Analysis of pressures generated in a piston-cylinder type apparatus

Pressures generated in a piston-cylinder type apparatus have been analyzed as a function of experimental path. From general consideration of solid pressure media and experimental history six characteristic P-T curve types of an arbitrary specimen have been deduced. The observed melting curve of a specimen is found to be dependent on a maximum initial pressure in an experiment cycling downward (defined herein) and also to be convergent to a certain upper boundary (i.e., its true melting curve) when the pressure cell used has a negative anvil effect. It is concluded that the variation of observed melting temperatures (or any other characteristic temperature or parameter) of a specimen at a given external pressure is bounded by its true melting temperature (or by its true physical parameter), which is an open upper bound. On the basis of these properties the so-called upper boundary method for close approximation to the true P-T curve of a specimen has been derived. When this method is used, the inherent strength of solid pressure media is simply obtainable as a by-product, which can be defined by the lower boundary of its melting temperatures measured at a given external pressure.