lower homologous temperatures; tests that otherwise take a very long time to complete at great expense.
SRRT‐based test technique for measuring elastic strain, ε e, delayed elastic strain, ε d, and viscous strain, ε v, was developed, as mentioned earlier, first for glass, an amorphous medium without any recognized “grain boundaries.” It was extended to polycrystalline ice, and grain‐size effect was introduced. The transparency of pure polycrystalline ice helped in identifying and quantifying stress and temperature dependence of the initiation and the multiplication of intergranular cavities and cracks, and the role of dislocations in the high‐temperature embrittlement processes. During primary creep period, the pile‐up of dislocations against grain boundaries may not be the major source for the initiation and multiplications of intergranular cracks. At a constant temperature, the first intergranular crack forms during the early primary creep when a critical des, ε d c, corresponding to a critical grain‐boundary shearing (gbs) displacement, x c, is reached irrespective of stress. The kinetics of crack multiplication depends exponentially on (ε d –ε d c ) corresponding to (x–x c ). This makes ε d the Achilles heel for creep activities. Yet, historically, materials scientists in general (metals, ceramics, and rocks) have not paid much attention to the primary creep, and certainly not to delayed elasticity. Traditionally the primary focus has been on minimum creep rate. Even though the rate of ε d decreases with time leading to a so‐called steady state, cracks are initiated during the primary creep and void density increases rapidly during the later stage of the primary creep, leading to minimum creep rate and ultimately to failure.
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