PSI - Issue 20

V.S. Kossov et al. / Procedia Structural Integrity 20 (2019) 212–217

215

V.S. Kossov et al. / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 1. The design of the double-layer impact protection unit of the 2 ТЭ 25 К ( А ) diesel locomotive cab.

In the practical solution, the system of equations is reduced to a linearized form of relatively small increments superimposed on the current equilibrium state of a dynamic system. Linearized equations in increments are represented as

M Д 

.

(1)

( ( ) ( )) + + + K G у

= R у Д Д

u

c

u

q

It was also taken into account that with the strain rate increase, the yield strength of steels increases both under compression and under tension, and this effect increases significantly with the static yield strength decrease. So, for carbon steels of type Ст 3 ( σ y = 250…280 MPa) at strain rates up to ε  = (0.44…0.67)·10 3 s -1 the ratio of yield strengths under dynamic and static loading is 2.3…2.4 by Krasyukov et al. (2006), Oganyan and Volohov (2013). Fig. 3 presents the results of tensile tests of round standard samples of steels St37 (Institute of Metallurgy and Metal Science of Germany), Ст 3 GOST 380 and 09 Г 2 GOST 19281 (JSC "VNIKTI"). The obtained data show that at strain rates ε  = 10 -5 …10 -2 s -1 , the yield strength of the indicated steel grades increases by 16…19% ("operational impacts") for "absorbed" impacts, by 25…27% (crashes) for "severe" impacts. At loading rates less than 10 -5 s -1 , the yield strength of steels Ст 3 and 09 Г 2 is slightly dependent on the strain rate. The stress-strain state of the driver’s cab design under study during a collision with an obstacle is defined as the result of the numerical solution of equations (2) describing the dynamic behavior of its nonstationary finite element model.