Effect of laser shock peening on surface integrity and tensile fatigue behavior of TB8 bolts

Abstract

Laser shock peening (LSP) treatment was introduced to improve tensile fatigue behavior of TB8 titanium alloy bolt. TB8 bolts surface integrity, tensile fatigue fracture and strengthening mechanism after LSP treatment were systematically investigated. Results showed that cracks and machining defects on the thread surface were eliminated, surface layer microhardness and compressive residual stress were increased after LSP treatment. Meanwhile, the grains sizes of the LSP treated bolts samples were reduced to 38.61 μm with the formation of high density dislocations. LSP treated bolts samples with 80 mJ laser energy exhibited the maximum average tensile fatigue life, which was increased from 66,452 cycles to 81,319 cycles. In addition, under the synergistic effect of compressive residual stress and grains refinement, cracks propagation path was changed, which were the primary factors for the improvement of TB8 bolt tensile fatigue life.