Effect of laser shock on residual stress distribution in transition arc region of titanium bar

In this paper, the influence of laser shock on the residual stress distribution in the transition arc region of tc4-dt titanium alloy circular bar with no obvious stress concentration is studied. The reasons for its pull-pull fatigue failure are also analyzed and discussed. The following important conclusions can be drawn:

(1) after laser shock processing, sample of round will be formed in the surface and near surface residual compressive stress layer, tensile stress area, in the center of the internal and surface residual compressive stress and tensile stress increases with the increase of impact load and internal, and tensile stress area is greater than the pressure stress layer area, the possibility of fatigue crack initiation and fatigue crack propagation speed.

(2) after the laser impact, the fatigue life gains of the impact end of the dual samples are all negative, indicating that the stress distribution in the section of the round bar is not conducive to the pull-pull fatigue test, and the loading characteristics can be carried out by torque or bending moment, which has certain reference for the subsequent relevant studies.

(3) laser shock mainly by changing the internal stress distribution of the sample to influence the fatigue properties of titanium alloy bar, sample did not impact the fatigue crack source is located at the surface, will produce a compressional stress on the surface after the impact, and produce tensile stress at the center, so to strengthen the weakened core surface, leading to fatigue crack source to internal transfer and the distance from the surface increases with the increase of impact load and; In addition, too much impact load makes the specimen section overall hardened, the material shows extremely high brittleness, and the fatigue expansion area of the fracture at the impact end is much smaller than that at the fracture at the non-impact end, while the instantaneous fracture area is just the opposite, all of which have adverse effects on the fatigue life of the sample.

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