The fine shot material, which is about 1.7 times in hardness and about 1.9 times in specific gravity compared with the conventional one, has been newly developed. And an improvement is investigated in the fatigue strength of the aluminum alloy A-5083-PO welding coupling in the peening treatment performing with this new shot material.
The results are summarized as follows.
(1) The fatigue strength of welding coupling is improved very well even in low projection air pressure 0.2–0.3MPa when the peening treatment is performed with the new developed shot material of the high hardness and specific gravity in particle size 150μm.
(2) This shot material is effective for the improvement of fatigue strength of a soft welding coupling such as aluminum alloy.
(3) The improvement using this shot material is more effective than that of conventional stainless steel shot material even if low projection air pressure is applied.
(4) This improvement of the fatigue strength is caused by not only that of hardness by peening treatment but also an addition of the residual stress.
(5) Under this conditions, it became clear that the fatigue strength is efected by hardness and compressive residual stress mostly, not by surface roughness.
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