ISSN:1058-9759    

DOI:10.1080/10589759408952818

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Neutron and gamma radiography measurements have been performed on absorption and compression type refrigerators. Both neutron and gamma radiation were obtained simultaneously from a thermal channel of the 8 MW ASTRA reactor of the Austrian Research Centre Seibersdorf. Radiography images were converted into light by neutron and gamma sensitive converter screens, detected by high sensitivity TV camera, displayed on a monitor, stored by S-VHS recorder and for further analysis a QUANTEL image processing system was used. Characteristic features or absorption aggregates were visualized during different conditions of working processes. Operating time, pressure, temperature, flow velocity, power consumption were measured and recorded as well. It was possible to detect the critical parts of the system responsible for breakdown in operation under extreme conditions. The behaviour of lubrication and cooling oil was observed for compression type refrigerators. The critical extent of foaming was determined before it caused troubles in functioning. Visualization together with a detailed knowledge of the working processes provide an effective tool for manufacturers to improve their products

ISSN:1058-9759    

DOI:10.1080/10589759408952819

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Unsharpness of neutron radiography (NR) image has been discussed usually two dimensionally. The unsharpness depends on size and shape of a neutron diaphragm, and on an object position and its shape. Although a circular diaphragm is often installed in the neutron collimator, rectangular diaphragms are also selected in some NR facilities. Anisotropic unsharpness is expected for these less symmetrical diaphragms. In this paper, the unsharpness is analyzed with respect to these parameters. The spatial unsharpness in depth direction should be required in case of thickness determinations and is analyzed in addition to the two dimensional unsharpness

ISSN:1058-9759    

DOI:10.1080/10589759408952820

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Many scientific studies have demonstrated the harmful effect of chloro-fluoro-carbons (CFC) on the stratospheric ozone layer and their contribution to the green-house effect. Facing this planetary ecological problem, the international community has committed itself to follow the agreement procedures defining the progressive reduction and final withdrawal of CFC production. The chlorine-free substitutes elaborated by chemists, the hydro-fluoro-carbons (HFC), raise difficult problems when applied to the fields of domestic refrigeration and automotive air-conditioning. In these applications, the refrigerants are associated to a lubricant which is necessary for operation of the compressor, Mineral oils which were efficient up to now cannot be used anymore with the new refrigerants TOTAL research teams have been asked to develop a synthetic oil able to solve this new problem. After examining different technics, Neutron Radiography has been considered capable to bring a decisive contribution to this research program. After feasability tests performed in 1989 on a simulation bench at Saclay, dynamic neutron imaging rapidly imposed itself for the observation of polyphasic flows in evaporators under actual operating conditions. Investigation programs scheduled in 1990 and 1991 have permitted to compare the behavior of various oil formulations with HFC. They have led to an industrial product fulfilling all the requested properties

ISSN:1058-9759    

DOI:10.1080/10589759408952821

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The remediation of soil contaminated with organic substances such as gasoline products is a subject of growing concern. One method often employed is flooding the soil with water or a water-surfactant mixture to wash the contaminant down to the water table. The organics are then pumped out of the subsurface with the ground water for treatment. This procedure has produced only limited results. It has been speculated that this lack of success is due in part to what is known as wetting front instability. Wetting front instability can occur during infiltration of a liquid into porous media, particularly when a fine soil layer is overlying a coarse layer. Instability of the wetting front implies that the interface between the advancing fluid and the portion of the porous media still at initial conditions does not advance as a flat front, but rather it breaks up into finger-like flow paths. Through the use of neutron radioscopy and three-dimensional, computer reconstruction, three dimensional infiltration experiments, with water and organic liquids infiltrating into layered porous media, were conducted in an attempt to evaluate the influences of initial moisture content, and type of infiltrating fluid on the formation of fingers. Experimental data was also evaluated for the purpose of calibrating dimensionless relations for predicting finger properties such as finger diameter and propagation velocity

ISSN:1058-9759    

DOI:10.1080/10589759408952822

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Experimental results were presented to visualize streak lines in a liquid metal by neutron radiography. Lead-bismuth eutectic was used as a working fluid for both natural and forced convention flows. Tracer and dye injection methods were employed for the visualization and the tracer made of gold-cadmium intermetallic compound and the dye made of lead-bismuth-cadmium alloy were developed. It was shown that both methods were applicable to a slow flow like natural convection and the liquid dye injection method and the tracer method were available to a fast flow

ISSN:1058-9759    

DOI:10.1080/10589759408952823

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Aluminium components and structures of aircrafts are susceptible to various types of corrosion due to aging, frequent changes of environment and moisture. Most of the corrosion types occurring on or in aluminium structures of aircraft contain hydrogen. Therefore, neutron radiography provides a very sensitive and informative imaging method for the detection and the investigation of corrosion attack.

ISSN:1058-9759    

DOI:10.1080/10589759408952824

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The nondestructive testings for structural fine ceramic materials have been evaluated by film method. Thickness effects on the detectability of neutron radiography have been studied theoretically and experimentally. Both methods with and without contrast enhancer are studied by using Kyoto University Reactor facility. The experimental detectabilities obtained have been in good agreement with the theoretical analyses. By using contrast enhancer, the small defects on the surface of silicon nitride ceramics being near 15 microns in width and depth have been clearly detected. For the case of non-enhancer, 0.6% of the detectability has been obtained over the thickness of 30 to 40 mm for the silicon nitride ceramics

ISSN:1058-9759    

DOI:10.1080/10589759408952825

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A comparison study of advanced nondestructive evaluation (NDE) imaging techniques demonstrates the merits of using neutron radiographs to characterize defects, particularly cracks, in fiberglass epoxy composites with stainless steel interfaces. Neutron radiographs of mockups of the arm pivot sockets used on the Hard Upper Torso of the Extravehicular Mobility Unit Spacesuits showed hairline cracks not detectable by x-ray radiography, x-ray computed tomography or ultrasonic C-scan images. The ultrasonic C-scans were more effective for detecting disbond and delamination defects associated with the composite material and stainless steel interface. A conceptual method of integrating nondestructive evaluation images from various techniques to generate mosaic images is introduced for enhancing detectability of flaws by using the optimum features of each NDE imaging technique

ISSN:1058-9759    

DOI:10.1080/10589759408952826

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Two new species of materials were studied by neutron radiography: lithium-bearing ceramics and glasses, and titanium aluminide alloys. Various types of discontinuities, including voids and bulk density reduction, were detected. Hydrogen absorption by a titanium aluminide alloy was measured as a function of exposure lime, with ‘as received’ and polished samples. The interaction of hydrogen with the metal lattice is likely to cause embrittlement, leading to material failure by the loss of tensile ductility. The effects of a rough surface and an oxide layer on the rate of hydrogen absorption were observed

ISSN:1058-9759    

DOI:10.1080/10589759408952827

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor