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论文题目： Study of high-speed-impact-induced conoidal fracture of Ti alloy layer in composite armor plate composed of Ti- and Al-alloy layers

发表时间：Available online 27 August 2020

刊源：Defence Technology, 2020. [ 点击下载PDF ]

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Crack propagation are shown in Fig. 10. In zone I, the distance between the tip of the main cracks and the target surface was approximately 4 mm, with sub-cracks growing perpendicular to the main crack. The plate underwent substantial plastic deformation upon penetration by the projectile, and the stress triaxiality in the shear region was between -2.0 and -1.0. From Fig. 4, it can be seen that the target materialwas in the shear fracture mode. During the penetration process, the shear stress dominate regions gradually decrease, at the same time gather below the projectile. In contrast, the red part, i.e., the area with triaxiality greater than 0, increased significantly from 18 μs; from 18 μs to 100 μs, the triaxiality in this zone was between 0 and 0.5 in this period, corresponding to the mixed mode of shear and ductile fracture. Further, from 22 μs to 40 μs, in zone III, cracks initiated and expanded gradually; the triaxiality was relatively large, i.e., between 1.0 and 1.9, indicating that the ductile fracture mode was dominant. Notably, the period in which cracks exist in zone III is dependent on the other two zones, and this period is within the period in which zone II exists.

Fig.10. Time-history analysis of stress triaxiality and timeline of crack propagation.

Because the adiabatic shear band was closely related to the loading condition, the numerical simulation method was used for the in-depth study of the target stress state. The shear stress nephogram and the maximum principal stress nephogram are shown in Fig. 12. From 4 μs to 6 μs, the shear stress remained concentrated in zone I, and the red and blue areas in the figure reflected the shear stress in the opposite directions. From Fig. 12 (a) and (c), we can see that the maximum value was about 0.9 GPa. Moreover, compared with the shear stress, the principal stress in this area was relatively dispersed, with the maximum value of about 0.2 GPa (Fig. 12(b) and (d)). Furthermore, the formation of cracks in zone I was mainly due to the shear stress.

Fig.12. Shear stress nephogram and the maximum principal stress nephogram of zone I: (a) shear stress nephogram at 4 ms; (b) maximum principal stress nephogram at 4 ms; (c) shear stress nephogram at 6 ms; and (d) maximum principal stress nephogram at 6 ms.