# Frictional Behaviour of the Microstructural Surfaces Created by Cylindrical Grinding Processes
## 1 Introduction  
Friction behaviour is a part of surface functions, and it is also critical for the energy consumption and the applicable life of machined component surfaces. Surface texturing acts as an effective approach for the surface modification to improve the surface functional performance, particularly at a micro scale. Nowadays, surface texturing has been widely recognized as a potential to reduce the friction resistance, and applied to the cylinder liner, sliding and other surfaces. [PERSON] et al. [1] presented a critical view at the fundamental effects of surface textures in different lubrication regimes. The studies in various operating conditions of experiments have also shown that the micro regularities (dimples, cavities, grooves) could successfully improve the friction behaviour under different lubrication regimes compared to untextured surfaces [2; 3; 4; 5; 6; 7; 8; 9]. [PERSON] and [PERSON] [2] investigated the grooves and square textures in the various sizes on PVD (physical vapour deposition) surface under dry and boundary lubrication conditions. The coefficient of friction exhibited excellent performance around 0.05 for small square and grooves texture during 200,000 cycles. [PERSON] et al. [3] studied the tribological performance of laser-textured 2024 aluminium alloy samples in unidirectional sliding tests under boundary lubrication conditions. The optimum area density was found at 8.5%, which agrees well with other research investigation [4] under boundary lubrication conditions. The benefits of surface texturing were also reported with experimental results under mixed lubrication and hydrodynamic lubrication as well as the regime transitions between them. [PERSON] et al. [5] depicted experimental and numerical investigations of the friction characteristics of micro textured surfaces in mixed lubrication. The experimental results showed the effect of microstructural surface for the applications under a constant load that lead to a lower friction, which was in accord with the simulation prediction. Similar friction reductions were also verified by [PERSON] et al. [6] and [PERSON] et al. [7] in the experiments of mixed lubrication conditions. [PERSON] et al. [8] further analysed the effect of texturing area of SiC samples under water lubrication, covering the transition from hydrodynamic lubrication to mixed lubrication. They defined a transition load as a workload on which the coefficient of friction increased sharply. The higher transition load indicated a better retention of lubrication. It was found when texture coverage area was 2.8%, the transition load could increase 20% comparing to a smooth surface. [PERSON] [9] studied the geometrical characteristics of textured surfaces in a lubrication regime transitioning from mixed to hydrodynamic lubrications, where the tests were carried out under contact and unidirectional sliding conditions. When compared with untextured surfaces, a substantial reduction in friction coefficient was observed with textured steel surfaces. All these experiment results convinced the effects of microstructure on the friction reduction, but when the surface structure dimension reached a macro level, the structure texture became less consistence and unprofitable due to the increasing costs per part in mass production. Hence, the suggestion was to use micro manufacturing processes, which could control the surface texture and production efficiently and precisely. Many manufacture techniques are available to create micro structural surface textures with high quality to improve the surface function, including the friction behaviour. These methods for the creation of defined surface microstructure with the feature size in the micrometre range include energy beam techniques [10; 11], etching [12], mechanical formation [13; 14] and others. Among these methods, laser surface texturing (LST) is considered as the most promising texturing technology.