Discontinuity Breakdown Research Articles

Chemographic relationships of biotite and cordierite in the McGerrigle thermal aureole, Gaspé, Quebec

Abstract Biotite and cordierite occur in a 1‐km wide zone of pelitic hornfelses around the McGerrigle pluton. These phases display systematic changes in XFe that can be attributed to continuous reactions involving chlorite or andalusite in the system KFMASH. Through much of the zone biotite and cordierite were products of the ‘breakdown’of chlorite. Close to the pluton this continuous reaction was terminated by a discontinuous reaction that introduced andalusite. Pelites which interdigitate with apophyses of the intrusive at the pluton margin contain assemblages that record a continuous reaction between biotite, cordierite, andalusite, muscovite, and quartz or, alternatively, the discontinuous breakdown of muscovite and quartz to K‐feldspar and andalusite.The mole fraction of Fe in biotite and cordierite increased significantly with the progress of the first continuous reaction and apparently decreased during the second continuous reaction. The KD of Fe‐Mg between the minerals decreased and apparently increased, respectively, during the two reactions.Biotite‐cordierite‐chlorite assemblages are interpreted to have been stable at temperatures between 525° C and 615° C and biotite‐cordierite‐andalusite assemblages stable at temperatures between 615° C and 635° C. The confining pressure was estimated to have been < 2 kbar.The results of this study suggest that the KD of Fe‐Mg between biotite and cordierite is a function of temperature, the Fe‐Mg exchange characteristics of the controlling continuous reaction and non‐ideal mixing of Fe and Mg.

Influence of the breakdown mechanism on the behavior of lead-antimony alloys with an alternating load

For the example of Pb-Sb alloys, the influence of aging is investigated, as a function of its mechanism, on the resistance to fatigue deformation, leading to rupture along the grain boundaries. It is shown that continuous breakdown increases the cyclic life, whereas discontinuous breakdown considerably reduces it. The most effective means of suppressing discontinuous breakdown, and hence increasing the resistance to grain-boundary fatigue breakdown, is by doping with elements which reduce the mobility of the grain boundaries, such as tellurium in led. Doping with elements that facilitate discontinuous breakdown (such as As in PbSb) leads to significant reduction in the fatigue resistance.

Ultrasonic vitrectomy ? an alternative technique to presently used mechanical procedures

The liquification of the corpus vitreum by ultrasound is a promising new alternative to presently used mechanical methods of vitrectomy. With regard to the duration time of insonation, as well as to the ultrasonic intensity, there exist thresholds, the exceeding of which causes a discontinuous breakdown of the vitreous frame in a spherical zone around the transducer tip which can be verified by ultrasonic pulse echo methods. Viscosity measurements showed that the vitreous isonified in this area has almost the same viscosity as water whereas its optical transparency remains unchanged. The dependence of the diameter of the liquified zone on insonation time was measured.

Breakdown of a discontinuity, taking account of the real equation of state of the detonation products from a condensed explosive

The problem is considered concerning the breakdown of an arbitrary discontinuity, due to the emergence of a detonation wave at the boundary of a condensed explosive charge. The real equation of state of the detonation products of Hexogen was used in the numerical calculations. A u vs p diagram is constructed, which allows graphical calculations to be carried out of the discontinuity breakdown for different media. A comparison is carried out of the calculated values of the initial shock-wave velocities with the experimental data obtained at a certain distance from the explosive charge. It is shown that an increase of the pressure of the gas in which dispersion of the explosion products occurs leads to a reduction of the initial shock wave velocity and to an enhancement of its attenuation during its further motion in the shock tube.