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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.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

The effect of ion plated silver and sliding friction on tensile stress-induced cracking in aluminum oxide

A Hertzian analysis of the effect of sliding friction on contact stresses in alumina is used to predict the critical load for crack generation. The results for uncoated alumina and alumina coated with ion plated silver are compared. Friction coefficient inputs to the analysis are determined experimentally with a scratch test instrument employing an 0.2 mm radius diamond stylus. A series of scratches were made at constant load increments on coated and uncoated flat alumina surfaces. Critical loads for cracking are detected by microscopic examination of cross sections of scratches made at various loads and friction coefficients. Acoustic emission (AE) and friction trends were also evaluated as experimental techniques for determining critical loads for cracking. Analytical predictions correlate well with micrographic evidence and with the lowest load at which AE is detected in multiple scratch tests. Friction/load trends are not good indicators of early crack formation. Lubrication with silver films reduced friction and thereby increased the critical load for crack initiation in agreement with analytical predictions.

Sliney, Harold E.↗
NASA NTRS1993

The effect of ion-plated silver and sliding friction on tensile stress-induced cracking in aluminum oxide

A Hertzian analysis of the effect of sliding friction on contact stresses in alumina is used to predict the critical load for crack generation. The results for uncoated alumina and alumina coated with ion plated silver are compared. Friction coefficient inputs to the analysis are determined experimentally with a scratch test instrument employing an 0.2 mm radius diamond stylus. A series of scratches were made at constant load increments on coated and uncoated flat alumina surfaces. Critical loads for cracking are detected by microscopic examination of cross sections of scratches made at various loads and friction coefficients. Acoustic emission (AE) and friction trends were also evaluated as experimental techniques for determining critical loads for cracking. Analytical predictions correlate well with micrographic evidence and with the lowest load at which AE is detected in multiple scratch tests. Friction/load trends are not good indicators of early crack formation. Lubrication with silver films reduced friction and thereby increased the critical load for crack initiation in agreement with analytical predictions.

Sliney, Harold E.↗
NASA NTRS2001

Constituent Effects on the Stress-Strain Behavior of Woven Melt-Infiltrated SiC Composites

The stress-strain behavior of 2D woven SiC fiber reinforced, melt-infiltrated SiC matrix composites with BN interphases were studied for composites fabricated with different fiber tow ends per unit length, different composite thickness, and different numbers of plies. In general, the stress-strain behavior, i.e., the 'knee' in the curve and the final slope of the stress-strain curve, was controlled by the volume fraction of fibers. Some of the composites exhibited debonding and sliding in between the interphase and the matrix rather than the more common debonding and sliding interface between the fiber and the interphase. Composites that exhibited this 'outside debonding' interface, in general, had lower elastic moduli and higher ultimate strains as well as longer pull-out lengths compared to the 'inside debonding' interface composites. Stress-strain curves were modeled where matrix crack formation as a function of stress was approximated from the acoustic emission activity and the measured crack density from the failed specimens. Interfacial shear strength measurements from individual fiber push-in tests were in good agreement with the interfacial shear strength values used to model the stress-strain curves.

Morscher, Gregory N.↗
NASA NTRS2004

GRABER: The Duct Tape of Space and JIMO Heat Conducting Foam

Crack formation in the space shuttle's heat shield during flight poses a major safety concern to everyone on board. Cracking weakens the structure of the shield and lessens the protection it offers against the high temperatures and forces encountered during re-entry. Astronauts need a way to mend these cracks while in space. This is GRABER s function; it can be spackled into the cracks by an astronaut. The material then hardens, or cures, due to being in a vacuum and the heat encountered when it faces the sun. A great deal of work and testing is necessary to create a material that will be workable in a vacuum over a wide range of temperatures, will cure without cracking, will adhere to the sides of the crack, and that can withstand the extreme temperatures of re-entry. A Brookfield PVS Rheometer is being used to characterize GRABER's viscosity at various temperatures and stirring rates. Various compositions of GRABER are being heat treated in a vacuum to determine probably curing times in space. The microstructures of cured samples of each composition are being examined using both optical and electron microscopy. Jupiter s Icy Moon Orbiter (JIMO) will be lifting off sometime around 2013. JIMO will have more power than its predecessor, Galileo, allowing it to change orbits to circle three of Jupiter s moons. Both of the engine types being considered require large heat dissipation systems. These systems will be comprised of heat conductive tubing and plates with a liquid flowing through them. In order to maximize the speed of heat transfer between the tubes and the panels, the in-between areas will be filled with heat conductive silicon carbide foam. Two different foam systems are being considered for this foam. Currently, experimentation is underway with adding Sic, carbon, and carbon fibers to a two part fuel retardant foam. The foam is them pyrolized and its mass and dimensional changes are measured. The structure of the foam will be examined using optical and electron microscopy as well. Work is also planned with a foam system developed by an Italian team.

Gamble, Eleanor A.↗
NASA NTRS1959

Engine Operating Conditions that Cause Thermal-Fatigue Cracks in Turbojet-Engine Buckets

Five engine tests were conducted to definitely establish the failure mechanism of leading-edge cracking and to determine which conditions of engine operation cause the failures. Five groups of S-616 and M-252 buckets from master lots were run consecutively in the same J47-25 engine. The tests included a steady-state run at full-power conditions, rapid cycling between idle and rated speed, and three different start-stop tests. The first start-stop test consisted of cycles of start and stop with 5 minutes of idle speed before each stop; the second included cycles of start and stop but with 15 minutes of rated speed before each stop; the third consisted of cycles of gradual starts and normal stops with 5 minutes at idle speed before each stop. The test results demonstrated that the primary cause of leading-edge cracking was thermal fatigue produced by repeated engine starts. The leading edge of the bucket experiences plastic flow in compression during starts and consequently is subjected to a tensile stress when the remainder of the bucket becomes heated and expands. Crack initiation was accelerated when rated-speed operation was added to each normal start-stop cycle. This acceleration of crack formation was attributed to localized creep damage and perhaps to embrittlement resulting from overaging. It was demonstrated that leading-edge cracking can be prevented simply by starting the engine gradually.

Johnston, James R.↗
DOE OSTI2024

FY24 Progress Report: SRNL Analysis of ICCWR LCM and WAMS data for Corrosion and Cracking

Algorithms for Machine Learning (ML) and data analysis for the 3013 Surveillance Program have been developed in an ongoing collaborative effort by the Savannah River National Laboratory (SRNL) and the University of South Carolina (USC). The objective of the algorithms is to automate the identification of corrosion and crack formation in the Inner Container Closure Weld Region (ICCWR) of the canister system used to store Pu-bearing material. Data for corrosion and cracking is collected from large binary files generated by a Laser Confocal Microscope (LCM), the Wide Area 3D Measurement System (WAMS), or,in a recent proposal, by a Scanning Electron Microscope (SEM). The ML software uses the physical attributes in the data files (e.g., one or more of: height, color, and 16-bit grayscale values as functions of position in a plane projection) to detect signs of surface corrosion and cracking after being trained on similar data, with the features to be detected. Although the initial scope included screening for broader indicators of corrosion, e.g., pitting, identification of potential cracks was prioritized for the past several years at the request of program leadership. Labeled training data is essential to developing the ML algorithm, and enhancements to data labeling capability have been developed to address this essential precursor to application of ML routines. Efficient labeling is particularly important in view of the large volume of data required to train ML algorithms and the relative rarity of cracks in the ICCWR data set. The updated program will read binary data from either LCM, WAMS or SEM files, interrogate data attributes, facilitate user labeling of data for training ML algorithms, execute ML algorithms, output parameters from trained ML algorithms, report ML model accuracy with respect to labeled data, and generate graphical representations for various analyses. In FY24, hourglass neural networks (HNNs) that were initiated in FY22 were further developed and tested using available LCM data, and their performance was tested against that of the alternative U-Net Neural Network algorithm structure. HNNs along with previously developed Convolutional Neural Networks (CNNs) and Deep Neural Networks (DNNs) comprise a suite of ML tools for identification of cracks in the ICCWR

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1995

Microcracking in composite laminates under thermal and mechanical loading

Composites used in space structures are exposed to both extremes in temperature and applied mechanical loads. Cracks in the matrix form, changing the laminate thermoelastic properties. The goal of the present investigation is to develop a predictive methodology to quantify microcracking in general composite laminates under both thermal and mechanical loading. This objective is successfully met through a combination of analytical modeling and experimental investigation. In the analysis, the stress and displacement distributions in the vicinity of a crack are determined using a shear lag model. These are incorporated into an energy based cracking criterion to determine the favorability of crack formation. A progressive damage algorithm allows the inclusion of material softening effects and temperature-dependent material properties. The analysis is implemented by a computer code which gives predicted crack density and degraded laminate properties as functions of any thermomechanical load history. Extensive experimentation provides verification of the analysis. AS4/3501-6 graphite/epoxy laminates are manufactured with three different layups to investigate ply thickness and orientation effects. Thermal specimens are cooled to progressively lower temperatures down to -184 C. After conditioning the specimens to each temperature, cracks are counted on their edges using optical microscopy and in their interiors by sanding to incremental depths. Tensile coupons are loaded monotonically to progressively higher loads until failure. Cracks are counted on the coupon edges after each loading. A data fit to all available results provides input parameters for the analysis and shows them to be material properties, independent of geometry and loading. Correlation between experiment and analysis is generally very good under both thermal and mechanical loading, showing the methodology to be a powerful, unified tool. Delayed crack initiation observed in a few cases is attributed to a lack of preexisting flaws assumed by the analysis. Some interactions between adjacent ply groups are attributed to local stress concentrations. These two effects are not captured by the analysis due to its global nature. The analysis is conservative in these cases and agrees well with data after the observed onset of cracking.

Maddocks, Jason R.↗
DOE OSTI2025

Manufacturability and performance response of developed Ni-based alloys for reactor environments

Under the Advanced Materials and Manufacturing Technologies program, two Ni-based alloys fabricated by laser powder bed fusion (LPBF) at ORNL and laser powder directed energy deposition (LP-DED) at INL have been evaluated: γ′-strengthened Haynes 282 and solution-strengthened Inconel 625. Printing defects were observed in the LPBF 282 alloy fabricated using a Renishaw AM250 machine, likely due to particle spattering during printing. For both the LPBF and LP-DED 282 alloys, annealing at 1,180°C for 1 h resulted in partial recrystallization and a bimodal grain distribution, while subsequent aging for 4 h at 800°C led to the formation of a high density of nano size γ′-strengthening precipitates. Creep testing performed at 750°C revealed lower creep life and ductility for the LPBF and LP-DED 282 compared with wrought 282. X-ray computed tomography combined with optical and scanning electron microscopy microstructural characterization revealed crack formation in the LPBF 282 alloy during creep testing, initiated either from printing defects or from creep cavitation at grain boundaries. Creep cavitation and cracking at grain boundaries were also observed for the LP-DED 282 alloy, and optimization of the printing strategies and post heat treatments will be needed to fabricate high performance 282 components for high temperature nuclear applications.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2025

Manufacturability and performance response of developed Ni-based alloys for reactor environments

Under the Advanced Materials and Manufacturing Technologies program, two Ni-based alloys fabricated by laser powder bed fusion (LPBF) at Oak Ridge National Laboratory and by laser powder directed energy deposition (LP-DED) at Idaho National Laboratory have been evaluated: γ′-strengthened Haynes 282 and solution-strengthened Inconel 625. Printing defects were observed in the LPBF 282 alloy fabricated using a Renishaw AM250 machine, likely due to particle spattering during printing. For both the LPBF and LP-DED 282 alloys, annealing at 1,180°C for 1 h resulted in partial recrystallization and a bimodal grain distribution, and subsequent aging for 4 h at 800°C led to the formation of a high density of nano-size γ′-strengthening precipitates. Creep testing performed at 750°C revealed lower creep life and ductility for the LPBF and LP-DED 282 compared with wrought 282. X-ray computed tomography combined with optical and scanning electron microscopy microstructural characterization revealed crack formation in the LPBF 282 alloy during creep testing, initiated either from printing defects or from creep cavitation at grain boundaries. Creep cavitation and cracking at grain boundaries were also observed for the LP-DED 282 alloy, and optimization of the printing strategies and postheat treatments will be needed to fabricate high-performance 282 components for high-temperature nuclear applications.

36 MATERIALS SCIENCE↗
NASA NTRS2007

Modeling Creep-Induced Stress Relaxation at the Leading Edge of SiC/SiC Airfoils

Anticipating the implementation of advanced SiC/SiC composites into internally cooled airfoil components within the turbine section of future aero-propulsion engines, the primary objective of this study was to develop physics-based analytical and finite-element modeling tools to predict the effects of composite creep and stress relaxation at the airfoil leading edges, which will generally experience large thermal gradients at high temperatures. A second objective was to examine how some advanced NASA-developed SiC/SiC systems coated with typical EBC materials would behave as leading edge materials in terms of long-term steady-state operating temperatures. Because of the complexities introduced by mechanical stresses inherent in internally cooled airfoils, a simple cylindrical thin-walled tube model subjected to thermal stresses only is employed for the leading edge, thereby obtaining a best-case scenario for the material behavior. In addition, the SiC/SiC composite materials are assumed to behave as isotropic materials with temperature-dependent viscoelastic creep behavior as measured in-plane on thin-walled panels. Key findings include: (1) without mechanical stresses and for typical airfoil geometries, as heat flux is increased through the leading edge, life-limiting tensile crack formation will occur first in the hoop direction on the inside wall of the leading edge; (2) thermal gradients through all current SiC/SiC systems should be kept below approx.300 F at high temperatures to avoid this cracking; (3) at temperatures near the maximum operating temperatures of advanced SiC/SiC systems, thermal stresses induced by the thermal gradients will beneficially relax with time due to creep; (4) although stress relaxation occurs, the maximum gradient should still not exceed 300oF because of residual tensile stress buildup on the airfoil outer wall during cool-down; and (5) without film cooling and mechanical stresses, the NASA-developed N26 SiC/SiC system with thru-thickness Sylramic-iBN fiber reinforcement and a typical EBC coating has the potential of offering a maximum long-term steady-state operating temperature of approx.3100 F at the surface of the EBC.

Lang, Jerry↗
NASA NTRSDate not supplied

Under Pressure: The Artemis I Heatshield Char Loss Investigation and Artemis II’s Successful Entry

Following the successful Artemis I skip reentry on December 11, 2022, unexpected char liberation from the Orion heat- shield prompted formation of an Anomaly Response Team to determine root cause and establish flight rationale and corrective actions for subsequent missions. Through a comprehensive investigation including detailed hardware analysis, modeling & simulation, and ground testing, the team determined that the low permeability Avcoat experienced extreme internal gas pressure buildup during the skip entry that could not adequately outgas, leading to crack formation and char liberation. Key discoveries included significant performance differences between permeable and impermeable heatshield regions and successful replication of the anomaly through ground testing. Based on extensive ground testing and analysis, Artemis II flew a modified trajectory without the skip entry to minimize crack-inducing conditions, and successfully splashed down on April 10, 2026 with significantly reduced char loss. For Artemis III and beyond, a corrective action was implemented to produce a more permeable version of Avcoat that will substantially reduce internal pressure accumulation during entry.

Artemis II↗
NASA NTRS1984

Ridges on basalt flows

Pressure ridges are surface features on basaltic lava flows and, as with other surface features, they may be related to the emplacement of a flow and the rheological properties of the lava. Since many ridges are of sufficient size to be detected on high resolution orbital images, an understanding of pressure ridges could provide a means for interpreting volcanic flows on other terrestrial planets. Some proposed formation mechanisms are reviewed and three different types of pressure ridges are identified on the basis of morphology. Type 1 ridges are the most common and are associated with multiple flow unit pahoehoe in which the ridges are embayed by secondary toe fed lava. They tend to be restricted to wider sections or margins of the flow and to be oriented longitudinal to flow direction; however, oblique or transverse orientation is not uncommon. Bulbous squeeze ups are common within cracks and may reflect relative timing of crack formation. The interior structure of type 1 ridges consists of an upper slab section which generally contains columnar joints and a lower massive section with an irregular surface. This basic distinction may mark the thickness of the surface crust when ridge formation was initiated. Type 2 ridges occur in association with type 1 and are very similar with the exception of the secondary squeeze out material. Instead of only filling cracks, the secondary material on these ridges originated from underneath a thin crust and flowed as toes or channels from the top and sides of the ridge. Type 3 ridges have much steeper sides (almost vertical at the top) than the other types. Medial cracks are very wide and the crack walls are convex upward. No squeeze ups are present. The main difference between type 3 and the others may be reflection of viscosity.

Theilig, E.↗
DOE OSTI2024

AI-Driven Crack Detection for Remanufacturing Cylinder Heads Using Deep Learning and Engineering-Informed Data Augmentation

Detecting cracks in cylinder heads traditionally relies on manual inspection, which is time-consuming and susceptible to human error. As an alternative, automated object detection utilizing computer vision and machine learning models has been explored. However, these methods often face challenges due to a lack of sufficiently annotated training data, limited image diversity, and the inherently small size of cracks. Addressing these constraints, this paper introduces a novel automated crack-detection method that enhances data availability through a synthetic data generation technique. Unlike general data augmentation practices, our method involves copying cracks from one location to another, guided by both random and informed engineering decisions about likely crack formations due to cyclic thermomechanical loads. The innovative aspect of our approach lies in the integration of domain-specific engineering knowledge into the synthetic generation process, which substantially improves detection accuracy. We evaluate our method’s effectiveness using two metrics: the F2 score, which emphasizes recall to prioritize detecting all potential cracks, and mean average precision (MAP), a standard measure in object detection. Experimental results demonstrate that, without engineering insights, our method increases the F2 score from 0.40 to 0.65, while maintaining a stable MAP. Incorporating detailed engineering knowledge further enhances the F2 score to 0.70 and improves MAP to 0.57, representing increases of 63% and 43%, respectively. These results confirm that our approach not only mitigates the limitations of traditional data augmentation but also significantly advances the reliability and precision of crack detection in industrial settings.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS2000

Fatigue Damage Mechanisms in Advanced Hybrid Titanium Composite Laminates

Hybrid Titanium Composite Laminates (HTCL) are a type of hybrid composite laminate with promise for high-speed aerospace applications, specifically designed for improved damage tolerance and strength at high-temperature (350 F, 177 C). However, in previous testing, HTCL demonstrated a propensity to excessive delamination at the titanium/PMC interface following titanium cracking. An advanced HTCL has been constructed with an emphasis on strengthening this interface, combining a PETI-5/IM7 PMC with Ti-15-3 foils prepared with an alkaline-perborate surface treatment. This paper discusses how the fatigue capabilities of the "advanced" HTCL compare to the first generation HTCL which was not modified for interface optimization, in both tension-tension (R = 0.1) and tension-compression (R=-0.2). The advanced HTCL under did not demonstrate a significant improvement in fatigue life, in either tension-tension or tension-compression loading. However, the advanced HTCL proved much more damage tolerant. The R = 0.1 tests revealed the advanced HTCL to increase the fatigue life following initial titanium ply damage up to 10X that of the initial HTCL at certain stress levels. The damage progression following the initial ply damage demonstrated the effect of the strengthened PMC/titanium interface. Acetate film replication of the advanced HTCL edges showed a propensity for some fibers in the adjacent PMC layers to fail at the point of titanium crack formation, suppressing delamination at the Ti/PMC interface. The inspection of failure surfaces validated these findings, revealing PMC fibers bonded to the majority of the titanium surfaces. Tension compression fatigue (R = -0.2) demonstrated the same trends in cycles between initial damage and failure, damage progression, and failure surfaces. Moreover, in possessing a higher resistance to delamination, the advanced HTCL did not exhibit buckling following initial titanium ply cracking under compression unlike the initial HTCL.

Johnson, W. Steven↗
DOE OSTI2026

Chemo-Mechanics of α-V 2 O 5 During Lithiation and Implications for Rechargeable Battery Cathodes

Chemo-mechanical degradation of layered oxide electrodes is strongly influenced by crystallographic anisotropy, local stress evolution, and ion insertion, yet the intrinsic mechanical response of layered materials remains incompletely understood. Indeed, most prior studies have focused on polycrystalline materials but single crystals enable direct observation of coupling between anisotropic ion diffusion and mechanical response. This study aims to determine how crystallographic anisotropy and lithiation affect deformation, fracture, and mechanical properties in single-crystal V 2 O 5 , and compares this behavior with polycrystalline counterparts. Polycrystalline V 2 O 5 thin films and single-crystal α-V 2 O 5 were studied using nanoindentation, scanning electron microscopy, focused ion beam cross-sectioning, and Raman spectroscopy. Single crystals were tested in pristine and chemically lithiated states, including experiments in which crystals were first plastically deformed via nanoindentation and subsequently lithiated. Polycrystalline films exhibited significantly higher hardness and elastic modulus than single crystals. Single crystals indented normal to the exposed (001) basal plane exhibited pronounced anisotropic deformation, including directional slip, crystallographically-guided cracking, anisotropic crack propagation, interlayer separation, and shear localization. Lithiation caused substantial softening, reduced hardness and modulus, and suppressed displacement bursts during nanoindentation, while previously indented regions showed crack formation and growth upon lithiation. Mechanical behavior of α-V 2 O 5 is strongly governed by crystallographic anisotropy and further altered by lithiation, with pre-existing deformation serving as a strong driver of fracture during ion insertion. These findings illuminate the coupling among ion insertion, deformation, and fracture in layered oxides and provide a basis for understanding and mitigating mechanical failure in electrochemical energy-storage materials.

Anisotropy↗
DOE OSTI2026

Ultra-grain refinement creates FCC pure cobalt with high strength and high ductility

Although pure cobalt is generally known to have a hexagonal close-packed (HCP) structure at room temperature, we show that its high-temperature face-centered cubic (FCC) phase can be strongly stabilized through grain refinement, resulting in FCC pure cobalt at room temperature. Ultrafine-grained (UFG) FCC cobalt exhibits a hierarchical microstructure consisting of dense stacking fault (SF) networks in the dominant FCC grains and numerous SFs and thin FCC layers within a few HCP plates. This unique microstructure leads to a high tensile strength exceeding 1 GPa, together with a tensile elongation of over 35%, thereby surpassing the well-known strength–ductility trade-off of pure metals. In-situ synchrotron X-ray diffraction revealed that the UFG FCC cobalt exhibited a markedly enhanced deformation-induced FCC→HCP martensitic transformation, which provided sustained strain hardening through the transformation-induced plasticity (TRIP) effect. Furthermore, ultra-grain refinement dramatically suppressed premature void and crack formation, causing a transition in the fracture mode from brittle to ductile. These findings advance the fundamental understanding of the phase stability and TRIP-assisted deformation in elemental cobalt and offer new guidelines for the microstructure-driven design of high-performance cobalt-based structural alloys.

Metastability↗
DOE OSTI2025

Interaction between dissolution and precipitation during olivine carbonation: Implications for CO 2 mineralization

Large-scale carbonation of olivine is considered a promising approach for in situ mineral carbonation, offering a permanent and stable method for CO 2 storage. A critical aspect of this process is understanding how dissolution and precipitation interact, as this could drive fracturing and enhance further reactions. In this study, we conducted carbonation experiments on olivine using CO 2 -saturated aqueous solutions of NaHCO 3 and NaCl. Two experimental setups were used: one representing an open geochemical system and the other a closed system, corresponding to reaction-limited and flow-limited scenarios, respectively. Further, post-reaction textural analysis using scanning electron microscopy (SEM) revealed surface coatings of reaction products in the closed system, while etch pits and etch channels were prevalent in the open system. Although no direct evidence of reaction-driven fracturing was observed, etch pits and etch channels may serve as initiation points for subcritical crack formation and growth, potentially maintaining permeability and exposing new unreacted surfaces. Using linear elastic fracture mechanics (LEFM) model, we estimate that microcracks could propagate under a pressure of 0.1 GPa if reaction products accumulate within the etch pits. Our findings offer new insights into the mechanisms governing olivine carbonation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗