Napkin ring

Napkin Rings = Serviettenringe". Bezeichnung fur serviettenringfdrmige Bestrahlungskorper, die aus einer Legierung von 5 % Plutonium und 95 % Alu-minium bestehen. 

Allen and Alsalim 22 compared the effect of various pretreatments of stainless steel (martensitic structure) on the torsional shear strength of napkin ring joints formed with an epoxy adhesive (Redux 319 (Bonded Structures Ltd.)). They concluded that... 

Fig. 14. Elfect of pentaerithritol tetra-thioglycolate (PETG) coupling agent treatment on the durability of steel/ epoxy napkin ring joints 1241...

Test Method for Shear Strength and Shear Modulus of Structural Adhesives (Napkin Ring Style Test Piece)... 

Today, bone is used by local populations all over the world, to make trinkets and souvenirs such as bracelets and pendants for the tourist trade. It is also used to make small, high-quality items. Examples of these are spoons, bowls, beakers, letter openers and napkin rings. 

Plastic imitations of mother-of-pearl are more tricky to detect. One simulant is made by suspendir mica in a clear synthetic polymer. The effect is very realistic with an apparent play-of-colour, but the shape is often a give-away as the material is moulded. For example, a round napkin ring with no joins in the material could not be made fi m one piece of shell. Small items such as buttons are more difficult to identify. 

Similarly, a round napkin ring made from one piece of mother-of-pearl suggests a moulded simulant, as no shell would be thick enough for this shape. 

The material to be irradiated is in the form of napkin rings," each consisting of plutonium metal mixed with another metal (a combination of metals known as an alloy) and covered by an aluminum jacket. 

The plutonium alloy is in the shape of an ordinary table napkin ring in order to make it possible to remove the heat developed in the nuclear fission reaction by a water-cooling process. 

The purpose of all this equipment is to isolate tiny quantities of the rare synthetic elements like americium, berke-lium, and einsteinium. They are present in the irradiated plutonium napkin rings along with the great quantity of highly radioactive fission products. 

A mass production run of the heavy synthetic elements took place in Berkeley in October 1956. The chemical steps involved had been worked out in detail, and chemists had practiced with the tongs for months, using dummy napkin rings. 

Ten hot napkin rings had been cooked with neutrons in the Arco reactor for more than two years. 

The first remote-controlled operation is that of opening the port in the bottom of the box. The hot napkin rings, worth thousands of times their weight in gold, are fished up out of the lead container beneath and drawn into the box. 

The first ring is then picked up by the tongs and placed in an alkaline solution which will disintegrate and partially dissolve it. The resulting dark, murky liquid is siphoned into a polyethylene bottle and stored while the other nine napkin rings are dissolved,... 

This dial is registering disintegrations of single atoms of einsteinium, element 99, which was isolated in the October 1956 napkin-ring operation. 

Gross Polypoid mass Circumferential growth producing a napkin-ring configuration... 

Results from EUROCOMP test programme at Helsinki University of Technology ) Napkin ring torsion tests Thick adherend test Sections in EUROCOMP Handbook... 

In conventional Shear tests, there is considerable non-uniformity of stress throughout the joint. The napkin ring test was introduced to provide a test where the variation of shear stress was minimal. It consists of two thin-walled tubes joined end to end by a thin layer of adhesive. The torque required to break the joint is recorded. 

Specific tests of adhesion are described in more detail under the following articles Blister test, Climbing drum peel test, Fracture mechanics. Napkin ring test. Peel tests. Rubber to metal bonding - testing. Shear tests. Tensile tests. Wedge test and in Refs. [1-5] see also Standards for adhesives and adhesion and Appendix. 

Napkin ring test D E PACKHAM Calculation of shear stress refinements... 

In this case, an independent check on the magnitude of t was found by deteimining the stress-strain curve of the adhesive layer when constrained between two aluminum plates in a napkin-ring test [60]. 

Ref, [13] contains further information about this instrument and test coupon. It should be noted that the amplification of the relative displacement signal is extremely great and that it has been found necessary to correct the initial modulus of the curve to compensate for the small distortions of the aluminum adherends themselves. This is accomplished by subjecting an equivalent one-piece notched coupon, with no adhesive layer, to the same loads as the bonded coupons, with the instruments mounted in the same locations. Although there were earlier such curves measured on napkin-ring test coupons, the coupons for that set-up were difficult to fabricate because the radial width of the bond layer was so narrow and the adhesive tended run out. In addition, it was diflicult to ensure uniformity of bond thickness around the perimeter. It is for these reasons that the Krieger... 

E-0229. Test Method for Shear Strength and Shear Modulus of Structural Adhesives. This method employs torsional shear loading on a napkin ring specimen to determine the shear strength and shear modulus of structural adhesives in thin gluelines on high modulus adherends. 

Uses a napkin ring test for determining shear modulus and shear strength of structural adhesives... 

---