PSI - Issue 28

L.A. Igumnov et al. / Procedia Structural Integrity 28 (2020) 1909–1917 Author name / Structural Integrity Procedia 00 (2019) 000–000

1911

3

3. Investigation results A numerical analysis of the effect of the strain rate on the dynamic strength of two-layered metal-plastic cylindrical shells was considered on the problem of their deformation under the action of a pressure pulse caused by a blast in a center of a shell of an explosion charge (EC), which describes the pressure profile in the incident shock wave by an empirical relation (Adishchev (1983))   3 0.35 0.35 / , , 3 1 0 0.35 / , mq l at t l q p t at t l q     Both homogeneous glass-fiber-reinforced plastic shells and two-layered cylindrical shells of length L=4R and thickness h=h 1 +h 2 (an internal steel layer of thickness h 1 =0.002 m and an external glass-fiber-reinforced plastic macro-layer of thickness h 2 ) were considered. The physicomechanical characteristics of unidirectional glass-fiber reinforced plastic shells were determined from the results of quasistatic tests on ring and plane unidirectional specimens by standard techniques for identifying the corresponding stiffness and strength characteristics (Rusak (2002)). For unidirectional glass-fiber-reinforced plastic shells, the stiffness and strength characteristics F ii P , F ii C , F ij in tension, compression and shear were as follows: E 11 =55 GPa, E 22 =E 33 =9.04 GPa, ν 12 =ν 23 =0.276, ν 13 =0.4, G 12 =G 13 =5.08 GPa, G 23 =5.2 GPa, ρ=2057 kg/m 3 , F 11 P =1.5 GPa, F 11 C =0.397 GPa, F 22 P =0.0267 GPa, F 22 C =0.0719 GPa, F 33 P =0.0267 GPa, F 33 C =0.0719 GPa, F 12 =0.0357 GPa, F 23 =0.0357 GPa, F 13 =0.0357 GPa. Parameters of the differential theory of plasticity for a steel layer: E =210 GPa, ν=0.3, σ * =0.35 GPa, g=0.5 GPa, ρ =7800 kg/m 3 .    where m is weight of the charge; q =4.77*10 6 J/kg is the caloric power of the charge; l is the distance from the center of the charge to a point on the internal surface of the shell.

Table 1 – Material Constants in Regression Function

Strength, GPa

Constants

P = F

C = F

12 = F 23 = F 13

F 11

F

F

F

F

P

C

P

C

11

22

33

22

33

α β

1.5

0.397

0.0267

0.0719

0.00357

0.0146951

0.5154558

0.0080424

0.0000719

0.0178477

γ 0.086 The strain rate dependence of the strength characteristics of glass-fiber-reinforced plastics is described by function (1), the parameters of which are given in table 1 (Shokrieh (2014)), where F ii P , F ii C , F ij are the initial strength characteristics in tension, compression and shear. The typical oscillograms of circumferential strains in the central section on the external surface of undestroyed glass-fiber-reinforced plastic and metal-plastic shells loaded by an explosive charge of weight m = 23.8 g are shown on Fig. 1. A fairly good agreement between numerical calculations and experimental data is observed. The presence of the plastically deforming reinforcing steel layer leads to fast damping of vibrations in the central zone of shells and, as a result, to a considerable decrease in the circumferential strains, and thereby stimulates an increase in the load-carrying ability of the metal-plastic shells. 0.886 0.0874 0.131 1.278