Damage formation, fatigue behavior and strength properties of ZrO[2]-based ceramics

It is suggested that a non-destructive testing technique using a three-dimensional X-raytomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO[2]-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91-0.98, 0.8-0.83, and 0.73-0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical propertiesof the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 10{5} stress cycles is in the range 33-34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material

Damage formation, fatigue behavior and strength properties of ZrO[2]-based ceramics

It is suggested that a non-destructive testing technique using a three-dimensional X-raytomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO[2]-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91-0.98, 0.8-0.83, and 0.73-0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical propertiesof the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 10{5} stress cycles is in the range 33-34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material

Crystallographic analysis of rock grain orientation at meso- and microscale levels

This paper studies the results of electron backscatter diffraction analysis of naturally deformedpolycrystalline olivine. It also defines the dependence of lattice-preferred orientations of grains on their microstructural position and size. The authors detect the basic mechanisms, consequence and thermal dynamic modes of deformation. They also show that the development of a polycrystalline structure is determined by the following consecutive activation of sliding systems (010)[100] → {0kl}[100] → (100)[010] → {100}[001] → {110}[001], when dislocation sliding and diffusion creep change under the temperature decrease from 1000°C to 650°C

Structure and properties of porous ceramics obtained from aluminum hydroxide

In this paper the study of porous ceramics obtained from aluminum hydroxide with gibbsite modification is presented. The dependence of porosity and mechanical characteristics of the material sintered at different temperatures was studied. It was shown that compressive strength of alumina ceramics increases by 40 times with decreasing the pore volume from 65 to 15%. It was shown that aluminum hydroxide may be used for pore formation and pore volume in the sintered ceramics can be controlled by varying the aluminum hydroxide concentration and sintering temperature. Based on these results one can conclude that the obtained structure is very close to inorganic bone matrix and can be used as promising material for bone implants production

Zirconia-based sintered ceramics for biomedical applications

A porous ceramics obtained from ultra-fine powders has been studied. The porosity of ceramic samples was from 15 to 80%. The structure of the ceramic materials was a cellular structure. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformations on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass

Properties of Zirconia after Plasma Treatment

The influence of high-frequency plasma treatment on the properties of zirconia powder is shown in the work. The powder was produced by a plasma-chemical method. The powders had a foamy form with the size of agglomerates of 5-10 [mu]m and crystallites of 20-50 nm. The powders were treated by the pulse plasma unit with dielectric barrier discharge generator. It was shown that the plasma processing changes the acidity of water-powder suspensions from 8.1 to 4.3 pH, which signifies the powders' wettability improvement. It was revealed that more intensive mixing using ultrasound influences the acidity level, reducing it in comparison with mixing by paddle-type agitator. It was shown that these changes of surface properties have relaxation by 4% per day and extrapolation of this dependence shows that the powder will have initial properties after 400 hours storage at room conditions

Imagery Processing System and Its Applications

The existing disproportion between high efficiency of imagery receipt process and low productivity of the ways of their processing makes actual the creation of an Imagery Processing System, which may be used for the estimation of the efficiency of new hardware and mathematical methods of picture processing. The main idea of hardware functional organization is compatibility of special purpose processors and input/output image units with a base computing system in external memory on the disks and tapes level. The base computing system includes three BESM-6 computers with the total external memory field on the disks. The terminal computer (minicomputer M-6000) serving specialized input-output image (phototelegraphic unit NEVA , System P-1700 photomation MARK-11, direct input channel, etc.) is connected with the base computing system. The software of Imagery Processing System includes system programs and functional processing programs. The system programs serve general structure of the system, providing the connection of a user with this system, the image input-output operations, the general control of image processing, the error search and logging, dynamic allocation memory, the maintenance of interface demands of the system, etc. The functional processing programs of the system are based on modular design. The program modules are arranged in the application program pack. The main part of the programs is related to the program pack of preprocessing, which is a preprocessor for all the other application program packs, since it has the program modules connected with the presentation of pictorial information and storage of it in the system (image registration, reformatting, enhancement, filtering, edge detection, geometric rectification, etc). Specialists of nature control institutes of the Siberian Branch of the USSR Academy of Sciences, who are the main users of Imagery Processing System, should play the leading role in the creation of special program packs. The main topics of application research are connected with the study of geological structure of the earth, mineral exploration, timber inventories, fire control, the mapping of agricultural regions of Siberia, environmental impact analysis, crop identification, environmental protection, etc. The theory of inverse problems of mathematical physics is important for remote sensing method. Mathematical statements of-inverse problems a rise in interpretation of multispectral scanner data. They are mathematical methods of inverse problems, that to all appearance, will come up to take place of widespread correlation method in imagery interpretation. The inverse problems, in particular, the inverse optic problems, are one of the main topics in research work of the Computing Center

Simulation of fracture of the bone implant with the porous structure

Different approaches to bone defects reconstruction with the use of ceramic materials have been developed recently. Ceramics are identical with bone matrix, provide biomedical compatibility with bone tissue and possess high strength. But with an overall high strength ceramic implants destruct in dynamic mode. The paper presents a study of the effect of the porosity gradient on the destruction of the bone implants under dynamic loading. It is shown that the fracture behavior of the bone implants is changed with increasing levels of the gradient of porosity

Mechanical Properties of Zirconium Ceramics with Hierarchical Porous Structure

The work studies porous ceramics produced from ultra-fine powders. The porosity of ceramic samples was from 15 to 80%. The ceramic materials had cellular structure. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations, which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformations on deformation diagrams is due to mechanical instability of cellular elements in a ceramic frame

Structure, phase content and mechanical properties of aluminium with hard particles after shock-wave compaction

The possibilities to combine metal and metal oxide powders in various compositions open a broad range of mechanical and thermal behavior. When using in nanostructured components the resulting materials might exhibit even more interesting properties, like product effectiveness, tensile strength, wear resistance, endurance and corrosion resistance. Intermetallics like TiAl could be obtained as TiAlx in a quality similar to that obtained from melting where only eutectic mixture can be produced. Similar effects are possible when compacting nanoceramic powders whereas these can be combined with intermetallics. Currently, it is very difficult to produce wires and special shaped parts from high temperature superconducting materials. The compacting by explosives could solve this problem.The present paper uses explosion compacting of Al nanoparticles to create nanocomposite with increased physico-mechanical properties. Russian civil explosive Uglenit was chosen as high energy material (HEM) for shock-wave compaction. The different schemes and conditions were suggested to run the explosion process. Al nanoparticles as produced by electric wire explosion contain 8-10% of aluminum oxide. That aluminum oxide can serve as strengthening material in the final nanocomposite which may be generated in various compositions by explosive compacting. Further modifications of nanocomposites were obtained when including nanodiamonds into the mixture with aluminum nanoparticles with different percentages. The addition of nanodiamonds results in a substantial strengthening effect