Dynamic Initiation Fracture Toughness Determination and Full-field Strain Measurements of Rock Material

The purpose of this paper is to present a detailed experimental procedure for the quantitative determination of initiation fracture toughness and full-field strain measurement of rock material under dynamic loads. Notched semi-circular bending tests were conducted using a split Hopkinson pressure bar (SPHB) system. Experimental setup, data acquisition and interpretation were described in detail. The digital image correlation (DIC) technique combining with a high-speed cameral was adopted for the measurement of surface deformation characteristics of rock specimens. To verify the accuracy of this technique, comparative tests were performed in which the strains in the specimens were simultaneously determined using the DIC technique and on-specimen strain gauges. Strain gauges were also used to determine the time-to-fracture. Experimental results show that (1) dynamic crack initiation toughness can be well determined; and (2) the high-speed DIC technique provides reliable full-field strain fields in the specimens under dynamic loads.