# Computer-Aided Analysis of the Formation of the Deformation Zone in the Burnishing Process
## 2 Analysis of the Stereometry of the Deformation Zone  
To numerically analyse the stereometry of the contact area of the burnishing tool with the processed material, a New Form Talysurf 2D/3D 120 Taylor Hobson profilographometer was used with the software \"Ultra Surface 5.16\" and \"TalyMap Platinum 5.1.1\". This instrument enables measurements of surface roughness and stereometry. A measuring head with a resolution of 3.2 nm was used for the tests. Reproducing the shape of the deformation area caused by burnishing required equipping the station with a measuring table enabling the displacement of the measured samples in a direction perpendicular to the direction of travel of the measuring tip (an area with given geometric dimensions depending on the type of test performed). Measurements were performed on the burnished object. It was a cylinder (shaft) with a diameter of 50 mm made of C55 (1.0535), very popular in the machinery industry (Table 1). The burnishing tools were balls and discs  
Figure 1: Surface profile: (**a**) before burnishing–turned zone (r = 0.4 mm, \(f_{\text{turn}}\) = 0.410 mm/rev), (**b**) ball burnished zone (R = 5 mm, F = 5 kN, \(f_{\text{bum}}\) = 0.410 mm/rev) (magn. 100\(\times\)). made of 100 Cr6 [34] bearing steel. It was a typical, real machining on a CU-500 conventional lathe. During the tests, the lowest possible spindle revolutions were used (18 rpm) due to the need to stop the process to obtain the geometry of the formed deformation centre. The analysis of the literature [3; 4; 32] allows us to conclude that due to the low rotational speeds used during static pressure burnishing carried out using balls or discs, the linear burnishing speed of several meters per minute is not a parameter that significantly affects the machining process. The most important parameters controlling the process are the tool geometry (radius of curvature) (R for ball and R\({}_{\text{k}}\) for disc), burnishing force (F) and feed (f\({}_{\text{burn}}\)). Therefore, during the described research, it was not a parameter analysed as a parameter controlling the machining process. Only the most characteristic results of the obtained tests are presented. As a rule, 10 repetitions of the surface examination were carried out with the given parameters. Burnishing is the last finishing treatment; therefore, any roughness remaining after the previous machining process, e.g., turning or milling, is permanently deformed. As a result, the geometric structure of the surface is completely changed. Its parameters are the result of the processes occurring during its formation. The spacing of the formed irregularities is close to the feed rate used during burnishing. The deformed material gradually fills the original grooves of the surface irregularities remaining after the previous machining. Optical observation (microscope) and computer-aided analysis show that a wave of irregularities is formed in front of the moving burnishing tool. The wave is shaped both in the axial direction--the direction of feed--and in the circumferential direction--the direction of the main movement (Figure 2). Figure 3 illustrates cross-sections of the deformation zone determined in the direction perpendicular and parallel to the main movement. The burnishing process parameters and the selected tool determine the machining results and the amount of surface strengthening. The software, which was used during the scientific research, enables a way to analyse differences in the height and distance of any indicated areas of the analysed zone. It becomes possible to determine the most important geometric parameters of the deformation zone. The presented analysis is therefore very important for the machinery industry because it enables the possibility of optimization of the burnishing process. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**C** & **Mn** & **Si** & **P** & **S** & **Cr** & **Ni** & **Mo** \\ \hline
0.52–0.60 & 0.60–0.90 & Max 0.40 & Max 0.045 & Max 0.045 & Max 0.40 & Max 0.40 & Max 0.10 \\ \hline \end{tabular}
\end{table}