Optimizing energy input for fracture by analysis of the energy required to initiate dynamic mode I crack growth

Abstract

A problem for a central crack in a plate subjected to plane strain conditions is investigated. Mode I crack loading is created by a dynamic pressure pulse applied at large distance from the crack. It was found that for a certain combination of amplitude and duration of the pulse applied, energy transmitted to the sample has a strongly marked minimum, meaning that with the pulse amplitude or duration moving away from the optimal values minimum energy required for initiation of crack growth increases rapidly. Results received indicate a possibility to optimize energy consumption of different industrial processes connected with fracture. Much could be gained in for example drilling or rock pounding where energy input accounts for the largest part of the process cost. Presumably further investigation of the effect observed can make it possible to predict optimal energy saving parameters, i.e., frequency and amplitude of impacts, for industrial devices, e.g., bores, grinding machines, etc. and hence significantly reduce the process cost. The prediction can be given based on the parameters of the media fractured (material parameters, prevalent crack length and orientation, etc.).

Energy-Based Analysis of Ultrasonically Assisted Turning

“…The important feature of the incubation time fracture criterion is its capability to predict fracture initiation conditions with reliability and precision for quasi-static cases of relatively slowly changing loads and geometry as well as for dynamic cases of high-rate loads and fast changes in geometry (see, e.g. [9][10][11][12][13]). Moreover, the criterion is supplying a smooth transition between these two cases [11].…”

Incubation time fracture criterion for FEM simulations

“…Lately an approach making it possible to embed the ITFC into numerical computational schemes based on finite element method (FEM) was developed [12][13][14]. Utilizing this approach simulation of several different experiments on dynamic impact fracture caused by high-rate loads was performed [12,15].…”

Incubation time approach in rock fracture dynamics

“…[15] amount of energy sufficient to initiate propagation of a mode I loaded central crack was extensively explored. It was demonstrated that energy to input into media containing a crack in order to advance this crack does strongly depend on the shape of the load pulse applied.…”

“…For example for granite with initial cracks of 5 mm fractured by rectangular shaped load pulses, if the frequency of the fracturing impacts differs from the optimal one by 10%, energy cost of fracture creation is exceeding the minimal value by 12% [15]. Taking into consideration the fact that the efficiency of rupture connected processes rarely exceeds a few percent, it gets evident that even a possibility of small improvement of energy input is of a great importance for industry.…”