Westinghouse Electric (Sweden)

Abstract The “vibration absorber” discussed in this paper consists of a small vibratory system tuned to the operating frequency of a larger machine and attached to it in a suitable location. When properly designed this will reduce the vibrations of the machine itself materially. The absorber, without damping, annihilates vibrations of its own frequency completely, but creates two other critical speeds in the machine system. Therefore it is suitable only for applications on constant-speed machinery. When damping is introduced into the absorber it constitutes a simple and efficient means of diminishing the vibrations of a machine of variable speed. An analysis of its operation in simple cases with and without damping is given in the paper, tests made on a model are described, and actual applications are discussed.

Abstract Pitting, as the term is used in this paper, means a form of failure which occurs on gear teeth near the pitch circle, on rollers, in anti-friction bearings, and on other machine parts where cylindrical surfaces come in rolling contact under heavy loads. The purpose of the investigation described in this paper is to study the manner in which pits develop, to discover the reason for their development, and to find what conditions must be fulfilled to prevent their occurrence. A testing machine was used in which steel rollers approximately 1.5 in. in diameter, rolling together and loaded as shown in Fig. 2, could be tested. More than eighty tests have been made with rollers of different materials, with different lubricants, and with various loads. Pits are found to have a definitely characteristic shape and orientation with respect to the direction of rolling. They were observed to develop from minute cracks in the roller surfaces which appear after about 500,000 revolutions. Photographs were taken tracing the growth of these pitting cracks from their earliest observed stage. The cracks from the very beginning have a characteristic shape and orientation. The principal findings in the tests on the steel rollers were: (1) That a lubricant must be present if pitting is to take place; (2) that if the lubricant is of a viscosity above a certain critical value which depends on the load, pitting can be prevented; (3) that the nature of the surface finish on the rollers greatly influences the tendency to pit, pitting being prevented on a highly polished surface and accelerated on a rough-machined surface; (4) that nitrided rollers will not pit under conditions that would result in severe pitting of quenched and tempered mild carbon-steel rollers, also that pits are smaller on harder surfaces, in general. In the theoretical section of the paper, the load-carrying capacity for the oil film between two rollers having a common peripheral velocity is calculated, and it is shown that the critical viscosity necessary to prevent pitting is far below that necessary to prevent metal-to-metal contact, a fact also checked experimentally. The normal and tangential oil forces on the rollers after metal-to-metal contact are also calculated, and the tangential component is found to be small compared with the normal component. Calculation showed that no tensile stress would exist at the surface, where pitting cracks appear to start, due to contact pressure or oil forces. However, it is found by analysis that a small crack in the surface, if filled with oil, will tend to grow, provided it has a certain initial direction. This direction is the same as that of the cracks which precede pitting. This strongly suggests that oil penetration of very small surface cracks with a certain initial direction is the reason for the growth of these cracks until a particle is separated from the main body of material, leaving a pit. The experimental results harmonize, also, with this theory.

Abstract Steady-state vibrations of mechanical systems damped by a combination of dry and viscous friction occur quite frequently, but until very recently no method for their calculation existed. A very satisfactory approximation was presented by L. S. Jacobsen before the A.S.M.E. in June, 1930. In the present paper the author gives the exact solution of the problem, together with a number of test results.

Abstract In 1889 Reinitzer,1 working with cholesteryl benzoate, discovered a state of matter that was later ter med cholesteric liquid crystals. It is doubtful whether the discovery of liquied crystals would have been made at that time if the optical properties of the cholesteric phase were less pronounced. Like other liquid crystals, matericals in this state act as birefringent fluids. however, at that point the resemblance endns. The optical properties may be summarized as follows:2

Methods are described for constructing a fatigue curve based on strain-fatigue data for use in pressure vessel design. When this curve is used, the same fatigue strength-reduction factor should be used for low-cycle as for high-cycle conditions. When evaluating the effects of combined mean and alternating stress, the fatigue strength-reduction factor should be applied to both the mean and the alternating component, but then account must be taken of the reduction in mean stress which can be produced by yielding. The complete fatigue evaluation of a pressure vessel can be a major task for the designer, but it can be omitted, or at least drastically reduced, if certain requirements can be met regarding design details, inspection, and magnitude of transients. Although the emphasis in this paper is on pressure vessel design, the same principles could be applied to any structure made of ductile metal and subjected to limited numbers of load cycles.

It has been found that the cathode is the only electrode which contributes vapor for the maintenance of an electric arc under very low gas pressure.The velocity of this vapor was determined by two methods. Method 1 consisted of measuring the force of reaction of the vapor on the cathode and the rate of vaporization of the cathode material. Method 2 consisted of determining the force exerted by the vapor on a vane suspended in front of the cathode spot and the rate of vapor condensation on the vane.Both these methods gave a vapor velocity of the order of 16\ifmmode\times\else\texttimes\fi{}${10}^{5}$ cm/sec. A temperature of around 500,000\ifmmode^\circ\else\textdegree\fi{} K results when this value for the cathode vapor velocity is substituted for $c$ in the equation: $\frac{1}{2}m{c}^{2}=3 \frac{\mathrm{KT}}{2}$.

The central impact of a mass on a simply supported laminated composite plate under initial stress is investigated. The contact force and the dynamic response of the plate are obtained by solving a nonlinear integral equation. The energy transferred from the mass to the plate during impact is also obtained by use of a normalized contact force. It is found that a higher initial tensile stress elevates the maximum contact force, but reduces the contact time, the deflection, and the stresses. It is also noted that a higher tensile initial stress results in less energy transfer from the striking mass to the plate.

The desire to improve the corrosion resistance of Zr cladding material for high burn-up has resulted in a general trend among fuel manufacturers to develop alloys with reduced levels of Sn. While commonly accepted, the reason for the improved corrosion performance observed for low-tin zirconium alloys in high-temperature aqueous environments remains unclear. High-energy synchrotron X-ray diffraction was used to characterize the oxides formed by autoclave exposure on Zr–Sn–Nb alloys with tin concentration ranging from 0.01 to 0.92 wt.%. The alloys studied included the commercial alloy ZIRLO® (ZIRLO® is a registered trademark of Westinghouse Electric Company LLC in the USA and may be registered in other countries throughout the world. All rights reserved. Unauthorized use is strictly prohibited.) and two variants of ZIRLO with significantly lower tin levels, referred to here as A-0.6Sn and A-0.0Sn. The nature of the oxide grown on tube samples from each alloy was investigated via cross-sectional scanning electron microscopy. Atom probe analysis of ZIRLO demonstrated that the tin present in the alloy passes into the oxide as it forms, with no significant difference in the Sn/Zr ratio between the two. Synchrotron X-ray diffraction measurements on the oxides formed on each alloy revealed that the monoclinic and tetragonal oxide phases display highly compressive in-plane residual stresses with the magnitudes dependent on the phase and alloy. The amount of tetragonal phase present and, more importantly, the level of tetragonal-to-monoclinic phase transformation both decrease with decreasing tin levels, suggesting that tin is a tetragonal oxide phase stabilizing element. It is proposed that in Zr–Nb–Sn alloys with low Sn, the tetragonal phase is mainly stabilized by very small grain size and therefore remains stable throughout the corrosion process. In contrast, alloys with higher tin levels can in addition grow larger, stress stabilized, tetragonal grains that become unstable as the corrosion front continues to grow further inwards and stresses in the existing oxide relax.

The nuclear industry strives to reduce the fuel cycle cost, enhance flexibility and improve the reliability of operation. This can be done by both increasing the fuel weight and optimizing rod internal properties that affect operational margins. Further, there is focus on reducing the consequences of fuel failures. To meet these demands Westinghouse has developed ADOPT (Advanced Doped Pellet Technology) UO2 fuel containing additions of chromium and aluminium oxides. This paper presents results from the extensive investigation program which covered examinations of doped and reference standard pellets both in the manufactured and irradiated states. The additives facilitate pellet densification during sintering and enlarge the pellet grain size. The final manufactured doped pellets reach about 0.5% higher density within a shorter sintering time and a five fold larger grain size compared with standard UO2 fuel pellets. The physical properties of the pellets, including heat capacity, thermal expansion coefficient, melting temperature, thermal diffusivity, have been investigated and differences between the doped and standard UO2 pellets are small. The in-reactor performance of the ADOPT pellets has been investigated in pool-side and hotcell Post Irradiation Examinations (PIEs), as well as in the Studsvik R2 test reactor. The investigations have identified three areas of improved operational behaviour: Reduced fission gas release, improved PCI performance thanks to increased pellet plasticity and higher resistance against post-failure degradation. Fuel segments have been exposed to ramp tests and enhanced power steady-state operation in the Studsvik R2 reactor after base-irradiation to above 30 MWd/kgU in a commercial BWR. ADOPT reveals up to 50% lower fission gas release than standard UO2 pellets. The fuel degradation behaviour has been studied in two oxidizing tests, a thermal-microbalance test and an erosion test under irradiation. The tests show that ADOPT pellets have a reduced rate of fuel washout, as compared to standard UO2 pellets. Fuel rods with ADOPT pellets have been irradiated in several light water reactors (LWRs) since 1999, including two full SVEA-96 Optima2 reloads in 2005.

Abstract A method is proposed for estimating the life of a machine part which is subjected to repeated applications of various stresses, some of which are above the fatigue limit.

A method is presented for the automatic synthesis of minimum drag hull shapes for axisymmetric vehicles of specified enclosed volume and constant speed submerged in incompressible, nonseparat-ing, noncavitating flow at zero incidence. The computer-oriented optimization procedure does not consider propulsion or maneuvering; drag reduction is accomplished solely through manipulation of the vehicle hull shape. The selected optimization formulation is a nongradient algorithm in a finite, constrained parameter space. This study considers an eight-parameter class of rounded-nose tail-boom bodies constrained to be well behaved as determined by previous hydrodynamic experience. The drag model, for nonseparating flows at zero incidence, is based on classical hydrodynamics and consists of computer programs from work available in the literature; the model is representative of state-of-the-art drag prediction methods. By exploiting laminar flow while avoiding turbulent sepa-ration, a body with a drag coefficient one-third below the best existing laminar design has been ob-tained. The evidence suggests that the method produces realistic hull shapes useful in engineering design. The optimization procedure is independent of any particular drag model so that the effects on minimum drag shapes due to alternate drag models can be studied. Nomenclature

CHARGING CONDITIONS and particle size are important factors in electrostatic gas cleaning. Particle mobility, the rate at which the particle moves in an electric field of unit strength, is a function of the charge and size of the particle. The minimum mobility and the particle size at which it occurs, are functions of the charging conditions.

The Mn + 1AXn phases (M = early transition metal; A = group A element and X = C and N) are materials exhibiting many important metallic and ceramic properties. In the present study powder processing experiments and density functional theory calculations are employed in parallel to examine formation of Zr2(Al1-xBix)C (0 ≤ x ≤ 1). Here we show that Zr2(Al1-xBix)C, and particularly with x ≈ 0.58, can be formed from powders even though the end members Zr2BiC and Zr2AlC seemingly cannot. This represents a significant extension of the MAX phase family, as this is the first report of a bismuth-based MAX phase.

Advancements in transmission electron microscopy allow us to draw correlations between evolving matrix chemistry environments and the resulting dislocation structures that form. Such phenomena are essential in predicting the lifetime of neutron reactor components, but are not well understood at the fundamental level. We investigate the effect of nano-scale matrix chemical evolution in Zircaloy-2 on dislocation formation after emulating commercial reactor irradiation conditions on a proton beamline. Similarity in the dislocation type, morphology, density and evolution between the different irradiation types establishes proton irradiation in this regard. For the first time, we observe chemical segregation of Fe, Ni and Cr to a-loop positions in basal traces and the segregation of Sn in alternate rows, anticorrelated to the positions of the light transition elements. The resulting layered structure with a periodicity of ∼50 nm creates an even greater anisotropy than that usually associated with HCP materials. Concurrent analysis of chemical effects and dislocation spatial relationships provides evidence that may explain the delayed onset of c-loop nucleation and accelerated dimensional instability regimes in its dependence on the alignment of a-loops parallel to the trace of the basal plane. This demonstrates the applicability of chemical-structural correlations towards key research questions regarding deformation behaviour.

This summarizes the important physical and electrical characteristics of these diverse and highly useful insulating materials. Factors of chemical structure which influence the resulting resin properties are discussed. The great variety of properties which can be achieved through variations in this one class of resins is emphasized. A range of applications of these resins is mentioned and illustrated.

PHENOMENA of vibration in transmission lines due to the action of a transverse wind are encountered most frequently at moderate wind velocities (about 5 miles per hr.) and are characterized by rather high frequencies (5 to 15 cycles per sec.) and small amplitudes (up to a few cable diameters). This type of vibration is caused by the “Karman” vortices forming behind the wire and is well understood.

Abstract In the design of thin plates bent by lateral loading, formulas based on the Kirchhoff theory which neglects stretching and shearing in the middle surface are quite satisfactory, providing the deflections are small compared to the thickness. If deflections are of the same order as the thickness, the Kirchhoff theory may yield results which are considerably in error and therefore a more rigorous theory which takes account of deformations in the middle surface should be applied. The fundamental equations for the more exact theory are known and approximate solutions have been developed for the case of a circular plate. This paper gives the general solution of the fundamental equations for the case of a circular plate bent to a figure of revolution. Particular solutions are found which satisfy one of the two boundary conditions, and stresses and deflections are calculated from these solutions. By interpolation, the stresses and deflections are then found for plates satisfying both boundary conditions. The deflections are compared with experimental results and with the approximate formulas. It is found that these deflections agree closely with the experimental results and also with those obtained by the approximate methods of A. Nadai and S. Timoshenko, as shown in Figs. 8 and 10.

The model previously proposed by Turner and Wilson is developed in detail and compared with experiment. Deviations from Shockley's classical theory can be accounted for in terms of a single quantity Γ, which is related to E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> the peak field for GaAs. A discussion of the physical mechanism of current saturtation shows that the formation of domains within the channel is hampered in a conventional GaAs FET. A <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</tex> -parameter analysis is presented that permits calculation of transconductance and the unity current gain frequency f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> . Measurements of drain current, transconductance, and f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> versus gate voltage all show good agreement with values predicted by the theory. Estimates are given which show that the current saturation mechanism described will be important in the design of GaAs microwave FET's.

Nuclear energy has been a part of the energy mix in many countries for decades. Today in principle all power producing reactors use the same techniqe. Either PWR or BWR fuelled with oxide fuels. This choice of fuel is not self evident and today there are suggestions to change to fuels which may be safer and more economical and also used in e.g. Gen IV nuclear power systems. One such fuel type is the nitrides. The nitrides have a better thermal conductivity than the oxides and a similar melting point and are thus have larger safety margins to melting during operation. In addition they are between 30 and 40% more dense with respect to fissile material. Drawbacks include instability with respect to water and a sometimes complicated fabrication route. The former is not really an issue with Gen IV systems but for use in the present fleet. In this paper we discuss both production and recycling potential of nitride fuels.

MCEN30014 Mechanical Design,2015 search, structured approaches to material selection, failure modes for engineering systems, failure predictors. The ASHE Mechanical Systems Handbook for Health Care Facilities provides detailed information to support the design, operation, and maintenance. Shigley's Mechanical Engineering Design. Rothbart H. A. (1985), Mechanical Design and Systems Handbook , 2nd edition, McGraw-Hill , Chapter 16.