raise is immediate, while the plastic strain follows in time. 7 The plot of the stress and strain pairs on the stress-strain plane gives points much higher than those corresponding to the static relation. 7 The apparent contradiction between (a) and (b) is eliminated by introducing the plastic flow, 14 -15 i.e., the time rate of plastic deformation as an essential parameter. The plastic strain results correctly as the resultant of plastic flow during the history of the impact. 12 -13 The time rate of plastic flow can be computed with sufficient approximation according to a relation of quasi-viscosity within a limited range of time rates of strain, above which the stress increases with the time rate of strain but less than linearly. A finite stress corresponds to time rates of strain tending to infinity. 7 ' 8 At every point of the bar the first stress raise is elastic. The plastic strain grows in time while the elastic strain decreases according to the end conditions. The plastic flow is stress-relieving, so that the region of the bar nearer to the end under impact after sufficient duration of the impact is found to undergo a stress lower than the static stress corresponding to the strain present (i.e., according to the strain hardening). This region of the bar moves with uniform velocit}^ and uniform stress, as predicted in the theory according to (a). 12It is also seen that within the region of quasi-viscous relation between the stress and the time rate of strain, the lines of equal strain rate are equal to the static stress-strain diagram, but displaced in the direction of Hooke's line. 6 -7 Therefore the derivative of such diagrams, i.e., ratio of stress increment to increment of plastic strain, versus plastic strain alone, is independent of the stress present. It is concluded that within the limit of the linear relation between the stress and the time rate of strain, it is impossible to conclude anything about the stress b}^ measuring only the distribution of plastic strain.
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