The growth of small corrosion fatigue cracks in alloy 2024

The corrosion fatigue crack growth characteristics of small surface and corner cracks in aluminum alloy 2024 is established. The damaging effect of salt water on the early stages of small crack growth is characterized by crack initiation at constituent particle pits, intergranular microcracking for a less than 100 micrometers, and transgranular small crack growth for a micrometer. In aqueous 1 percent NaCl and at a constant anodic potential of -700 mV(sub SCE), small cracks exhibit a factor of three increase in fatigue crack growth rates compared to laboratory air. Small cracks exhibit accelerated corrosion fatigue crack growth rates at low levels of delta-K (less than 1 MPa square root of m) below long crack delta-K (sub th). When exposed to Paris regime levels of crack tip stress intensity, small corrosion fatigue cracks exhibit growth rates similar to that observed for long cracks. Results suggest that crack closure effects influence the corrosion fatigue crack growth rates of small cracks (a less than or equal to 100 micrometers). This is evidenced by similar small and long crack growth behavior at various levels of R. Contrary to the corrosion fatigue characteristics of small cracks in high strength steels, no pronounced chemical crack length effect is observed for Al by 2024 exposed to salt water

Experimental Investigation of Sublimation of Ice at Subsonic and Supersonic Speeds and Its Relation to Heat Transfer

An experimental investigation was conducted in a 3.84- by 10-inch tunnel to determine the mass transfer by sublimation, heat transfer, and skin friction for an iced surface on a flat plate for Mach numbers of 0.4, 0.6, and 0.8 and pressure altitudes to 30,000 feet. Measurements of rates of sublimation were also made for a Mach number of 1.3 at a pressure altitude of 30,000 feet. The results show that the parameters of sublimation and heat transfer were 40 to 50 percent greater for an iced surface than was the bare-plate heat-transfer parameter. For iced surfaces of equivalent roughness, the ratio of sublimation to heat-transfer parameters was found to be 0.90. The sublimation data obtained at a Mach number of 1.3 showed no appreciable deviation from that obtained at subsonic speeds. The data obtained indicate that sublimation as a means of removing ice formations of appreciable thickness is usually too slow to be of mach value in the de-icing of aircraft at high altitudes

The recent history and future of the subterranean estuary

During the past century, anthropogenic forces changed the composition of water in coastal aquifers. These changes were brought about by excessive mining of coastal groundwater, dredging and pier construction, wetland draining, and hard surface expansion. These forces caused an increase of salinity in the subterranean estuary, which led to a series of biogeochemical reactions. These changes continue today

APPLICATION OF FEDERAL INCOME, ESTATE AND GIFT TAX LAWS TO COMMUNITY PROPERTY

The ganancial or community concept of property ownership, by which husband and wife have equal, vested, undivided, one-half interests in property held by them as tenants in community, has been a thorn in the side of federal tax laws ever since some tax-conscious community income earner decided to report as taxable only one-half of the community income, leaving the other half to be reported by and taxed to his wife upon her separate return. Such procedure first became authorized in community property jurisdictions recognizing the wife\u27s interest as vested in 1920. Not long thereafter the realization began to dawn upon outsiders that residents of community property jurisdictions were enjoying distinct tax advantages not available to them, and from that moment to the present day, criticism of the tax effect of community property laws has been frequent. That the tax laws have operated favorably upon earners of community income is an indictment of the federal tax statutes rather than of the community property laws. This is especially evident when it is realized that in all jurisdictions except two, community property laws were in force long before the Sixteenth Amendment to the United States Constitution was adopted

Implications of Tort Liability in Utah for Accidents in Physical Education and Related Areas

The purpose of this study is to review the literature of the past twenty years as it relates to tort liability of school districts, boards of education, and teachers, with special emphasis on the field of physical education and related activities such as intramurals and inter-scholastic competition. Recent legislation passed by the Utah legislature is cited. In certain instances this will be contrasted with older laws and practices which still prevail in a good number of states

Use of Marker Bands for Determination of Fatigue Crack Growth Rates and Crack Front Shapes in Pre-Corroded Coupons

Groups of striations called marker bands generated on a fatigue fracture surface can be used to mark the position of an advancing fatigue crack at known intervals. A technique has been developed that uses the distance between multiple sets of marker bands to obtain a vs. N, crack front shape, and fatigue crack growth rate data for small cracks. This technique is particularly usefull for specimens that require crack length measurements during testing that cannot be obtained because corrosion obscures the surface of the specimen. It is also useful for specimens with unusual or non-symmetric shapes where it is difficult to obtain accurate crack lengths using traditional methods such as compliance or electric potential difference in the early stages of testing

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