Strainrange partitioning behavior of the nickel-base superalloys, Rene' 80 and in 100

A study was made to assess the ability of the method of Strainrange Partitioning (SRP) to both correlate and predict high-temperature, low cycle fatigue lives of nickel base superalloys for gas turbine applications. The partitioned strainrange versus life relationships for uncoated Rene' 80 and cast IN 100 were also determined from the ductility normalized-Strainrange Partitioning equations. These were used to predict the cyclic lives of the baseline tests. The life predictability of the method was verified for cast IN 100 by applying the baseline results to the cyclic life prediction of a series of complex strain cycling tests with multiple hold periods at constant strain. It was concluded that the method of SRP can correlate and predict the cyclic lives of laboratory specimens of the nickel base superalloys evaluated in this program

The strainrange partitioning behavior of an advanced gas turbine disk alloy, AF2-1DA

The low-cycle, creep-fatigue characteristics of the advanced gas turbine disk alloy, AF2-1DA have been determined at 1400 F and are presented in terms of the method of strainrange partitioning (SRP). The mean stresses which develop in the PC and CP type SRP cycles at the lowest inelastic strainrange were observed to influence the cyclic lives to a greater extent than the creep effects and hence interfered with a conventional interpretation of the results by SRP. A procedure is proposed for dealing with the mean stress effects on life which is compatible with SRP

Bending fatigue of electron-beam-welded foils. Application to a hydrodynamic air bearing in the Chrysler/DOE upgraded automotive gas tubine engine

A hydrodynamic air bearing with a compliment surface is used in the gas generator of an upgraded automotive gas turbine engine. In the prototype design, the compliant surface is a thin foil spot welded at one end to the bearing cartridge. During operation, the foil failed along the line of spot welds which acted as a series of stress concentrators. Because of its higher degree of geometric uniformity, electron beam welding of the foil was selected as an alternative to spot welding. Room temperature bending fatigue tests were conducted to determine the fatigue resistance of the electron beam welded foils. Equations were determined relating cycles to crack initiation and cycles to failure to nominal total strain range. A scaling procedure is presented for estimating the reduction in cyclic life when the foil is at its normal operating temperature of 260 C (500 F)

An update of the total-strain version of SRP

An updated procedure for characterizing an alloy and predicting cyclic life by using the total strain range version of strainrange partitioning (TS-SRP) has been developed. The principal feature of this update is a new procedure for determining the intercept of time dependent elastic strain range versus cyclic life lines. The procedure is based on an established relation between failure and the cyclic stress-strain response of an alloy. The stress-strain response is characterized by empirical equations presented in this report. These equations were determined with the aid of a cyclic constitutive model. The procedures presented herein reduce the testing required to characterize an alloy. Failure testing is done only in the high strain, low life regime; cyclic stress-strain response is determined from tests conducted in both the high and low strain regimes. These tests are carried out to stability of the stress-strain hysteresis loop but not to failure. Thus both the time and costs required to characterize an alloy are greatly reduced. This approach was evaluated and verified for two nickel base superalloys, AF2-1DA and Inconel 718

Application of strainrange partitioning to the prediction of creep-fatigue lives of AISI types 304 and 316 stainless steel

As a demonstration of the predictive capabilities of the method of Strainrange Partitioning, published high-temperature, low cycle, creep-fatigue test results on AISI Types 304 and 316 stainless steel were analyzed and calculated, cyclic lives compared with observed lives. Predicted lives agreed with observed lives within factors of two for 76 percent, factors of three for 93 percent, and factors of four for 98 percent of the laboratory tests analyzed. Agreement between observed and predicted lives is judged satisfactory considering that the data are associated with a number of variables (two alloys, several heats and heat treatments, a range of temperatures, different testing techniques, etc.) that are not directly accounted for in the calculations

Strainrange partitioning: A total strain range version

Procedures are presented for expressing the Strainrange Partitioning (SRP) method for creep fatigue life prediction in terms of total strain range. Inelastic and elastic strain-range - life relations are summed to give total strain-range - life relations. The life components due to inelastic strains are dealt with using conventional SRP procedures while the life components due to elastic strains are expressed as families of time-dependent terms for each type of SRP cycle. Cyclic constitutive material behavior plays an important role in establishing the elastic strain-range - life relations as well as the partitioning of the inelastic strains. To apply the approach, however, it is not necessary to have to determine the magnitude of the inelastic strain range. The total strain SRP approach is evaluated and verified using two nickel base superalloys, AF2-1DA and Rene 95. Excellent agreement is demonstrated between observed and predicted cyclic lifetimes with 70 to 80 percent of the predicted lives falling within factors of two of the observed lives. The total strain-range SRP approach should be of considerable practical value to designers who are faced with creep-fatigue problems for which the inelastic strains cannot be calculated with sufficient accuracy to make reliable life predictions by the conventional inelastic strain range SRP approach

Total strain version of strainrange partitioning for thermomechanical fatigue at low strains

A new method is proposed for characterizing and predicting the thermal fatigue behavior of materials. The method is based on three innovations in characterizing high temperature material behavior: (1) the bithermal concept of fatigue testing; (2) advanced, nonlinear, cyclic constitutive models; and (3) the total strain version of traditional strainrange partitioning

Application of strainrange partitioning to the prediction of MPC creep-fatigue data for 2 1/4 Cr-1Mo steel

Strainrange partitioning is used to predict the long time cyclic lives of the metal properties council (MPC) creep-fatigue interspersion and cyclic creep-rupture tests conducted with annealed 2 1/4 Cr-1Mo steel. Observed lives agree with predicted lives within factors of two. The strainrange partitioning life relations used for the long time predictions were established from short time creep-fatigue data generated at NASA-Lewis on the same heat of material

O pivô geográfico da história

En la era poscolombina nos hallamos con un sistema político cerrado y, sin embargo, de alcance mundial, y por primera vez en condiciones de intentar la determinación más o menos completa, de la correlación que existe entre las más amplias generalizaciones geográficas e históricas. La “región pivote” (pivot area) de la política mundial es esa extensa zona de Eurasia que es inaccesible a los buques, pero que antiguamente estaba abierta a los jinetes nómadas, y está hoy a punto de ser cubierta por una red de ferrocarriles; en ella han existido y existen las condiciones de una movilidad de poder militar y económico de gran alcance y, sin embargo, limitado. Rusia ha remplazado al Imperio mongol. Fuera de la región pivote, en un gran “cinturón interior” (inner crescent), se hallan Alemania, Austria, Turquía, India y China, y en un “cinturón exterior” (outer crescent), Inglaterra, Sudáfrica, Australia, los Estados Unidos, Canadá y el Japón. Desde este punto de vista, la verdadera división entre el Oriente y el Occidente debe buscarse en el océano Atlántico. El vuelco del equilibrio de poder en favor del Estado pivote, como resultado de su expansión por las tierras marginales de Eurasia, permitiría la utilización de los amplios recursos continentales para la construcción de una flota, y un imperio de alcance mundial estaría a la vista.In the post-Columbian age, we have to deal with a closed political system, and none the less that it will be one of worldwide scope, and we are for the first time in a position to attempt, with some degree of completeness, a correlation between the larger geographical and the larger historical generalizations. The pivot region of the world’s politics is that vast area of Euro-Asia which is inaccessible to ships, but in antiquity lay open to the horse-riding nomads, and is to-day about to be covered with a network of railways. There have been and are here the conditions of a mobility of military and economic power of a far-reaching and yet limited character. Russia has replaced the Mongol Empire. Outside the pivot area, in a great inner crescent, are Germany, Austria, Turkey, India, and China, and in an outer crescent, Britain, South Africa, Australia, the United States, Canada, and Japan. From this point of view the real divide between east and west is to be found in the Atlantic Ocean. The oversetting of the balance of power in favour of the pivot state, resulting in its expansion over the marginal lands of Euro-Asia, would permit of the use of vast continental resources for fleet-building, and the empire of the world would then be in sight.Encontramo-nos, na era pós-colombina, com um sistema político fechado e de alcance mundial, e por primeira vez em condições de provar a determinação mais ou menos completa da correlação existente entre as generalizações geográficas e históricas mais amplas. A “região pivô” (pivot area) da política mundial é esta extensa zona da Eurásia que é inacessível aos buques, mas que antigamente estava aberta aos cavaleiros nômades, e está hoje a ponto de ser coberta por uma rede ferroviária; nela existiram e existem as condições de uma mobilidade do poder militar e econômico de grande alcance e, ao mesmo tempo, limitado. Rússia substituiu o Império mongol. Fora da região pivô, no interior de uma grande “cinturão interior” (inner crescent), encontram-se Alemanha, Áustria, Turquia, Índia e China; e, no “cinturão exterior” (outer crescent), Inglaterra, África do Sul, Austrália, os Estados Unidos, Canadá e o Japão. Desde este ponto de vista, a verdadeira divisão entre Oriente e Ocidente deve ser buscada no Oceano Atlântico. A inclinação do equilíbrio de poder em favor do Estado pivô, como resultado de sua expansão em terras marginais da Eurásia, permitiria a utilização dos amplos recursos continentais para a construção de uma frota, e um império de alcance mundial estaria à vista

Restricted Rotator Thermodynamic Properties from the Old Quantum Theory

Accurate partition functions and free energies are calculated for the hindered internal rotator from the old quantum theory based upon the quantization rule of Wilson and Sommerfeld. The description of the system is incomplete and the energy levels may even be incorrectly placed, but the partition functions are surprisingly close to those now accepted as correct. In the course of the development the lowest energy state of the harmonic oscillator turns up in its correct position at the half‐quantum level.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70358/2/JCPSA6-15-9-645-1.pd