Modeling Spin Test Using Location Specific Material Properties

Jet engine disk components are increasingly subjected to higher operating temperatures. To meet the demands of increasing thrust and higher operating temperatures, a newer generation of nickel based superalloys such as LSHR, Alloy 10, Rene104 and RR1000 are being processed with dual microstructure distributions. Fine grain, high strength, fatigue resistant bore properties are contrasted with coarser grain, creep resistant rim properties. In order to optimize bore and rim properties of the engine disk, innovative dual microstructure heat treatment methods (DMHT) are employed where the bore is heated and cooled from sub-solvus temperature while the rim is heated and cooled from super-solvus temperature. The reliability of jet engine disks processed via DMHT method are evaluated by traditional spin testing where the disk is subjected to cyclical loading. Of particular interest is the performance within the transition zone between the bore and rim of the disk as it transitions between a supersolvus coarse microstructure to a subsolvus fine microstructure. The proposed work focuses on developing and enhancing DEFORM system to model turbine disk spin testing and potentially in-service performance with location specific material properties. Models developed will have the ability to consider location specific bulk residual stresses and microstructure features induced from prior manufacturing processes. The effects of thermal loading, cyclic loading, gravity, centrifugal forces, creep, and precipitation coarsening can be coupled to predict the evolution of residual stresses, resulting distortion and microstructure evolution if necessary. In this project, it is proposed to develop and implement appropriate strength and creep models that can link the evolution of microstructural features to property response during thermo-mechanical processing as well as spin test and service conditions. Models developed will be validated against LSHR and Alloy 10 disk spin test experiments conducted by NASA Glenn. BENEFIT: Currently, there is no modeling system available to the industry which would take location specific material properties including microstructural features into consideration in predicting the disk behavior during spin test. The industry lacks a modeling system that is capable of predicting mechanical property response such as strength, creep, flow stress and fatigue resistance due to prior thermo-mechanical processing, accompanying microstructural changes and exposure to service conditions. The proposed work will address the shortcomings of the current capability and the needs of the industry in modeling spin tests. It is anticipated that after successful implementation of the proposed features in the DEFORM system, analytical models will be able to take into account the thermal transients and the cyclical loading conditions in the disk during spin testing to analyze the effects of grain size and precipitate size on plastic strain, tensile strength and residual stress redistribution. As a result of this proposed work, jet engine OEMs would be able to have a better understanding of the interaction of microstructural features and disk behavior under service conditions. The modeling infrastructure and methodology developed in this program will serve as a solid platform to develop microstructure and property prediction models during thermo-mechanical processing and performance under service conditions. Integrating these models into a thermodynamically and kinetically bounded simulation tool, which accounts implicitly for microstructure variability due to process variability, can assist in the accelerated insertion of materials into the jet engine industry.