Current Research Projects

Researcher(s): Patrick Kirsch
Sponsor(s): Office of Naval Research (ONR)
Project Description: Over the last three decades, additive manufacturing (AM) has evolved from rapid prototyping to an industrial prototyping level and is maturing toward the mass manufacturing/production level. Insertion of AM components into the supply chain to impact the production rate for US Navy (USN) weapon systems can enable a significant increase in production rate, which justifies the exploration of these challenges. This project investigates the use of AM ER-100S-1 high-strength low-alloy steel (HSLA) produced via direct energy deposition (DED) as a potential replacement for traditional HY-80 steel used in naval shipbuilding. Environmental assisted cracking (EAC), including corrosion fatigue (CF) and stress corrosion cracking (SCC) are tested in various conditions to mimic real-world environments. Crack growth kinetics are acquired using the direct current potential drop method, which allows for micron-scale crack extension measurements. The unique capability at UVa allows for rapid engagement to perform baseline mechanical, electrochemical, and environmental cracking experiments to enable materials insertion, and has the potential to reduce lead times and decrease costs associated with supply-chain management.

Researcher(s): Sarah Blust
Sponsor(s): Department of Energy's Nuclear Energy University Program (DOE NEUP)
Project Description: One of the frontiers of corrosion science is stress corrosion cracking (SCC) under atmospheric conditions. This project takes previous stress corrosion cracking experiments performed on Stainless Steel 304L and 316L series alloys under full immersion conditions, and seeks to expand it to various atmospheric environments such as misting, differing salt concentrations, temperatures and other parameters. In particular it will determine to what degree the mechanisms of stress corrosion cracking previously developed for full immersion conditions can be extended to atmospheric conditions. Crack growth kinetics will be measured using direct current potential drop, which allows for micron scale crack extension measurements. The generated SCC crack growth rates will be used to generate lifetime predictions of components using a linear-elastic fracture mechanics-based model. This project will be directly applied to stainless steel used for spent nuclear waste canisters currently in service.

Researcher(s): Michael Roach
Sponsor(s): Office of Naval Research
Project Description: Additively manufactured (AM) alloys offer many potential benefits for the construction of engineering components of importance to the Navy, from reducing waste and time-to-availability to the opportunity for radically new mechanical designs which cannot be constructed from conventionally processed stock products (e.g., plate, rod, sheet). They also may allow the introduction of graded composition within components. Corrosion resistant alloys (e.g., stainless steels, nickel alloys, titanium alloys) are often the base material from which AMA parts are constructed. More recently, precipitation hardened, martensitic stainless steels (e.g., 17-4PH) have become of increasing interest due to their higher strength than austenitic stainless steels. Structural marine applications that require higher strength levels often use precipitation hardened martensitic stainless steels. For such steels manufactured via conventional methods, environmental cracking is often a prominent failure mode in chloride-rich environments; H-embrittlement has been implicated as governing mechanisms for such cracking. As such, it is critical to evaluate the environmental cracking behavior of AM materials to provide rigorous vetting of these materials that will ensure a safe extension to structural applications.

Researcher(s): Alex Jennion, Zach Harris
Sponsors(s): Rolls-Royce
Project Description: The objective of this research is to understand the relative contribution of oxidation, creep and cyclic damage accumulation to high temperature fatigue crack growth in nickel-based superalloys. In air, fatigue crack growth rates increase with increasing temperature. Under  dwell fatigue loading, which are more representative of actual loading conditions, growth rates are higher, increase with increasing temperature, and then decrease at temperatures above 650 ˚C. Current component lifetime models do not account for this change in growth rate and are too  conservative. Fatigue testing in air and vacuum at different temperatures, stress intensity ranges, and dwell times will isolate the contribution of specific damage mechanisms. By applying a multi-length scale characterization method to the fracture surface and crack tip, the contribution of oxidation, creep and fatigue can be quantified. This investigation with better inform fatigue-life modeling and design of new high-temperature fatigue resistant alloys.