Search NASA⌕ Search

SEARCH · Search NASA

Results for “creep performance”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

High temperature inelastic deformation under uniaxial loading - Theory and experiment

The elevated-temperature uniaxial inelastic deformation behavior of an Ni-base alloy, B1900 + Hf, is investigated by performing isothermal tensile, creep, cyclic, stress relaxation, and thermomechanical fatigue tests. The range of strain rates examined is from 10 to the -7th to 100 per sec, while the test temperatures range from 25 to 1093 C. This extensive constitutive data base has been used for evaluating the unified constitutive models of Bodner and Partom (1972) and of Walker (1972) which apply for the small-strain regime. Comparison of test results with independent model predictions indicates good agreement over a broad range of loading conditions, demonstrating the applicability of the unified-constitutive-equation approach for describing the strongly nonlinear and temperature-dependent response of meals under a wide range of deformation and thermal histories. Thus the results give confidence that the unified approach is an effective and efficient approach in which complex history-dependent thermoviscoplastic flow can be represented within a single inelastic strain-rate term.

Chan, K. S.↗
NASA NTRS1990

Analytical and experimental studies on creep behavior of polymeric matrix composites

The creep behavior of graphite/epoxy composites is studied both analytically and experimentally. In the analytical study, a special finite element procedure was developed for the accurate and efficient analysis of creep response in anisotropic materials. This procedure was used to study the stress and strain distributions and histories in composite laminates containing circular holes. In the experimental study, creep tests were performed to investigate the time-dependent response of graphite/epoxy composites at elevated temperature. The moire interferometry technique was employed to determine the deformation histories in notched composites. The experimental results were compared with the analytical predictions and good agreement was observed.

Lin, K. Y.↗
DOE OSTI2025

Micromechanical Surrogate Machine Learning Model for Creep Deformation Modeling

Process variability during the manufacture of gas turbine engine hot section components can significantly affect the material’s resulting microstructure. In casting, for instance, geometric variation within a component (thin sections versus thick sections, radial location) influences cooling rates and the resulting grain size. The high temperature creep response is known to be sensitive to grain size owing to a diffusional creep mechanism which occurs more readily along grain boundaries. Microstructural variation correspondingly drives mechanical behavior which propagates into component scale performance uncertainty. These factors are essential when planning inspection, maintenance, and repair strategies within a reliability framework. These benefits provide opportunities to increase overall energy efficiency through refined margins. Critically, there is an opportunity to bolster existing data-driven reliability models using physics-driven process-structure-property relations. Here we present recent work establishing a framework for evaluating the probabilistic creep performance of high-temperature materials. A novel microstructure-sensitive crystal plasticity finite element model is established that captures both grain boundary and crystallographic deformation effects. The computationally expensive physics model is calibrated using a statistical approach and this high-fidelity model is subsequently used to train a computationally efficient machine learning surrogate model. The surrogate model is essential for sampling a large ensemble of simulated structure-property pair results. The ensemble data are then mined to extract salient trends to be incorporated into a microstructure-sensitive reliability model. The proposed approach represents a novel way to capture microstructure-sensitive trends from physics-based models within a modern reliability framework.

Fernandez-Zelaia, Patxi [ORNL]↗
DOE OSTI2023

Small Scale Creep Testing of 14YWT via In-situ Transmission Electron Microscopy Irradiation and Nanoindentation

The next generation of nuclear materials must withstand harsh operating conditions such as high temperatures and irradiation doses. Nanostructured ferritic alloys like oxide dispersion strengthened steels, especially 14YWT, have shown promise as a structural material to withstand these harsh operating conditions. For application, understanding the irradiation enhanced creep of the structural components is fundamental to evaluating the service life in a reactor. Challenges with evaluating irradiation enhanced creep are related to the limited space in nuclear reactors and the expense of conducting post irradiation experiments on irradiated cladding. Ion irradiations are considered to expedite irradiation testing, but such experiments have restricted depth of penetration into the material, limiting the ability to characterize changes to material properties after irradiation. Small scale mechanical testing can be used with ion beam irradiations as a potential avenue to evaluate the irradiation enhanced creep of materials. In this study, in-situ transmission electron microscopy nanopillar creep studies on 14YWT were performed and simultaneously ion beam irradiated with 2.8 MeV Au4+ ions. It was observed that the ion beam irradiation did increase the measured strain rate of the materials. In addition, ex-situ nanoindentation creep studies were performed over a range of temperatures on control 14YWT, and it was observed that there was a change in the deformation mechanism between 873 K and 1073 K that agrees well with macro-scale mechanical testing. Furthermore, these results show promise for applying these techniques to nuclear materials in the future.

14 YWT↗
DOE OSTI2021

Irradiation-enhanced diffusion and diffusion-limited creep in U 3 Si 2

U 3 Si 2 is an advanced fuel candidate due to its relatively high fissile density and attractive thermal properties. Compared to standard UO 2 fuel, there are significant data gaps for the thermophysical and thermomechanical properties of U 3 Si 2 . Point defect concentrations and mobilities under irradiation govern a number of important fuel performance properties, such as creep and fission gas release. In this work, we utilized density functional theory (DFT) data to inform a cluster dynamics framework to predict point defect concentrations in U 3 Si 2 under irradiation. Molecular dynamics (MD) simulations were used to examine the contribution of atomic mixing during ballistic cascades to diffusion, as well as the diffusivity of U and Si at grain boundaries. These atomic scale models for diffusivity were then used to inform a creep model based on bulk (Nabarro-Herring) and grain boundary (Coble) diffusional creep, and climb-limited dislocation creep. The model compares well against available experimental data and has been implemented in the BISON fuel performance code. Finally, a demonstration case using simple power profiles has been carried out, showing that negligible creep occurs due to the low temperatures experienced by U 3 Si 2 in-reactor, a consequence of its high thermal conductivity.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

Creep properties of advanced austenitic steel 709 determined through short experiments under in-situ neutron diffraction followed by TEM characterization

Here in this study, the creep mechanisms at play in Alloy 709 (Fe-20Cr-25Ni) are investigated by performing short-term creep-type tests under in-situ neutron diffraction experiments. Short tests are performed in the temperature range of 500 to 900 °C under constant load with a load ranging from 50 to 150 MPa. The creep exponent and activation energy are determined using the Bird-Mukherjee-Dorn relation and compared to that obtained from conventional longer creep tests from the literature. Scanning transmission electron microscopy (S/TEM) of the post-creep microstructure indicates that interaction of dislocations with precipitates are a dominant mechanism at play. Furthermore, local elemental mapping indicated chemical segregation at grain boundaries and formation of complex precipitates.

36 MATERIALS SCIENCE↗
NASA NTRS2001

Long-Term Creep and Creep Rupture Behavior of Woven Ceramic Matrix Composites

Tensile creep behavior of SiC/SiNC ceramic matrix composites at elevated temperatures and at various stress levels have been investigated for turbine engine applications. The objective of this research is to present creep behavior of SiC/SiCN composites at stress levels above and below the monotonic proportional limit strength and predict the life at creep rupture conditions. Tensile creep-rupture tests were performed on an Instron 8502 servohydraulic testing machine at constant load conditions up to a temperature limit of 1000 C. Individual creep curves indicate three stages such as primary, secondary, and tertiary. The creep rate increased linearly at an early stage and then gradually became exponential at higher strains. The stress exponent and activation energy were also obtained at 700 and 1000 C. The specimen lifetime was observed to be 55 hrs at 121 MPa and at 700 C. The life span reduced to 35 hrs at 143 MPa and at 1000 C. Scanning electron microscopy observations revealed significant changes in the crystalline phases and creep damage development. Creep failures were accompanied by extensive fiber pullout, matrix cracking, and debonding along with fiber fracture. The creep data was applied to Time-Temperature-Stress superposition model and the Manson-Haferd parametric model for long-time life prediction.

Haque, A.↗
DOE OSTI2020

Mechanical Properties and Deformation Behavior of Additively Manufactured 316L Stainless Steel (FY2020)

The Transformational Challenge Reactor (TCR) program plans to build most of the TCR core components through additive manufacturing (AM) processes. These processes include laser powder bed fusion (LPBF) for the metallic (316L) components and the newly developed combined process of binderjet printing and chemical vapor infiltration (CVI) for the SiC fuel matrix. Mechanical testing and characterization tasks have been carried out since the beginning of the TCR program to (1) build a property database for the AM materials that will be used in TCR core and (2) to assess the materials’ performance in TCR-relevant conditions. This document reports the outcome of the testing and characterization efforts for the fiscal year with a focus on the mechanical performance data of AM 316L stainless steel (SS). Baseline tensile testing over a wide temperature range of room temperature–600 °C was completed for the AM 316L alloy in as-built, stress-relieved, and solution-annealed conditions. The as-built 316L showed the highest strength, and the alloy after the post-build treatments showed reduced strengths in the low-strain range. However, the strength differences among the AM materials became insignificant in the later part of deformation. Furthermore, regardless of post-build processing, the AM 316L SS showed higher strength and comparable ductility when compared with wrought 316L SS. Thermal creep testing and microstructural evolution during creep deformation were also performed under selected conditions. It was found that the AM 316L steel showed the best creep resistance in the stress-relieved condition. In-situ tensile tests were performed using scanning electron microscopy and 1-ID beamline at the Advanced Photon Source to elucidate the deformation and fracture behavior of AM 316L and the evolution of crystalline stress, dislocations, and pore distribution. Using these in-situ testing data, an in-depth analysis of the roles of microstructural features in deformation and fracture processes is presented herein. The final section of the document introduces ongoing and future activities for materials testing and characterization, including irradiation effect studies and ball punch testing on AM 316L and AM IN718 alloys.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS1975

Determination of structural engineering properties of incoloy 903 and CTX-1 alloys

Tension, notched tension, compression, density, thermal conductivity, and thermal expansion tests were conducted on Incoloy 903 over the temperature range 20 K (-423 F) through 1033 K (1400 F). Fracture toughness tests were performed at room temperature (RT). Creep and rupture tests were conducted at 811 K (1000 F), 922 K (1200 F), and 1033 K (1400 F) for this alloy. Transverse unnotched and notched fatigue tests at R = 0.1 were performed at RT and 922 K (1200 F). For CTX-1 alloy, tension, Charpy V-notch impact, density, thermal conductivity, and thermal expansion tests were conducted over the temperature range 20 K (-423 F) through 1033 K (1400 F). Poisson's ratio was determined at RT, 811 K (1000 F), 922 K (1200 F), and 1033 K (1400 F). Notched tension and compression tests were performed at 20 K (-423 F), RT, and 922 K (1200 F); plane strain fracture toughness tests were conducted at RT, 77 K (-320 F), and 20 K (-423 F). Creep and rupture tests were performed at 811 K (1000 F), 922 K (1200 F), and 1033 K (1400 F); longitudinal unnotched and notched fatigue tests at R = 0.1 were conducted at RT and 922 K (1200 F). Results are presented and discussed.

Ruff, P. E.↗
DOE OSTI2023

Compare Mechanistic Predictions for Doped UO 2 Mechanical Response and Other Properties with Empirical Models and Experimental Measurements

The U.S. Department of Energy’s Nuclear Energy Advanced Modeling and Simulation program develops predictive capabilities using computational methods for the analysis and design of advanced reactor and fuel cycle systems. This program has been supporting the development of BISON, a high-fidelity, high resolution fuel performance tool at the engineering scale. As part of its development, additional modeling capabilities and improvements have been developed for relevant fuel forms. In this work, a fuel creep deformation model for Cr-doped fuel has been implemented into BISON, along with improvements to the empirical UO 2 fuel creep model based on experimental data and improvements to the radial power factor calculation for doped fuels. This work allows for more accurate simulation analyses for both UO 2 and doped-UO 2 fuels.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

FY20 Status Report on Creep Rupture Testing to Support the Development of Alloy 709 Code Case

This report provides an update on the status of the creep rupture testing on the first commercial heat of Alloy 709 in support of the Alloy 709 Code Case development. A creep test laboratory has been set up at ANL that comprises of 15 indirectly loaded test frames capable of testing ASTM-size specimens of the commercial heat of Alloy 709. The systems are equipped with high temperature furnaces capable of operation up to 1000°C in an air environment. During FY18, uniaxial ASTM-sized creep specimens were fabricated from 9 Alloy 709 plates that were processed by AOD, ESR, and ESR-homogenized routes and subsequently solution annealed at 1050, 1100, and 1150°C, and creep-rupture tests were performed at 330MPa and 600°C. The test results led to the down selection of the ESR-1100°C condition to support the code case. In FY19, 15 creep-rupture tests of the ESR-1100°C material, requiring the use of Type K thermocouples, were initiated to support the 100,000-hour Code Case. 8 tests were completed in FY19. In FY20, 6 tests were completed at the time of writing this report. In addition, 1 more test were loaded in FY20, using Type S thermocouples, and was completed. This report presents the data from the completed tests in FY20 and also the microstructural characterization of the fractured specimens. The creep data enabled the preliminary analysis of the creep behavior of this material. The characterization showed that in brittle fractures, the pores were narrow and thin, and elongated in the direction perpendicular to the loading direction, while in ductile fractures, the pores were much rounder. Dense precipitates were observed in all the samples, the size of which grew with test temperature. Some of the precipitates could be identified to be M23C6 based on their cuboid shape.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1985

Cumulative creep damage for polycarbonate and polysulfone

The literature for creep to failure cumulative damage laws are reviewed. Creep to failure tests performed on polycarbonate and polysulfone under single and two step loadings are discussed. A cumulative damage law or modified time fraction rule is developed using a power law for transient creep response as the starting point. Experimental results are approximated well by the new rule. Damage and failure mechanisms associated with the two materials are suggested.

Zhang, M.↗
NASA NTRS1985

Cumulative creep damage for polycarbonate and polysulfone

Creep to failure tests performed on polycarbonate and polysulfone under single and two step loadings are discussed. A cumulative damage law or modified time fraction rule is developed using a power law for transient creep response as the starting point. Experimental results are approximated well by the new rule. Damage and failure mechanisms associated with the two materials are suggested.

Zhang, M. J.↗
DOE OSTI2026

Creep in multi-principal element materials –– A review

The ongoing push towards enhanced energy efficiency and reduced emissions has necessitated the creation of materials with superior performance, especially under extreme conditions. Modern industries, such as aerospace, energy production, and nuclear power, rely heavily on materials that can withstand elevated temperatures without compromising structural integrity. At these heightened temperatures, materials, even when subjected to mechanical stresses well below their yield strength, may experience slow deformation leading to eventual rupture — a phenomenon known as creep. With the expansive design space that comes with the high entropy concept and their reported excellent high temperature strength, multi-principal element materials (MPEMs) have attracted interest in the scientific community for high-temperature applications. Here, this review offers a comprehensive examination of existing studies on creep in MPEMs, which includes multi-principal element−alloys, −bulk metallic glasses, −ceramics, and −superalloys, comparing published findings on MPEMs with pure elements, traditional alloys, bulk metallic glasses, and superalloys. The sub-topics covered include a comparison among different creep-testing methods, creep mechanisms, creep exponents, creep strain rates, activation volume, and creep-activation energy. Modeling efforts for predicting creep behavior of MPEMs are also reviewed. Methods for improving creep resistance by performing heat treatments and/or modifying microstructures are discussed. Overall, the current state of MPEMs has not yet surpassed the creep performance of commercial alloys. Finally, directions for future efforts are suggested, such as experimenting in various controlled environments, expanding the number of compositions tested, exploring advanced manufacturing techniques, and using machine-learning to predict creep properties based on compositions and microstructures.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Reanalysis of Cost and Moist Air Oxidation Performance for CF8C-Plus and Other Alloys for AUSC Applications

This report provides an economic analysis of CF8C-Plus and other candidate materials for Advanced Ultra Supercritical (AUSC) applications, including 347HFG, HR6W, Sanicro 25, Super 304H, Grade 92, SAVE12AD, Inconel 617, and Inconel 740H. An assessment of their moist air oxidation performance is also included. When compared with the aforementioned alloys, CF8C-Plus shows a favorable balance between cost, creep strength and moist air oxidation resistance in the temperature range of 600-700°C. Furthermore, its castability makes it additionally attractive from a manufacturing perspective. Materials with higher Ni content, such as HR6W, Sanicro 25, Inconel 617, and Inconel 740H, have better creep strength but the improved performance comes with increased cost. Stainless steel 347HFG exhibits inferior creep strength and lower moist air oxidation resistance, but at a greater cost, compared with CF8C-Plus. Super 304H, another stainless steel, has similar creep strength and cost compared to CF8CPlus at 700°C, but may not have as good moist air oxidation resistance. Grade 92 has lower creep strength and unfavorable economy compared with CF8C-Plus. SAVE12AD also has lower creep strength than CF8C-Plus, but has lower cost to use at 600°C. Both Grade 92 and SAVE12AD are also limited to the maximum use temperature of 649°C per ASME code case requirements.

36 MATERIALS SCIENCE↗
NASA NTRS1980

Creep rupture behavior of unidirectional advanced composites

A 'material modeling' methodology for predicting the creep rupture behavior of unidirectional advanced composites is proposed. In this approach the parameters (obtained from short-term tests) required to make the predictions are the three principal creep compliance master curves and their corresponding quasi-static strengths tested at room temperature (22 C). Using these parameters in conjunction with a failure criterion, creep rupture envelopes can be generated for any combination of in-plane loading conditions and ambient temperature. The analysis was validated experimentally for one composite system, the T300/934 graphite-epoxy system. This was done by performing short-term creep tests (to generate the principal creep compliance master curves with the time-temperature superposition principle) and relatively long-term creep rupture tensile tests of off-axis specimens at 180 C. Good to reasonable agreement between experimental and analytical results is observed.

Yeow, Y. T.↗
DOE OSTI2023

Variation of γ′ Formers and Refractory Elements for Enhanced Creep resistance and Phase Stability of HAYNES® 282® Alloy

Modifications to the chemistry of alloy 282 were performed to improve the alloy’s resistance to long term creep deformation as well as phase stability. Alloys were prepared using vacuum induction melting, computationally optimized homogenization heat treatment and hot working. Phase stability studies were carried out for up to 5,000 hours at 800°C and 900°C while creep testing was performed at conditions leading to lives past 7,000 hours for temperatures ranging from 740°C to 900°C. The formation of σ and μ phases were reduced in the modified alloy. Atom probe tomography (APT) was performed on the specimens from the phase stability study to investigate changes in the elemental partitioning to the γ and γ′ phases. Post deformation microstructures were analyzed using EBSD and TEM to study the influence of the detrimental phases on damage accumulation during creep.

Detrois, Martin↗