INFLUENCE OF DEGREE OF THICKNESS REDUCTION RATIO ON DEVELOPMENT OF STRUCTURE IN THE STEEL 1 . 5710
Intensity of structural changes during forging is usually determined in dependence on the forging ratio. Forging ratio at elongation is most often calculated with use of simple relations, which are based on the change of cross-section of the forged pieces. The intensity of structure development is influenced not only by the simple change of cross-sections, but also by relative length of the stroke, magnitude of deformation in individual passes, manner of edging, temperature, friction and shape of anvils. The paper gives an analysis of influence of the relative length of the stroke on the forging ratio.
ANALYSIS OF NEW TECHNOLOGY FORGING MONOLITHIC FORGED BOTTOMS
The pressure vessel itself consists of several characteristic components, the working stress of which in its complex determines unequivocally the state of stress of the reactor on the whole, although this stress achieves from the viewpoint of local judgment and assessment of individual parts of the pressure vessel mutually different levels. Development of new technology for manufacture of bottoms of pressure vessel for nuclear power engineering is oriented on future demands of market with respect to ecology and energetic. It is necessary to propose new technology for production of forged bottom with flange for power engineering, namely by forging from one ingot without use of welding of the bottom to the flange. The objective is to verify for this forging technology an optimum shape of tools, which will make it possible to forge the bottom with a minimum loss of metal at forging and final processing. High degree of forging and also the required quality of products, characterised by high values of mechanical properties, will be achieved by minimum extra metal allowances for forging. After implementation of the new technology for forging of bottoms with flange the manufacturer will be able to offer on the world market a peak technology and sophisticated completely new products – monolithic forged bottom with flange for high quality pressure vessels for nuclear power plants.
Effect of Calcium Glycerophosphate on Demineralization in an in vitro Biofilm Model
The aim was to investigate the anti-caries properties of calcium glycerophosphate (CaGP) using an in vitro bacterial flow cell model. Four flow cells, inoculated from a chemostat containing a seven-organism bacterial consortium, were pulsed with sucrose twice daily, to provide an acidic challenge and pH-cycling conditions. Blocks of enamel and dentine were mounted in each flow cell. In a study on the effect of CaGP concentration, CaGP was pulsed into three of the flow cells, at the same time as the sucrose, to give concentrations of 0.10, 0.25 and 0.50%. Water was pulsed into the fourth flow cell with the sucrose. Microradiography revealed a significant dose response of decreasing demineralization as CaGP concentration increased. Reductions at 0.25 and 0.5% were significant when compared to the control. A second study investigated the effect of timing of CaGP pulsing, relative to sucrose, on enamel and dentine demineralization. CaGP (flow cell concentration 0.2%), was pulsed 1 h before, during or 1 h after the sucrose pulse; a water control was employed. In enamel, pulsing CaGP before the sucrose reduced demineralization significantly compared to concurrent pulsing, which in turn gave a significant reduction compared to pulsing after sucrose, which did not reduce demineralization significantly compared to the water control. In dentine, CaGP reduced demineralization significantly only when pulsed before the sucrose. The findings suggest that in vivo, the anti-caries potential of CaGP may be greater if it is applied before a cariogenic challenge.