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Experimental results are presented for the piercing of circular holes in sheet metal using pads of conventional rubber or polyurethane. An empirical equation has been obtained for calculating the required loads and an attempt has been made to interpret this equation in terms of rubber hardness and the work-hardening characteristic of the metal. It is shown that the deformation behaviour of the polyurethane is different from that of the rubber and that it is misleading to treat polyurethane as though it is merely a rubber with a higher Shore hardness. [ABSTRACT FROM AUTHOR]

In this paper, measures of division of labor are derived for 44 manufacturing industries, and the hypothesis that the division of labor increases as the hardness of product increases is investigated. Two dimensions of the division of labor, structural differentiation and dispersion-concentration, are shown to be related to product hardness as predicted. Analysis suggests that although complexity of the product, machine technology, and industry size may influence the relationship, the relationship between hardness of product and division of labor remains. Production technology appears clearly to modify the effects of hardness, and may account for some of the deviant and marginal cases; for soft-product industries, the effects of hardness and production technology appear to conflict. The relevance of the findings for a theoretical perspective on complex organizations is considered. [ABSTRACT FROM AUTHOR]

Heat treatment caused an increase in ductility. Aging caused an increase in strength and hardness with a decrease in ductility. Overaging caused decreases in strength and ductility. Solution treating resulted in a single phase. The precipitation of coherent intermetallic compounds caused maximum strengthening with minimum loss of ductility. [ABSTRACT FROM AUTHOR]

Copyright of Rock Mechanics (00357448) is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Five composites and one acrylic resin were investigated. The strength specimens were contaminated with water during mixing and the hardness specimens after condensation. The transverse strength was tested after 24 hours and the surface microhardness after 24 hours and after two months. Water contamination reduced the transverse strength of the acrylic resin by ∼ 50 % and that of three of the composites by 21-26 %. The decrease of the surface hardness caused by moisture contamination was ∼ 45 % for the acrylic resin and 28-57 % for four of the composites. The microhardness values obtained after two months did not differ significantly from the respective values obtained after 24 hours. [ABSTRACT FROM AUTHOR]

Tumble-drying techniques similar to those which might be encountered in home laundering are investigated. The effects of fabric dimensions and aesthetic softness and limpness are studied, and a tentative explanation of the aesthetic changes in terms of observed physical differences is offered. [ABSTRACT FROM PUBLISHER]

X-ray diffraction studies of several proprietary dental gold alloys demonstrated that hardening probably is a dual mechanism of precipitation and order-hardening. Lattice parameter measurements showed that the ordered structure was AuCu. In addition, it was shown that maximum hardness occurs at about 75% full order. [ABSTRACT FROM AUTHOR]

The nature and cause of dulling and crazing of freshly exposed surfaces of silicate cements are discussed with the effects of liquid composition and preparative and environmental variables. [ABSTRACT FROM AUTHOR]

The use of iron-platinum constituents in gold alloys can promote significant hardening. The alloys will solution heat-treat at temperatures used to fuse porcelains and precipitation-harden during slow air cooling. The hardening mechanism appears to involve the reaction: FePt3 ⇄ FePt. The precipitation reaction will vary with casting temperature. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dental Research is the property of Sage Publications Inc. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article looks at the effects of residual monomer within restorative dental resins. The mechanical properties of dental resins are discussed, including elasticity, hardness, and yield strength. Attempts to decrease the residual monomer have resulted in an improvement of the properties of resins and less irritation of the pulp and soft tissue.

The article discusses the use of gold foil and mat gold as restorative dental materials and examines the structural density of gold. Details are provided about a study which sought to use quantitative information to determine the structural density of compacted gold. The hardness of gold is explored and the effectiveness of gold in dental operations is described.

The article focuses on the physical properties of impression pastes composed of zinc oxide and eugenol. It states that zinc oxide-eugenol mixtures were used as dental cements before the 1930s and are widely used as temporary dental cements. It comments on an examination of the hardness, brittleness, ease of separation, and tackiness of different zinc oxide-eugenol impression materials.

The article examines the relationship between the structure and microhardness of dentin in humans. Experimental procedures are described and results are discussed. Dentin in the vicinity of the dentinoenamel junction was found to be softer than the surrounding dentin. Dentin next to the pulp chamber was softer than nearby dentin.

The article investigates the microhardness of dentin and enamel. An experimental procedure is described and results are discussed. Knoop hardness numbers were derived for both enamel and dentin, with 15% of the values representing outliers for unusually low or high hardness. The area just below the occlusal surface was found to exhibit the greatest variation in hardness for enamel.

The article reports on research that examined the impact that temperature has on the setting time of plaster of Paris. The author notes that individuals who frequently use the substance are aware that setting time can be increased by using warm water or implementing some other method to heat the substance during the setting phase. The paper is designed to provide factual evidence of this process. The author discusses the impact that heat had on the setting process.

The article discusses research performed on the radiopaque surface layer present on dental enamel and dental caries. Details are provided about the solubility and hardness of this layer. The hardness of enamel on teeth affected by incipient caries and proximal caries is described. Several figures illustrating teeth with caries surfaces are also included.

A conference paper is presented which discusses hardness tests performed on teeth. It discusses the instruments used in hardness testing and examines the penetration and abrasion of teeth and the resistance of teeth to these actions. Charts illustrating the results of the test are included. Details are also provided about previous studies on tooth hardness and the various means used in these studies.

A study is made of the optimum size and hardness of sites for the storage of a certain portion of the national stockpile of nuclear weapons. These weapons can be stored in existing nuclear sites, nonnuclear sites converted for the storage of nuclear weapons, and new sites built for this purpose. The principal questions considered are. To what extent should existing and converted sites be used for this purpose? Should unoccupied sites be used as decoys? What are the optimum size and hardness of new sites? Should the sites be compact or dispersed over large areas? Methods are developed to answer these questions under certain limitations. The rough estimates obtained from this analysis would need to be adjusted to allow for variations from the average conditions at the individual sites [ABSTRACT FROM AUTHOR]