Finite element modeling and computer simulation of stresses and strains in diamond anvil cell devices

Diamond anvil cells (DAC) are extensively utilized in the study of material properties at extreme conditions of pressures and temperatures. The pressures in excess of 400 GPa and temperatures in excess of 4000 K have been reported in DAC devices. Most studies on the optimization of diamond geometry and gasket materials used in diamond anvil cell devices have been carried out by trial and error using experimental high pressure data. This dissertation addresses design and optimization issues in DAC using finite element modeling (FEM) and computational analysis. The computational approach is centered around the recent advances in the growth of isotopically enriched 13 C layers on diamond anvil and their use as pressure sensor in diamond anvil cell devices.;In the dissertation the following results were obtained: (1) The validation of the modeling approaches. The first part of dissertation deals with the benchmarking issues. Pressure distribution results obtained on DAC compression model were verified using existing literature data; (2) DAC compression model in Nike2D computer code was investigated for different types of boundary and initial conditions, verified on several practical applications and theoretical results; (3) The experimentally measured pressure distribution in DAC to a peak pressure of 213 GPa by X-ray diffraction methods using a diamond coated rhenium gasket was compared with the finite element modeling results and a good agreement was obtained; (4) The role of a thin film of the 13C layer and its use as a universal sensor in DAC to 156 GPa and corresponding mechanisms involved were analyzed; (5) Finally, the role of diamond geometry and gasket materials were investigated to get a realistic estimate of the ultra high pressure conditions that can be generated in diamond anvil cells. The radial and axial stresses as well as shear stresses were examined and a failure criterion for diamond anvils in high pressure devices was developed.