*2.5. Model Confirmation*

Residual stress predictions using the model discussed in the previous sections were compared against experimental stress measurements. From previous studies, the value of α was set to 0.09 and γ was 1.3. The measured residual stress profiles were extracted from two laser-peened test samples of 12.7-mm-thick Al2024-T351 aluminum (unclad) using incremental hole drilling (IHD). The IHD diameter was 2 mm and the depth increments ranged from 32 to 128 μm to a total hole depth of 1408 μm. Each sample (IHD-1 and IHD-2) was peened with a single 5 mm × 5 mm square spot located sufficiently far from the boundaries to avoid edge effects and using a power density of 3 GW/cm<sup>2</sup> and a pulse width of 18 ns. The residual stresses were measured at the spot center.

Results from the comparison are shown in Figure 3. The FE results represent the average principal stresses over the equivalent volume of material removed at each IHD step and are reported depthwise at the center of the IHD increment. Numerical integration over the disk-shaped IHD region was used to compute the averages. As is shown, the predicted stresses agree well with the stress measurements, confirming the performance of the model for LP applications.

**Figure 3.** Comparison of predicted residual stresses against measured values.
