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Information × Registration Number 0200U004131, 0197U017349 , R & D reports Title Development of the physical concept of construction of structure sensitive diagrams of mechanisms of failure and fracture toughness of materials popup.stage_title Head Podrezov Yurij Mykolajovych, Registration Date 15-05-2000 Organization Frantzevich Insitute for Materials Science Problems of the Ukranian National Academy of Sciences popup.description2 The experimental research of influence of the grain size, the dislocation substructure and the porosity on strength and fracture toughness of BCC-metals is carried out at presence of micro- and macrodefects. The isomechanical conditions of failure of polycrystals are determined. In these conditions the influence of a degree of deformation on fracture toughness and mechanisms of fail-ure of deformed metals is investigated. The uniform dependences of fracture toughness on a degree of deformation for iron, molybdenum and chromium are obtained. The influence of poros-ity on fracture toughness in powder materials is generalized as the structure sensitive scheme. The scheme is based on the competition between different failure mechanisms and demonstrates a dependence of fracture charachteristics on such structural parameters, as bulk and plane porosity, contact quality et. al. The different stages of interface fracture was studied. These stages are: crack nucleation, its propagation through alone grain facet , overcoming of triple point and catastrophical crack propagation. The model experiments was made, permitting energetic features of intergranular crack propagation to be revealed. The conditions of brittle cracks nucleation at grain boundaries of polycrystalline BCC-metals are analysed. Initiation of these cracks is modelled as accumulation of grain boundary dislocations, a decreasing of surface energy due to segregation being taken into account in energetic balance of the process. Decreasing of grain boundary fracture energy by factor 10 is shown can result in nucleation of intergranular crack. The size of the crack is found can reach that of grain boundary facet. The obtained results are used to analyse interparticle fracture of powder materials and interface fracture of composite materials. The results of the project show that microcrack criterion can be used as basis for obtaining universal dependences of limited mechanical charachteristics on structural parameters for different BCC-metals. This confirm s the expediency of usage of the criterion to obtain structure-sensitive maps of fracture mechanisms in ductile-brittle transition temperature region. Product Description popup.authors popup.nrat_date 2020-04-03 Close