EMBRITTLEMENT

Metals do not remain in the state in which they were purified from their ore and industrially treated for the purpose they are to serve. Metal fatigue causes a metal to fail (break, tear, bend) under far smaller stress than originally tested for. The cause used to be as mysterious as the aging of living organisms, but it has been known for decades that fatigue is the result of surface cracks that increase in size especially under cyclic loading (periodic on-off stress, or stress alternating in direction).

Not far off is the process of embrittlement, which causes a metal to lose some or most of its elasticity and to become prone to cracks. We have met it several times in connection with neutron embrittlement, which causes the pressure vessel and other metallic parts of a nuclear reactor to become brittle if exposed to a suffi-ciently high flux of neutrons for a sufficiently long time. (Contrary to antinuke allegations, the process is well understood and its dangers minimized by reactor design, frequent inspections, and ultimately by decommissioning the reactor.)

But embrittlement of metals can also be caused by hydrogen, as described in any textbook on materials science (see below). All metals contain microcracks, fractions of a micrometer (micron) across and tens of microns in length. They reduce the strength (maximum stress withstood without permanent damage) of a metal. Hydrogen enters them, accumulates at its tip, and causes the crack to progress in tiny steps. In the final stage, the crack propagates with high speed, explosively, and the energy piled up in the internal stresses of the material (even in the absence of exter-nal loads) is given off as heat.

AbuTahu showed this experimentally by simple tensile tests on metals, in which a machine pulls at the two ends of a metal sample until it begins to flow and finally breaks. As the sample is stretched toward its elasticity limit, "strain" energy is increased in it, which is analogous to the energy stored in an expanded spiral spring. The sample remains cold, as it must, since the stored energy is needed lo return the sample to its original dimensions when released. But if stretched beyond its yield point, the sample not only breaks, but grows hot, for the strain energy, previously concentrated in the tips of the microcracks, is released as heat, or "heat of fracture."

Although apparently all metals are subject to hydrogen embrit-tlement, palladium is particularly prone to it because of its surface and crystalline structure; and as for deuterium, which was used in the cold fusion experiments, this hydrogen isotope is up to 30% more effective than simple (regular) hydrogen in embrittling it.

[The reasons for this are not discussed in the AbuTahu papers, but this may well support the theory that H2 molecules are large enough to act as a wedge opening the crack tips, whereas single H atoms will diffuse through the metal. Deuterium molecules would thus be even more effective.]

In short, the energy put into the palladium by the manufacturer when he melted it was partly stored in it as stress energy when il cooled; it was released as the deuterium entered the palladium cracks and liberated as heat of fracture.