PSI - Issue 20

E.S. Oganyan et al. / Procedia Structural Integrity 20 (2019) 42–47

45

E.S. Oganyan et al. / Structural Integrity Procedia 00 (2019) 000–000

4

C 0,5 ln( 1 ) ψ = − −

(4)

From the above models of strain accumulation, the model described by expression (3) allows us to consider most fully the load acting on the coupler. It takes into account the load of different types and levels in the elastic and elastoplastic domain in various extent of their combination. In this generalized model given by Oganyan and Volokhov (2013), the evaluation of loading cycles to fracture is based on the choice of the residual strain limiting value in the critical element of the coupler part. In the present study, it was assumed to be 0.0020 and 0.0018. Table 1 presents the results of the calculations performed at some variants of type and magnitude combination of the loads acting on the coupler. Table 1. Estimated lifetimes of the coupler casting with various combinations of the type and level of loads acting on it. Loading mode σ -1 ∂ , MPa P 0.2 , MN P lim , MN μ N ℓ s , cycle N 1 /10 3 , cycle Δ ε p = 0,0020 Δ ε p = 0,0018 N/10 3 , cycle Т , years N/10 3 , cycle Т , years

I

40 40 40 45

2,5 2,5 2,5 2,0

4,5 4,5 4,5 4,5

0,5 0,5

10

20

410 450 570 650

20,5 25,7 32,6 37,1

535 600 780 900

26,5 34,3 44,6 51,4

6 − −

17,5

− −

III

0 0

3.2. During train haulage: in the process of train movement – accompanied by compression and stretching, impacts and jerks, as well as during acceleration and braking The coupler operation in train conditions corresponds to standard loading mode III by Standards (1996). The forces arising in this case are predominantly alternating cyclical in nature with a large number of relatively small (at the level of 50–300 kN) forces, but capable of causing fatigue damage to the coupler, as well as less frequent longitudinal forces reaching 700–1,000 kN during transient modes of running. The stresses in the coupler are in the elastic domain in this case. The values of such forces in the coupler and the nature of their variation are obtained on the basis of modeling in UM software for movement of a freight train along a virtual section of the track, including a statistically representative set of the track layout (straight track, curves, rises and descents) with the specified length. The model of a train weighing 7 thousand tons consisted of identical one-dimensional four-axle cars and a coupled group of several three-dimensional solid finite element models of the same cars in the middle of the train (fig. 2). At the same time, to determine the dependence of the forces acting on the coupler on the weight standards of the cars, the following combinations of consists were considered: of cars with the axial load of 196, 245, 294 kN and of cars weighing 80, 100, 170 tons. Then, obtained in UM distributions of forces on coupler and the results of the static calculation of its stress-strain state were transferred to Fatigue software for calculating the lifetime. Here it was determined by the number of passages of the intended sections, and this number of passages is endured by the critical area of the coupler until the initiation of macrocracks in it. Fig. 3 shows diagrams representing the result of processing by the rainflow method the records of the processes of the indicated forces. Obtained in Fatigue results of calculations for fatigue resistance lifetime are in agreement with those obtained analytically using formula (3) (see table 1). Knowing the average annual mileage of the car, you can transform the number of passages of the “intended sections” before fracture into the service life – the number of years of operation before fracture. Thus, the calculated lifetime of the coupler bar according to highlighted areas (fig. 3) with the axial load of up to 196–294 kN was 45–48 years. The lifetime can be adjusted by parameter refinement of the coupler loading, the actual distribution of forces acting on the coupler in various conditions of the coupler operation.