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At least 127 records · Page 7

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NASA NTRS1991

Thermomechanical and bithermal fatigue behavior of cast B1900 + Hf and wrought Haynes 188

High temperature thermomechanical and bithermal fatigue behavior was investigated for two superalloys: cast nickel-base B1900+Hf and wrought cobalt-base Haynes 188. Experimental results were generated to support development of an advanced thermal fatigue life prediction method. Strain controlled thermomechanical and load-controlled, strain-limited, bithermal fatigue tests were used to determine the fatigue crack initiation and cyclic stress-strain response characteristics of superalloys. Bithermal temperatures of 483 and 871 C were used for B1900+Hf, and 316 and 760 C for Haynes 188. Thermomechanical fatigue tests were conducted by using maximum and minimum temperatures corresponding to those for the bithermal experiments. Lives cover the range from about 10 to 3000 cycles to failure. Isothermal fatigue results obtained previously are also discussed.

Halford, Gary R.↗

NASA NTRS2018

Performance and Durability of Advanced Environmental Barrier Coating Systems

This paper summarizes recent NASA environmental barrier coating (EBC) material advances for protecting the SiC/SiC Ceramic Matrix Composites (CMCs) for meeting next generation turbine engine performance requirements. We particularly present an advanced multicomponent rare earth silicate EBCs with HfO2-Si bond coat system, the temperature capability, environmental stability, and thermomechanical durability, advanced laboratory testing toward subelement demonstrations. Fundamental coating properties of the coating system will also be discussed, with the emphasis on the coating diffusion barrier performance and Calcium Magnesium Alumino-Silicate (CMAS) resistance.

Zhu, Dongming↗

NASA NTRS1992

Creep fatigue life prediction for engine hot section materials (isotropic)

This Final Report covers the activities completed under the optional program of the NASA HOST Contract, NAS3-23288. The initial effort of the optional program was report-in NASA CR189221, which consisted of high temperature strain controlled fatigue tests to study the effects of thermomechanical fatigue, multiaxial loading, reactive environments, and imposed stresses. The baseline alloy used in the tests included B1900+Hf (with or without coating) and wrought INCO 718. Tests conducted on B1900+Hf included environmental tests using various atmospheres (75 psig oxygen, purified argon, or block exposures) and specimen tests of wrought INCO 718 included tensile, creep, stress rupture, TMF, multiaxial, and mean stress tests. Results of these testings were used to calibrate a CDA model for INCO 718 alloy and to develop modifications or corrections to the CDA model to handle additional failure mechanisms. The Socie parameter was found to provide the best correlation for INCO multiaxial loading. Microstructural evaluations consisting of optical, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) techniques, and surface replication techniques to determine crack initiation lives provided data which were used to develop life prediction models.

Nelson, R. S.↗

DOE OSTI2025

Three-Dimensional Heat Flux and Thermal Analysis of Angled Tungsten Samples on DIII-D

ITER-grade tungsten and dispersoid-strengthened tungsten samples with the top surface angled at ~15° towards the incident plasma flux were exposed to 9 H-mode discharges with edge-localized modes (ELMs) in the lower divertor of DIII-D tokamak using the Divertor Material Evaluation System (DiMES). Surface damage included cracking and flaking of material on the two samples farthest away from the plasma strike point, and significant melting of the two samples closest to the strike point. Heat flux and thermal analysis tools new to DIII-D have been applied to better understand this material response and to help optimize the exposure conditions for future experiments. SMITER field-line tracing simulations based on IRTV data and EFIT equilibria estimate an average inter-ELM perpendicular heat flux, 𝑞⊥,𝑖nter−𝐸LM , on the angled surfaces of 10.1 – 19.6 MW/m² for a majority of the 9 discharges, increasing to 15.6 – 24.5 MW/m² for the single, higher-power shot where samples melted. Fast camera data showed shallow intra-ELM melting and re-solidification, which transitioned to bulk inter-ELM melting with melt motion in the 𝐽⃗ 𝑥 𝐵⃗ direction. About 50% of the protruding volume of the most affected sample was displaced via melt-motion. SIERRA thermal modeling software was able to reproduce an onset time of melting consistent with fast camera data and final sample conditions, within < 200 ms. Maximum surface temperatures of 3122 K and 2787 K are estimated for the samples farthest away from the strike point, while the closest samples achieve melting at 4067 ms and 4750 ms into the ~5000 ms plasma exposure. A +10% increase in both the SMITER 𝑞⊥,𝑖nter−𝐸LM calculations and the estimated ELM heat loads 𝑞⊥, 𝐸LM was required to achieve this result, which is within the uncertainty of the diagnostic data but likely accounts for non-ideal geometry effects plus other physics uncertainties not included in this first iteration of modeling. This work provided valuable estimates of the 3D temperature evolution to help better understand the observed surface morphology and internal recrystallization of samples, which are discussed in detail in a complementary manuscript [1]. Benchmarking efforts with more diagnosed DIII-D experiments are underway to further refine the SMITER and SIERRA models for DiMES. Future use of these tools will enable researchers to precisely target heat flux exposure conditions in DIII-D to test, but not exceed, the thermomechanical limitations of novel plasma-facing materials.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1983

Influence of physical aging on the time-dependent properties of network epoxies and epoxy-matrix composites

The matrix-dominated properties of a network epoxy and its carbon fiber-reinforced composite are noted to be affected by sub-glass transition temperature T(g) annealing in a nitrogen atmosphere. The damping behavior, stress relaxation rate, and enthalpic state of the matrix material were found to decrease as functions of sub-T(g) annealing time. This time-dependent change in physical properties is explained on the basis of a free-volume collapse which is related to the recovery process of the nonequilibrium glassy network of the epoxy. The physical aging in network epoxies has been demonstrated to be thermoreversible. Aging kinetics are studied by means of differential scanning calorimetry, stress relaxation tests, dynamic mechanical analysis, and thermomechanical analysis.

Kong, E. S. W.↗

NASA NTRS2004

Causes and Mitigation of Fuel Pilot Operated Valve Pilot Seal Extrusion in Space Shuttle Orbiter Primary RCS Thrusters

Extrusion of a polytetrafluoroethylene (PTFE) pilot seal located in the Space Shuttle Orbiter Primary Reaction Control Subsystem (PRCS) thruster fuel valve has been implicated in 68 ground and on-orbit fuel valve failures. A rash of six extrusion-related in-flight anomalies over a six-mission span from December 2001 to October 2002 led to heightened activity at various NASA centers, and the formation of a multidisciplinary team to solve the problem. Empirical and theoretical approaches were used. For example, thermomechanical analysis (TMA) and exposure tests showed that some extrusion is produced by thermal cycling; however, a review of thruster service histories did not reveal a strong link between thermal cycling and extrusion. Calculations showed that the amount of observed extrusion often exceeded the amount allowed by thermally-induced stress relief. Failure analysis of failed hardware also revealed the presence of fuel-oxidizer reaction product (FORP) inside the fuel valve pilot seal cavity, and differential scanning calorimetry (DSC) showed that the FORP was intimately associated with the pilot seal material. Component-level exposure tests showed that FORP of similar composition could be produced by adjacent oxidizer valve leakage in the absence of thruster firing. Specific gravity data showed that extruded fuel valve pilot seals were less dense than new pilot seals or oxidizer valve pilot seals, indicating permanent modification of the PTFE occurred during service. It is concluded that some thermally-induced extrusion is unavoidable; however, oxidizer leakage-induced extrusion is mostly avoidable and can be mitigated. Several engineering level mitigation strategies are discussed.

Waller, Jess M.↗

NASA NTRS2007

Characterization of Nonlinear Rate Dependent Response of Shape Memory Polymers

Shape Memory Polymers (SMPs) are a class of polymers, which can undergo deformation in a flexible state at elevated temperatures, and when cooled below the glass transition temperature, while retaining their deformed shape, will enter and remain in a rigid state. Upon heating above the glass transition temperature, the shape memory polymer will return to its original, unaltered shape. SMPs have been reported to recover strains of over 400%. It is important to understand the stress and strain recovery behavior of SMPs to better develop constitutive models which predict material behavior. Initial modeling efforts did not account for large deformations beyond 25% strain. However, a model under current development is capable of describing large deformations of the material. This model considers the coexisting active (rubber) and frozen (glass) phases of the polymer, as well as the transitions between the material phases. The constitutive equations at the continuum level are established with internal state variables to describe the microstructural changes associated with the phase transitions. For small deformations, the model reduces to a linear model that agrees with those reported in the literature. Thermomechanical characterization is necessary for the development, calibration, and validation of a constitutive model. The experimental data reported in this paper will assist in model development by providing a better understanding of the stress and strain recovery behavior of the material. This paper presents the testing techniques used to characterize the thermomechanical material properties of a shape memory polymer (SMP) and also presents the resulting data. An innovative visual-photographic apparatus, known as a Vision Image Correlation (VIC) system was used to measure the strain. The details of this technique will also be presented in this paper. A series of tensile tests were performed on specimens such that strain levels of 10, 25, 50, and 100% were applied to the material while it was above its glass transition temperature. After deforming the material to a specified applied strain, the material was then cooled to below the glass transition temperature (Tg) while retaining the deformed shape. Finally, the specimen was heated again to above the transition temperature, and the resulting shape recovery profile was measured. Results show that strain recovery occurs at a nonlinear rate with respect to time. Results also indicate that the ratio of recoverable strain/applied strain increases as the applied strain increases.

Volk, Brent↗

NASA NTRS1988

Isothermal and bithermal thermomechanical fatigue behavior of a NiCoCrAlY-coated single crystal superalloy

Specimens of single crystal PWA 1480 with group of zone axes (100) orientation, bare, or with NiCoCrAlY coating PWA 276, were tested in low cycle fatigue (LCF) at 650, 870, and 1050 C, and in simplified bithermal thermomechanical fatigue (TMF) tests between these temperatures. These tests were examined as a bridge between isothermal LCF and general TMF. In the bithermal test, an inelastic strain is applied at one temperature, T sub max, and reversed at T sub min. The out-of-phase (OP) test type imposing tension at T sub min and compression at T sub max received most study, since it was more damaging than the in-phase type. Specifically investigated were the effects of: inelastic strain range, the coating, delta T, T sub max, T sub min, and the environment.

Gayda, J.↗

NASA NTRS1988

Isothermal and 'bithermal' thermomechanical fatigue behavior of a NiCoCrAlY-coated single crystal superalloy

Specimens of single crystal PWA 1480 with group of zone axes (100) orientation, bare, or with NiCoCrAlY coating PWA 276, were tested in low cycle fatigue (LCF) at 650, 870, and 1050 C, and in simplified bithermal thermomechanical fatigue (TMF) tests between these temperatures. These tests were examined as a bridge between isothermal LCF and general TMF. In the bithermal test, and inelastic strain is applied at one temperature, T sub max, and reversed at T sub min. The out-of-phase (OP) test type imposing tension at T sub min and compression at T sub max received most study, since it was more damaging than the in-phase type. Specifically investigated were the effects of: inelastic strain range, the coating, delta T, T sub max, T sub min, and the environment.

Gayda, J.↗

DOE OSTI2025

Pursuing small-scale measures of penetration resistance in Ti-5553 alloy

This work was originally proposed to illustrate the performance of a particular set of differently processed Ti-5553 plates under dynamic threats. It became clear that the larger question, at present, is whether the small-scale shaped charge design of an RP-4 detonator can be employed to efficiently explore the dynamic penetration resistance of representative test articles. The initial penetration testing that employed three variants of thermomechanical processing of Ti-5553 plates appeared to demonstrate that there was a noticeable difference in their performance. The remaining pertinent question was regarding the variation in the shaped charge performance and how it compares to the variation from the three titanium plate tests. Based on the limited testing presented here the RP-4 shaped charge detonator appears to have an average depth of penetration in 6061 aluminum of 90mm with a 1.5CD stand off.

shaped charge penetration↗

DOE OSTI2024

Schema Elements for Granta Annual Report: FY2024

Granta: Materials Intelligence (Granta: MI) is a commercial database software distributed by Ansys, Inc. that is utilized by the Nuclear Security Enterprise (NSE) to organize and store relevant materials data. Lack of standard and well-documented database schema is the primary obstacle to an NSE materials data management solution, so the objective of this project is to create and document such a schema. In FY21, an approach for designing, documenting, and managing a standard database schema was described based on the creation of schema elements (collections of attributes used to describe particular aspects of the data) to be used as building blocks for creating various database tables without duplication. In FY22, these methods were applied through a multi-site collaboration to create and document the schema elements necessary to build a thermogravimetric analysis (TGA) testing table. In FY23 the schema was expanded to include elements for a differential scanning calorimetry (DSC) table, along with schema for supporting metadata tables including Instruments, Projects, Documents, and Testing Series. In FY24 the following progress was made, again through multi-site collaboration: • The existing schema elements were modified to accommodate thermomechanical analysis (TMA) data, and a table, Test Data: TMA, was created for managing TMA data. • The elements necessary for the following additive manufacturing (AM) data tables (directed at data specific to selective laser sintering AM technology) were created: • AM Builds • AM Processes • AM Part Designs • Built AM Parts • AM Feedstock Materials • AM Feedstock Material Batches • The elements necessary for creating a Calibrated Material Models table were created, and the Calibrated Material Models table was created. In FY25 the existing schema will be deployed on the production enterprise Granta instance on the enterprise secure network. Schema elements will be appended, and new elements created as necessary, to allow the creation of tables specifically to support materials testing, AM process development, and design and analysis for modernization programs.

36 MATERIALS SCIENCE↗

NASA NTRS2000

Fastrac Nozzle Design, Performance and Development

With the goal of lowering the cost of payload to orbit, NASA/MSFC (Marshall Space Flight Center) researched ways to decrease the complexity and cost of an engine system and its components for a small two-stage booster vehicle. The composite nozzle for this Fastrac Engine was designed, built and tested by MSFC with fabrication support and engineering from Thiokol-SEHO (Science and Engineering Huntsville Operation). The Fastrac nozzle uses materials, fabrication processes and design features that are inexpensive, simple and easily manufactured. As the low cost nozzle (and injector) design matured through the subscale tests and into full scale hot fire testing, X-34 chose the Fastrac engine for the propulsion plant for the X-34. Modifications were made to nozzle design in order to meet the new flight requirements. The nozzle design has evolved through subscale testing and manufacturing demonstrations to full CFD (Computational Fluid Dynamics), thermal, thermomechanical and dynamic analysis and the required component and engine system tests to validate the design. The Fastrac nozzle is now in final development hot fire testing and has successfully accumulated 66 hot fire tests and 1804 seconds on 18 different nozzles.

Peters, Warren↗

NASA NTRS1985

Thermomechanical deformation in the presence of metallurgical changes

Nonisothermal testing that can be used as a basis of a nonisothermal representation is discussed. Related tests regarding metallurgical changes that occur in other high temperature structural alloys are discussed. A viscoplastic constitutive model capable of qualitatively representing the behavioral features was formulated. This model is used to assess the differences in ultimate life prediction in some typical nonisothermal structural problems when the constitutive model does or does not account for metallurgically induced thermomechanical history dependence.

Robinson, D. N.↗

NASA NTRS1988

Life prediction of thermomechanical fatigue using total strain version of strainrange partitioning (SRP): A proposal

A method is proposed (without experimental verification) for extending the total strain version of Strainrange Partitioning (TS-SRP) to predict the lives of thermomechanical fatigue (TMF) cycles. The principal feature of TS SRP is the determination of the time-temperature-waveshape dependent elastic strainrange versus life lines that are added subsequently to the classical inelastic strainrange versus life lines to form the total strainrange versus life relations. The procedure is based on a derived relation between failure and flow behavior. Failure behavior is represented by conventional SRP inelastic strainrange versus cyclic life relations, while flow behavior is captured in terms of the cyclic stress-strain response characteristics. Stress-strain response is calculated from simple equations developed from approximations to more complex cyclic constitutive models. For applications to TMF life prediction, a new testing technique, bithermal cycling, is proposed as a means for generating the inelastic strainrange versus life relations. Flow relations for use in predicting TMF lives would normally be obtained from approximations to complex thermomechanical constitutive models. Bithermal flow testing is also proposed as an alternative to thermomechanical flow testing at low strainranges where the hysteresis loop is difficult to analyze.

Saltsman, James F.↗

NASA NTRS1988

Constitutive response of Rene 80 under thermal mechanical loads

The applicability of a classical constitutive model for stress-strain analysis of a nickel base superalloy, Rene' 80, in the gas turbine thermomechanical fatigue (TMF) environment is examined. A variety of tests were conducted to generate basic material data and to investigate the material response under cyclic thermomechanical loading. Isothermal stress-strain data were acquired at a variety of strain rates over the TMF temperature range. Creep curves were examined at 2 temperature ranges, 871 to 982 C and 760 to 871 C. The results provide optimism on the ability of the classical constitutive model for high temperature applications.

Kim, K. S.↗

DOE OSTI2024

Summary of FY2024 Experimental Results to Support Development of New Inelastic Material Models and Validation of Section III, Division 5, Class A Design Rules

To address the data gap crucial for updating existing viscoplastic constitutive material models for the Class A materials in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section III, Division 5, High Temperature Reactors (ASME, 2023) for inelastic design analysis, Oak Ridge National Laboratory (ORNL) conducted experimental studies on Alloy 800H and Alloy 617 across a range of temperatures up to their maximum temperature limits in Section III, Division 5. The studies aim to characterize the materials' deformation behavior under both strain-controlled mechanical cyclic loading and thermal cycling conditions. This report summarizes ORNL's FY 2024 experimental findings on Alloy 800H and Alloy 617, focusing on pure fatigue tests, cyclic stress-strain curves, thermomechanical fatigue experiments, and verification of the high temperature cyclic damage summation design rules.

36 MATERIALS SCIENCE↗

NASA NTRS1975

Mechanical behavior of the directionally solidified gamma/gamma prime - delta eutectic alloy

The eutectic alloy Ni-20.0%Cb-2.5%Al-6.0%Cr was tested in short-term creep and long-term exposure to service conditions to assess its suitability for high temperature turbine blade applications. Long-time exposure showed the lamellar microstructure of the alloy to be exceptionally stable. Other properties tested were notch sensitivity, isothermal and thermomechanical fatigue strength, shear strength, and transverse ductility. It was shown that this alloy is superior to the best currently available directionally solidified superalloys over the temperature/stress conditions encountered in turbine airfoils.

Barkalow, R. H.↗

NASA NTRS1985

Experimental and analytical study of ceramic-coated turbine-tip shroud seals for small turbine engines

The results of an experimental and analytical evaluation of ceramic turbine tip shrouds within a small turbine engine operating environment are presented. The ceramic shrouds were subjected to 1001 cycles between idle and high power and steady-state conditions for a total of 57.8 engine hr. Posttest engine inspection revealed mud-flat surface cracking, which was attributed to microcracking under tension with crack penetration to the ceramic and bond coat interface. Sections and micrographs tend to corroborate the thesis. The engine test data provided input to a thermomechanical analysis to predict temperature and stress profiles throughout the ceramic gas-path seal. The analysis predicts cyclic thermal stresses large enough to cause the seal to fail. These stresses are, however, mitigated by inelastic behavior of the shroud materials and by the microfracturing that tensile stresses produce. Microfracturing enhances shroud longevity during early life but provides the failure mechanism during life but provides the failure mechanism during extended life when coupled with the time dependent inelastic materials effects.

Biesiadny, T. J.↗