Abstract
In order to prove the advantages of a directly-irradiated laser peening with double spots (DSLP) over a
conventional directly-irradiated laser peening with a single spot (SSLP), we investigated the changes in
residual stress onto the surface of a metal treated with two varying parameters, the spot distance (dspot = 0
- 1.5 mm) and the shifting distance (dshift = 50 - 500 μm). The following were found from experimental
results. (1) Respective compressive regions of residual stress were formed by double spots and overlapped
each other when dspot ＞ ~1.0 mm. (2) The enhanced compressive residual stress, which was almost
the same as the results of a SSLP treatment, was observed at dspot = 1.48 mm and dshift = 250 -
350 μm. We believe that the formation of the enhanced compressive residual stress observed after a
DSLP treatment could be attributed to the overlapping effect of the compressive residual stress regions.
