The quasi-static setup—shown in Fig. 6.3—attaches the die fixture—disk assembly through a connecting rod to the load cell of a 245 kN hydraulic load frame and the punch to the frame’s actuator. Cameras are again positioned on either side of the slotted die fixture to record the deformation of the specimen rear surface for DIC measurement. Contact force is measured by the load cell and punch motion is measured by the LVDT of the hydraulic actuator. 6.3 Results and Discussion Detailed results are shown from dynamic and quasi-static tests using the hemispherical (12.17 mm radius) punch. Dynamic test results are shown in Figs. 6.4, 6.5 and 6.6. The impact velocity of the striker in this test is 17.6 m/s. Figure 6.4 shows elastic waves recorded at the midpoint of the incident and transmitter bars. The incident wave amplitude is 400 kN, and the maximum contact force from the transmitter bar wave is 110 kN. Six images of the maximum principle strain from DIC measurements on the rear surface of the specimen are shown in Fig. 6.5. These images (a–f) correspond to the specimen immediately before loading, 40, 90, 130, 180, and 230μs after load initiation, respectively. Figure 6.5f corresponds to the instant that fracture is observed. The DIC measurements can be used to generate a wide variety of data. Figure 6.6, for example, shows the history of principal strains at the specimen center point as well as at the point where fracture is first observed. The principal strains at the Fig. 6.2 Hemispherical (12.17 mm radius) punch Fig. 6.3 Quasi-static experimental setup 6 DIC in Dynamic Punch Testing 29
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