# Roughness Evaluation of Burnished Topography with a Precise Definition of the S-L Surface
## 3 Results
### Selection of Procedure for a High-Frequency Errors Reduction for S-Surface Definition
Each of the Gaussian (GRF or RGRF) or spline (SF) methods caused serious distortions of these features. Deviation from the required results can be observed with the deviations in the reference line (Figure 9f-j)--this was far from the cylindrical. More relevant results were obtained when the least-square fitting methods (POLY2 and POLY4) were applied. From the analysis of both profiles (Figure 9a,c), the one received by the usage of POLY2 seemed to be flatter and, respectively, the total height of the profile (_Pt_) was smaller. However, for surfaces containing oil pockets, the minimisation of the maximum height is not always required, and correspondingly, in some cases, can indicate the flatness of some features, especially deep and wide dimples [14; 16; 40]. This can affect the classification of properly made parts as a lack. Profile of the surface after L-surface definition by the POLY2 (Figure 9a) method was further considered for high-frequency measurement noise detection and reduction, and the definition of the S-surface. Results after various filtering (GRF, RGRF, SF, MDF and FFTF) were compared, analysed, and are presented in Figure 10. In the presented example, differences were observed for each of the data presented, the S-L profile (left column), S-profile (middle), and PSD graphs, defined for the S-profiles. From the studies of S-profiles received by the application of GRF (Figure 10b), RGRF (Figure 10e), and SF (Figure 10h), some extraordinary features were found, examples of which are indicated by the arrows. These features, located in other than a high-frequency domain, were visible on the PSD graphs. The S-profile defined by the MDF application contained, comparatively, areas where the noise did not occur, also indicated by the arrow. This seems to be out of the logic that, respectively, the vibration, which is usually affecting the high-frequency measurement noise occurrence, influences the whole measurement data, and not only those selected. However, it was not considered in this or previous studies. Out of all of the filters proposed for the reduction in high-frequency measurement errors, the application of the FFTF seems to be the most suitable. Figure 8: Examples of profiles extracted from the raw measured data of the plateau-honed cylinder liner surface topography including three dimples and two valleys (**a**), two dimples and one valley (**b**), one dimple and four valleys (**c**), one dimple and three valleys (**d**), one dimple and two valleys (**e**), and one dimple and one valley (**f**). Figure 9: Profiles after L-surface definition (left column) and form removal (right column) received from the example presented previously in Figure 8a by application of Poly2 (**a**,**b**), Poly4 (**c**,**d**), GRF (**e**,**f**), RGRF (**g**,**h**), and SF (**i**,**j**), cutoff = 0.8 mm. Figure 10: Profiles after S-L surface definition (left column), removed S-surface (middle), and its PSD (right column) after the application of GRF (**a–c**), RGRF (**d–f**), SF (**g–i**), MDF (**j–l**), and FFTF (**m–o**) method with a cutoff = 0.015 mm. From the above analysis, for the removal of form and a reduction in the high-frequency measurement noise, derived from the plateau-honed cylinder liner surface containing oil pockets (dimples) created by the burnishing techniques, the most encouraging methods (from all of those considered) were POLY (for L-surface definition) and FFTF (S-surface calculation), when the S-L surface needs to be precisely determined.