PSI - Issue 34

N. Lammens et al. / Procedia Structural Integrity 34 (2021) 247–252 N. Lammens/ Structural Integrity Procedia 00 (2019) 000 – 000

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Figure 2. Distortion prediction after support removal

3.2. Porosity prediction Typically, the process parameters are optimized on simple geometries (for example cubes) for a given material and 3D printer configuration. As such, it is very likely to encounter small pores within the print of a complex geometry with varying geometrical features. Porosities act as localized stress-raisers in a material that, if present at a highly stressed region of the component, can lead to an accelerated deterioration of the component performance and premature failure. Simulation tools can help in locating zones of high probability for porosities to occur, in order to account for them in the final component performance simulations. Figure 3 compares the results of such an analysis on a coupon specimen against CT-scan data of the actual printed coupon. Although no perfect match is achieved (due to the statistical nature), these results clearly show the ability to capture the impact of scan pattern on occurrence, trend and location of pores within the volume.

Figure 3. Comparison of measured porosities using µCT scans of the actual component (left) and numerical prediction of porosity probabi lity (right)

This simulation approach presents an alternative to experimental based assessment of porosity (e.g. via statistics of extremes approaches on coupons) and may provide more insights into understanding the causes and resolutions to high porosity regions. 3.3. Microstructural simulations The thermal history of (a zone within) the component during printing and post-processing can have a significant impact on the resulting microstructure both in terms of grain morphology and phase content, resulting in different material properties such as Young’s modulus, (an)isotropy, yield point and fatigue behavior. Furthermore, changes in how a component is printed (e.g. reorienting in the build chamber, changing scanning strategy…) can affect the resulting local properties.