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This study investigates the disparate impact of internal pores on the fracture behavior of two metal alloys fabricated via laser powder bed fusion (L-PBF) additive manufacturing (AM)—316L stainless steel and Ti-6Al-4V. Data from mechanical tests over a range of stress states for dense samples and those with intentionally introduced penny-shaped pores of various diameters were used to contrast the combined impact of pore size and stress state on the fracture behavior of these two materials. The fracture data were used to calibrate and compare multiple fracture models (Mohr-Coulomb, Hosford-Coulomb, and maximum stress criteria), with results compared in equivalent stress (versus stress triaxiality and Lode angle) space, as well as in their conversions to equivalent strain space. For L-PBF 316L, the strain-based fracture models captured the stress state dependent failure behavior up to the largest pore size studied (2400 µm diameter, 16% cross-sectional area of gauge region), while for L-PBF Ti-6Al-4V, the stress-based fracture models better captured the change in failure behavior with pore size up to the largest pore size studied. This difference can be attributed to the relatively high ductility of 316L stainless steel, for which all samples underwent significant plastic deformation prior to failure, contrasted with the relatively low ductility of Ti-6Al-4V, for which, with increasing pore size, the displacement to failure was dominated by elastic deformation.
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This content will become publicly available on February 4, 2026
Ductile Fracture Modeling of Flaw-Containing Additively Manufactured SS316L: Application to Complex Structures
Background To ensure reliability of additively manufactured components in structural applications, an understanding of the combined behavior of pores and stress state on failure behavior is required. Objective This research aims to identify the capabilities and limitations of stress- and strain-based fracture models in describing failure in complex additively manufactured structures. Methods SS316L brackets with a three-dimensional truss-based geometry, in which stress state and pore size varied among struts, were fabricated with laser powder bed fusion. Fracture models considering both stress state and pore size, formulated in terms of stress (pore-size dependent Mohr–Coulomb, or P-MC) and strain (pore-size dependent Modified Mohr–Coulomb, or P-MMC), were calibrated and used to predict the fracture behavior of the brackets. Results The P-MMC fracture model correctly predicted the experimentally observed fracture locations for 11 out of 12 samples, while the P-MC fracture model correctly predicted 10 out of 12 samples. Below a critical pore size, stress state effects dominated the fracture behavior, and above this, pore size was the critical factor, where capturing both factors was crucial at intermediate pore sizes. Conclusions The P-MC fracture model was appropriate for predicting the maximum load-bearing capacity for all samples in this study, while the P-MMC fracture model was shown to be only applicable for samples containing small pores. The importance of incorporating both stress state and the presence of pores in a fracture model is necessary to ensure confidence in the load carrying capacity of additively manufactured structures.
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- Award ID(s):
- 1652575
- PAR ID:
- 10583618
- Publisher / Repository:
- Experimental Mechanics
- Date Published:
- Journal Name:
- Experimental Mechanics
- ISSN:
- 0014-4851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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