Thermally activated dislocation movement at plastic deformation

Selected Topics on Material Strength and Thermally Activated Deformation Processes

“…We have also found that activation volume obtained by strain-rate change tests during tensile deformation of aged specimens increases with temperature from nearly 50b 3 at 77 K to 500b 3 at 423 K where b is the magnitude of the Burgers vector.…”

“…Therefore, it is reasonable to conclude that the increase in yield stress due to spinodal decomposition is temperature independent, in agreement with our experimental results. 11) We can also say that the observed values, 50b 3 to 500b 3 , of the activation volume, mentioned in Chapter 2, are not related to the spinodal decomposition but are originated from short-range thermal obstacles of solidsolution Sn atoms in the Cu-Ni alloy matrix.…”

Reliability Theory of Stochastic Fracture Processes in Sustained Loading: Part I

“…All major studies of thermally activated fracture employ a rate theory [3][4][5][6][7][8][9] (usually called transition state theory, or activated complex theory, or absolute rate theory [10,11]), which considers that these processes occur by passing through an energy state associated with an activated complex of atoms that take part in the bond breaking or healing step [12][13][14][15][16][17],…”

“…The mechanism of the process can be studied by the investigation of the stress and temperature dependence of this average rate constant k and its relation to the velocity. Attention is drawn in this respect to the thoughts of Schoeck [3] and to the excellent review of Wielke [8] on the analysis of thermally activated processes in solids. Because in the threshold zone the stochastic approach differs significantly from the deterministic theories, it is in this zone where experimental comparisons and verification can be sought, using the principles and techniques discussed by Schoeck [3], Wielke [8], and Krausz and Eyring [18].…”

“…Attention is drawn in this respect to the thoughts of Schoeck [3] and to the excellent review of Wielke [8] on the analysis of thermally activated processes in solids. Because in the threshold zone the stochastic approach differs significantly from the deterministic theories, it is in this zone where experimental comparisons and verification can be sought, using the principles and techniques discussed by Schoeck [3], Wielke [8], and Krausz and Eyring [18]. While the critical tests will be both difficult and time consuming to perform, the results could be valuable in comparing the various models for the understanding of slow crack propagation in brittle solids and in engineering applications where the commonly employed high safety factors [5] may then be reduced.…”