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Elements of a unified theory of the mechanical behavior of concrete, from no-load to fracture under short-time loading, are developed, based on observed microcrack behavior and on a statistical distribution of mortar strength. [ABSTRACT FROM AUTHOR]

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This paper presents the results of experiments conducted with extracted human and bovine teeth. The teeth were subjected to thermal cycling at temperatures between 140 and 90 F. The results offer conclusive evidence that thermal fracture may be induced by the thermal stresses caused by the temperature cycling. Less than 3,000 thermal cycles cause severe cracking or the propagation of cracks previously existing in the teeth, or both. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to study the flexural strength of concrete beam specimens after repeated loading. The test results showed that some specimens produced an increase in flexural strength after repeated loading. An attempt is made to explain this strength increase. It appears likely that microcrack propagation is responsible for this increase in flexural strength. [ABSTRACT FROM AUTHOR]

A mathematical model is developed to emulate the strain-stress and fracture behavior of concrete in a planar structural frame. The strain-stress and fracture law is formulated to account for creep, shrinkage, and cracking in the concrete. A linear relation in integral equation form is used to relate stress to creep strain. A step-forward integration technique is devised to evaluate the integral equa-tion. Three examples are studied to demonstrate the accuracy of the integration method. An additional example is presented to show the need for a law which accounts for creep, shrinkage, and cracking in the concrete. [ABSTRACT FROM AUTHOR]

Research on the properties of concrete is taking place in many universities, in specialist research institutions, at ready-mixed concrete and precast concrete plants, and within construction companies throughout the world. The need for more work is questioned and discussed in relation to research on the behavior of concrete under load, and subjected to different environmental histories, with particular reference to the current strength and deformation studies at the Cement and Concrete Association. [ABSTRACT FROM AUTHOR]

This article discusses research on force in dental impression materials. The article reports on photoelastic stress analysis related to elastic strains, permanent strains and distortions, and material fractures. Information is also provided on the process of taking dental impressions, noting that undercut areas around teeth and cavities should be eliminated beforehand.

The article presents a discussion of the failure of dental amalgam restorations. The question is raised of whether amalgam failures are caused by the alloy or by the operators creating the alloy. Several physical characteristics of amalgam are discussed, including plasticity, tamping, and condensation.

Marginal fracture characteristics of clinical restorations made from three amalgam alloys were evaluated during a four-year period. Marginal fracture increased with age; the rate of increase was different among alloys, and the ranking of alloys remained the same during the four years. [ABSTRACT FROM AUTHOR]

The strength of barnacle cement was compared with commercial dental polymeric restorative materials and cements by use of a fracture mechanics approach in conjunction with a blister technique. Barnacles were "grown" on various surfaces and the adhesive fracture energy of the cements was determined. These values were compared quantitatively with available commercial materials. On a wet surface, barnacle cement was favored. [ABSTRACT FROM AUTHOR]

A method is proposed for evaluating the strength of an adhesive joint. It is basically a fracture mechanics approach which recognizes that the strength of a joint depends on adhesive thickness, elastic properties of adhesive and teeth, joint geometry, sizes of flaws, and other factors. The "blister" technique is proposed as a useful means of quantitatively determining the quality of an adhesive joint. [ABSTRACT FROM AUTHOR]