Bead geometry–induced stress concentration factors in material extrusion polymer additive manufacturing
ISSN: 1355-2546
Article publication date: 11 April 2023
Issue publication date: 3 July 2023
Abstract
Purpose
Material extrusion additive manufacturing processes inevitably produce bead-shaped surface patterns on the walls of parts, which create stress concentrations under load. This study aims to investigate the influence of such stress concentrations on the strength along the build direction (“Z-strength”).
Design/methodology/approach
This work consists of two main parts – an experimental demonstration to show the significance of stress concentrations on the Z-strength, followed by numerical modeling to evaluate the theoretical stress concentration factors (kt) for such shapes. Meso-scale finite element analysis (FEA) was performed to evaluate kt at the roots of the intersecting bead shapes. The critical bead shape parameters influencing kt were identified, and parametric FEA studies were performed on different bead shapes by varying the normalized parameters.
Findings
The experimental results showed that up to a 40% reduction in the effective Z-strength could be attributed only to the presence of surface bead shapes. Bead overhang and root radius were identified as critical shape parameters influencing kt. The results of the parametric FEA studies were used to generate a single empirical equation to determine kt for any bead shape.
Originality/value
Predictive models for Z-strength often focus on crystallization kinetics and polymer chain interdiffusion to predict interlayer adhesion strength. The authors propose that the results of such studies must be combined with surface bead-shape induced stress concentration factors to obtain the combined, “effective” Z-strength.
Keywords
Acknowledgements
This work was supported by the US Army Corps of Engineers, Engineer Research and Development Center (ERDC) under OTA# W52P1J-20–9-3021; PPA CS-20–1201. The authors would also like to thank Mansura Islam, Charles Simpson, and John Hana from Eaton Research Labs, Eaton Corp. for their help with optical microscopy and waterjet machining.
Citation
Kundurthi, S., Tran, F., Chen, S., Mapkar, J. and Haq, M. (2023), "Bead geometry–induced stress concentration factors in material extrusion polymer additive manufacturing", Rapid Prototyping Journal, Vol. 29 No. 7, pp. 1438-1452. https://doi.org/10.1108/RPJ-11-2022-0404
Publisher
:Emerald Publishing Limited
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