Using a reciprocating rig to simulate the piston ring-cylinder liner contact, we show that macro-scale surface texture yields friction reductions in the hydrodynamic regime of up to 35%. Based on these experimental observations, we put forward a new macro-texture induced friction reduction mechanism and validate it through theoretical 1D modelling. This “Shear-Area Variation” mechanism involves macro-texture reducing both the sheared contact area (acting to decrease friction) and hydrodynamic load support/lubricant film thickness (acting to increase shear-rate and hence friction). Provided the oil film is thick enough to prevent asperity contact, the area reduction effect dominates the friction response. This has implications for machine efficiency improvements, as friction is reduced around mid-stroke where sliding speed and energy dissipation is greatest. It also complements the majority of surface texture research which involves micro-scale texture that is only effective at low speeds in the mixed and boundary regimes (around top and bottom- dead centre).

采用往复运动的钻机来模拟活塞环-缸套接触，我们表明，宏尺度的表面织构在水动力状态下可将摩擦降低多达35％。基于这些实验观察，我们提出了一种新的宏观纹理引起的摩擦减小机制，并通过理论上的一维建模对其进行了验证。这种“剪切面积变化”机制涉及宏观纹理，既减小了剪切接触面积（起到减小摩擦的作用），又减小了流体动力负载支撑/润滑剂膜的厚度（起到增大剪切速率并因此增大摩擦的作用）的作用。如果油膜足够厚以防止粗糙接触，则面积减小效果将主导摩擦响应。这对提高机器效率具有重要意义，因为在行程中部（滑动速度和能量耗散最大）时，摩擦力减小了。