The theory is based on first physical principles hence, it is not an engineering  failure criterion: The first  pages are dedicated to the physical basis, arriving to a constitutive equation for multi axial stress states. The rest of  170 pages, are dedicated to verify  the theoretical results with practical problems well known in the literature, and some other predictions likely to occur, but not yet verified. In the first case, it is shown

that the empirical Hoeck-Brown 1981 equation and the 1991 modified version, largely used in Geology, can be derived from the theory. The same can be said for the empirical Consideré- Brandzaeg  result for concrete under triaxial loading.

In the field of Geophysics it is shown that liquid magma in the outer core and in earth´s mantle is generated by local mechanical failure in the mantle that allows extrusion of materials, and this enables the heat production and heat flow up  to the earth surface. The liquid outer core generated by the extrusion through the core-mantle boundary generates local cyclones of magma at D´´ boundary,  which in turn is responsible for the magnetic anomalies on the earth surface.

Spin inversion of the inner  core is responsible for earth´s  magnetic reversals. It is suggested that the arrival of heat flow  from the mantle to the earth crust, influences the conveyor belt current and supplies the energy necessary for the ocean dynamics and the Atlantic Gulf stream. The arrival of great magmatic bubbles to Lehman´s discontinuity  influences the heat flow at the crust and global climate changes as well as

the erratically cyclic oscillations of El Niño-La Niña and geophysical catastrophes in Caribbean sea and in Indonesia, including atmospheric cyclones. Hence, climate changes are driven fundamentally by earth geophysical activity while it is shown that CO2 anthropogenic emissions does not contribute to them. From physical point of view, the two basic concepts in the strength theory are the cohesive stress and the internal

friction forces. The first is due to the electrostatic attraction between ion cores or holes and electrons. The latter, to the trend to conserve the total angular momentum  of electron pairs.

Santa Cruz de Tenerife, January, 2010 Luis B. Cabrera

Yield & Strength Theory of Materials

by Luis Blas Cabrera