Efficacy of the inherent strain method for residual stress determination of additively manufactured IN718 selective laser melted specimens
Abstract
Selective laser melting (SLM) is an additive manufacturing (AM) technology that is able to produce metallic components of high complexity using hard to machine alloys such as Inconel 718 (IN718). Throughout the SLM process the effect of the lasers thermal input to melt and fuse layers of powder metallic material causes residual stresses (RS) to arise. These stresses may lead to numerous detrimental effects such as distortion or cracking of the components and failure of the SLM machine.
To counter-act this, simulation models which use the inherent strain method (ISM) have been developed to predict RS development. These predicted RS results may then be used to determine suitable SLM process parameters such as component build orientation, laser power, laser scan rate, and scanning strategies. Therefore, the problem under investigation in this dissertation was the efficacy of these simulation models in predicting the RS arising from the process parameters utilized for component production.
In order to develop ISM models, a cantilever geometry was used to determine inherent strains resulting from the process parameters and variation of the scanning strategy. These inherent strains were then applied in the simulation of non-calibration geometries to predict the RS during and after manufacture. To ascertain the accuracy of these models for RS build up, the neutron diffraction (ND) technique was used, determining the triaxial stress state of components produced with the same process parameters as were calibrated.
Using both mechanical and temperature dependent thermo-mechanically coupled variants of the ISM, a direct comparison of the simulated and measured RS indicated that the simulations were able to accurately portray the distribution of the triaxial state RS.
Collections
- Engineering [1403]