Evaluation of energy saving operational modes for industrial fracture connected processes on the basis of incubation time fracture criterion

Abstract

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 a large distance from the crack. It was found that for a certain combination of amplitude and duration of the pulse applied, the 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. The results obtained indicate a possibility to optimise 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, 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.).A possibility to optimise the amount of energy, required to fracture materials is of a large interest in connection with many applications. Energy inputs for fracture induced by short impulse loadings are of major importance in such areas as percussive, explosive, hydraulic, electro-impulse and other means of mining, drilling, pounding. In these cases energy input usually accounts for the largest part of the process cost (see Ref.[1]). Taking into consideration the fact that the efficiency of the mentioned processes rarely exceeds a few percent the importance of energy inputs optimization gets evident.The purpose of the present investigation is to find and explore the amount of energy sufficient to initiate the propagation of a mode I loaded central crack in a plate subjected to plane strain deformation. Two ways to apply the dynamic load to the body are studied. In the first case the load is applied at infinity. The study involves the analysis of interaction of the wave package approaching from infinity with an existing central crack in a plane. The existing crack is oriented parallel to the front of the wave package. In the second case the load is applied at the crack faces. Tractions are normal to the crack faces.Following the superposition principle these two loading cases should produce identical stress-strain field in the vicinity of the crack tip. It will be shown later that the amount of total energy applied to the body that needed to initiate crack growth is depending on the load application manner in different ways for the two cases under investigation.