*3.3. FEM Results*

The distribution of the normal stress σ*xx* n the peened area is shown in Figure 10. The treated area extends 2 mm left and right from the origin (O), also shown in the figure. Compressive residual stresses are present in this region, with compression peaks as high as 210 MPa. The σ*xx* component shown here acts in the same direction of the bending stress in the tests. The finite elements analysis also provides information on the in-depth distribution of the stresses. The in-depth residual stress σ*xx* in Figure 11 is computed at location O, perpendicularly to the surface of the notch. A compressive peak is found at a depth of about 0.2 mm, while a strong stress gradient is observed close to the surface. At depths greater than 0.7 mm, a tractive residual stress field is present as a consequence of equilibrium.

**Figure 10.** Distribution of residual stress σ*xx* in the peened strip, bounded by the red lines.

**Figure 11.** Residual stress distribution in the in-depth direction. The FEM results are plotted together with the hole drilling measurements in the literature [22] (blue and red dots) and to their extrapolation (dashed line).
