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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Fracture Control and Structural Certification Guidance for Additive Manufactured Spacecraft Structures

This paper offers a NASA perspective on guidance for fracture control and structural certification of "fracture critical" additive manufactured spacecraft structures. Results of a recent industry survey on the need for maturing NASA guidance for AM certification are presented for the first time. The survey results are placed in the context of a description of what NASA standards in this area already exist, where the gaps are, and what work to address the gaps is underway.

McElroy, Mark↗
NASA NTRS2006

Fracture Control Requirements for Composite and Bonded Vehicle and Payload Structures

The document presents a minimum set of fracture control requirements to be used across MSFC programs in designing and assessing composite and bonded structures. The scope includes manned launch, retrieval, transfer, and landing vehicles, space habitats, and payloads or experiments that are launched, retrieved, stored, or operated during any portion of a manned spaceflight mission. It is applicable to in-house and contract activities. The requirements apply to fiber reinforced polymer matrix composites, sandwich construction (bonded metallic and nonmetallic), and bonds between metallic or composite parts fall within the scope of this document.

McGill, Preston↗
NASA NTRS1981

The application of fracture control to a weld specification

An approach used on the external tank (ET) portion of the Space Shuttle Program which employs fracture control to establish defect acceptance criteria in a welding specification is discussed. Weld acceptance criteria developed for the ET fabricated from 2219 aluminum are demonstrated using as an example one of the actual ET welds. A table of weld grades as a function of acceptable defect length is presented. The design drawing specifies the weld grade for a particular weld; then the inspector uses the grade to determine the defect length for radiographic and penetrant acceptance of the weld. By allowing each weld to be judged by its own defect requirement instead of using the tightest requirement, the number of weld repairs has been minimized, resulting in lower cost with no compromise in performance.

Bolstad, D. A.↗
NASA NTRS1979

Reusable solid rocket motor case - Optimum probabilistic fracture control

A methodology for the reliability analysis of a reusable solid rocket motor case is discussed in this paper. The analysis is based on probabilistic fracture mechanics and probability distribution for initial flaw sizes. The developed reliability analysis can be used to select the structural design variables of the solid rocket motor case on the basis of minimum expected cost and specified reliability bounds during the projected design life of the case. Effects on failure prevention plans such as nondestructive inspection and the material erosion between missions can also be considered in the developed procedure for selection of design variables. The reliability-based procedure that has been discussed in this paper can easily be modified to consider other similar structures of reusable space vehicle systems with different fracture control plans.

Hanagud, S.↗
NASA NTRS1974

Design, fracture control, fabrication, and testing of pressurized space-vehicle structures

The relationship between analysis, design, fabrication, and testing of thin shells is illustrated by Saturn S-IVB, Thor, Delta, and other single-use and reusable large-size cryogenic aluminum tankage. The analyses and design to meet the design requirements are reviewed and include consideration of fracture control, general instability, and other failure modes. The effect of research and development testing on the structure is indicated. It is shown how fabrication and nondestructive and acceptance testing constrain the design. Finally, qualification testing is reviewed to illustrate the extent of testing used to develop the Saturn S-IVB.

Babel, H. W.↗
NASA NTRS1981

Fracture control plan for propellant and pressurant tanks

To assure the functional integrity of the GLL-RPM fuel and pressurized gas tank, all activities during entire lifetime of the tank, from manufacture to the end of the mission, must be monitored. Specifications are given for all procedures which influence the tank structure including design, manufacture, cleaning, test operations, and storage. Tests to be conducted to demonstrate that requirements of the fracture control plan are satisfied include static tests, cyclic load tests, proof tests, He-leak test, and acceptance tests.

Source record↗
NASA NTRS1974

Space Shuttle Orbiter Fracture Control Plan

The criteria are presented for preventing space shuttle structural failure associated with crack initiation or propagation during fabrication, test, handling, and the operational life of the vehicle. The criteria discussed include: engineering responsibilities, assurance management, production, operation and test, procurement, critical parts selection, design, and structural analysis.

Fracture control↗
NASA NTRS1977

Probabilistic Fracture Mechanics and Optimum Fracture Control Analytical Procedures for a Reusable Solid Rocket Motor Case

A methodology for the reliability analysis of a reusable solid rocket motor case is discussed. The analysis is based on probabilistic fracture mechanics and probability distribution for initial flaw sizes. The developed reliability analysis is used to select the structural design variables of the solid rocket motor case on the basis of minimum expected cost and specified reliability bounds during the projected design life of the case. Effects of failure prevention plans such as nondestructive inspection and the material erosion between missions are also considered in the developed procedure for selection of design variables. The reliability-based procedure can be modified to consider other similar structures of reusable space vehicle systems with different failure prevention plans.

Hanagud, S.↗
NASA NTRS1975

Fracture control method for composite tanks with load sharing liners

The experimental program was based on the premise that the plastic sizing cycle, which each pressure vessel is subjected to prior to operation, acts as an effective proof test of the liner, screening out all flaws or cracks larger than a critical size. In doing so, flaw growth potential is available for cyclic operation at pressures less than the sizing pressure. Static fracture and cyclic life tests, involving laboratory type specimens and filament overwrapped tanks, were conducted on three liner materials: (1) 2219-T62 aluminum, (2) Inconel X750 STA, and (3) cryoformed 301 stainless steel. Variables included material condition, thickness, flaw size, flaw shape, temperature, sizing stress level, operating stress level and minimum-to-maximum operating stress ratio. From the empirical data base obtained, a procedure was established by which the service life of composite tanks with load sharing liners could be guaranteed with a high degree of confidence.

Bixler, W. D.↗
DOE OSTI2021

Role of Mineralogy in Controlling Fracture Formation

The presence of fractures in caprocks can pose increased risks in subsurface energy systems and processes like CO 2 sequestration by introducing high-permeability leakage paths. Fracture apertures and permeability can be altered through mineral dissolution and precipitation reactions, but the reactive evolution of fractures is not well understood. In fractures, minerals that are otherwise inaccessible to reactive fluids can become exposed, resulting in mineral reactions unpredicted by bulk formation data. This work seeks to understand the relationship between mineralogy and fracture formation to enhance our understanding of reactive fracture evolution and CO 2 leakage potential. Here, the mineral compositions of mechanically induced fracture surfaces in samples of the Mancos and Marcellus shales have been quantified and compared to those of the near-fracture matrices using imaging and bulk X-ray diffraction (XRD) data. In the Mancos shale, the concentrations of clay minerals are enhanced along fracture surfaces with respect to the bulk, and the fracture is most likely to form at kaolinite–kaolinite interfaces. Further, evaluation of the mineralogical spatial variability through cross-correlation analysis of the surrounding matrix in images of samples cut perpendicular to the fracture shows that clay is 16.7 times more likely to be present than carbonate minerals near the fracture surface. The high correlation persists roughly 200 μm into the surrounding matrix for the Mancos sample and implies that the fracture formed within a defined clay-rich lithofacies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

Space shuttle orbiter fracture control plan

The criteria are presented for preventing space shuttle structural failure associated with crack initiation or propagation during fabrication, test, handling, and the operational life of the vehicle. The criteria discussed include: engineering responsibilities, assurance management, production, operation and test, procurement, critical parts selection, design, and structural analysis.

Space Division↗
NASA NTRS1977

Fracture control of H-O engine components

An investigation was made to obtain the material characterization and fatigue crack propagation data necessary to establish the salient characteristics of a Ti-6Al-2.5Sn(ELI) alloy fuel pump impeller to be used in a cryogenic service environment. Testing variables considered were: coupon orientation, frequency, load range ratio, and temperature. Data analysis correlated crack propagation data from conventional laboratory coupons with data from a parallel sided rotating disk used to model rotor stresses. Four major design recommendations when bore regions of fuel pump impellers to be operated in cryogenic environments are to be relatively highly stressed are discussed.

Ryder, J. T.↗