Incubation time approach in rock fracture dynamics
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The paper is summarizing latest results connected with application of the incubation time approach to problems of dynamic fracture of rock materials. Incubation time based fracture criteria for intact media and media with cracks are discussed. Available experimental data on high rate fracture of different rock materials and incubation time based fracture criteria are used in order to evaluate critical parameters of causing fracture in these materials. Previously discovered possibility to optimize (minimize) energy input for fracture is discussed in connection to industrial rock fracture processes. It is shown that optimal value of momentum associated with critical load in order to initialize fracture in rock media does strongly depend on the incubation time and the impact duration. Existence of optimal load shapes minimizing momentum for a single fracturing impact or a sequence of periodic fracturing impacts is demonstrated.
Keywordsincubation time dynamic fracture rocks dynamic strength fracture toughness crack resistance energy and momentum input fracture process optimization
List of main symbols
incubation time of a fracture
characteristic size of a fracture process zone
stress intensity factor for mode I loading
quasistatic limit for stress intensity factor for mode I loading (critical stress intensity factor)
displacement in direction x i .
stress in direction ij
Heaviside step function
longitudinal wave speed
transversal wave speed
time to fracture
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