Process modeling for metal additive manufacturing

AiM2XL project

Can Ayas

A major issue in the metal AM process is the deformations and residual stresses induced during laser powder bed fusion which originate from thermal expansion/contraction cycles, shrinkage due to solidification and other volume changes due to solid state phase transformations. Severe deformations may disqualify the product for use and can cause jamming of the recoater of the AM machine, while residual stresses may cause failure, if a critical level is exceeded during the build.

AM process models, capturing the essential physics of the process can be used to predict the temperature transients and the resulting deformation and residual stress for a given set of process parameters. During the typical powder bed fusion process, steep temperature gradients are present due to the local nature of laser heating. The laser beam has a spot radius typically on the order of tens of micrometres, while parts produced have dimensions typically on the order of tens of millimetres. This mismatch of characteristic length scales becomes prohibitive for conventional numerical methods.

We make use of the superposition of analytical and numerical correction fields that bridges the characteristic length scales of the laser spot and the part being built for the inherently multi-scale problem at hand.

Cube geometry considered with for the process simulation and the snapshots of normalised temperature distribution during the scanning of the last layer.
The distribution of σ11 after completing thin walled structure comprising 4 layers with wire arc additive manufacturing process.
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