Constant fatigue life under laser shot peening using different surface coatings

Abstract EN

Laser peening (LP) is a surface treatment technology for metallic materials.

LP has shown a great improvement in the fatigue strength and life.

A study of fatigue under constant rotating bending stress programs has been conducted on 7049 AL alloy at a stress ratio (R =-1) and room temperature using laser peening technique .Four groups of tests have been designed.

The first group (15 specimens) tested under unpeened condition.

The second group (15 specimens) tested under air laser peening (ALP) while the third group (15 specimens) tested under water laser peening (WLP).

The last group was designed to examine the fatigue behavior under black paint laser peening (BPLP).

All the above groups were designed to establish the S-N curve.

The results show no effect of laser peening LP at higher stresses (above 300 MPa), while this effect appears clearly at low stresses (200 and 250 MPa).

The results also indicated that the WLP is more effective than the ALP.

The fatigue life improvement factor (FLIF %) was 39, 18.9 and 4.65 under WLP for 200 MPa, 250 MPa and 300 MPa stress levels respectively.

while a clear effect was observed for black paint laser peening (BPLP),it was found that the FLIF % was 93.25 at 300 MPa , 103.24 at 250 MPa and 116 at 200 MPa compared to unpeened data .