PSI - Issue 4

Zoran Odanovic / Procedia Structural Integrity 4 (2017) 56–63 Author name / Structural Integrity Procedia 00 (2017) 000 – 000

58

3

Zona ispitivanja Axle journal and dimensions

Testing zone

Zona loma Fracture location

Fig. 3. Details of the tested railway axle, geometry with the dimensions in [mm], fracture location and tested zone

The other available data has shown that the axle was designed and manufactured 35 years ago, according to the requirements of the national standard SRPS P.F2.310:1968 (now replaced with similar standard SRPS EN 13261:2010). The investigated axle was manufactured as solid and coated axle. Available user’s data show that similar axle fractures were not evidenced before and the railway axle is regularly periodically inspected and overhauled.

3.2. Chemical composition

Ispitani radijus A

Ispitani radijus B

Chemical composition of the axle material was analyzed by the OES method. Analysis was done on the plate samples prepared according to the standard EN 13261 procedures. Results are presented in Table 1.

Table 1. Chemical composition of the axle material (in mass. %)

Chemical element

C

Si

S

P

Mn

Ni

Cr

Mo

V

Ti

W

Al

Fe

Tested sample

0.441 0.260 0.005 0.009 0.640 0.034 0.097 0.012 <0.003 <0.003 0.020 0.069 rest

Specified according to EN 13261:2010 standard

max. 0.40

max. 0.50

max. 0.020

max. 0.020

max. 1.20

max. 0.30

max. 0.30

max. 0.08

max. 0.06

-

-

-

rest

Requirements for chemical composition of steels for rail vehicles axles specified by standard EN 13261:2010 and national standard SRPS EN 13261:2010, are also presented in Table 1. Comparison of the results leads to the conclusion that chemical composition of the investigated axle material is in accordance with the standard requirements. Only the carbon content falls outside the specified limits.

3.3. Mechanical properties

Samples for the testing of mechanical properties were cut from the wheel seat of the axle next to the fracture location as presented in Fig. 3. Results for the tensile properties in longitudinal and transverse direction are presented in Table 2. A comparison between the tensile properties in longitudinal direction, yield strength - Re and tensile strength - Rm, and the requirements specified by standard EN 13261, has shown that the obtained values are substantially below the recommended standard values. The results from the transverse direction tests are also unsatisfying. Only the results of the elongation - A5 for longitudinal direction meet the corresponding standard requirements. Extreme difference for the elongation - A5 and contraction – Z values between the longitudinal and transverse direction are evidenced. Deviation of yield stress from a specified standard value is substantially higher compared to tensile strength deviation. Impact energy test results are given in Table 3. The results indicate that the axle material impact energy in longitudinal direction is approximately 30% lower than the standard values. In addition, impact energy in transverse direction is approximately 45% lower compared to the standard values.