17:15 〜 18:30
[SIT18-P03] GHz ultrasonic velocity measurement of iron beyond bcc-hcp transition III: FEM analysis on GHz-DAC ultrasonics
キーワード：鉄、GHz音速法、hcp相、有限要素法、核
In order to perform the GHz-DAC ultrasonics to measure sound velocities, it is critically important to develop in-situ techniques to measure sample length under high pressure. Here are several possible ways to realize it;
(1) X-ray imaging from the direction perpendicular to the axis of symmetry of the diamond anvil.
(2) Elastic deformation of diamond anvil under constrains of generated pressure and applied load.
(3) Optical observation and refractive index correction from the axis of symmetry of the diamond anvil.
In this presentation, we will report on (2). As for (1), please refer to another presentation with GHz data in this session. (3) will be examined in future study.
The distance between the backs of the diamond anvils can be measured with an accuracy of 0.1 μm using an advanced optical rangefinder. Therefore, if the elastic deformation of the diamond anvil under high pressure can be accurately evaluated, we can constrain the sample length within 0.1 μm accuracy. Finite element method (FEM*) analyses was applied to evaluate elastic deformation of diamond anvil under constraining generated pressure and applied load; generated pressure can be monitored by the ruby-scale method, while applied load can be monitored by a newly devised method measuring contraction of Belleville springs (Sara-bane) in symmetric DAC.
As a result of FEM analysis, it was found that, if the generated pressure and applied load were fixed, the length change in diamond anvil can be evaluated within accuracy of 1 μm or less, even if load distributions in the gasket were varied. As a result of the present systematic FEM assessments, we are confident that the sample length in DAC can be constrained within accuracy of 1 μm or less.
FEM analysis is able to predict travel time of the GHz wave propagating in the diamond anvil. The estimated travel time change was ~ 1ns at 15 GPa pressure generation. On the other hand, we analyzed P and S waves data acquired at15 GPa, and found the accuracy of 1 ns or less expected in both cases If FEM analysis is consistent with travel time variation, we can claim the estimated sample length with high reliability and confidence.
*FEM analysis was conducted by using COMSOL (trademark).
(1) X-ray imaging from the direction perpendicular to the axis of symmetry of the diamond anvil.
(2) Elastic deformation of diamond anvil under constrains of generated pressure and applied load.
(3) Optical observation and refractive index correction from the axis of symmetry of the diamond anvil.
In this presentation, we will report on (2). As for (1), please refer to another presentation with GHz data in this session. (3) will be examined in future study.
The distance between the backs of the diamond anvils can be measured with an accuracy of 0.1 μm using an advanced optical rangefinder. Therefore, if the elastic deformation of the diamond anvil under high pressure can be accurately evaluated, we can constrain the sample length within 0.1 μm accuracy. Finite element method (FEM*) analyses was applied to evaluate elastic deformation of diamond anvil under constraining generated pressure and applied load; generated pressure can be monitored by the ruby-scale method, while applied load can be monitored by a newly devised method measuring contraction of Belleville springs (Sara-bane) in symmetric DAC.
As a result of FEM analysis, it was found that, if the generated pressure and applied load were fixed, the length change in diamond anvil can be evaluated within accuracy of 1 μm or less, even if load distributions in the gasket were varied. As a result of the present systematic FEM assessments, we are confident that the sample length in DAC can be constrained within accuracy of 1 μm or less.
FEM analysis is able to predict travel time of the GHz wave propagating in the diamond anvil. The estimated travel time change was ~ 1ns at 15 GPa pressure generation. On the other hand, we analyzed P and S waves data acquired at15 GPa, and found the accuracy of 1 ns or less expected in both cases If FEM analysis is consistent with travel time variation, we can claim the estimated sample length with high reliability and confidence.
*FEM analysis was conducted by using COMSOL (trademark).