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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Sierra/SolidMechanics 5.10 In-Development Manual

This user’s guide documents capabilities in Sierra/SolidMechanics which remain “in-development” and thus are not tested and hardened to the standards of capabilities listed in Sierra/SM 5.10 User’s Guide. Capabilities documented herein are available in Sierra/SM for experimental use only until their official release. These capabilities include, but are not limited to, novel discretization approaches such as the conforming reproducing kernel (CRK) method, numerical fracture and failure modeling aids such as the extended finite element method (XFEM) and J-integral, explicit time step control techniques, dynamic mesh rebalancing, as well as a variety of new material models and finite element formulations.

42 ENGINEERING↗
DOE OSTI2023

Go/No-Go Decision Point 1 Report

To satisfy the G/NG point 1 we have employed GEOS hydraulic fracturing module to simulate one of the Diagnostic Fracture Injection Tests conducted at well 58-32. The hydraulic fracturing solver relies on a finite element discretization of the mechanics fully coupled to a finite volume discretization of the fluid flow. Fractures are explicitly modeled as lower dimensional manifolds and discretized by 2D elements sitting at the boundary of cell elements. We have calibrated our model to reproduce the DFIT corresponding to Zone 2 Cycle 4 of the injection tests that took place at well 58-32.

15 GEOTHERMAL ENERGY↗
DOE OSTI2023

Sierra/SolidMechanics 5.16 Capabilities in Development Manual

This user’s guide documents capabilities in Sierra/SolidMechanics which remain “in-development” and thus are not tested and hardened to the standards of capabilities listed in Sierra/SM 5.16 User’s Guide. Capabilities documented herein are available in Sierra/SM for experimental use only until their official release. These capabilities include, but are not limited to, novel discretization approaches such as the conforming reproducing kernel (CRK) method, numerical fracture and failure modeling aids such as the extended finite element method (XFEM) and J-integral, explicit time step control techniques, dynamic mesh rebalancing, as well as a variety of new material models and finite element formulations.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Atomistic Modeling of the Interphase Structure between Alumina and Al12Fe2Cr Quasicrystal Approximant

Molecular dynamics simulations are performed to study the stability of an fcc metallic interlayer phase between an iron aluminide quasicrystal approximant (QCA) phase (84.2 Al, 5.7 Fe, 5.4 Ni, and 4.7 at.% Cr) and aluminum oxides (α-Al 2 O 3 and γ-Al 2 O 3 ). The presence of the interlayer phase was experimentally observed in some regions of the inner diameter surface of a TPBAR cladding tube. The simulations employed existing many-body (MEAM and EAM) interatomic potentials to describe atomic interactions in the interlayer and QCA phases, and Buckingham+Coulomb pair interactions for the alumina and between the alumina and the QCA (or fcc). Interface systems of QCA/alumina, fec/alumina, and QCA/fcc are modeled and the fracture energy of the interfaces is calculated. Based on the fracture energies, for the γ-Al 2 O 3 , both MEAM and EAM suggest that the fcc interlayer phase would not form. For the α-Al 2 O 3 , the MEAM predicts that the fcc phase would form, however, the EAM predicts that it forms only if the α-Al 2 O 3 is Al-terminated at the interface. For the O-terminated α-Al 2 O 3 , the EAM predicts the fcc phase would not form, consistent with the results for γ-Al 2 O 3 .

36 MATERIALS SCIENCE↗
NASA NTRS1985

Structural Integrity and Durability of Reusable Space Propulsion Systems

A two-day conference on the structural integrity and durability of reusable space propulsion systems was held on June 4 and 5, 1985, at the NASA Lewis Research Center. Presentations were made by industry, university, and government researchers organized into four sessions: aerothermodynamic loads; structural dynamics, fatigue, fracture, and constitutive modeling; and instrumentation. The principal objectives of the conference were to disseminate research results to date and future plans in each of the four areas. This publication contains the extended abstracts and the visual material presented during the conference.

Stanley J Marsik↗
NASA NTRS1984

Ultrasonic probing of the fracture process zone in rock using surface waves

A microcrack process zone is frequently suggested to accompany macrofractures in rock and play an important role in the resistance to fracture propagation. Attenuation of surface waves propagating through mode I fractures in wedge-loaded double-cantilever beam specimens of Westerly granite has been recorded in an attempt to characterize the structure of the fracture process zone. The ultrasonic measurements do not support the generally accepted model of a macroscopic fracture that incrementally propagates with the accompaniment of a cloud of microcracks. Instead, fractures in Westerly granite appear to form as gradually separating surfaces within a zone having a width of a few millimeters and a length of several tens of millimeters. A fracture process zone of this size would necessitate the use of meter-sized specimens in order for linear elastic fracture mechanics to be applicable.

Swanson, P. L.↗
NASA NTRS1985

Fracto-emission from the peeling of pressure sensitive adhesives

The electron emission, positive ion emission, photon emission, and long wavelength electromagnetic radiation accompanying the peeling of pressure sensitive adhesives in vacuum are examined. These results are interpreted in terms of a previously presented model involving fracture-induced microdischarges which excite the fracture surfaces by particle bombardment.

Dickinson, J. T.↗
NASA NTRS1987

Structural Integrity and Durability of Reusable Space Propulsion Systems

A two-day conference on the structural integrity and durability of reusable space propulsion systems was held on May 12 and 13, 1987, at the NASA Lewis research Center. Aerothermodynamic loads; instrumentation; fatigue, fracture, and constitutive modeling; and structural dynamics were discussed.

Source record↗
NASA NTRS1990

Reports on block rotations, fault domains and crustal deformation

Studies of block rotations, fault domains and crustal deformation in the western United States, Israel, and China are discussed. Topics include a three-dimensional model of crustal fracture by distributed fault sets, distributed deformation and block rotation in 3D, stress field rotation, and multiple strike slip fault sets.

Nur, Amos↗
NASA NTRS1990

Investigation of mechanical and thermal properties of microwave-sintered lunar simulant materials using 2.45 GHz radiation

The mechanical and thermal properties of lunar simulant material were investigated. An alternative method of examining thermal shock in microwave-sintered lunar samples was researched. A computer code was developed that models how the fracture toughness of a thermally shocked lunar simulant sample is related to the sample hardness as measured by a micro-hardness indentor apparatus. This technique enables much data to be gathered from a few samples. Several samples were sintered at different temperatures and for different times at the temperatures. The melting and recrystallization characteristics of a well-studied binary system were also investigated to see if the thermodynamic barrier for the nucleation of a crystalline phase may be affected by the presence of a microwave field. The system chosen was the albite (sodium alumino silicate) anorthite system (calcium alumino silicate). The results of these investigations are presented.

Meek, T. T.↗
NASA NTRS1991

Origin of periodically spaced wrinkle ridges on the Tharsis Plateau of Mars

The mechanism responsible for the periodic spacing of wrinkle ridges observed on the Tharsis Plateau of Mars is investigated by examining the characteristics of the spacing of ridges in six major provinces on the plateau; these regions were further divided into domains on the basis of ridge orientation. The ridges are interpreted to be folds resulting from buckling, followed by reverse to thrust faulting (flexure-fracture). Several buckling models that may account for the periodic nature of the ridges are analyzed. The model that would account for the periodic spacing and the asymmetric fold geometry of the ridges involves plastic yielding confined to the hinge area, that would result in rapid closing of the fold and, with continued horizontal shortening, the eventual development of reverse to thrust faulting.

Watters, Thomas R.↗
NASA NTRS1992

Finite-element analyses and fracture simulation in thin-sheet aluminum alloy

A two-dimensional, elastic-plastic finite-element analysis was used with a critical crack-tip-opening angle (CTOA) fracture criterion to model stable crack growth in thin-sheet 2024-T3 aluminum alloy under monotonic loading after precracking at different cyclic stress levels. Tests were conducted on three types of specimens: middle-crack, three-hole-crack and blunt-notch tensile specimens. An experiment technique was developed to measure CTOA during crack growth initiation and stable tearing using a high-resolution video camera and recorder. Crack front shapes were also measured during initiation and stable tearing using a fatigue marker-load technique. Three-dimensional elastic-plastic finite-element analyses of these crack shapes for stationary cracks were conducted to study the crack-front opening displacements. Predicted load against crack extension on middle-crack tension specimens agreed well with test results even for large-scale plastic deformations. The analyses were able to predict the effects of specimen size and precracking stress history on stable tearing. Predicted load against load-line displacements agreed well with test results up to maximum load bu the analyses tended to overpredict displacements as crack grew beyond the maximum load under displacement-controlled conditions. During the initiation phase, the measured CTOA values were high but decreased and remained nearly constant after a small amount of stable tearing. The constant value of CTOA agree well with the calculated value from the finite-element analysis. The larger CTOA values measured at the sheet surface during the initiation phase may be associated with the crack tunneling observed in the tests. Three-dimensional analyses for nonstraight crack fronts predicted much higher displacements near the free surface than in the interior.

Newman, J. C., Jr.↗
NASA NTRS1991

Structural Integrity and Durability of Reusable Space Propulsion Systems

A two-day conference on the structural integrity and durability of reusable space propulsion systems was held on 14 to 15 May 1991 at the NASA Lewis Research Center. Presentations were made by industry, university, and government researchers organized into four sessions: (1) aerothermodynamic loads; (2) instrumentation; (3) fatigue, fracture, and constitutive modeling; and (4) structural dynamics. The principle objectives were to disseminate research results and future plans in each of four areas. This publication contains extended abstracts and the visual material presented during the conference. Particular emphasis is placed on the Space Shuttle Main Engine (SSME) and the SSME turbopump.

Source record↗
NASA NTRS1993

A fracture criterion for widespread cracking in thin-sheet aluminum alloys

An elastic-plastic finite-element analysis was used with a critical crack-tip-opening angle (CTOA) fracture criterion to model stable crack growth in thin-sheet 2024-T3 aluminum alloy panels with single and multiple-site damage (MSD) cracks. Comparisons were made between critical angles determined from the analyses and those measured with photographic methods. Calculated load against crack extension and load against crack-tip displacement on single crack specimens agreed well with test data even for large-scale plastic deformations. The analyses were also able to predict the stable tearing behavior of large lead cracks in the presence of stably tearing MSD cracks. Small MSD cracks significantly reduced the residual strength for large lead cracks.

Newman, J. C., Jr.↗