A commercially available, densely sintered alpha silicon carbide was tested in air from room temperature to 1700°C using a modified instrumented pendulum unit and standard Charpy size test specimens. The resistan...
Acoustic emission analysis showed that the failure of some low density aluminous cement bonded perlite composites cannot be explained adequately using the classical Griffith type approach in which it is assumed that f...
Acoustic emission analysis showed that the failure of some low density aluminous cement bonded perlite composites cannot be explained adequately using the classical Griffith type approach in which it is assumed that failure is caused by the catastrophic propagation of the most severe flaw. It was found that the general concept of cumulative weakening could be applied to the failure of these composites. A change in failure mode from that of cumulative weakening to Griffith type fracture occurred when the bulk density of the composite was greater than about 1.6 lb/bd ft and/or the cement content of the material was greater than approximately 30%. In addition, microscopic examination showed a change in fracture surface morphology from primarily interparticle failure at low density or low cement contents to primarily transparticle failure at high density or high cement content. L'analyse d'émission acoustique montre qu'on ne peut pas suffisamment expliquer la fracture de certains composites en perlite, liés par du ciment alumineux de densité basse, en utilisant une approche de type traditionnel comme celle de Griffith; celle-ci affirme que la fracture est causée par la propagation destructive de la plus sévère craquelure. On a prouvé qu'on peut appliquer le concept de l'affaiblissement cumulatif à la fracture de ces composites. La fracture type “affaiblissement cumulatif” est remplacé par fracture type Griffith lorsque la masse volumique est plus grande que 1.6 lb/bd ft et/ou le contenu en ciment des matériaux est approximativement plus grande que 30%. En outre, un changement apparait dans la morphologie de la fracture en surface selon la densité et le contenu en ciment: Fracture surtout intraparticulaire pour un ciment de basse densité et en faible quantité et plutôt transparticulaire pour un ciment de haute densité et en grande quantité.
The room‐temperature strength distributions of a sintered and a hot‐pressed Si3N4were examined in the as‐machined condition, after oxidation at 1370°C and after oxidation under load at 1370°C. The strengt...
The room‐temperature strength distributions of a sintered and a hot‐pressed Si3N4were examined in the as‐machined condition, after oxidation at 1370°C and after oxidation under load at 1370°C. The strength‐controlling flaw populations were highly transient in nature. Both the duration of oxidation and the magnitude of the applied load were observed to effect changes in strength. This dynamic situation is related to both strengthening and weakening processes, which at times may occur simultaneously in the same strength dis
The fracture toughnesses and Young\'s elastic moduli of several metaphosphate glasses were measured by the indentation technique. The results show that the normal glasses lie along a KIcvs E line between (0.4, 40)...
The fracture toughnesses and Young\'s elastic moduli of several metaphosphate glasses were measured by the indentation technique. The results show that the normal glasses lie along a KIcvs E line between (0.4, 40) and (0.7, 60) MPa‐m112and GPa, respectively. The abnormal ZnO and MgO metaphosphates appear to be tougher and are above the line of the normal glasse
Observations of the formation of multiple-mist regions on the fracture surfaces of soda-lime-silicate and fused silica glasses are reported. These regions occur only in high-strength specimens. The same empirical equa...
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This communication directs attention to laboratory data which demonstrate that intense planar orientation of clay minerals in natural sediments does not necessarily imply the deposition of these minerals as individual...
This communication directs attention to laboratory data which demonstrate that intense planar orientation of clay minerals in natural sediments does not necessarily imply the deposition of these minerals as individual microlites (platelets) from deflocculated suspensions;they could equally well have been deposited as flocs. -from Author
We present quasi-elastic light-scattering spectroscopic measurements of the polymer distribution and parallel determinations of the catalytic activity of bovine glutamate dehydrogenase in solution, in order to examine...
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