Residual stress induced cracking is still a bottleneck restricting the industrial application of laser melting deposition for large structures. Therefore

it is very important to explore the evolution law of residual stress and the microstructure correlation of residual stress – induced crack initiation and propagation in the process of laser melting deposition manufacturing of large components. Based on the fracture morphology analysis of large titanium alloy components and the macroscopic thermal-force coupling finite element calculation

the unique three-stage asymmetric cyclic loading mode of thermal stress during laser melting deposition is first found

namely

the stable cycle–burst loading stage

the nonlinear cyclic loading stage and the linear cyclic loading stage. The damage degree of three thermal stress loading modes on the unique basket structure of laser melting deposition is studied using coupled damage crystal plasticity simulation

and it is found that the linear cyclic loading mode is the most destructive

followed by the stable cycle–burst loading mode

and the nonlinear cyclic loading mode is the least destructive. This thermal stress loading mode

fracture morphology and microstructure analysis further show that the residual stress-induced cracking phenomenon is controlled by multiple factors such as excessive stress accumulation

geometric characteristics of parts

thermal stress loading mode and forming defects

rather than a single factor. It also provides a direction for systematic control of cracking from the aspects of timely stress relief

optimization of parts structure and process parameters

and reduction and suppression of defects.