Determination of a New Type of Cutting Ceramic Material Elastic Modulus
When the dental ceramic material is used in the mouth, it interacts with the natural tooth and generates stress and strain. At room temperature, the ceramic is basically an elastic body that obeys Hooke's law. Its elastic deformation and strain are largely determined by the elastic modulus of the material. In view of the fact that the types of dental cutting ceramic materials are still small and their performance is still not ideal, the authors have developed a new type of glass ceramic cutting ceramic materials. Different from the previous machinable glass-ceramic materials, the main crystal phase of this new ceramic is a new type of mica-calm mica, which aims to increase the strength of mica glass ceramics by using the higher field strength of calcium ions. The elastic modulus of this material was studied.
Materials and Methods 43101 Four sets of new cutting ceramic materials with different crystallization treatments, six test pieces in each group, and a diamond inner circle cutter cutting 2mm test bars. Tests were performed using an Instron Model 4302 Mechanical Tester (UK).
2 Determination of elastic modulus Three-point flexural strength test method, span 16mm, loading speed 0. 5mm / min. Record the stress-strain curve of the test piece, using Hooke's law = bit to calculate the elastic modulus of the material E (For stress, e for strain) The elastic modulus of the four groups of the junction 101 is 52.5±4.8GPa, and the difference analysis shows that there is no significant difference in the elastic modulus between the four groups (P> 1. The ceramic material is brittle) At room temperature, the plastic deformation can hardly occur, but the elastic deformation occurs within the elastic deformation range. Therefore, the elastic properties of the ceramic are particularly important. 12. The elastic deformation of ceramics is actually under the action of external forces. As a result of small displacements, the allowable critical value of the tiny displacement between atoms is very small, beyond which a chemical bond breaks (at room temperature in a ceramic) or an atomic plane slip plastic deformation (at a high temperature The modulus of elasticity reflects the magnitude of the external force required for small changes in the distance between atoms. Although the range of the elastic displacement allowed by the atomic spacing is small (about 0.1% at room temperature, 1231), The required external force is very large.The external force required for elastic deformation is related to the bonding force between the atoms and the binding energy, that is, the important factor affecting the elastic modulus is the interatomic binding force, ie, the chemical bond 21. Therefore, the elastic modulus is also related to the microstructure. Insensitive, once the material type is determined, the elastic modulus is changed by heat treatment process is extremely limited 124. The elastic variables of glass and their chemical composition have an approximate additive relationship 5, the elastic modulus of a multi-phase ceramics It is also a summation function of the various properties of the crystalline phase and the glassy phase. It can be expected that the elastic modulus of the glass-ceramic substantially depends on the elastic constant of the crystalline phase 16. 2 There are two commonly used test methods for the elastic modulus, one method The elastic modulus is determined by measuring the resonant frequency of the material on a specific device, but this method is accurate but the cost is high.The other method is to directly measure the strain generated with the stress is simple and easy, this experiment adopts this method. In addition to the elastic deformation of the material, it also includes other aspects, such as the deformation and deflection of the fixture, the measurement results have a certain error 71. The stress strain of the sample in this experiment Turning point both appear online.
According to the analysis, the part before the turning point includes the non-material elastic deformation factor. In this experiment, when the elastic modulus was measured, all were calculated based on the elastic deformation of the material above the turning point, so that the influence of non-material elastic deformation factors was largely avoided, and the result was more accurate.
3. In this experiment, the four groups of ceramics are all mica-based glass-ceramics. The difference is only due to the different degree of crystallization heat treatment, resulting in different levels of mica crystal phase. From the theory described above, we can see that the differences between the four groups of ceramic elastic moduli should be relatively limited. The test results of this experiment are in good agreement with it. This, on the other hand, shows that the research method used in this experiment is credible.
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