  Velocity jumps observed for crack propagation under a static boundary
condition have been used as a controlling factor in developing tough rubbers.
However, the static test requires many samples to detect the velocity jump. On
the contrary, crack propagation performed under a dynamic boundary condition is
timesaving and cost-effective in that it requires only a single sample to
monitor the jump. In addition, recent experiments show that velocity jump
occurs only in the dynamic test for certain materials, for which the velocity
jump is hidden in the static test because of the effect of stress relaxation.
Although the dynamic test is promising because of these advantages, the
interrelation between the dynamic test and the more established static test has
not been explored in the literature. Here, by using two simulation models, we
elucidate this interrelation and clarify a universal condition for obtaining
the same results from the two tests, which will be useful for designing the
dynamic test.
