Unraveling High-Temperature Creep-Fatigue-Oxidation Interactions in Metals (FY2019-000087-AS)
Abstract
As the US Navy fleet continues to age, a greater portion of the Navys budget will be required to ensure safe and effective operations beyond the designservice life. However, the insidious and pervasive effects of corrosion make it difficult to reach this goal by reducing availability, deteriorating performance, and ever-increasing total ownership cost of warfighting systems and infrastructures. Hence, better predicting the performance of structures under such extreme conditions can optimize the prognosis of warfighting capability, fleet operational availability, and expected service life of Navy vehicles which will improve safetyand save billions of dollars. This high demand for safety and cost reduction culminates in the case of materials systems operating under extreme environments. They are used in the hot section of marine, turboshaft, and jet engines and are, therefore, subjected to high-temperature viscoplasticdeformations due to creep and fatigue loadings that interact to cause shorter lifetimes. In addition, these harsh in-service thermo-mechanical environments also induce oxidation that degrades the mechanical properties of the alloys by promoting even more detrimental creep-fatigue interactions.So, a technical approach consisting of a multi-scale experimental and modeling approach involving high-temperature creep, fatigue, and dwell/fatigue loadings under vacuum and in air will be followed. In practice, the material will be characterized by advanced techniques, such as in situ high-temperature X-ray tomography and X-ray spectroscopy. They will respectively provide information at the micro-scale by characterizing the sub-scale pores related to the rate of vacancies injected into the materials by the oxidation process and at the nano-scale by characterizing the chemical processes responsible for the initial oxidation kinetics. These data will serve for gaining insights into the damage process due to oxidation and how surface roughness and viscoplasticdeformation modify the oxidation kinetics. A plasticity-coupled damage model also depending on the evolution of the thickness of the oxide scale will also be developed and validated using the obtained experimental results. The anticipated outcome will, therefore, be a state-of-the-art microstructure-sensitive chemo-thermo-mechanically-coupled constitutive and damage modelwritten in a crystal plasticity framework. This framework will take into account the interactions between creep, fatigue, and oxidation based on the multi-scale experimental and modeling results. It will be extended to polycrystalline structures by the use of a homogenization method specifically tailored to account for oxidation. The proposed multi-scale framework will enhance understanding of the performance of metals in extreme environments and contribute to a long-term engineering solution for taming oxidation. This newly gained knowledge may be transferable through a close collaboration with metallurgiststo develop new alloys better withstanding thermo-mechanical loading in oxidizing environments. This may result in an increase in the in-service temperature of engines which will improve their efficiency and reduce their emission of pollutant gases. For these reasons, this study will have alarge impact on DoD capabilities by providing the keys to develop higher performing, yet safer high-temperature thermo-mechanical systems, pushing materials to the limit of their properties while better evaluating materials for cost-savings and life-cycle management.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 20, 2020
- Source ID
- N000142012528
Entities
People
- Jean-briac Le Graverend
Organizations
- Office of Naval Research
- Texas Engineering Experiment Station
- United States Navy