Effect of forming direction on cyclic plastic behavior near crack tip of additive manufacturing titanium alloy

LIU Qing; LI Jian; ZHAO Xun; SUN Tao; GE Junming; QUAN Shichao; CHEN Sihan; ZHANG Jiadi

doi:10.16579/j.issn.1001.9669.2026.06.013

Abstract：[Objective]To reveal the influence mechanism of forming direction on the cyclic plastic behavior near the crack tip of selective laser melted TC4 titanium alloy,and provide reference for the anti-fatigue design of additive manufactured titanium alloy load-bearing components.[Methods]Firstly,compact tension specimens with three forming directions of 0°(L1),45°(L2)and 90°(L3)were prepared,and the cyclic constitutive parameters of materials in different directions were obtained by tests to provide basis for numerical modeling.Secondly,based on the Chaboche mixed hardening constitutive model,the finite element model of the cracked specimen was established by Abaqus software,and 9 groups of schemes with different load parameters were designed to analyze the evolution law of cyclic plasticity near the crack tip.Then,fatigue loading tests were carried out by digital image correlation technology to obtain the field data of the crack tip area.Finally,the numerical calculation results were compared with the test results to verify the reliability of the analysis method.[Results]The results show that the forming direction has a significant effect on the plastic strain at the crack tip and the plastic strain energy of the component.Under the same load condition,the cumulative plastic strain and plastic strain energy at the crack tip in L3 direction are the largest,followed by those in L2 direction,and the smallest in L1 direction,and the difference increases continuously with the increase of cycle number.The stress concentration at the crack tip is more significant under high load ratio and high load amplitude conditions,with higher plastic strain,average elastic and plastic strain energy.The forming direction has no significant effect on the local stress ratio near the crack tip and the overall elastic strain energy of the component.