Lee A. James

Review and synthesis of stress intensity factor solutions applicable to cracks in bolts

Abstract The available literature for stress intensity factor solutions for cracks in round bars, both threaded and unthreaded, subjected to either tension or bending, is reviewed. The results are synthesized into a form that is appropriate for the analysis of bolts and studs.

Fatigue-crack propagation behavior of type 304 stainless steel in a liquid sodium environment

The fatigue crack growth of Type 304 stainless steel in a liquid sodium environment at 800 and 1000°F was characterized using a linear-elastic fracture mechanics approach. Tests were conducted in low (< 2.0 ppm) and high (20-40 ppm) oxygen sodium and the results were compared to those of tests conductedin vacua and in air. Similar crack propagation characteristics in air at room temperature and at elevated temperatures in sodium and vacuum is evidence that the thermally activated component of crack propagation observed in air is an environmental effect. Related work on environmental effects on fatigue or crack propagation properties are reviewed and discussed.

Effect of heat treatment and heat-to-heat variations in the fatigue-crack growth response of Alloy 718

The fatigue-crack growth behavior of seven heats of Alloy 718 was studied at five different test temperatures. These seven heats represented at least four different producers, four different product forms, two melt practices, and most of the heat were tested in two different heat-treated conditions. Heat-to-heat variations were noted; these were most obvious in material given the conventional heat-treatment. 8 figs., 5 tabs.

The effect of grain size upon the fatigue-crack propagation behavior of alloy 718 under hold-time cycling at elevated temperature

Abstract Fatigue-crack propagation tests were conducted in air at 538°C on several specimens of Alloy 718 representing several different producers, melt practices and product forms. This variety resulted in a range of grain sizes from ASTM Size 5 to 11.5. Tests at low cyclic frequency employing a tensile hold-time revealed a relationship between crack growth rates and grain size: higher growth rates were associated with fine-grain material and lower rates with larger-grain material. The lowest crack growth rates were associated with a necklace microstructure, whereby large grains are associated with necklaces of very small grains.

The effect of fast neutron irradiation upon the fatigue-crack propagation behavior of two austenitic stainless steels

The effect of fast neutron irradiation (454° 0.1 MeV) on the fatigue-crack growth behavior was investigated for annealed Type 304 and 20% coldworked Type 316 stainless steels using linear-elastic fracture mechanics techniques. Irradiation to this fluence had little or no effect upon the crack growth behavior of annealed Type 304 at a test temperature of 427° C, nor upon the behavior of 20% cold-worked Type 316 at test temperatures of 427° C and 538° C. Irradiation to this fluence did tend to decrease crack growth rates slightly, relative to unirradiated material, in annealed Type 304 at a test temperature of 538° C.

Fatigue-crack propagation behaviour of Inconel 600

Abstract The techniques of linear-elastic fracture mechanics were employed to characterise the effects of several parameters upon the fatigue-crack propagation behaviour of Inconel 600. The parameters studied included temperature, cyclic frequency, stress ratio, thermal ageing and a limited amount of testing in a liquid sodium environment.

Fatigue-crack propagation and fracture toughness behavior of cast stainless steels

Abstract The fatigue-crack growth and fracture toughness behavior of two cast stainless steels, ASME SA 351 Grades CF8 and CF8M, was investigated over a wide range of temperatures. The effect of a number of material-related parameters such as ferrite level, crack orientation, and heat-to-heat and alloy-to-alloy variations was studied. In addition, the crack growth and J- integral toughness of cast CF8 subjected to neutron irradiation was characterized.

Fatigue-crack propagation behavior of HT-9 steel

Abstract The fatigue-crack propagation (FCP) behavior of two heats of HT-9 steel, representing two different producers and product forms, was characterized at five test temperatures over the range 24–593°C. Comparisons are also made to the behavior of a similar martensitic stainless steel, the modified 9Cr-1Mo steel (ASTM A387-91), tested at the same conditions of temperature, cyclic frequency, and stress ratio.

The effect of temperature and neutron irradiation upon the fatigue-crack propagation behavior of ASTM A533-B steel

The fatique-crack propagation behaviour of A533-B steel was studied within the framework of linear-elastic fracture mechanics. Tests were conducted at 75° F (24° C) and 550° F (288°C) on unirradiated material, and on material irradiated at 550° F to 2.3 – 2.8 × 1019 n/cm2 and 5.3 – 5.7 × 1019 n/cm2 (E > 1 MeV). In general, at the cyclic frequency used (600 cpm), neither temperature nor neutron irradiation had a significant effect on the fatigue-crack propagation.

Surface-crack aspect ratio development during corrosion-fatigue crack growth in low-alloy steels

Abstract The development of aspect ratios (crack depth/half-crack length), was studied for semi-elliptical surface cracks in low-alloy steel undergoing corrosion-fatigue in an elevated temperature aqueous environment. Water-enhanced crack growth behavior is influenced by the concentration of hydrogen sulfide at the crack tip, and the sulfide concentration is in turn influenced by mass-transport considerations. The mass-transport characteristics of surface cracks may be different from those of more common test specimens; e.g. compact tension specimens. It is also shown that the method of preparing surface-cracked specimens can have an influence upon the crack growth behavior; surface cracks emanating from crack-starter notches may behave differently than ‘natural’ surface cracks because of differences in the mass-transport paths. It is also shown in that the rate of water flow along the length of a surface crack can affect the resulting crack aspect ratio and crack growth rates.