The effect of shot peening on fatigue life of Q345D T-welded joint

• River-Sea-Going Ship (RSGS) is one kind of advanced ship navigating between the Yangtze River and sea in China without changing any equipment and transit link.
• T-welded structure is one of the typical joints used in River-Sea-Going Ship (RSGS).
• Our work was to investigate the influence of shot peening on fatigue life and analyze the reason for optimum SP parameter of T-welded joint specimen.
• The fatigue test results show choosing suitable peening intensity (PI = 0.3 mmA) could obtain the best fatigue life of T-welded joint specimens, which could prolong 100% fatigue life compared with the unpeened specimen.
• CRSF and surface integrity are the most important but contradictory influence factors on fatigue property and should be considered comprehensively in engineering field.

Shot peening (SP) is an efficient mechanical surface treatment to improve the fatigue property of metallic component. T-welded structure made from Q345D steel via CO2 gas shielded arc welding, which is one of the typical joints used in River-Sea-Going Ship (RSGS), was chosen as research object for fatigue analysis before and after SP. The surface properties of near weld toe region, such as micro-hardness, metallographic phase, residual stresses, roughness and surface topography were characterized with the aim of investigating the SP influence on fatigue life and analyzing the reason for optimum SP parameter of T-welded joint specimen. The cyclic loading mode of fatigue test was based on the actual working condition with loading amplitude of 7.2 kN, stress ratio of 0.1 and loading frequency of 10 Hz. The fatigue test results showed choosing suitable peening intensity (PI = 0.3 mmA) could obtain the best fatigue life of T-welded joint specimens, which could prolong 100% fatigue life compared with the unpeened specimen.