Finite element analysis of in-situ distortion and bulging for an arbitrarily curved additive manufacturing directed energy deposition geometry

Abstract

With the recent rise in the demand for additive manufacturing (AM), the need for reliable simulation tools to support experimental efforts grows steadily. Computational welding mechanics approaches can simulate the AM processes but are generally not validated for AM-specific effects originating from multiple heating and cooling cycles. To increase confidence in the outcomes and to use numerical simulation reliably, the result quality needs to be validated against experiments for in-situ and post-process cases. In this article, a validation is demonstrated for a structural thermomechanical simulation model on an arbitrarily curved Directed Energy Deposition (DED) part: at first, the validity of the heat input is ensured and subsequently, the model's predictive quality for in-situ deformation and the bulging behaviour is investigated. For the in-situ deformations, 3D-Digital Image Correlation measurements are conducted that quantify periodic expansion and shrinkage as they occur. The results show a strong dependency of the local stiffness of the surrounding geometry. The numerical simulation model is set up in accordance with the experiment and can reproduce the measured 3-dimensional insitu displacements. Furthermore, the deformations due to removal from the substrate are quantified via 3D-scanning, exhibiting considerable distortions due to stress relaxation. Finally, the prediction of the deformed shape is discussed in regards to bulging simulation: to improve the accuracy of the calculated final shape, a novel extension of the model relying on the modified stiffness of inactive upper layers is proposed and the experimentally observed bulging could be reproduced in the finite element model.

Automated Tool‐Path Generation for Rapid Manufacturing of Additive Manufacturing Directed Energy Deposition Geometries

“…To validate the path‐planning algorithms, a DED component was built using the zig‐zag and contour‐parallel tool‐path generation. The geometry was chosen to be a filled turbine blade cross‐section used already in thin‐walled form for prior investigations by Biegler et al [ 13 ] and is shown in Figure 6 .…”

In Situ Monitoring of Additive Manufacturing Using Digital Image Correlation: A Review

“…Biegler et al [ 73 ] presented a new approach based on full-field measurements to experimentally quantify the distortions of parts obtained by laser metal deposition (LMD) AM. Moreover, full-field data were used to validate the numerical simulation of the AM process [ 74 ]. In this case, the in situ DIC measurements were advantageously applied to measure distortions on the wall geometry produced by LMD.…”

“…These numerical models can be relevant to predict the mechanical behaviour of parts during the manufactured process itself. Biegler et al [ 74 ] validated a structural thermomechanical simulation model in a direct energy deposition (DED) part using in situ measurements. The validation of an elasto-plastic finite element model for the deposition of directed energy from AM was shown in an arbitrarily curved geometry.…”

“…In order to have sufficient light for the optical measurements, an 808 nm defocused monochromatic laser beam from a DILAS compact diode laser was used. This DIC-based set-up was also used by the research group in other studies [ 74 , 75 , 82 ]. Xie et al [ 76 , 78 ] successfully obtained full-field strain measurements on a manufactured thin-wall during the LENS AM process using 2D DIC.…”

Numerical Simulation Development and Computational Optimization for Directed Energy Deposition Additive Manufacturing Process

“…Numerous attempts have been made to develop the thermo-mechanical numerical model and experimental validation for the DED process using the weld model [ 15 ]. A limited resource was reported in optimizing computational time for the DED process considering a large number of layers in the printed sample.…”