Guiding principles for generation of ultra high pressures, such as massive support of anvils, conditional intensification of pressure, elastic design of anvils, compressibility matching between pressure medium and gaskets, and mechanical property of compressible gaskets, are briefly discussed.
Applying these guiding principles to an MA8 type apparatus, the requirements for the mechenical property of compressible gaskets are derived. The use of single component gaskets is shown to be difficult to generate very high pressures, and the use of “composite metal gaskets” is proposed in order to satisfy all the requirements for the optimum designing of pressure generation. The newly devised composite metal gaskets are examined experimentally for pressure generation up to 15-18GPa in 0.05cm3.
Theoretical analysis of the experimental results is made by calculating the distribution of stress in anvils from the data of strength of metals used for the gaskets, and also the distribution of plastic strain in anvils from the data on plastic deformation of anvils. Combining the calculated stress and plastic strain in anvils, a safety limit of -4.5GPa in terms of allowable differential stress is derived for cemented tungsten carbide anvils used in the present work.
The problem concerning scaling-up of system is discussed; effects disturbing Wakatsuki's scaling law of compressible gaskets are analyzed. The correlation between probability of blowout and scale of system is also analyzed. Stable generations of 8GPa in 15cm3 and 15GPa in 1.8cm3 averelized by means of the metal gaskets with a special care on the blowout.
