OVERVIEW

Although additively-manufacturing (AM) technologies have been continued to demonstrate potential for full-scale production and repair of highly-customized and complex parts, the mechanical behavior, and thus trustworthiness of components fabricated via AM is not yet fully realized.

This, in turn, creates a barrier to more widespread adoption of AM technologies in various engineering applications such as aerospace, automotive, and biomedical. To overcome this challenge, the process-structure-property-performance relationships for various AM processes (e.g. laser-powder bed fusion and direct laser deposition) and material systems must be established. Since the fabrication (process parameters) and microstructure (structure) of AM parts dictate their mechanical behavior (property), specifically their fatigue resistance, it is imperative that all of these phases be taken into consideration. The results from our research are utilized toward calibrating predictive microstructure-sensitive fatigue models as well as accelerating certification for functional AM components. 

Combined corrosion-fatigue behavior of additively-manufactured parts for biomedical application

Image result for additive manufacturing orthopedic implants

Generally, when a material is cyclically stressed in a corrosive environment (also called corrosion-fatigue), the material deterioration will increase more rapidly as compared to either factor alone. In this study, we aim to investigate the durability of AM metallic parts subjected to cyclic loadings in simulated fluid environment. This type of loading condition is chosen to mimic the actual service loading of parts commonly found in biomedical applications such as orthopedic metallic implants. A series of mechanical testing on AM parts and computational analyses will be performed to assess their lifespans, and compared to those of identical parts fabricated using subtractive manufacturing process.

The Influence of Microstructural Defects on Fatigue Performance of Additively Manufactured Nickel-Based Superalloy at Very High-Cycle Loading

Many components in aerospace applications, such as engine components, are commonly subjected to cyclic loadings at very high frequency during their service lifetime that commonly exceeds a million cycles (> 10,000,000 cycles) or known as the very high-cycle fatigue (VHCF) regime. In this study, we intend to evaluate the influences of process-induced defects and their characteristics on the cyclic mechanical responses of AM Inconel 718, a nickel-based superalloy, parts at VHCF regime (i.e. gigacycle). Due to its exceptional mechanical properties at elevated temperatures, Inconel 718 is increasingly used in many extreme temperature applications including liquid-fueled rocket engine spaceflight hardware, which are subjected to cyclic loadings at very high frequency.

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