and the normal load. The torque value in the partial slip state is higher than that of the complete slip state. The actual torque under different angular displacement is similar to that of the calculation curve, revealing the torsion. The dynamic friction model can approximately predict the torque of polymer materials under elastic deformation.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TH117.1

【参考文献】