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Results for “FRACTURE TOUGHNESS”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

A study of the effect of subcritical crack growth on the geometry dependence on nonlinear fracture toughness parameters

The effect of subcritical crack growth on the geometry dependence of nonlinear fracture toughness parameters was studied by comparing the toughness values for different specimen geometries at the onset of subcritical crack growth and at the initiation of unstable crack propagation. Center-cracked thin sheet specimens of 2024-T3 and 7075-T6 aluminum alloys were tested by varying the specimen length L, width w, and crack length-to-width ratio c/w. When the onset of unstable crack propagation was selected as the critical point, the nonlinear energy toughness and the R curve toughness increased with increasing w and decreasing L and c/w. However, when the onset of subcritical crack growth was taken as the critical point, energy toughness and the linear toughness values were independent of these geometrical variables.

Jones, D. L.↗
NASA NTRS1977

The influence of composition, annealing treatment, and texture on the fracture toughness of Ti-5Al-2.5Sn plate at cryogenic temperatures

The plane strain fracture toughness K sub Ic and conventional tensile properties of two commercially produced one-inch thick Ti-5Al-2.5Sn plates were determined at cryogenic temperatures. One plate was extra-low interstitial (ELI) grade, the other normal interstitial. Portions of each plate were mill annealed at 1088 K (1500 F) followed by either air cooling or furnace cooling. The tensile properties, flow curves, and K sub Ic of these plates were determined at 295 K (room temperature), 77 K (liquid nitrogen temperature), and 20 K (liquid hydrogen temperature).

Vanstone, R. H.↗
NASA NTRS2026

Cryogenic Mixed Mode I – Mode II Fracture Toughness of Various Polymer Composite Materials

The present study investigates the mixed mode interlaminar fracture toughness of six polymer matrix composite materials at both room temperature and cryogenic liquid nitrogen temperature. The single leg bending test employed gives a mix of Mode I (opening) and Mode II (in-plane shearing) cracking. The tested thermoplastic-matrix composites were shown to have total mixed mode toughnesses 3.1–4.3 times higher than those of representative thermoset resin composites.

Carbon fiber↗
NASA NTRS1975

Fracture toughness testing data: A technology survey

Technical abstracts for about 90 significant documents relating to fracture toughness testing for various structural materials including information on plane strain and the developing areas of mixed mode and plane stress test conditions are presented. An overview of the state-of-the-art represented in the documents that have been abstracted is included. The abstracts in the report are mostly for publications in the period April 1962 through April 1974. The purpose of this report is to provide, in quick reference form, a dependable source for current information in the subject field.

Stuhrke, W. F.↗
NASA NTRS1974

The circumferentially notched cylindrical bar as a fracture toughness test specimen

A brief review is given of the application of the notched cylinder as a screening specimen for use in sorting materials in respect to their relative levels of plane strain fracture toughness and a discussion of fracture mechanics applications including Irwin's important contributions in this area. In addition, practical problems encountered in application of this specimen will be presented.

Brown, W. F., Jr.↗
NASA NTRS1976

Correlations among ultrasonic propagation factors and fracture toughness properties of metallic materials

Empirical evidence was developed to show that a close relation exists among fracture toughness, yield strength, and ultrasonic attenuation properties of metallic materials. The evidence was obtained by ultrasonic probing of specimens of two maraging steels and a titanium alloy. It was concluded that nondestructive ultrasonic methods can be used to indirectly evaluate fracture-related material properties. The results suggest that these nondestructive ultrasonic measurements can also serve as an adjunct to destructive testing, measurement, and analysis of fracture properties.

Vary, A.↗
NASA NTRS1976

Correlations among ultrasonic propagation factors and fracture toughness properties of metallic materials

Empirical evidence was developed to show that a close relation exists among fracture toughness, yield strength, and ultrasonic attenuation properties of metallic materials. The evidence was obtained by ultrasonic probing of specimens of two maraging steels and a titanium alloy. It was concluded that nondestructive ultrasonic methods can be used to indirectly evaluate fracture-related material properties. The results suggest that these nondestructive ultrasonic measurements can also serve as an adjunct to destructive testing, measurement, and analysis of fracture properties.

Vary, A.↗
NASA NTRS1983

Specimen size and geometry effects on fracture toughness of Al2O3 measured with short rod and short bar chevron-notch specimens

Plane strain fracture toughness measurements were made on Al2O3 using short rod and short bar chevron notch specimens previously calibrated by the authors for their dimensionless stress intensity factor coefficients. The measured toughness varied systematically with variations in specimen size, proportions, and chevron notch angle apparently due to their influence on the amount of crack extension to maximum load (the measurement point). The toughness variations are explained in terms of a suspected rising R curve for the material tested, along with a discussion of an unavoidable imprecision in the calculation of K sub Ic for materials with rising R curves when tested with chevron notch specimens.

Shannon, J. L., Jr.↗
NASA NTRS1991

The effect of temperature on the fracture toughness of Weldalite(TM) 049

The uncertain effect of temperature is characterized on the deformation and fracture behavior of Weldalite(TM) 049 from cryogenic to elevated temperatures. Fracture resistance is measured and the determination of fracture mechanisms emphasized, including slip plane cracking, high angle boundary delamination, subgrain boundary cracking, and microvoid coalescence. Microstructure is controlled to produce either predominantly T(sub 1) or T(sub 1) + delta (after Blankenship and Starke) and to examine the effect of dislocation-precipitate interaction on fracture toughness.

Lach, Cynthia L.↗
NASA NTRS2006

Fracture Toughness of Thin Plates by the Double-Torsion Test Method

Double torsion testing can produce fracture toughness values without crack length measurement that are comparable to those measured via standardized techniques such as the chevron-notch, surface-crack-in-flexure and precracked beam if the appropriate geometry is employed, and the material does not exhibit increasing crack growth resistance. Results to date indicate that 8 < W/d < 80 and L/W > 2 are required if crack length is not considered in stress intensity calculations. At L/W = 2, the normalized crack length should be 0.35 < a/L < 0.65; whereas for L/W = 3, 0.2 < a/L < 0.75 is acceptable. In addition, the load-points need to roll to reduce friction. For an alumina exhibiting increasing crack growth resistance, values corresponding to the plateau of the R-curve were measured. For very thin plates (W/d > 80) nonlinear effects were encountered.

Salem, Jonathan A.↗
NASA NTRS1988

Interlaminar fracture toughness of thermoplastic composites

Edge delamination tension and double cantilever beam tests were used to characterize the interlaminar fracture toughness of continuous graphite-fiber composites made from experimental thermoplastic polyimides and a model thermoplastic. Residual thermal stresses, known to be significant in materials processed at high temperatures, were included in the edge delamination calculations. In the model thermoplastic system (polycarbonate matrix), surface properties of the graphite fiber were shown to be significant. Critical strain energy release rates for two different fibers having similar nominal tensile properties differed by 30 to 60 percent. The reason for the difference is not clear. Interlaminar toughness values for the thermoplastic polyimide composites (LARC-TPI and polyimidesulfone) were 3 to 4 in-lb/sq in. Scanning electron micrographs of the EDT fracture surfaces suggest poor fiber/matrix bonding. Residual thermal stresses account for up to 32 percent of the strain energy release in composites made from these high-temperature resins.

Hinkley, J. A.↗