Aluminum critical constants

Expander-compressor shafts are preferably designed to operate below the first lateral critical speed and torsional resonance. A flame-plated band of aluminum alloy or similarly suitable material is generally applied to the shaft in the area sensed by the vibration probes to preclude erroneous electrical runout readings. This technique has been used on hundreds of expanders, steam turbines, and other turbomachines with complete success. Unless integral with the shaft, expander wheels (disks) are often attached to the shaft on a special tapered profile, with dowel-type keys and keyways. The latter design attempts to avoid the stress concentrations occasionally associated with splines and conventional keyways. It also reduces the cost of manufacture. When used, wheels are sometimes secured to the tapered ends of the shaft by a common center stretch rod which is pre-stressed during assembly. This results in a constant preload on each wheel to ensure proper contact between wheels and shaft at the anticipated extremes of temperature and speed. 

All other conditions being held constant, there appeared to be a minimum required mass of aluminum to cause an explosion, but an excess over this critical quantity did not lead to more damaging events. The critical mass was in the range of 4-5 kg for normal tests. 

H) W. Fickett W.W. Wood, The Physics of Fluids 1 (6), 528-34 (Nov-Dec 1958) (Detonation-product equations of state, known as "constant-/ and "constant-)/ , obtained from hydrodynamic data) I) J.J. Erpenbeck D.G. Miller, IEC 51, 329-31 (March 1959) (Semiempirical vapor pressure relation based on Dieterici s equation of state J) K.A. Kobe P.S. Murti, IEC 51, 332 (March 1959) (Ideal critical volumes for generalized correlations) (Application to the Macleod equation of state) Kj) S. Katz et al, jApplPhys 10, 568-76(April 1959) (Hugoniot equation of state of aluminum and steel) K2) S.J. Jacobs, jAmRocketSoc 30, 151(1960) (Review of semi-empirical equations of state)... 

Form groups of three. Each person should select a material from the three categories under consideration for this application (steel, aluminum alloy, and titanium alloy) other than the three listed in Table 8.3 and should perform a similar analysis—that is, calculate or look up yield strength, fracture toughness, critical crack size, number of cycles to failure, and the constants A and m in the Paris equation. Combine your results and compare your answers. Do you obtain a result similar to that in Table 8.3 ... 

The fact that the aluminum cylinder is constantly under pressure is believed to be a contributing factor for stress corrosion. The moisture content is very critical since condensation occurs when pressure changes rapidly. Therefore, moisture content and slow refilling procedure are strictly regulated. Carbon dioxide content is also critical since it increases its dissolubility as pressure increases. As a result, it could bring the pH value of condensed water below the level where aluminum oxide is no longer stable. 

Neutral and Polymeric Aluminum and Iron. The association constants and enthalpies of aluminum and iron hydroxides have been evaluated by comparing the critically selected data of Baes and Mesmer (51) with that of R. M. Siebert and C. L. Christ (personal communication, 1976). Differences between the two data sets are negligible and the final selection was from Baes and Mesmer (51) because data on more complexes are found there. Important new species added to tjjie model are the polynuclear complexes Fe2(0H)2 and Fes(OH). Some controversy has arisen over the existence of Fe(0H) and A1(0H)3. Baes and Mesmer (51) have indicated that although the formation constant of A1(0H)3 is only known from one measurement (52) and has a large uncertainty, it is real, with a log K < -15.0 for the reaction... 

Important features of the selective oxidation process are shown schematically in Figure 1. The slow growth rates of alumina and silica, illustrated in the plot of parabolic rate constants versus temperature at lower right, makes the formation of one of these oxides as a continuous surface layer necessary for long term oxidation protection. This requires that the protective oxide be more stable thermodynamically than the more rapidly growing oxides. The plot of standard free energy of formation as a function of temperature at lower left shows that the Ni-Al system satisfies this condition. Alumina is stable, relative to NiO, even when the activity of aluminum in the alloy is very low. However, when the Al concentration is low the alumina forms as internal oxide precipitates and is non-protective allowing an external layer of NiO to form (illustrated in the cartoon at top). Therefore, a critical concentration of Al exists above which out-... 

The consumption of raw materials, already from the industrial revolution time, has been on constant increase worldwide. Available data, recorded and analyzed, mainly during the last 50-60 years, widely prove this fact for a number of materials being critical for manufacturing activities, such as steel, aluminum, copper, nickel, zinc, wood, etc. As far as steel is... 

The temperature of aging was a critical parameter no particles were produced below 90°C, while the best results were obtained at 98°C. Finally, the particles had reasonably constant chemical composition, which indicates that one or more well-defined aluminum basic sulfate complexes were the precursors to the nucle-ation of particles. 

Margerum DW, Cayley GR, Weatherburn DC, Pagenkopf GK (1978) Kinetics and mechanisms of complex formation and ligand exchange. In Martell AE (ed) Coordination chemistry, vol 2. American Chemical Society, Washington, p 1 Marsden CD (1987) Wilson s disease. Q J Med 65 959-966 Martell AE, Smith RM (1974) Critical stability constants. Plenum, New York Martin RB (1986) The chemistry of aluminum as related to biology and medicine. Clin Chem 32 1797-1806... 

Plastic materials subjected to a constant stress can deform continuously with time and the behavior under different conditions such as temperature. This continuous deformation with time is called creep or cold flow. In some applications the permissible creep deformations are critical, in others of no significance. But the existence of creep necessitates information on the creep deformations that may occur during the expected life of the product. Materials such as plastic, RP, zinc, and tin creep at room temperature. Aluminum and magnesium alloys start to creep at around 300°F. Steels above 650°F must be checked for creep. 

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