*4.3. The E*ff*ect of Texture Pitch (Px)*

In Figures 15 and 16, the simulation results show the effect of different values for texture pitch based on starved and non-starved lubrication for grooves and chevrons. In Figure 15a, in the case of a groove pattern when the pitch is around 0.4, according to the results from the study on film thickness [57] the lubricant film is thicker; when the lubrication is in a mixed lubrication regime the thicker film results in a lower solid-solid contact. Therefore, the friction has the lowest value when *Px* = 0.4. In Figure 15b, the limited input film thickness is applied in order to calculate the friction in the starved lubrication. The results in Figure 15b show that when the lubrication is in the starved regime the calculated coefficient of friction for different values of texture size is tending to the same values, therefore the Stribeck curves are merging together. Texturing properties for calculations of Figures 15 and 16 are shown in Table 4.

**Table 4.** Texturing properties.


**Figure 15.** Stribeck curves as a function of texture pitch for grooves when the lubrication is: (**a**) Non-starved, (**b**) starved, and *hoil* = 10 μm.

In Figure 16a, in case of a chevron pattern similar to the groove pattern, the lowest coefficient of friction in the case of non-starved lubrication is achievable when the pitch is around 0.5. In Figure 16b, it is possible to observe the same behaviour of the merging in Stribeck curves for chevrons in Figure 12b, for the groove pattern. Therefore, due to the limit in lubricant supply, which results in limited lubricant film growth, the same trend of behaviour is also predictable for other patterns when the starvation in lubrication happens, i.e. triangular pockets and circular pockets.

**Figure 16.** Stribeck curves as a function of texture pitch for chevrons when the lubrication is: (**a**) Non-starved, (**b**) starved, and *hoil* = 10 μm.
