异质材料凸起切向变形动摩擦研究

基于三角形凸起假设,提出截止研合角、截止位形角等概念,建立不同材料弹性模量下的凸起切向变形摩擦模型。讨论等倾角异质材料弹性模量、凸起变形、摩擦因数三者之间的理论联系。认为坚硬材料副三角形变形符合n/(n+2)原理,软材料副三角形变形符合1/(2n+1)原理。异质材料的情况,摩擦因数的"决定因子"主要由坚硬副来决定。弹性模量不同的同粗糙度的两个材料,摩擦因数一般倾向于比同材料的大,摩擦因数倾向于由高刚度材料决定。凸起在长期变形下形成左右不对称的三角形,接触面逐渐平缓,倾角逐渐变小,摩擦因数逐渐变小。这就是三角形凸起的跑合后的摩擦因数变小的重要原因。提出放大系数、细观摩擦因数等概念、计算了理论动静比(理论的动摩擦因数和静摩擦因数之比值)、放大系数和凸起倾角、n、细观摩擦角几者之间的关系。经实例计算分析,材料的动摩擦因数随着凸起倾角和细观摩擦角的增加而增加,细观摩擦角减小,放大系数也明显减小,静摩擦因数大约为动摩擦因数的1.4~1.5者居多,也许导致静摩擦因数存在巨大差异的原因。

Dynamic Tribology of Heterogeneous Materials basedon Asperities Tangential Deformation

Based on the " Triangular Asperities Hypothesis", the paper proposed " Repose shaped Angle ", "Repose Angle of lapping surface " and so on , to create some deform friction models of different surface inclination and different modulus of elasticity of those materials. It is discussed respectively the relationship of material elastic modulus, asperities deformation, and friction coefficient. And in the paper the deformation of those hard materials is considered to be in conformity with the principle and the deformation of those soft materials in conformity with the principle. In consideration of different materials, the " determining factor " of friction coefficient is mainly determined by the high elasticity . The friction coefficient between two materials with different elastic modulus tends to be larger than that between the same materials generally. Friction coefficient tends to be determined by stiffness and steep Asperities. The asperities becomes smoother on long asymmetrical deformation and inclination angle becomes smaller and the friction coefficient becomes larger. This is an important reason that the friction coefficient of a triangular asperities becomes smaller after running. The theoretical Ratio of Dynamic/Static Friction Coefficient, the Amplification Ratio and the Asperities Original Inclination, n and so on , were calculated. The Dynamic/Static Friction Coefficient is always increases with the increase of the Asperities Original Inclination Angle and the Mesoscopic Friction Angle. The Amplification Ratio will decreases obviously with the decreases of the Mesoscopic Friction Angle also. The friction angle of the tire can be reduced not only by the friction angle of the tire, but also by the friction angle. The Static Friction Coefficient which always of about 1.4-1.5 times the Dynamic Friction Coefficient were the majority, that should be the reasons why the Static Friction Coefficient be caused a huge difference.