Figure 2. Quasi-static testing of CT specimen with the loading fixture 3: Experimental Work 3.1 Quasi-static fracture toughness tests with CT samples Quasi-static tests were conducted on CT specimens in a screw-driven Instron 5567 machine with full control of loading rates in the range of 1 to 100 mm/min and full records of load and displacement (see Figure 2). 3.2 Dynamic fracture experiments Dynamic fracture toughness tests were conducted on the SHTB facility to obtain the tensile stress-strain curves at high strain rates from 102 to 103 s-1 [6, 7]. SHTB consists basically of a striker tube, an incident bar and a transmitted bar (see Figure 3). The specimen was cemented between the incident and transmitted bars. Figure 3. Schematic drawing of the SHTB test While testing, the striker tube was projected towards the flange by a gas gun. Upon impacting, an incident wave εi(t) was generated, and reflected at the flange free end, presenting tensile stress wave, and then propagated backwards to the interface between the incident bar and the specimen. At this interface, part of the incident wave, εr(t) was reflected back into the incident bar. The rest went through the specimen and, finally developed the transmitted wave, εt(t) in the transmitted bar. The incident, reflected and transmitted waves were recorded by the strain gauges and the dynamic strain recording machine. From one-dimensional wave theory, the stress at the bar end is given by: Flange Incident bar Transmitted bar Striker tube Strain gauges Strain gauges Specimen
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