13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- minimum section is expressed as ( ) net gross D d σ σ = . Here, we consider 5 cases as shown in Table 2. Table 2 shows the tensile speed and the maximum forced displacement at the grip end with the time of that appear. In Case 5, the tensile speed 5000 u t mm s = corresponds to the impact speed when someone drops a call phone to the ground. The maximum displacement 1.5mm corresponds to the brittle fracture appears for high speed tensile test. The maximum displacement 0.1mm corresponds to an example of nondestructive case of for high speed tensile test. Figure 5 shows the dynamic stress at the notch root A for Cases 1-5. Also Fig. 5 shows the detail of the dynamic stress oscillation with each case. From Fig. 4 and Fig. 5, it is seen that the maximum dynamic stress max σ appears at almost the same time of the maximum forced displacement. Defined the maximum value of dynamic stress as max σ in each case. After several oscillations due Case ① ② ③ ④ ⑤ Maximum displacement max u 0.1 mm t=0.00100s 0.1 mm t=0.00029s 1.5 mm t=0.00429s 1.5 mm t=0.00150s 1.5 mm t=0.00030s Condition Tensile speed u t 100 mm/s t<0.00100s 350 mm/s t<0.00029s 350 mm/s t<0.00429s 1000 mm/s t<0.00150s 5000 mm/s t<0.00030s Table 2. Maximum displacement and tensile speed given at the grip end Figure 5. Dynamic stress at notch root A for ρ=0.03mm 100 105 110 115 120 8 9 10111213 (a) Case 1 Time [s] x10 -4 Dynamic stress σ yA at the notch root A [MPa] 100 105 110 115 120 2 3 4 5 6 7 (b) Case 2 Time [s] Dynamic stress σ yA at the notch root A [MPa] x10 -4 1665 1670 1675 1680 1685 42 43 44 45 46 47 Time [s] Dynamic stress σ yA at the notch root A [MPa] x10 -4 (c) Case 3 1600 1650 1700 1750 13 14 15 16 17 18 (d) Case 4 Dynamic stress σ yA at the notch root A [MPa] Time [s] x10 -4 1600 1650 1700 1750 2 3 4 5 6 7 (e) Case 5 Dynamic stress σ yA at the notch root A [MPa] Time [s] x10-4 0 500 1000 1500 2000 0 0.001 0.002 0.003 0.004 0.005 Dynamic stress σ yA at the notch root A [MPa] Time [s] max st σ σ− max st σ σ− max st σ σ− max st σ σ− max st σ σ− st σ ③④⑤ (e) (b) ( )t σ ② ( )t σ ③ ( )t σ ④ (a) A y x st σ ①② (d) (c) ( )tσ ① ( )t σ ⑤
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