Strength of a Ceramic at High Temperatures Under Biaxial and Uniaxial Tension

A design is presented for a fixture to test concentric-ring loaded disks and four-point loaded plates at high temperatures. In this fixture the loading plunger is guided by flexure plates to determine the load path with accuracy. The uniaxial and equibiaxial tensile strengths of a brittle material were measured at 982°C with this fixture. For lapped surfaces, the equibiaxial tensile strength of dense, isostatically pressed, sintered alumina was 16.0% lower than the uniaxial tensile strength. The uniaxial strength at 982°C was 42.3% lower than the previously reported value for comparable tests at room temperature. The effect of frictional forces and lateral constraint, of specimen and loading geometry, and of local stresses on the nominal stress are discussed.     

Biaxial and Uniaxial Data for Statistical Comparisons of a Ceramic's Strength

The uniaxial and equibiaxial tensile strengths of a brittle material were measured in bending. Equibiaxial tension was attained by concentric ring loading of disks and uniaxial tension by four-point line loading of plates. The two specimen designs give equal volumes, surface areas, and stress gradients. Ground surfaces and lapped surfaces were tested. The equibiaxial tensile strength of a dense alumina was lower than the uniaxial tensile strengths for both ground and lapped surfaces, 8.5 and 8.1%, respectively. The Batdorf theory of flaw statistics, in which biaxial tensile strengths can be predicted from the statistical distribution of uniaxial tensile strength measurements, agreed with the data.     

Microbiological quality of ice creams commercialized in some cities in the state of Rio de Janeiro, Brazil

The microbiological quality of 60 ice cream samples of three commercial brands (A, B and C) of various flavours, commercialized in some towns in the State of Rio de Janeiro, Brazil, was evaluated. Total bacteria count (TCB), coliforms at 35°C (CT), coliforms at 44°C (CF) and presence of Staphylococcus aureus were performed on all samples. TCB ranged from 2.0 × 10 ² to 6.9 × 10 ⁵ cfu/mL, CT from < 3–≥ 2400 MPN/mL, CF from < 3–1100 MPN/mL and S. aureus from < 10–1.4 × 10 ⁶ cfu/mL. The level of bacterial contamination found in this study reflects the unhygienic conditions prevalent in manufacturing and storage of ice creams. Actions are thus necessary by the Brazilian regulatory agencies to require the ice cream processing plants to adopt quality guarantee systems, such as good manufacturing practices and hazard analysis and critical control points system.