General Electric (Czechia)

Failure of composite consisting of matrix stiffened by uniaxially oriented fibers, when subjected to uniaxial tensile load parallel to fiber direction

This paper provides simplified mathematical representations of heavy-duty gas turbines that are suitable for use in dynamic power system studies and in dynamic analyses of connected equipment. The full range of heavy-duty, single-shaft gas turbines, from 18 MW (24,000 HP) and 106 MW (142,000 HP), is covered, as well as both liquid and gas fuel systems, parallel and isolated operation, droop and isochronous governors, and the impact of both air- and hydrogen-cooled generators on the characteristics of the model. Alterations to the models, for the purpose of further simplification, are also discussed.

Composite tensile-failure modes, discussing failure load prediction, experimental data and statistical analysis of stress concentration effects

Abstract This paper presents a method of computing the factor of safety of a structural member with reference to a stated life, when operating under stress at high temperature when the temperature varies or when the stress varies moderately according to some definite pattern. The formulas presented herein are based on the supposition that the expenditure of each particular fraction of the life span at elevated temperature is independent of and without influence upon the expenditure of all other fractions of the life to rupture. The author makes no claim that this assumption is wholly true. The suggested procedure is offered simply to provide a means for making engineering estimates with some greater validity than always to assume that the worst conditions are present all the time. The desirability of taking account of certain additional influences which may differ from one material to another is recognized.

Abstract The Griffith-model of brittle fracture of elastic solids and the model by Irwin and Orowan for the brittle fracture of elastic-plastic solids predict the propagation of cracks on the basis of energy supplied by the work of externally impressed forces and by the change of strain energy. Previous discussions have neglected the three-dimensional viewpoint and the body forces. Since the Irwin method of fracture-strength analysis has become of increased interest, especially with respect to rotor fracture, a general analysis of energy supply is presented. The analysis uses Clapeyron’s theorem and Betti’s reciprocal theorem. One of the results is that the energy supplied for crack extension equals the strain energy of the difference of the two stress fields before and after crack extension.

Cascaded H-bridge multilevel power electronic converters generally require several dc sources. An alternative option is to replace all the separate dc sources feeding the H-bridge cells with capacitors, leaving only one H-bridge cell with a real dc voltage source. This will yield a cost-effective converter. However, the required capacitor voltage balancing is challenging. In this paper, using the phase-shift modulation approach, a new control method for cascaded H-bridge multilevel converters fed with only one independent dc source is presented. The proposed method has a wide voltage regulation range for the replacement capacitors in the H-bridge cells. Experimental and simulation results support the proposed control method.

A method is presented for predicting the performance of modern steam turbine-generator units designed for high efficiency levels. This method is based on recent developmental and analytical results. The necessary curves, tables, and instructions are provided for the application of the method to a large variety of units of various kilowatt ratings, types, and steam conditions. Relative heat-rate curves are presented and mathematical expressions are provided for computer applications.

Accommodation coefficient (alpha) values which can be confidently applied to a solution of satellite-drag and heat-transfer problems must be obtained from experiments with gas molecules whose velocities match those of satellites. The problem of generating in the laboratory a nearly monoenergetic beam of molecules in the range 1 - 10 eV with adequate flux has not been solved. Experimental facilities such as shock and arc tunnels which may produce molecular flows of nearly adequate velocities are not readily adaptable to alpha measurements. For these measurements the transient flow obtained in a shock tunnel is extremely inconvenient, while the composition and energy distribution of the gas obtained in an arc tunnel is not known with sufficient accuracy. The composition of a satellite surface in orbit, and hence the accommodation coefficient, will most probably differ appreciably from that of an untreated surface of the same material exposed to a laboratory vacuum of, say only, 10 to the -7th power mm of Hg. Furthermore, in orbit, satellite surface composition may change with changing surface temperature and ambient gas pressure, resulting in corresponding changes in alpha.

A study of non-equilibrium ionized multi-component air laminar boundary layer on a cone-shaped body at high velocity and temperature is made. The method of analysis utilizes a non-similar development of the boundary layer by finite difference scheme. The results of this investigation shows that electron density of the order of 10 to the 7th power to 10 to the 10th power electron/cc. can be generated by the viscous dissipation in the boundary layer. This investigation also shows the importance of considering the nonequilibrium aspects of the flow rather than the limiting cases of frozen or equilibrium flow. The study of the chemical reactions show that atomic oxygen is mainly produced from the dissociation of molecular oxygen while atomic nitrogen results mainly from two of the shuffle reactions. The production of nitric oxide comes from the shuffle reactions. For distances up to 15 ft. downstream from the tip and for conditions considered, none of the chemical reaction are near equilibrium. (Author)

A new system has been designed and built to validate the concept of 3D computerized angiography (CA). This system can acquire a set of 2D digital subtracted angiography images while rotating around a patient and then, using these images, reconstruct a 3D representation of the opacified vasculature. The design principles and main characteristics of the system are described, with special attention paid to data processing aspects. An initial in vivo evaluation of this system performed on anaesthetized animals and human volunteers is presented. The influence on the quality of the 3D reconstruction of different factors such as volume resolution, estimation method, source trajectory and number of projections is discussed.

Abstract The application of polymers at ever-increasing temperatures has given impetus to research on the chemistry of thermal decomposition. In recent years polymers have been used for a variety of high-temperature applications, such as cooking vessels, motor insulation, and re-entry vehicle heat shields. Interest in chemistry of decomposition has been found in such industries as tobacco and grinding-wheels. Because of the vast number of polymers that are available and the variety of applications thousands of papers have appeared in the literature. Rather than give a complete review the purpose of this paper is to give a brief survey of topics that have been emphasized in the author's research, namely kinetics, mechanisms, and gaseous decomposition products at elevated temperatures.

Research Papers Effect of Temperature Variation on the Creep Strength of Steels Ernest L. Robinson Ernest L. Robinson Turbine Engineering Department, General Electric Co., Schenectady, N. Y. Search for other works by this author on: This Site PubMed Google Scholar Author and Article Information Ernest L. Robinson Turbine Engineering Department, General Electric Co., Schenectady, N. Y. Trans. ASME. Apr 1938, 60(3): 253-259 (7 pages) https://doi.org/10.1115/1.4020680 Published Online: February 10, 2023 Article history Published: April 1, 1938 Online: February 10, 2023

The elastic properties of polycrystalline monoclinic Gd 2 O 3 were determined by the sonic‐resonance method. Volume‐fraction porosity varied from 0.025 to 0.367 and temperature from room temperature to 1400°C. The Young's and shear moduli are linear functions of volume‐fraction porosity, but the rate of their decrease with increasing porosity is less than that expected. The moduli decreased more rapidly than expected with increasing temperature. The Debye temperature is 362°K. With increasing temperature, the first Grueneisen constant, γ, decreases, whereas the second Grueneisen constant, δ, increases.

This paper, based on research done for the Army's Nike X Missile Defense Project, investigates the inviscid behavior of a supersonic vortical flow undergoing a rapid expansion. The origin, character, and strength of the reflected waves produced by the presence of entropy gradients are examined in detail. This work, which is of obvious interest for vortical flows produced by curved bow shock waves, also provides fundamental insights into the role that a supersonic boundary layer plays in a rapid expansion. For weak expansion fans, 6 < 10°, analytical results are obtained which give the variation of flow properties along centered Mach waves in a rotational expansion. For large angle expansions, rotational characteristic solutions are presented for representative laminar and turbulent boundary-layer shear profiles. It is shown also that the method of rotational characteristics is a valuable means of analyzing the detailed behavior of freshly separated flows, e.g., the formation of the separation shock wave and the experimentally observed structure of the free shear layer in the base flow problem.

A method of calculating accurate solutions of the three-dimensional laminar boundarylayer equations has been developed. The method is applied to a problem that exhibits interesting crossflow phenomena, such as a flow reversal driven by crossflow convective terms and crossflow influences with zero freestream crossflow velocity. The method of solution used is an implicit finite difference scheme, and the stability and convergence properties of this scheme seemed to be good. Also, the important question of initial conditions for threedimensional boundary-layer flow is discussed, and a method of obtaining initial conditions is derived.

An extension to Binggeli's test for possible large-scale alignment of clusters of galaxies is presented. Marginally statistically significant evidence is found to indicate that clusters and their first-ranked galaxies tend to point toward neighbors, which is in the direction of Binggeli's result, but the effect is small and at a level that might be influenced by systematic errors. No pronounced correlation of anisotropy with cluster separation was found. Also, the effect is not significantly enhanced by using only systems where the dominant galaxy is aligned with the cluster, or by using only richer clusters. The tendency of clusters or their dominant galaxies to be parallel, independent of their relative positions was also examined. The results here are consistent with isotropy. As an upper bound on a real tendency for clusters or their dominant members to point toward nearby clusters, it is concluded that the mean value of the relative position angle can not differ from isotropy (45 deg) by more than 5 deg.

Equations are given for the determination of transient and residual stresses in plates subject to transient temperature distributions, based on the assumption of a viscoelastic, perfectly plastic material obeying a von Mises temperature-dependent yield condition. A numerical procedure for integrating the equations is developed and applied to the case of a symmetrically cooled plate. It is found that, for steel, viscoelasticity has little effect on the residual stress distribution, but the temperature dependence of yield stress is important. The types of residual stress distribution after cooling are similar to those for an elastic-plastic material with constant yield stress, and for this case the residual stress is given approximately by formulas developed earlier for a slowly varying heat input.

The nonequilibrium boundary layer is considered as a binary mixture of atoms and molecules with finite dates of dissociation and recombination. To obtain accurate solutions to the partial differential equations for this type of flow without any necessary simplifying assumptions, an implicit finite-difference scheme is developed for solving these equations with a digital computer. Accurate solutions to the nonequilibrium boundary-layer equations have been obtained in a reasonable amount of computer time and are presented for a flat plate, cone, and hemisphere cylinder. The results show that the nonequilibrium boundary-layer temperature and composition can be considerably different from local equilibrium and frozen results. For a cone at 21,000 fps and 100,000 ft alt, the computations show that, at 60 ft from the tip, the flow has not reached equilibrium.

Abstract This paper presents the results of bursting tests of large, bored, and effectively notched disks removed from long rotor forgings. Most of the tests were conducted at room temperature. For the particular disk geometry employed, the net average tangential stress at bursting speed was as low as 25,000 psi for brittle behaving materials and as high as 77,000 psi for materials approaching ductile behavior. These correspond to 26 per cent and 92 per cent of yield strength, respectively. The Griffith-Irwin theory of crack propagation is adapted to the calculation of Gc, fracture toughness, from notched-disk bursting-test results. It is shown that Gc from disk tests agrees with Gc obtained from slow notched-bend tests, and therefore appears to be a property of material, largely independent of specimen size. The actual magnitude of Gc permits the classification of forgings by the degree of their susceptibility to brittle fracture in the presence of discontinuities. Gc and the ratio Kys of room temperature bursting strength to yield strength are found to correlate well with the material Charpy V-notch fracture appearance transition temperature. As the latter is reduced, Gc and Kys are increased.

Structural efficiency of orthotropic materials for cylindrical shells under axial load, including examination of fibrous composites characteristics