Method for assessing impact of pores in additively manufactured components on structural performance
Abstract
While additive manufacturing (AM) of metallic components has potential for use in structural applications, the effect of pores, in the form of gas pores or lack of fusion pores, on the strength and ductility of components is not understood. Knowledge of how suchpores reduce strength and ductility, and impact statistical distributions of these properties, is required for the safe adoption ofAM in structural applications. Additionally, as the amount of ductility a material has depends on the stress state of the material,to use AM in load-bearing components, there must be a clear understanding of: (1) the maximum stress or strain that additively manufactured components can withstand over the wide range of potential stress states accessed in service, whether or not pores are present and (2) the confidence levels of the measured and predicted failure stresses and strains. This will allow one to determine how bad a pore is for component performance. This research will perform fundamental research to uncover the impact of relative and absolute pore size on the stress state dependent failure behavior of alloys through the studying of a model material system - Ti-6Al-4V made by laser powder bed fusion (PBF-LB) AM. The primary objectives of this research are to develop a framework that: (1) identifiesthe absolute and relative impact of pores on the failure behavior, in terms of stress or strain, of an additively manufactured alloy over a wide range of stress states accessed in components, (2) establishes uncertainty bounds on the failure stresses or strains, as a function of stress state and pore size, and (3) quantifies the effect of multiple pores on the failure behavior of an additively manufactured alloy.This research will employ an experimental-computational approach to investigate and model the relationships between pore features (relative and absolute size, number) on failure behavior of Ti-6Al-4V made by PBF-LB AM. Sample geometries will be designed to access a wide range of stress states, and internal pores will be fabricated within components, where both pore size and sample size will be varied. These experiments, paired with corresponding finite element analysis simulations, will allow for thedetermination of the impact of pore size on the stress state dependent failure. The combined experimental-computational approach will be used to develop, calibrate, and validate fracture models.The key results of this research will be a fundamental understandingof: (1) how absolute and relative pore sizes within an additively manufactured alloy impact its failure behavior over a wide range of stress states; (2) how the statistics of failure vary with stress state and pore size within an additively manufactured alloy, and (3) how multiple pores interact within an additively manufactured alloy to impact the failure behavior and component performance.An understanding of the impact of pores, with varying size (with respect to component geometry and microstructural features), on fracture behavior under realistic multiaxial loads seen in service will provide a pathway for adoption of AM for load-bearing componentsin the Department of Defense. Critically, the tools provided will allow engineers to inspect parts to identify defects, and if defects are detected, to determine if the defects are worrisome or not based on the structural requirements of the component. Approved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 15, 2024
- Source ID
- N000142412345
Entities
People
- Allison M Beese
Organizations
- Office of Naval Research
- Pennsylvania State University
- United States Navy