Eigenstrain reconstruction of residual stress and its application in extreme high-speed laser material deposition

Extreme high-speed laser material deposition (EHLA) allows the additive manufacturing to a mass production due to its enhanced scanning speed and reduced detrimental to the substrate. It provides the potential for feasible repair of valuable metal engineering structures those are complex in geometry. In the process of EHLA the material inherits a memory of the complex thermal and mechanical history in the form of microstructural changes and residual stress distribution. Numerical modelling of the residual stresses within EHLA produced mechanical components is of great significance for improving the quality and reliability of design for structural integrity. In the present study, we proposed a procedure for constructing residual stress field caused by heat involved processes through eigenstrian method. Eigenstrain variation is expressed by a series of functions of the distance from the object boundary in the cross-sectional plane of a deposition. We applied this procedure to the reconstruction of residual stress for EHLA produced AISI 4140 structures, and validated the results by experimental data from the electronic speckle pattern interferometry (ESPI) associated hole drilling measurement. The good consistency of predicted results and experimental data indicates that the procedure provides an approach for evaluating the residual stresses of an EHLA manufactured component. Fatigue performance of a deposited structure is assessed according to Dang Van criterion with considering the initial stress introduced by the cladding processes.