PSI - Issue 52

Chen Zhou et al. / Procedia Structural Integrity 52 (2024) 234–241 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3.2. Effect of different moment ratios under dynamic loading To investigate the effect of dynamic loading on fracture characteristics of the DCB-UBM specimen, two different kinds of impulse loading (Load A and Load B) in the form of a step function are applied to the two arms of the sandwich specimen. The amplitude of impulse loading A(t) is shown in Fig. 3, and the t 0 is set to 10ms, 1ms, and 0.1ms respectively. The two impulse load values are shown in Eq. (11) and Eq. (12) respectively. The material properties are shown in Table 1. * 1 1 ( ) M M A t = (10) * 2 2 ( ) M M A t = (11)

Fig. 3. Impulse loading: (a) Load A; (b)Load B

For a clear comparison with the results under static loading, the oscillation factor K is introduced, which can be expressed as follows, Dynamic Static C K C = (12) where C Dynamic denotes ERR and PA value under dynamic loading; C Static denotes the ERR and PA value under static loading, that is, Dynamic ERR Static ERR K ERR = , Dynamic PA Static PA K PA = (13) Different from the way of extracting results under static load, we follow the rules of Burlayenko et al. (2019) to extract dynamic mechanical fields at each time increment. The results are shown in Fig. 4. When the t 0 is set to 10ms, the results of ERR and PA quickly tend towards the results of constant bending moment action as time increases. When the t 0 is reduced to 1ms and 0.1ms, it is obvious that oscillation occurs in both ERR and PA, which is caused by inertia, as shown in Fig. 4 (b)-(c) and Fig. 4 (e)-(f). The results are consistent with the phenomenon described by Burlayenko et al. (2019). For load A, the ERR and PA converge to static values after oscillation; For load B, the ERR value drops quickly to a minimum value when the load rapidly goes to zero, but there is a sudden increase in the PA value. For both two kinds of impulse loads, the oscillation amplitude of the ERR is significantly larger than that of the PA, indicating that the inertial generated by the dynamic loading has a greater effect on the ERR and a smaller effect on the PA. We extracted the maximum values of K for ERR and PA and collated them as shown in Table 3. As can be seen in Table 3, the maximum K value of ERR is 1.05 and the maximum K value of PA is 1.23 when t 0 is set to 10ms, however, for t 0 with significant inertial effects (t 0 =1ms and 10ms), the maximum K value of ERR is 4.26 and the maximum K value of PA is 1.51. The results of MCSDE are in good agreement with those of the FEM solution.