Influencing effects of variant laser pulse energy on fatigue behavior induced by LSP

The set objective in this study is to understand the effects of laser shock processing of variant laser pulse energies on residual compressive stress, microhardness, fatigue fracture and fatigue life in the application of aircraft lug material. The effects of three variant laser pulse energies of 3.0, 4.0 and 5.7 J were examined along with laser processing parameters. A Q-switch (neodymium (Nd)-doped yttrium aluminum garnet) laser system was used in this experiment with a wavelength, a pulse width, a spot diameter and an overlapping ratio of 1046 nm, 10 nm, 3 mm and 50%, respectively. After laser shock peening (LSP), the superficial layer stress state showed varied results from tensile to residual stress of 50 to −225, −260 and −301 MPa after 3.0, 4.0 and 5.7 J, respectively. The microhardness of the as-received specimen was 137 HV. However, after LSP, it increased to 198, 210 and 223 HV, respectively. The fatigue life performance also significantly increased up to 53 371 (2 × 10⁵) cycles.