Integrated Simulation Research On "Forming Process-fatigue Performance" Of Selective Laser Melting Of TC4 Titanium Alloy

In selective laser melting(SLM)additive manufacturing technology,the local area of the powder bed undergoes multiple severe cyclic temperature gradients in a short period of time,resulting in complex and severe residual stresses distributed within the manufactured parts.These residual stresses can cause structural stress corrosion and reduce fatigue strength,significantly affecting the fatigue life and load stability of the parts.Thus,studying the impact of residual stresses caused by thermal gradients in SLM on fatigue life is of great significance in optimizing process parameters and improving fatigue performance of parts.Therefore,in this study,ABAQUS software is used to conduct an integrated simulation research on “forming process-fatigue performance” for TC4(Ti-6Al-4V)titanium alloy in SLM technology.The specific steps are as follows:(1)Multi-layer multi-track SLM forming simulation experiments were conducted by changing process parameters.The results show that the temperature of the melt pool increases with the increase of laser power and preheating temperature and decreases with the increase of laser radius,laser scanning interval,and laser scanning speed.The influence of interlayer scanning direction and scanning trajectory on temperature field is relatively small.(2)The results of temperature field under different process parameters are used as predefined fields for stress field calculation.The results show that residual stress increases with the increase of laser power and laser scanning distance,and decreases with the increase of preheating temperature,laser radius and laser scanning speed.The scanning direction and scanning trajectory between layers do not change the size of Mises stress.(3)Fatigue crack propagation simulation experiments were performed on selective laser melting additive manufacturing CT specimens and compared with conventionally manufactured models.The results show that the fatigue life decreases with the increase of warm-up temperature,laser power and laser scanning distance,and increases with the increase of laser scanning speed and laser radius.Interlayer scanning direction and scanning trajectory have different effects on fatigue life.Selective laser melting additively manufactured CT specimens have lower fatigue life than conventionally manufactured CT specimens.