Research On Crack Growth Life Of Additive Manufactured Titanium Alloy

Titanium alloy with the properties of high specific strength,specific stiffness and high temperature corrosion resistance has been widely used in the aviation field.However,titanium alloy parts have too many production processes,low material utilization and high processing cost,which restrict the development of aviation titanium alloy.Wire arc additive manufacturing is a rapid prototyping technology,which is suitable for manufacturing large-scale components with complex shapes,making up for the shortcomings of the difficulty of titanium alloy processing and forming.For the key fracture parts of aviation titanium alloy,it is an important premise for damage tolerance design and aircraft structure safety to master the crack propagation law for the purpose of avoiding catastrophic fracture accidents.The residual strength and fatigue crack growth life of wire arc additive manufactured TC11 titanium alloy are studied by experimental test and numerical simulation.Firstly,the tensile mechanical property test,fracture toughness test and fatigue crack growth test of titanium alloy were designed,and the Paris formulas of crack growth rate in different directions and stress ratios were obtained by the least square method.The results show that the tensile mechanical properties and crack growth properties of titanium alloy are anisotropic,which is attributed to the different microstructure in the two directions observed by the section.Then,considering the two-dimensional orthotropic characteristics of fracture toughness and crack growth rate of titanium alloy,the elliptical function expression of crack growth resistance and Paris formula parameters with arbitrary crack angle is given,and the prediction theory of residual strength and growth life of cracked titanium alloy structure are established based on the maximum circumferential stress criterion of two-dimensional mixed mode crack.Finally,the threepoint bending short beam model and the central hole plate model are established respectively based on the extended finite element method.The numerical simulation results are compared with the test results to verify the accuracy and reliability of the prediction theory,while the error causes are analyzed and the prediction theory is optimized.