Simulation On The Microcosmic Mechanics Response Of Duplex Titanium Alloy Under Cyclic Loading

A large number of accidents were caused by material fatigue failure in engineering. People have done a lot of research work on fatigue theory and method in the design application for a long time, due to fatigue failure of engineering structure are with great hazard, even often produce disastrous accidents. Ti-6A1-4V is a kind of α/β type duplex titanium alloy and it is applied widely because of its good comprehensive mechanical properties. In order to meet the demand of design and manufacture of components, the following two aspects study are complemented with two phase a/β type titanium alloy Ti-6A1-4V as the research object:1. The Chaboche model simultaneously contained kinematic hardening and isotropic hardening is proposed in order to predict the elasto-plastic response of Ti-6A1-4V undergoing cyclic loadings. This paper provides material parameters for structure design based on Chaboche model making up the shortage of just considering kinematic hardening behavior of the previous study. The numerical simulation reproduces the plastic deformation behavior of Ti-6A1-4V in the cycle load, such as the Bauschinger effect, cyclic softening, plastic stability etc.2. The cyclic plasticity material parameters of α/β phase were established and the micromechanics2d and3d finite element model were built with ABAQUS. Mesoscopic mechanics under monotonic loading and microscopic plastic strain accumulation under cyclic loading are discussed using2d finite element model; By introducing fatigue indicating parameter method based on local plastic shear strain, the effect of a volume fraction, a grain size, mean stress and stress ratio on the fatigue performance is discussed using3d finite element model.Research shows that:the PMPSS amplitude can achieve greater values as the a-phase volume fraction is bigger. This may account for that restraint decrease when a-phase volume fraction grows; The resistance ability of fatigue crack initiation of the microstructure fall subsequently with the alpha grain size d increases; When the largest stress is higher than the tensile yield stress, there is a peak value of element number that achieve a certain magnitude of PMPSS value; In the circumstances of the biggest stress same, the PMPSS amplitude can achieve greater values as the stress ratio increase. This is mainly due to there is a lot of ratchet strain.