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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Modeling material failure with a vectorized routine

The computational aspects of modelling material failure in structural wood members are presented with particular reference to vector processing aspects. Wood members are considered to be highly orthotropic, inhomogeneous, and discontinuous due to the complex microstructure of wood material and the presence of natural growth characteristics such as knots, cracks and cross grain in wood members. The simulation of strength behavior of wood members is accomplished through the use of a special purpose finite element/fracture mechanics routine, program STARW (Strength Analysis Routine for Wood). Program STARW employs quadratic finite elements combined with singular crack tip elements in a finite element mesh. Vector processing techniques are employed in mesh generation, stiffness matrix formation, simultaneous equation solution, and material failure calculations. The paper addresses these techniques along with the time and effort requirements needed to convert existing finite element code to a vectorized version. Comparisons in execution time between vectorized and nonvectorized routines are provided.

Cramer, S. M.↗
DOE OSTI2024

Exploring battery material failure mechanisms through synchrotron X-ray characterization techniques

Rechargeable battery cycling performance and related safety have been persistent concerns. Here, it is crucial to decipher the capacity fading induced by electrode material failure via a range of techniques. Among these, synchrotron-based X-ray techniques with high flux and brightness play a key role in understanding degradation mechanisms. In this comprehensive review, we summarized recent advancements in degradation modes and mechanisms that revealed by synchrotron X-ray methodologies. Subsequently, an overview of X-ray absorption spectroscopy and X-ray scattering techniques are introduced for the characterizing failure phenomena at local coordination atomic environment and long-range order crystal structure scale, respectively. At last, we envision the future of material failure mechanism exploration.

25 ENERGY STORAGE↗
DOE OSTI2021

Material Failure Mechanisms of Alkaline Zn Rechargeable Conversion Electrodes

Zinc (Zn) alkaline electrodes hold great importance and promise in the battery technology community, yet their behavior in real-world applications is still poorly understood. Here, we report a study of failure mechanisms and material evolution during cycling of 27 zinc–manganese dioxide (Zn–MnO 2 ) cells wherein the percent utilization of the Zn electroactive material is systematically varied between 1 and 16%. Cell fabrication is kept typical of the prevailing industrial cell design. The cycle life ranges from 2800 to 60, depending inversely on the Zn utilization. In all cases, the Zn material microstructure sheds the polytetrafluoroethylene (PTFE) binder and forms zinc oxide (ZnO) rods, with longer rods formed by lower current per Zn mass. Irreversible side reactions such as the hydrogen evolution reaction (HER), short circuits, or gas crossover cause the Zn anode’s charging efficiency to average 92% (as low as 86%), which in turn causes the baseload of metallic Zn to gradually disappear. Cell failure occurs after the baseload of metallic Zn is exhausted. The total lifetime discharge capacity remains constant near 12 ± 5 Ah/g Zn invariant of Zn utilization, which suggests that the aforementioned processes of Zn microstructural evolution and side-reaction destruction of baseload metallic zinc both progress linearly with cell capacity throughput. Manual reproduction of individual Zn failure mechanisms is performed in 22 fresh cells. Tight packing of the microstructure can lead to poor mass transfer, which causes supersaturation of soluble Zn and finally produces a high overvoltage during discharge. Here, the low charging current density yields poor coulombic efficiency due either to the competitive HER or soft short circuits.

25 ENERGY STORAGE↗
DOE OSTI2026

ACT University Collaboration Proposal: Role of manufacturing defects on material failure under dynamic loading for developing enhanced failure models and theories (Final Report)

Research on the tensile behavior of additively manufactured 316L stainless steel coupon specimens at increasing strain rates was conducted over the past year at Penn State. Dynamic loading rates into the 1000 1/s loading rates were performed on specimens with nearly 1.32” gage lengths. Stress-strain plots show ductile and plastic behavior well beyond 12% strain with necked specimens, having smaller effective gage lengths showing up to 56% ultimate strain. Additional tests performed on compact tension specimens helped with simulation work to understand the deformation behavior. Using finite elements, it was possible to determine the feasibility of a comprehensive experimental validation study towards an improved model for AM material failure – specifically, the Bai-Wierzbicki approach which accounts for lode angle and triaxiality. A non-significant number of tests are projected for eight specific failure nodes, with additional replicates to provide strain-rate capabilities to the existing formulation. One such correction factor is explored for quasi-static, notched specimens. Finally, stress intensity factor was explored using a set of compact-tension specimens which would also provide useful validation data for any simulation work.

36 MATERIALS SCIENCE↗
DOE OSTI2023

A robust interface finite element formulation for modeling brittle material failure problems

Abstract Failure of many brittle materials and structures can be modeled using interface‐oriented finite elements combined with intrinsic cohesive zone models. The discontinuous Galerkin (DG) finite element method provides an innovative framework for modeling brittle crack propagation with zero‐thickness interface elements, which can accommodate extrinsic cohesive laws to avoid the artificial compliance required in intrinsic cohesive models. However, robust formulations and implementations of DG methods are critical in alleviating the well‐known convergence issues for both crack nucleation and propagation with reduced instability. This paper presents a robust interface element formulation by modifying the incomplete interior penalty Galerkin (IIPG) method, which successfully avoids the initial element interface penetration across elements that occurs prior to crack nucleation, and thereby greatly reduces the instability issue as cracks open. We further verified and validated our implementation by using a bar tension test and a beam fracturing benchmark. The robustness of our proposed interface element method was demonstrated by a micromechanics fiber/matrix debonding problem with 64 fibers embedded in a bulk matrix.

Liu, Ruijie↗
NASA NTRS1999

Knowledge Discovery Process for Characterization of Materials Failure Mechanism

It is the intent of this project to provide a platform to visualize the various data collected from stress-strain testing of composite ceramic matrix materials. The data collected from the stress-strain tests are acoustic emissions (AE). As a material is subjected to a stress-strain test, various failure mechanisms occur in the material. The recorded sounds emitted during the test may correspond to various failure mechanisms. This project, thus, will give a possible way to visualize the data and data derived from the recorded AE. The stress-strain testing was performed on several composite matrix material combinations. Each of these tests produced anywhere from 1000 to 10,000+ AE events. For each AE event recorded, several characteristics in both the time and frequency domains are created. This project has two goals. First, this project will provide a summation page for a selected waveform. This page will include all of the characteristics determined from the AE event waveform along with graphs of the AE event waveform and its corresponding Power Spectrum. The other function of this project is to retrieve and display selected AE event waveforms for comparison.

Cios, Krzysztof J.↗
DOE OSTI2022

The Role of Grain Boundary Structure and Chemistry in Materials Failure

The objective of this project was to reveal how we can design materials with a tunable mechanical behavior through interface engineering. To do so we focused on understanding slip transmission across internal surfaces and how it relates to the strength and chemistry of the internal surface. In doing so we followed an interdisciplinary approach that employed theory, experiments and molecular dynamic (MD) simulations. Our guideline was that interfaces are characterized by their own mechanically induced interface parameter. New dislocation-grain boundary interaction mechanisms were revealed and the strengthening effects of non-traditional interfaces. We began studying simple grain boundaries in Fe systems, and then moved on to newly explored systems such as graphene-metal and nanolayer composites.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Mechanics-Driven Anode Material Failure in Battery Safety and Capacity Deterioration Issues: A Review

Abstract High-capacity anodes, such as Si, have attracted tremendous research interest over the last two decades because of the requirement for the high energy density of next-generation lithium-ion batteries (LIBs). The mechanical integrity and stability of such materials during cycling are critical because their volume considerably changes. The volume changes/deformation result in mechanical stresses, which lead to mechanical failures, including cracks, fragmentation, and debonding. These phenomena accelerate capacity fading during electrochemical cycling and thus limit the application of high-capacity anodes. Experimental studies have been performed to characterize the deformation and failure behavior of these high-capacity materials directly, providing fundamental insights into the degradation processes. Modeling works have focused on elucidating the underlying mechanisms and providing design tools for next-generation battery design. This review presents an overview of the fundamental understanding and theoretical analysis of the electrochemical degradation and safety issues of LIBs where mechanics dominates. We first introduce the stress generation and failure behavior of high-capacity anodes from the experimental and computational aspects, respectively. Then, we summarize and discuss the strategies of stress mitigation and failure suppression. Finally, we conclude the significant points and outlook critical bottlenecks in further developing and spreading high-capacity materials of LIBs.

Mechanics↗
DOE OSTI2020

Distended clads gas pressurization and material failure timescales

This document presents timescales for additional failure modes, including pressurization of void space in the pellet to the estimated tensile strength of the pellet. Because helium is known to be captured in the fuel as well as evolved as gas, previous timescales are adjusted to account for the substantial dissolution of helium in the matrix of the fuel at normal fuel temperatures. Helium arises from the decay of the 238Pu in the fuel, and can appear as a gas, creating bubbles within the fuel. The majority of helium is known to be captured within the fuel matrix at the operating temperatures of an isolated clad.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2006

Nitrile/Buna N Material Failure Assessment for an O-Ring used on the Gaseous Hydrogen Flow Control Valve (FCV) of the Space Shuttle Main Engine

After the rollout of Space Shuttle Discovery in April 2005 in preparation for return-to-flight, there was a failure of the Orbiter (OV-103) helium signature leak test in the gaseous hydrogen (GH2) system. Leakage was attributed to the Flow Control Valve (FCV) in Main Engine 3. The FCV determined to be the source of the leak for OV-103 is designated as LV-58. The nitrile/Buna N rubber O-ring seal was removed from LV-58, and failure analysis indicated radial cracks providing leak paths in one quadrant. Cracks were eventually found in 6 of 9 FCV O-rings among the three Shuttle Orbiters, though none were as severe as those for LV-58, OV-103. Testing by EM10 at MSFC on all 9 FCV O- rings included: laser dimensional, Shore A hardness and properties from a dynamic mechanical analyzer (DMA) and an Instron tensile machine. The following test data was obtained on the cracked quadrant of the LV-58, OV-103 O-ring: (1) the estimated compression set was only 9.5%, compared to none for the rest of the O-ring; (2) Shore A hardness for the O.D. was higher by almost 4 durometer points than for the rest of the O-ring; and (3) DMA data showed that the storage/elastic modulus E was almost 25% lower than for the rest of the O-ring. Of the 8 FCV O-rings tested on an Instron, 4 yielded tensile strengths that were below the MIL spec requirement of 1350 psi-a likely influence of rubber cracking. Comparisons were made between values of modulus determined by DNA (elastic) and Instron (Young s). Each nitrile/Buna N O-ring used in the FCV conforms to the MIL-P-25732C specification. A number of such O-rings taken from shelf storage at MSFC and Kennedy Space Center (KSC) were used to generate a reference curve of DMA glass transition temperature (Tg) vs. shelf storage time ranging from 8 to 26 years. A similar reference curve of TGA onset temperature (of rubber weight loss) vs. shelf storage time was also generated. The DMA and TGA data for the used FCV O-rings were compared to the reference curves. Correlations were also made between the DMA modulus (at 22 C) and Shore A hardness for all 9 of the FCV O-rings used among the three Shuttle Orbiters. The radial cracking in the FCV O-rings was determined to be due to ozone attack, as nitrile/Buna N rubber is susceptible to such attack. Nitrile/Buna N material under MIL-P25732C should be used in a hydraulic fluid environment to help protect it from cracking. However, the FCV O-rings were used in an air only environment. The FCV design has as much as a 9-mil gap that allows the O.D. of the O-ring to be directly exposed to ozone, pressurized air and some elevated temperatures, accelerating the weathering process that leads to O-ring cracking. Space Shuttle flights will likely not continue past 2010. Therefore, Shuttle management decided to continue using the nitrile/Buna N material for the FCVs, but have each O-ring replaced after 3 years to minimize any chances for crack initiation.

Wingard, Doug↗
NASA NTRS1992

Bending response of thin-walled laminated composite cylinders

Closed-form linear response solutions are presented for the bending response of thin-walled laminated composite cylinders. Displacements and intralaminar stresses are computed using the Donnell theory, and interlaminar stresses are computed using 3D equilibrium equations of elasticity. Laminates with stacking sequencies and an aluminum cylinder are used to illustrate the displacement response, intralaminar, and interlaminar stresses for two length-to-radius ratios of 1 and 5. Data obtained indicate that if only fiber breakage causes ultimate failure, material failure will occur on the compression side of the cylinders, at the ends, due to fiber compression. The interlaminar normal stress is an order of magnitude smaller than the interlaminar shear stresses and it is not likely to initiate failure.

Fuchs, H. P.↗
DOE OSTI2024

Strain Field Around Individual Dislocations Controls Failure

Understanding material failure on a fundamental level is a key aspect in the design of robust structural materials, especially for metals and alloys capable to undergo plastic deformation. In the last decade, significant progress is made in quantifying the stresses associated with failure in both experiments and simulations. Nonetheless, the processes occurring on the most essential level of individual dislocations that govern semi-brittle and ductile fracture are still experimentally not accessible, limiting the failure prediction capabilities. Therefore, in the present work, a one-of-a-kind nanoscale fracture experiment is conducted on a single crystalline Cr bending beam in situ in the transmission electron microscope and for the first time quantify the transient strains around individual dislocations, as well as of the whole dislocation network during crack opening. The results reveal the importance of both pre-existing and newly emitted dislocations for crack-tip shielding via their intrinsic strain field and provide guidelines to design more damage tolerant materials.

36 MATERIALS SCIENCE↗
NASA NTRS1964

Structural materials.

Failure modes of structural materials for manned spacecraft, considering effects of space environment

MANNED SPACECRAFT↗
NASA NTRS2011

Compression Behavior of Fluted-Core Composite Panels

In recent years, fiber-reinforced composites have become more accepted for aerospace applications. Specifically, during NASA s recent efforts to develop new launch vehicles, composite materials were considered and baselined for a number of structures. Because of mass and stiffness requirements, sandwich composites are often selected for many applications. However, there are a number of manufacturing and in-service concerns associated with traditional honeycomb-core sandwich composites that in certain instances may be alleviated through the use of other core materials or construction methods. Fluted-core, which consists of integral angled web members with structural radius fillers spaced between laminate face sheets, is one such construction alternative and is considered herein. Two different fluted-core designs were considered: a subscale design and a full-scale design sized for a heavy-lift-launch-vehicle interstage. In particular, axial compression of fluted-core composites was evaluated with experiments and finite-element analyses (FEA); axial compression is the primary loading condition in dry launch-vehicle barrel sections. Detailed finite-element models were developed to represent all components of the fluted-core construction, and geometrically nonlinear analyses were conducted to predict both buckling and material failures. Good agreement was obtained between test data and analyses, for both local buckling and ultimate material failure. Though the local buckling events are not catastrophic, the resulting deformations contribute to material failures. Consequently, an important observation is that the material failure loads and modes would not be captured by either linear analyses or nonlinear smeared-shell analyses. Compression-after-impact (CAI) performance of fluted core composites was also investigated by experimentally testing samples impacted with 6 ft.-lb. impact energies. It was found that such impacts reduced the ultimate load carrying capability by approximately 40% on the subscale test articles and by less than 20% on the full-scale test articles. Nondestructive inspection of the damage zones indicated that the detectable damage was limited to no more than one flute on either side of any given impact. More study is needed, but this may indicate that an inherent damage-arrest capability of fluted core could provide benefits over traditional sandwich designs in certain weight-critical applications.

Schultz, Marc R.↗
NASA NTRS1997

Design Criteria for X-CRV Honeycomb Panels: A Preliminary Study

The objective of this project is to perform the first step in developing structural design criteria for composite sandwich panels that are to be used in the aeroshell of the crew return vehicle (X-CRV). The preliminary concept includes a simplified method for assessing the allowable strength in the laminate material. Ultimately, it is intended that the design criteria be extended to address the global response of the vehicle. This task will require execution of a test program as outlined in the recommendation section of this report. The aeroshell of the X-CRV is comprised of composite sandwich panels consisting of fiberite face sheets and a phenolic honeycomb core. The function of the crew return vehicle is to enable the safe return of injured or ill crewpersons from space station, the evacuation of crew in case of emergency or the return of crew if an orbiter is not available. A significant objective of the X-CRV project is to demonstrate that this vehicle can be designed, built and operated at lower cost and at a significantly faster development time. Development time can be reduced by driving out issues in both structural design and manufacturing concurrently. This means that structural design and analysis progresses in conjunction with manufacturing and testing. Preliminary tests results on laminate coupons are presented in the report. Based on these results a method for detection material failure in the material is presented. In the long term, extrapolation of coupon data to large scale structures may be inadequate. Test coupons used to develop failure criteria at the material scale are typically small when compared to the overall structure. Their inherent small size indicates that the material failure criteria can be used to predict localized failure of the structure, however, it can not be used to predict failure for all failure modes. Some failure modes occur only when the structure or one of its sub-components are studied as a whole. Conversely, localized failure may not indicate failure of the structure as a whole and the amount of reserve capacity, if any, should be assessed. To develop a complete design criteria experimental studies of the sandwich panel are needed. Only then can a conservative and accurate design criteria be developed. This criteria should include effects of flaws and defects, and environmental factors such as temperature and moisture. Preliminary results presented in this report suggest that a simplified analysis can be used to predict the strength of a laminate. Testing for environmental effects have yet to be included in this work. The so called 'rogue flaw test' appears to be a promising method for assessing the effect of a defect in a laminate. This method fits in quite well with the philosophy of achieving a damage tolerant design.

Caccese, Vincent↗