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Item type:Publication, Access status: without files , Impact of thermal shock on the R-curve and subcritical damage behaviour of flame-sprayed alumina compoundsAn alumina rich Al2O3–ZrO2–TiO2 compound was used for the preparation of self-supporting parts via the rod flame spraying technology. The as-sprayed material was compared to self-supporting parts, fabricated from commercially available alumina rods. For both materials, the flexural strength, the fracture resistance, and the behaviour under subcritical loading was evaluated and compared, either before as well as after cold thermal shock. While the flexural strength and the subcritical damaging of both materials were basically affected through thermal shock in a similar manner, the Al2O3–ZrO2–TiO2 compound showed an outstanding behaviour in terms of its fracture resistance, which was only barely reduced after thermal shock quenching.Publicationtype: Journal Article13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , On the fracture behaviour of niobium–alumina castablesThe present study addresses the characterisation of niobium–alumina composites in terms of their fracture behaviour. Fine-grained Nb–Al2O3 composites with a niobium content of 60 vol% and produced from different alumina sources (tabular alumina or white fused alumina) were prepared by castable technique. The sintered castables were tested for their sensitivity towards subcritical crack advance, their R-curve behaviour, and the work of fracture. All properties were derived from slow, cyclic four-point flexure tests at room temperature, which allowed for the initialisation and the manual and automatic control of a stable growing crack. Overall, the investigated composites showed measurable R-curve behaviour and were more sensitive towards subcritical crack damage than pure alumina.Publicationtype: Journal Article35 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Automated control of stable crack growth for R-curve measurements in brittle materialsStable crack advance is required for a reliable crack growth resistance (R-Curve) measurement. In bending experiments, manual control of the mechanical load and observation of the growing crack is still being done by the operator. This work presents an approach to partly and fully automated R-curve measurements, where stable crack growth is achieved solely via computer control. The experimental setup in conjunction with an intelligent control algorithm leads to reliable results, even for brittle materials like alumina ceramics, silicon nitride, and glass. Furthermore, it allows for a novel type of measurement, because the device detects any kind of energy release in the specimen, actually also without visible crack extension. The setup has been used successfully for about 3 years. The operating principle is explained and some of the results are presented exemplarily. The method is realized in 4-point-bending, but can be implemented also for other types of specimen and loading to automatically achieve stable crack growth. © 2012 Society for Experimental Mechanics.Publicationtype: Journal Article86