研究目的
To propose a fully coupled thermomechanical analytical model for the rapid and accurate prediction of residual stress in additively manufactured parts, considering the effects of scan strategies, heat loss at part’s boundaries, and energy needed for solid-state phase transformation.
研究成果
The proposed thermo-mechanical analytical model is a valuable, reliable, and rapid tool for the prediction of stress state within the part which then can be used for the optimization of process parameters and control of the build process through inverse analysis. The model works for all material systems as long as the thermo-mechanical material properties are known.
研究不足
The proposed analytical model does not consider the effect of geometry. Moreover, the bulk temperature dependent material properties are considered for the simulation of residual stress.
1:Experimental Design and Method Selection:
A moving point heat source approach is used to predict the temperature field by considering the effects of scan strategies, heat loss at part’s boundaries, and energy needed for solid-state phase transformation. The thermal stress is obtained using Green’s function of stresses due to the point body load. The Johnson–Cook flow stress model is used to predict the yield surface of the part under repeated heating and cooling.
2:Sample Selection and Data Sources:
IN718 parts built via laser powder bed fusion (L-PBF) were used. Experimental measurement of residual stress was conducted using X-ray diffraction.
3:List of Experimental Equipment and Materials:
Tong Tai AM250 selective laser melting (SLM) machine, equipped with a 50–400 W YAG laser, and a commercial X-ray Diffractions machine (D8 Discover Bruker) were used.
4:Experimental Procedures and Operational Workflow:
The residual stress on the side walls of the samples was measured by X-ray Diffractions using the sin2Ψ method. For each point, the through-thickness residual stresses along the build direction and along the scan direction were measured.
5:Data Analysis Methods:
The predicted residual stress was compared with measured residual stress of IN718.
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