This result is important because it predicts that applying a hydrostatic(P>0) pressure to a reaction should slow it down, and vice versa. Physically, this can be more easily appreciated by considering a diatomic molecular bond: That a tensile stress along the axis of the bond must enhance the rate at which rupture occurs, and consequently its chemical reactivity,is obvious.
If the crack velocity is assumed to be directly relate to the reaction rate Kr and P is proportional to KI at the crack tip, then Eq.(12.27) can be recast as (see prob. 12.5)
V = v0 exp(-∆H+βK)/RT