Spontaneous thermal runaway as an ultimate failure mechanism of materials.
The first theoretical estimate of the shear strength of a perfect crystal was given by Frenkel [Z. Phys. 37, 572 (1926)10.1007/BF01397292]. By assuming that two rigid atomic rows in the crystal would move over each other along a slip plane, he derived the ultimate shear strength to be about one-tenth of the shear modulus. Here we present a theoretical study showing that catastrophic failure of viscoelastic materials may occur below Frenkel's ultimate limit as a result of thermal runaway. The thermal runaway failure mechanism exhibits progressive localization of the strain and temperature profiles in space, thereby producing a narrow region of highly deformed material, i.e., a shear band. We calculate the maximum shear strength sigma_{c} of materials and then demonstrate the relevance of this new concept for material failure known to occur at scales ranging from nanometers to kilometers.
Braeck
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Physics of Geological Processes (PGP), University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway. simen.brack@fys.uio.no
Podladchikov
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