Stainless Steel Shell Research Articles

Observation of the midfrequency enhancement of tone bursts backscattered by a thin spherical shell in water.

A prominent feature predicted for the backscattering by thin spherical shells is an enhancement of the guided wave contributions in the midfrequency range [L. G. Zhang etal., J. Acoust. Soc. Am. 91, 1862–1874 (1992)]. This feature may be useful for certain inverse problems and is associated with a strongly coupled slightly subsonic wave denoted by some authors as the a0− wave. The present research gives a comparison between a ray analysis and experiments in which tone bursts having carrier frequencies ω=kc in the range 35<ka<70 were incident on an empty stainless steel shell in water. The sphere’s radius to thickness ratio is a/h=43.8. Time records of echoes provided a means for measuring the guided wave contribution relative to that of the specular reflection. As predicted the guided wave echo can be over three times larger than the specular echo and the ka dependence generally follows the predicted hump. [Work supported by ONR. The author acknowledges the advice of P. L. Marston.]

Midfrequency enhancement of the backscattering of tone bursts by thin spherical shells

A broad enhancement of the form function f(ka) for steady-state backscattering by thin spherical shells in the midfrequency range has been noted by several investigators. Consequences of this enhancement on the backscattering of tone bursts are investigated with a Fourier synthesis of the temporal response from the exact f(ka). The emphasis is on incident bursts that are sufficiently short so that scattering consists primarily of distinct echoes associated with the specular reflection and different circumnavigations of a dominant surface guided wave. That wave lies on the subsonic branch of the lowest antisymmetric Lamb mode for a fluid-loaded shell designated as a0− by some authors. A ray method, previously verified for echo amplitudes from leaky (or supersonic) Lamb waves on thick shells [S. Kargl and P. Marston, J. Acoust. Soc. Am. 85, 1014–1028 (1989)], is generalized to subsonic waves. The ray method well approximates echo amplitudes from the Fourier synthesis provided the incident burst is sufficiently long that effects of dispersion are weak. Over a broad frequency range, the amplitude of the earliest a0− echo is enhanced relative to the specular echo. For the 2.5% thick stainless steel shell in water considered, the enhancement factor peaks near ka≊46 where the amplitude ratio ≊3.1. The ray theory suggests that the peak ratio depends only weakly on shell thickness and material parameters provided certain conditions hold. The a0− wave is also found to contribute a prominent wave packet to the far-field impulse response of the shell. The radiation damping and velocity of relevant surface waves were computed from the complete elastic equations and those results may be helpful for testing thin shell approximations near the coincidence frequency.

Ray synthesis of leaky Lamb wave contributions to backscattering from thick cylindrical shells

The ray representation of the scattering from an empty cylindrical shell is compared with the exact results of the partial-wave series. The specific example considered is a thick stainless steel shell having the same parameters as a previous synthesis for spheres illustrated by Kargl and Marston [J. Acoust. Soc. Am. 89, 2545–2558 (1991)]. The present computation demonstrates a general agreement with the exact result for ka down to 7 and confirms the applicability of a simple approximation for the complex coupling coefficient.

Computational structural acoustics applied to scattering of sound by spherical shells.

Computational structural acoustics is the use of exact large-scale computations and computer graphics to study the behavior of elastic waves in structures. This approach is applied here to the scattering of sound by spherical shells in water. It is shown that rotational waves, found earlier in solid spheres and cylinders [Hickling etal., J. Acoust. Soc. Am. 89, 971–979 (1991)], continue to occur even for shells that are quite thin. In particular, when a thin shell in water is excited by incident sound, small rotational waves occur, similar to roller bearings, whose center of rotation and surrounding rotational displacement are inside the boundaries of the shell structure. Such waves occur when the boundary conditions require a rapid change in direction of the displacement. It is also shown that fluid loading has a major effect on a thin shell, in contrast to the effect that it has on a solid body. The damping induced by the loading combined with the dense congregation of the fundamentals of the free modes of vibration make it hard to excite any particular mode. Computational structural acoustics is also used to examine the limits of thin-shell theory. For example, elementary thin-shell theory appears to be valid for ka less than 50, for aluminum and stainless steel shells with b/a=0.99.

Mid-frequency enhancement of the backscattering of tone bursts from thin elastic shells: Fourier synthesis and ray model.

A broad enhancement of the form function for these shells is known to be present in the mid-frequency range. A ray model of the form function in this region was previously demonstrated for cylinders and spheres [N. H. Sun and P. L. Marston, J. Acoust. Soc. Am. 89, 1949 (1991)] and the enhancement was found to be associated with contributions to the scattering from the subsonic surface guided wave frequently designated as A<lu>0<bu>−<lux>. The consequences of this enhancement were investigated for spherical shells by synthesizing the response to tone bursts from an evaluation of the exact partial wave series over the sampled spectrum of the burst [L. Zhang, M. S. dissertation, Washington State University, 1991]. This was compared with a ray approximation for the earliest contribution for this wave, which circumnavigates only the backside of the shell. The amplitude from the ray model is ‖f0,l‖ ≊ 8πβl(c/cl)exp(−πβl), where the surface wave parameters cl and βl are found from the exact elastic equation for the roots of Dν(ka)=0. Both the Fourier synthesis and ray models show a broad enhancement which for a 2.5% stainless steel shell peaks at ka≊46 where ‖f0,l‖ ≊ 3.1 and the exact results differ by only 3%. Neglecting dispersion the peak occurs where βl=π−1. [Work supported by ONR.]

Ray synthesis of the form function for backscattering from an elastic spherical shell: Leaky Lamb waves and longitudinal resonances

An acoustic ray analysis is employed in synthesizing the form function for backscattering, f(θ=π,ka), from a fluid-loaded evacuated elastic spherical shell where k is the wave number of the incident plane wave and a is the outer radius of the shell. The synthesis contains a component associated with a specular reflection, fsp, and contributions from leaky Lamb waves. The contribution fl of the lth leaky Lamb wave is expressible in a Fabry–Pérot resonator form [P. L. Marston, J. Acoust. Soc. Am. 83, 25–37 (1988)]. A comparison of the ray synthesis for f(ka) with the exact partial-wave series representation for a 440c stainless-steel shell verifies the usefulness of the ray synthesis for the present case of a shell. The present synthesis is also new in that it includes the effects of longitudinal resonances on fsp. A novel ray synthesis of fsp indicates a significant resonance effect near the condition kLh=nπ (n=1,2,…). The thickness of the shell is h, and kL=ω/cL is the longitudinal wave number where cL is the longitudinal speed of sound in the elastic material. The ray synthesis demonstrates that the curvature of the shell is essential to the modeling of longitudinal resonances. Although acoustic ray modeling is generally a high-frequency technique, the ray synthesis of f(ka) for a 440c stainless-steel shell appears to be applicable for ka as small as 7. Certain anomalies in the synthesis are investigated to better understand the limitations of the present ray model.

A thin I-125 seed eye plaque to treat intraocular tumors using an acrylic insert to precisely position the sources

A thin re-usable stainless steel ophthalmic applicator is described. The radioactive Iodine-125 sources are inserted in an acrylic button which fits neatly into a stainless steel shell 1 mm thick. The applicator can be assembled with the radioactive sources precisely positioned without the use of adhesives or mechanical devices such as clamps or screws in a matter of a few minutes, (under sterile conditions if necessary). The applicator can be dismantled in seconds after which it is ready for cleaning and re-sterilization. The overall thickness of the plaque is 2.6 mm, but this has the potential to be reduced to 2.1 mm. Suture holes are provided on a flange subtending 120° around the circumference of the shell and are exactly matched on a stainless steel template.

GTD synthesis of resonance amplitudes in the backscattering from an elastic spherical shell

An elastic generalization of the geometrical theory of diffraction [P. L. Marston, J. Acoust. Soc. Am. 83, 25–37 (1988)] was used to describe the backscattering of short tone bursts from an elastic spherical shell in water [S. G. Kargl and P. L. Marston, J. Acoust. Soc. Am. 85, 1014–1028 (1989)]. In the present research, steady‐state backscattering amplitudes are synthesized. The GTD model contains explicit terms for the specular reflection and individual Lamb surface wave contributions in a Fabry‐Perot form. Numerical calculations compare the exact partial‐wave series result with the GTD synthesis for the frequency range 7 < kA < 100. These computations correspond to a stainless steel shell with an inner‐to‐outer radius ratio b/a = 0.838. An important feature of the GTD model is that only two parameters are needed to fully describe the individual Lamb wave resonance amplitudes. These parameters are the ratio of the Lamb wave phase velocity to the velocity of sound in water (c1/c) and the radiation damping β1. These should depend on local properties of the shell‐water system. This simple parametrization of the direct scattering problem should facilitate novel approaches to the inverse problem. Identification of a scatterer may be achieved through an examination of the Lamb wave resonances via a numerical fitting of these parameters. [Work supported by ONR.]

An idea for the easy construction of a high field magnet

A new method for the easy construction of a pulsed field magnet is developed. Alumina powder with ice is used as a reinforcement spacer in a stainless steel shell. Magnetic fields up to 35 T have been produced at liquid N 2 temperature by a 23.4-kJ capacitor bank.

Observations and modeling of the backscattering of short tone bursts from a spherical shell: Lamb wave echoes, glory, and axial reverberations

Tone bursts having durations of 3 or 4 cycles were incident on an air-filled stainless steel shell in water. The resulting sequence of echoes included a specular reflection and echoes radiated by Lamb waves on the shell. Echo structure was studied for ka of 24 to 75, where a denotes the outer radius; b/a=0.838, where b denotes the inner radius. The amplitudes of Lamb wave echoes were modeled using an elastic generalization of the geometrical theory of diffraction (GTD) [P. L. Marston, J. Acoust. Soc. Am. 83, 25–37 (1988)]. The required Lamb wave parameters (the phase velocity cl and damping βl ) were found by the Sommerfeld–Watson method; an efficient numerical method for the computation of the required complex root νl is described. The echoes were identified by comparing arrival times with predictions; bursts reflected from a solid tungsten carbide sphere were used for a reference amplitude. Measurements with ka=24 of the largest Lamb wave echo (which was due to a flexural wave) were made at various backscattering angles γ. The echo was largest for small γ in agreement with predictions. This is a manifestation of the glory pertinent to other bistatic measurements. The ringing of longitudinal wave reverberations (which could be seen following the specular reflection) may be useful for determining the thickness of a shell.

Performance of Four 4.5 M Two-in-One Superconducting R &amp; D Dipoles for the SSC

Four 4.5 m long superconducting dipoles built to specifications similar to those for SSC Reference Design A have been successfully tested. They were wound with NbTi cable in two-layer cos? coils of 3.2 cm inner diameter. The coil ends were flared to increase thie minimum bending radius, anticipating coils wound from prereacted Nb3Sn. The coils were mounted in a reusable two-in-one iron yoke prestressed by means of a bolted stainless steel shell. The first two magnets as well as the fourth one, a special magnet designed to study cross-talk between the bores, used CBA/Tevatron cable. The third utilized cable with improved (high homogeneity) NbTi conductor. All four reached central fields corresponding to their short sample limits at 4.5K without training, nearly 6. OT for the first two magnets, 6.5T for the third, and 5.4T for the fourth. At 2.5K modest training was required to reach short sample limits of 7.2T, 7.1T, 7.8T, and 6.6T respectively. The measured values of the allowed harmonics were within several × 10-4 of the calculated ones.

Test results from two 5m two-in-one superconducting magnets for the SSC

Two 5m long superconducting dipole magnets with specifications similar to the reference design for the proposed Superconducting Super Collider have been successfully tested. The " <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\cos \theta</tex> " coils of the magnets were made from two layers of "standard" CBA/Tevatron NbTi superconductor, keystoned to an angle of 2.8 degrees. The inner diameter of the inner layer was 3.2 cm. The ends of the coils were flared to increase the minimum bending radius so that future magnets can be wound from prereacted Nb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Sn. The windings of the two-aperture magnets were clamped in a "two-in-one" iron yoke with a tensioned stainless steel shell. The fields of the two apertures were closely coupled, since the flux in one aperture returned through the other. The inner and outer layers of the coil were powered separately so that their short-sample limits would be reached simultaneously. With minimal training the magnets reached a central field of 6 T, the short sample limit of the conductor at the 4.5 K temperature of the liquid helium bath. At 2.6 K, a central field in excess of 7 T was reached, again with minimal training. The measured values of the allowed sextupole and decapole harmonics are within 10% of the calculated values and the non-allowed harmonics are all small or zero, as predicted.

Description of breeding blanket test modules for TASKA-M

TASKA-M is a conceptual design of a low power, low cost test reactor based on a tandem mirror without thermal barriers utilizing physics which is presently in hand, or which should be available by 1985. The main purpose of the reactor is to study plasma engineering and provide a reasonable cost test bed for qualifying materials and investigating different blanket concepts. The central cell which is nominally 4.25 m long is divided into five zones: a liquid metal test module, a solid breeder test module, two material test modules and a central cell shield insert. This paper describes the structural, thermal hydraulics and neutronic aspects of the breeding test modules. Two liquid metal test blanket modules, one using Li 17Pb 83 and the other elemental Li are designed to fit into the same slot within the central cell and will, therefore, be tested consecutively. The solid breeder test module is designed to test all kinds of breeding materials rather than as a reactor prototypical module with a high breeding ratio. The main emphasis is on fast, easy insertion and withdrawal of the solid breeder material samples. A breeding ball blanket concept has been developed, where the Li-ceramic is contained in spherical stainless steel shells which are inserted into pressure tubes coiled around the plasma.

Effects of factors on the stability of casting in horizontal continuous casting.

The horizontal continuous casting machine of 2 ton laboratory scale was installed to investigate the basic problems associated with casting round billets of carbon steels and stainless steels.The main results obtained are as follows:(1) The intermittent withdrawal is essential for the prevention of breakout during casting of the billets in the operation of the horizontal continuous casting without mould oscillation.(2) For joining the mould to the tundish, the gap between the mould and the refractory nozzle of the tundish has to be minimized to prevent the molten steel penetration into the gap forming fin shape solidification shell which results in breakout. Nitride refractories, e.g, boron nitride refractory, has been found to give satisfactory results.(3) The deference of the inner diameter of the mould and the refractory nozzle has to be minimized to decrease the discontinuity of solidification morphology beneath the surface of the pull mark.(4) The friction force between mould and solidified shell of stainless steel is larger than that of carbon steel. Nickel plating with solid particle dispersion as a lubricating agent enormously decreases the friction force between the mould and the solidified shell, which enabled casting 150-260mmφ stainless steel billets.

照射後試験燃料輸送用ＮＨ‐２５型容器による燃料輸送の経験

Since the Japan Atomic Energy Research Institute and Nippon Nuclear Fuel Development Co. hot laboratories are located far off from the port which can handle spent fuel shipping casks, it is necessary to use a trailer-mounted cask which can be transported by public roads, bridges and intersections for the transportation of spent fuel specimens to these hot laboratories.Model NH-25 shipping cask was designed, manufactured and qualification tested to meet Japanese regulations and was officially registered as a BM type cask. The NH-25 cask accomodates two BWR fuel assemblies, one PWR assembly or one ATR fuel assembly using interchangeable inner containers. The cask weight is 29.2t. The cask has three concentric stainless steel shells. Gamma shielding is lead cast between the inner shell and the intermediate shell. Neutron shielding consists of ethylene-glycol-aqueous solution layer formed between the intermediate shell and the outer shell.The NH-25 cask now has been in operation for 2.5 yr. It was used for the transportation of spent fuel assemblies from six LWR power plants to the port on shipping cask carrier "Hinouramaru" on the sea, as well as from the port to the hot laboratory on a trailer. The capability of safe handling and transporting of spent fuel assemblies has been well demonstrated.

Selective Pumping of an 800 000 Liter Chamber

A new 38.5-ft-diam spherical vacuum chamber with a selective pumping system has just been completed. The pumping system for this 800 000 liter chamber consists of mechanical roughing, 80 K liquid-nitrogen-cooled shroud, 20 K cryopanels, and ion and titanium sublimation pumps. The chamber and pumping system are described. Extensive acceptance tests were run on the chamber. These tests included pumping speed measurements and ultimate pressure measurements with various combinations of the pumping units operating. Data on the outgassing of the 5 000 000-cm2 stainless-steel shell is presented. From residual gas analysis, approximate pumping speeds for helium and neon were determined. At ultimate pressure of the chamber, water vapor outgassing from the stainless-steel shell was found to be the limiting factor.

The explorer XVII satellite

Explorer XVII, the first Aeronomy satellite, employed for instrument housing, a vacuum-tight stainless steel sphere, whose construction reflected the most useful and established ultra-high vacuum techniques. The sensors carried included ionization gages, magnetic mass spectrometers and electrostatic probes, each mounted in and projecting through the stainless steel shell. Accessory equipment to provide the necessary supporting functions for the experiments included a PCM telemetry system, a command and control system, and a silver-zinc battery power supply which provided for fifty hours of satellite operation over a period of 100 days commencing 3 April 1963. The quantity of data obtained greatly surpasses all previous rocket data, and provides new information about the atmosphere for altitudes and geographical locations not previously explored.

A Simplified Gastrointestinal Biopsy Capsule

Summary A simplified capsule for obtaining multiple intestinal biopsy specimens in the office or at the bedside is described. The capsule consists of 2 stainless steel shells, like the halves of an ordinary gelatin capsule, attached to a fine plastic catheter. Holes in each of the shells are superimposed when the capsule is open. Mucosa sucked into the hole by a syringe is sheared off as the capsule telescopes shut with suction. A small mercury bag facilitates rapid passage through the pylorus and along the small bowel without fluoroscopic manipulation. Except for the capsule itself, all other parts (mercury bag, plastic tubing, and syringe) are easily replaced from common hospital supplies. Over 350 consecutive biopsy specimens have been obtained without any complications. The occurrence of complications, however, remains as a possibility with this instrument just as it does with others now in use.