A Microscopical Model for Incubation Time and Its Associated Dynamic Load-Carrying Capacity

In recent decades, the incubation time has become a critical parameter to study dynamic failures for materials, but its underlying physical meaning is still vague and the corresponding model remains lacking. In this study, we first established a theoretical framework to evaluate incubation time, wherein a double atomic chain model with atomic thermal vibrations is leveraged. We leveraged three external force loading conditions to analyze incubation time and its associated dynamic load-carrying capacity (DLC). It can be found that the theoretical results for three metal materials (iron, tungsten and aluminum) exhibit reasonable consistencies with the experimental data, thus the model can be used to conduct preliminary studies for incubation time and DLC. The model suggests that, under the ramp loading with a platform amplitude of static strength, the amplitude duration does not remain constant but can quickly reach a constant with increasing ramp or loading rate, which implies that treating incubation time as a constant parameter is reasonable and thus lays a solid foundation for the previous macroscopic models on basis of incubation time. Meanwhile, it also suggests that the rate enhancement effect of failure strength can be obtained from external load and the constant atomic bond parameters without involving microscopic changes in material properties. Therefore, we microscopically unravel the rate enhancement effect of failure strength. Our study indicates that this effect is indeed a structural response, which accords with the previous macroscopical model.