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All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Modeling Creep Effects in Advanced SiC/SiC Composites

Because advanced SiC/SiC composites are projected to be used for aerospace components with large thermal gradients at high temperatures, efforts are on-going at NASA Glenn to develop approaches for modeling the anticipated creep behavior of these materials and its subsequent effects on such key composite properties as internal residual stress, proportional limit stress, ultimate tensile strength, and rupture life. Based primarily on in-plane creep data for 2D panels, this presentation describes initial modeling progress at applied composite stresses below matrix cracking for some high performance SiC/SiC composite systems recently developed at NASA. Studies are described to develop creep and rupture models using empirical, mechanical analog, and mechanistic approaches, and to implement them into finite element codes for improved component design and life modeling

Lang, Jerry↗
NASA NTRS2005

NASALIFE - Component Fatigue and Creep Life Prediction Program

NASALIFE is a life prediction program for propulsion system components made of ceramic matrix composites (CMC) under cyclic thermo-mechanical loading and creep rupture conditions. Although the primary focus was for CMC components, the underlying methodologies are equally applicable to other material systems as well. The program references empirical data for low cycle fatigue (LCF), creep rupture, and static material properties as part of the life prediction process. Multiaxial stresses are accommodated by Von Mises based methods and a Walker model is used to address mean stress effects. Varying loads are reduced by the Rainflow counting method or a peak counting type method. Lastly, damage due to cyclic loading and creep is combined with Minor s Rule to determine damage due to cyclic loading, damage due to creep, and the total damage per mission and the number of potential missions the component can provide before failure.

Gyekenyesi, John Z.↗
NASA NTRS2012

Self-Healing Wire Insulation

A self-healing system for an insulation material initiates a self-repair process by rupturing a plurality of microcapsules disposed on the insulation material. When the plurality of microcapsules are ruptured, reactants within the plurality of microcapsules react to form a replacement polymer in a break of the insulation material. This self-healing system has the ability to repair multiple breaks in a length of insulation material without exhausting the repair properties of the material.

Parrish, Clyde F.↗
NASA NTRS2012

In-Situ Nondestructive Evaluation of Kevlar(Registered Trademark)and Carbon Fiber Reinforced Composite Micromechanics for Improved Composite Overwrapped Pressure Vessel Health Monitoring

NASA has been faced with recertification and life extension issues for epoxy-impregnated Kevlar 49 (K/Ep) and carbon (C/Ep) composite overwrapped pressure vessels (COPVs) used in various systems on the Space Shuttle and International Space Station, respectively. Each COPV has varying criticality, damage and repair histories, time at pressure, and pressure cycles. COPVs are of particular concern due to the insidious and catastrophic burst-before-leak failure mode caused by stress rupture (SR) of the composite overwrap. SR life has been defined [1] as the minimum time during which the composite maintains structural integrity considering the combined effects of stress level(s), time at stress level(s), and associated environment. SR has none of the features of predictability associated with metal pressure vessels, such as crack geometry, growth rate and size, or other features that lend themselves to nondestructive evaluation (NDE). In essence, the variability or surprise factor associated with SR cannot be eliminated. C/Ep COPVs are also susceptible to impact damage that can lead to reduced burst pressure even when the amount of damage to the COPV is below the visual detection threshold [2], thus necessitating implementation of a mechanical damage control plan [1]. Last, COPVs can also fail prematurely due to material or design noncompliance. In each case (SR, impact or noncompliance), out-of-family behavior is expected leading to a higher probability of failure at a given stress, hence, greater uncertainty in performance. For these reasons, NASA has been actively engaged in research to develop NDE methods that can be used during post-manufacture qualification, in-service inspection, and in-situ structural health monitoring. Acoustic emission (AE) is one of the more promising NDE techniques for detecting and monitoring, in real-time, the strain energy release and corresponding stress-wave propagation produced by actively growing flaws and defects in composite materials [3,4,5,6,7,8]. To gain further insight into the mechanisms responsible for composite rupture, broadband modal acoustic emission analysis was used. Also, since AE data reduction proved to be very time consuming, specialized data reduction software was written to automate the process.

Waller, Jess↗
NASA NTRS2012

Failure Analysis of T-38 Aircraft Burst Hydraulic Aileron Return Line

During maintenance troubleshooting for fluctuating hydraulic pressures, a technician found that a right hand aileron return line, on the flight hydraulic side, was ruptured (Fig. 1, 2). This tubing is part of the Hydraulic Flight Control Aileron Return Reducer to Aileron Manifold and is suspected to be original to the T-38 Talon trainer aircraft. Ailerons are small hinged sections on the outboard portion of a wing used to generate rolling motion thereby banking the aircraft. The ailerons work by changing the effective shape of the airfoil of the outer portion of the wing [1]. The drawing, Northrop P/N 3-43033-55 (6/1960), specifies that the line is made from 0.375 inch OD, aluminum 5052-0 tubing with a 0.049 inch wall thickness. WW-T-787 requires the tube shall be seamless and uniform in quality and temper [2]. The test pressure for this line is 3000 psi, and the operational pressure for this line is estimated to be between 45 psi and 1500 psi based on dynamic loading during flight. Examination of the fracture surface found evidence of arrest bands originating on the inner diameter (Fig 3). Ductile dimples are observed on the tube fractures (Fig. 4). The etched cross-section revealed thinning and work-hardening in the burst region (Fig. 5). The wall thickness just outside the work-hardened fracture region measured 0.035". Barlow's Formula: P = 2St/D, where P is burst pressure, S is allowable stress, t is wall thickness and D is the outer diameter of tube. Using the ultimate tensile strength of 28 ksi and a measured wall thickness of 0.035 inches at burst, P = 5.2 ksi (burst pressure). Using the yield of 13 ksi (YS) for aluminum 5052-0, plastic deformation will happen at P = 2.4 ksi suggesting plastic deformation occurred at a proof pressure of 3.0 ksi. Conclusion: The burst resulted from high stress, low-cycle fatigue. Evidence of arrest bands originating on the inner diameter. Fracture is predominately shear dimples, characteristic of high load ductile fractures (Fig 6). Section wall reduction in the burst region. Plastic deformation and thinning of the out-of-specification tube wall likely happened during the initial proof testing years ago. Metallography of tubing away from rupture site confirmed tubing was seamless. Based on the tube microstructure, it is likely that the initial wall thickness was about 30 % thinner than the requirement of 0.049 inches. Fracture initiated on the ID and progressed to the OD (shear lip). The tube is made of the correct material of 5052-0 aluminum as verified using Optical Emission Spectroscopy (Table 2). The tubing hardness tested 77 HV100 (77 HRE). This hardness is slightly above the requirement for 70 HRE maximum for aluminum 5052-0 in AMS 2658C [3].

Martinez, J. E.↗
NASA NTRS2012

Seismic Imager Space Telescope

A concept has been developed for a geostationary seismic imager (GSI), a space telescope in geostationary orbit above the Pacific coast of the Americas that would provide movies of many large earthquakes occurring in the area from Southern Chile to Southern Alaska. The GSI movies would cover a field of view as long as 300 km, at a spatial resolution of 3 to 15 m and a temporal resolution of 1 to 2 Hz, which is sufficient for accurate measurement of surface displacements and photometric changes induced by seismic waves. Computer processing of the movie images would exploit these dynamic changes to accurately measure the rapidly evolving surface waves and surface ruptures as they happen. These measurements would provide key information to advance the understanding of the mechanisms governing earthquake ruptures, and the propagation and arrest of damaging seismic waves. GSI operational strategy is to react to earthquakes detected by ground seismometers, slewing the satellite to point at the epicenters of earthquakes above a certain magnitude. Some of these earthquakes will be foreshocks of larger earthquakes; these will be observed, as the spacecraft would have been pointed in the right direction. This strategy was tested against the historical record for the Pacific coast of the Americas, from 1973 until the present. Based on the seismicity recorded during this time period, a GSI mission with a lifetime of 10 years could have been in position to observe at least 13 (22 on average) earthquakes of magnitude larger than 6, and at least one (2 on average) earthquake of magnitude larger than 7. A GSI would provide data unprecedented in its extent and temporal and spatial resolution. It would provide this data for some of the world's most seismically active regions, and do so better and at a lower cost than could be done with ground-based instrumentation. A GSI would revolutionize the understanding of earthquake dynamics, perhaps leading ultimately to effective warning capabilities, to improved management of earthquake risk, and to improved public safety policies. The position of the spacecraft, its high optical quality, large field of view, and large field of regard will make it an ideal platform for other scientific studies. The same data could be simply reused for other studies. If different data, such as multi-spectral data, is required, additional instruments could share the telescope.

Sidick, Erkin↗
NASA NTRS2013

Effects of Microstructural Parameters on Creep of Nickel-Base Superalloy Single Crystals

Microstructure-sensitive creep models have been developed for Ni-base superalloy single crystals. Creep rupture testing was conducted on fourteen single crystal alloys at two applied stress levels at each of two temperatures, 982 and 1093 C. The variation in creep lives among the different alloys could be explained with regression models containing relatively few microstructural parameters. At 982 C, gamma-gamma prime lattice mismatch, gamma prime volume fraction, and initial gamma prime size were statistically significant in explaining the creep rupture lives. At 1093 C, only lattice mismatch and gamma prime volume fraction were significant. These models could explain from 84 to 94 percent of the variation in creep lives, depending on test condition. Longer creep lives were associated with alloys having more negative lattice mismatch, lower gamma prime volume fractions, and finer gamma prime sizes. The gamma-gamma prime lattice mismatch exhibited the strongest influence of all the microstructural parameters at both temperatures. Although a majority of the alloys in this study were stable with respect to topologically close packed (TCP) phases, it appeared that up to approximately 2 vol% TCP phase did not affect the 1093 C creep lives under applied stresses that produced lives of approximately 200 to 300 h. In contrast, TCP phase contents of approximately 2 vol% were detrimental at lower applied stresses where creep lives were longer. A regression model was also developed for the as-heat treated initial gamma prime size; this model showed that gamma prime solvus temperature, gamma-gamma prime lattice mismatch, and bulk Re content were all statistically significant.

MacKay, Rebecca A.↗
NASA NTRS2013

Multi-Dimensional Damage Detection for Surfaces and Structures

Current designs for inflatable or semi-rigidized structures for habitats and space applications use a multiple-layer construction, alternating thin layers with thicker, stronger layers, which produces a layered composite structure that is much better at resisting damage. Even though such composite structures or layered systems are robust, they can still be susceptible to penetration damage. The ability to detect damage to surfaces of inflatable or semi-rigid habitat structures is of great interest to NASA. Damage caused by impacts of foreign objects such as micrometeorites can rupture the shell of these structures, causing loss of critical hardware and/or the life of the crew. While not all impacts will have a catastrophic result, it will be very important to identify and locate areas of the exterior shell that have been damaged by impacts so that repairs (or other provisions) can be made to reduce the probability of shell wall rupture. This disclosure describes a system that will provide real-time data regarding the health of the inflatable shell or rigidized structures, and information related to the location and depth of impact damage. The innovation described here is a method of determining the size, location, and direction of damage in a multilayered structure. In the multi-dimensional damage detection system, layers of two-dimensional thin film detection layers are used to form a layered composite, with non-detection layers separating the detection layers. The non-detection layers may be either thicker or thinner than the detection layers. The thin-film damage detection layers are thin films of materials with a conductive grid or striped pattern. The conductive pattern may be applied by several methods, including printing, plating, sputtering, photolithography, and etching, and can include as many detection layers that are necessary for the structure construction or to afford the detection detail level required. The damage is detected using a detector or sensory system, which may include a time domain reflectometer, resistivity monitoring hardware, or other resistance-based systems. To begin, a layered composite consisting of thin-film damage detection layers separated by non-damage detection layers is fabricated. The damage detection layers are attached to a detector that provides details regarding the physical health of each detection layer individually. If damage occurs to any of the detection layers, a change in the electrical properties of the detection layers damaged occurs, and a response is generated. Real-time analysis of these responses will provide details regarding the depth, location, and size estimation of the damage. Multiple damages can be detected, and the extent (depth) of the damage can be used to generate prognostic information related to the expected lifetime of the layered composite system. The detection system can be fabricated very easily using off-the-shelf equipment, and the detection algorithms can be written and updated (as needed) to provide the level of detail needed based on the system being monitored. Connecting to the thin film detection layers is very easy as well. The truly unique feature of the system is its flexibility; the system can be designed to gather as much (or as little) information as the end user feels necessary. Individual detection layers can be turned on or off as necessary, and algorithms can be used to optimize performance. The system can be used to generate both diagnostic and prognostic information related to the health of layer composite structures, which will be essential if such systems are utilized for space exploration. The technology is also applicable to other in-situ health monitoring systems for structure integrity.

Williams, Martha↗
NASA NTRS2014

On-Orbit Engineering and Vehicle Integration Poster Presentation

One of the duties of the MER Managers is getting the consoles to review and sign Electronic Flight Notes (EFN) and Mission Action Requests (Chit) before they are due. Chits and EFNs and are accessible through the Mission Control Center - Houston (MCC-H) Gateway. Chits are the official means of documenting questions and answers, technical direction, real-time changes to Flight Rules (FR) and procedures, request for analysis, etc. between various consoles concerning on-orbit operations. EFNs are documents used by the Flight Control Team (FCT) to communicate precise details between console positions and manage real time changes to FR and Systems Operation Data File (SODF) procedures. On GMT 2013/345 the External Active Thermal Control System (EATCS) on the Columbus (COL) Moderate Temperature Loop (MTL) Interface Heat Exchanger (IFHX) shut down due to low temperatures. Over the next couple of days, the core temperature of COL MT IFHX dropped due to the failure of the Flow Control Valve (FCV). After the temperature drop was discovered, heaters were turned on to bring the temperatures back to nominal. After the incident occurred, a possible freeze threat was discovered that could have ruptured the heat exchanger. The COL MT IFHX rupturing would be considered a catastrophic failure and potentially result in a loss of the vehicle and/or the lives of the International Space Station (ISS) crew members

Heimerdinger, Madison↗
NASA NTRS2014

NASALIFE - Component Fatigue and Creep Life Prediction Program

NASALIFE is a life prediction program for propulsion system components made of ceramic matrix composites (CMC) under cyclic thermo-mechanical loading and creep rupture conditions. Although the primary focus was for CMC components, the underlying methodologies are equally applicable to other material systems as well. The program references empirical data for low cycle fatigue (LCF), creep rupture, and static material properties as part of the life prediction process. Multiaxial stresses are accommodated by Von Mises based methods and a Walker model is used to address mean stress effects. Varying loads are reduced by the Rainflow counting method or a peak counting type method. Lastly, damage due to cyclic loading and creep is combined with Minor's Rule to determine damage due to cyclic loading, damage due to creep, and the total damage per mission and the number of potential missions the component can provide before failure.

CMC Vane↗
NASA NTRS2015

Effect of Notches on Creep-Fatigue Behavior of a P/M Nickel-Based Superalloy

A study was performed to determine and model the effect of high temperature dwells on notched low cycle fatigue (NLCF) and notch stress rupture behavior of a fine grain LSHR powder metallurgy (PM) nickel-based superalloy. It was shown that a 90 second dwell applied at the minimum stress (min dwell) was considerably more detrimental to the NLCF lives than similar dwell applied at the maximum stress (max dwell). The short min dwell NLCF lives were shown to be caused by growth of small oxide blisters which caused preferential cracking when coupled with high concentrated notch root stresses. The cyclic max dwell notch tests failed mostly by a creep accumulation, not by fatigue, with the crack origin shifting internally to a substantial distance away from the notch root. The classical von Mises plastic flow model was unable to match the experimental results while the hydrostatic stress profile generated using the Drucker-Prager plasticity flow model was consistent with the experimental findings. The max dwell NLCF and notch stress rupture tests exhibited substantial creep notch strengthening. The triaxial Bridgman effective stress parameter was able to account for the notch strengthening by collapsing the notched and uniform gage geometry test data into a singular grouping.

Dwell Notch Fatigue↗
NASA NTRS2018

Modeling of Time-Dependent Strength Degradation of SiC/SiC Ceramic Matrix Composites via MAC/GMC Computer Code

Silicon carbide fiber reinforced silicon carbide (SiC/SiC) ceramic matrix composites (CMCs) display time-dependent strength degradation at intermediate temperatures (600 to 900 degrees Centigrade). This is generally believed to be an oxidation induced phenomenon. The understanding of the effect of temperature with environment (oxidation) is key towards development of SiC/SiC CMCs with a reliable load carrying capacity. Various theories have been proposed to explain the strength degradation. One suggests that the boron nitride (BN) coating deposited on the fibers oxidizes causing fusion of fibers. Another theory proposes that the SiC fibers are oxidized forming a silica scale leading to premature fiber failure. A more recent theory suggests that SiC fiber strength is intrinsically time-dependent due to slow crack growth of flaws in the fibers. An empirical model, termed as a "fiber classic model," which is based on a standard slow crack growth type power-law, has been implemented within NASA's micromechanics-based MAC/GMC computer code as a user routine. Model parameters for this "classic model" were calibrated from stress-rupture data of Hi-Nicalon (TM) monofilaments using the maximum likelihood estimation (MLE) technique. This new capability in the MAC/GMC computer code was then used to predict the stress-rupture behavior of Hi-Nicalon (TM) tows as well as 2-D SiC/SiC composites reinforced with Hi-Nicalon (TM) fibers. Results demonstrate that the MAC/GMC with this new capability successfully predicts the time-to-failure vs. applied stress within the intermediate temperature range at various scales as well as laminated composites in an oxidizing environment.

Environmental degradation↗
NASA NTRS2018

Columbus IFHX Ammonia Leak Analysis

After the Columbus Moderate Temperature Loop (MTL) InterFace Heat eXchanger (IFHX) low temperature event of GMT 345-2013, NASA investigated relevant transient scenarios involving IFHX rupture after water freezing and subsequent thawing. NASA recommended development of a Fault Detection Isolation and Recovery (FDIR) plan that would, in the event of a heat exchanger freeze event, close the Water On/Off Valves (WOOVs) to isolate the heat exchanger and prevent ammonia from the external flow loops from spreading into the cabin. NASA performed a preliminary simplified analysis for the reference case of IFHX rupture, but for a deeper understanding TAS developed detailed SINDA-FLUINT models of the Columbus ITCS that were built and run through the SINAPS GUI. This allowed simulation of the ammonia leakage physics including the variation of environmental parameters, thus providing more accurate and specific input to the FDIR under development. The result was finalization of the IFHX WOOVs closure sequence and wait times to contain the ammonia propagation to Columbus and allow identification of the leaking IFHX. In addition, the analysis results provided reference pressure profiles to be used on console and by the Engineering as support for the telemetry data assessment in case of failure.This paper gives an overview on the issue and focuses on the analytical aspects of the multiphase fluid dynamics involved.

Tilloca, A.↗
NASA NTRS2018

ISS Columbus Heat Exchanger Close Call Investigation Case Study

During International Space Station (ISS) Expedition 38, just days before Christmas 2013, the External Active Thermal Control System (EATCS) on the ISS Columbus Moderate Temperature Loop (MTL) Interface Heat Exchanger (IFHX) shut down due to low temperatures. Engineers on the ground scrambled for several days to troubleshoot a pump module Flow Control Valve (FCV) problem, however; no one recognized that the core temperature of the Columbus MTL IFHX was continuing to drop, to the point that water in the system could freeze. Freezing could rupture the core, resulting in high pressure ammonia entering the cabin of the ISS. With no way to clean up the ammonia, ISS crew would have to evacuate the U.S. segment of the station. Columbus MTL IFHX rupture is considered a catastrophic failure and could potentially result in a loss of crew/loss of vehicle. How did engineers miss this potentially catastrophic issue?

Joyce B Abbey↗
NASA NTRSDate not supplied

Adding GPU Support to the Markov Chain Monte Carlo Code Catmip

In geophysics, we are confronted with many under-determined inverse problems. For example, all of our observations of earthquakes are made at the Earth’s surface. So, when we try to infer how slip during an earthquake evolves in space and time, we find that there are many potential slip histories that are consistent with our limited observations and our understanding of earthquake physics. One way to approach these problems is with Bayesian analysis which allows us to infer the ensemble of all potential slip models that satisfy the observations and our prior knowledge of earthquake physics. In Bayesian analysis, our prior knowledge is known as the prior probability density function or prior PDF, the fit to the data is known as the data likelihood, and the target PDF that satisfies both the prior PDF and data likelihood is known as the posterior PDF. However, simulating the posterior PDF typically requires using Markov Chain Monte Carlo (MCMC) to draw tens of billions of random realizations of earthquake slip models, which may not be computationally feasible. To make this and similar geophysical inversions computationally tractable, we developed the Cascading Adaptive Transitional Metropolis In Parallel (CATMIP) algorithm. CATMIP is an efficient parallel Markov Chain Monte Carlo (MCMC) sampler that is used for model fitting and uncertainty quantification in geophysics. Example use cases are earthquake rupture modeling, determining mineral composition on Mars, reconstructing the history of ocean salinity, and historical earthquake relocation. CATMIP employs many parallel instances of the Metropolis algorithm for sampling in a transitioning framework. Transitioning is a process in which a set of random samples at equilibrium with a known probability density function (PDF) are used as seeds for the Markov chains to sample successive target PDFs that incrementally move the distribution from the starting seeds to the final desired PDF that describes the relative plausibility of potential values for the model parameters. The algorithm is implemented as a Master-Worker model employing MPI for communication. The worker processes are loosely coupled with global parameters periodically optimized by the master process. This provides a very high amount of parallelism with little communication between updates. During the presentation we will discuss the history of the algorithm and elaborate the earthquake rupture modeling use case for the CATMIP package. Our first step toward GPU optimization was to optimize the code for the CPU. CPU profiling revealed that most of the compute time is spent in calls to level 2 BLAS routines and calls to GSL random number generators. We revised the algorithm to employ level 3 BLAS routines instead. In our presentation we will describe how this was accomplished. Adding GPU support to CATMIP consisted mostly of replacing the calls to GSL with calls to GPU vendor-provided library routines. A small number of loops were directly implemented in CUDA. In the presentation will provide implementation details. Finally, we will discuss methods for profiling and opportunities for further optimizing GPU execution. By creating a code with the flexibility to run on either a CPU or GPU architecture, CATMIP can be used on systems ranging from large CPU-based HPC environments to single servers with GPU acceleration and everything in between.

HECC↗
NASA NTRS2024

Effects of Oxide Dispersion on Failure Modes in an Additively Manufactured Superalloy

Additive manufacturing opens new paths for introducing oxide particles into superalloys, to potentially provide oxide dispersion strengthening (ODS) at high temperatures. This provides opportunities to study how such dispersions can influence failure modes for a given superalloy, after nearly identical material processing paths. The objective of this study was to compare monotonic failure modes for additively manufactured superalloys with versus without an introduced oxide dispersion. The superalloy for each case was produced by laser powder bed fusion additive manufacturing. Specimens were subsequently given consistent thermal treatment paths and then tested in tensile and creep tests at varied temperatures. Failure modes were then compared. Additively manufactured NiCrAl without ODS had randomly oriented equiaxed grains while this alloy with 0.25 wt% Y 2 O 3 ODS additions had elongated [001] oriented grains in the build direction. Material made without ODS (“No-ODS”) was nearly completely single phase gamma, while ODS additions resulted in gamma, chromium carbide, and Y-Al-Cr oxide phases, with carbide and oxide phases contents estimated at no more than 13 and 1 vol%, respectively. Compared to No-ODS, material made with ODS had higher tensile strengths at room, 760 and 1093 °C. The elongation of ODS material was lower than No-ODS at room temperature, but higher at 760 °C. At 1093 °C ODS material had higher elongation than No-ODS when tested in the build direction, however elongation was lower for ODS material in the transverse direction at 1093 °C. Creep rupture strain, life, and area reduction at 760 and 1093 °C were all much higher for ODS material compared to No-ODS; 760 °C rupture life was nearly 100 times longer for ODS material. The presence of Y in the ODS material significantly improved oxidation resistance.

supperalloys↗
NASA NTRSDate not supplied

Surge Pressure Testing of Flight-Like Components

This project studies the transient surge pressure effects (such as those observed during propulsion system priming) on flight components. A water flow setup was used to impart transient surge pressures on flight-like components. The project compared the point of component failure for transient surge pressures versus static proof pressures. Results showed that designing to keep surge pressures below component proof pressures is overly conservative, because the components can handle higher transient pressures. The tests performed on burst discs showed that the rupture pressure under a transient surge pressure was at least 20% above the static rupture pressure. A tested pressure transducer remained fully functional and accurate after surge pressures 60% above its specified proof pressure. A thruster valve was exposed to transient surge pressures four times its specified proof pressure and showed no indications of damage.

propulsion components↗