However, the
critical pressures are somewhat higher compared with the one at 50[degrees]C (see Table 1).
It is easy to see that the critical horizon radius and temperature and consequently the critical pressure are solely determined by the YM charge.
After plotting the isobars one sees that when above the critical pressure there is only an "ideal gas" phase, when below the critical pressure, there are two stable regions corresponding, respectively, to large/small black hole phases with an unstable medium region, which implies the existence of the large/small black hole phase transition; this thermal behavior of black hole is in analogy to the one of van der Waals gas.
Repeating the experiment at different levels of pressure determines at a given temperature the characteristic critical pressure beyond which the crack propagates over more than 90% of the pipe length.
Once the gas company has determined its MOP, the RCP requirement is the critical pressure of the pipe must be (at least) 1.5 times the MOP.
Comparison of the minimum required and measured FS critical pressures in Table 4 shows that the FS Pc results are greater; thus, the unimodal MDPE pipe tested in this study have sufficient RCP resistance for use in gas distribution systems.
Unimodal MDPE pipe in diameters up to 219 mm exhibits RCP critical pressures that exceed the Minimum Required Critical Pressure for use in gas distribution systems, thereby delivering very adequate RCP performance.
However, during crack "propagation" (as distinct from "initiation") in gas-pressurized pipe, the strain energy release rate is considerably exceeded by pressure work, even at the relatively low critical pressures below [T.sub.cS4].
Harry (15) concluded that shear lips provide the bulk of the pipe resistance to RCP, as seen from the significant reduction in RCP critical pressure [P.sub.c] when the pipe bore was notched and thus the shear lip was "removed." He also concluded that the toughness of PE100 increases with crystallinity.
Ashcroft gauges and pressure transducers were utilized to monitor all
critical pressures at the station.
However, the
critical pressures are controlled by the true stresses at the walls, and these are only affected by the geometry of the entrance region and the die itself.
The collapse failure will occur if the supporting pressure is lower than the
critical pressure. In this case, the supporting pressure is not a load, because it prevents the failure to appear.