13th International Conference on Fracture June 16–21, 2013, Beijing, China -3- generally used. Table 1 shows the effect of boundary conditions on the static stress concentration factor. From Table 1, it is seen that the stress concentration factor is almost the same between the rigid grip tension and simple tension. Also, Table 1 shows the FE model in Fig. 2 shows less than 1% error compared to the exact stress concentration factor obtained by the approximate formula[12]. 3. Dynamic stress concentration for high speed tensile test specimen Figure 4 shows the forced displacement u given at the end of the specimen. The average stress gross σ is also indicated, which is expressed as ( ) ( ) 0.867 gross t E u t l σ = ⋅ from FEM. The stress at the (a)Rigid grip tension (b)Simple tension Table 1. Static stress concentration factor by FEM Kt in Fig.3(a) Kt in Fig.3(b) Ref. [12] in Fig.3(b) ρ=0.03, t=5 14.46 14.48 14.49 ρ=0.2, t=5 6.14 6.15 6.12 Figure 3. Boundary condition 0 0.5 1 1.5 2 0 10 20 30 40 50 60 70 0 0.001 0.002 0.003 0.004 0.005 Displacement u(t) at the fixed end [mm] Gross stress σ gross =0.867E ・ u(t)/l at the fixed end [MPa] Time [s] 0 0.05 0.1 0.15 0 1 2 3 4 5 0 0.0005 0.001 0.0015 Displacement u(t) at the fixed end [mm] Time [s] Gross stress σ gross =0.867E ・ u(t)/l at the fixed end [MPa] (b) Detail of displacement Figure 4. Loading conditions max 1.5 u mm = ③④⑤ (a) Displacement vs. time max 0.1 u mm = ①② ④ ② ① ③ ⑤ ④ ② ① ③ ⑤
RkJQdWJsaXNoZXIy MjM0NDE=