PSI - Issue 4

Author name / Structural Integrity Procedia 00 (2017) 000 – 000

4

Zoran Odanovic / Procedia Structural Integrity 4 (2017) 56–63

59

Table 2. Results of material tensile properties testing

Yield strength Re (MPa)

Tensile strength Rm (MPa)

Elongation A5 (%)

Contraction Z (%)

Test specimens position

Longitudinal Transverse

235 233

534 523

30.70 16.25

51.58 17.86

Specified by standard EN 13261 for longitudinal test specimens

min 320

550 - 650

min 22

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Table 3. Impact energy results of the steel axle

Test specimens position

Test temperature T(°C)

Mean value KU 5/300 (J)

Standard EN 13261 KU 5/300 (J)

Longitudinal Transverse

+ 20 + 20

21.8

min. 30 J min. 25 J

11.33

Preparation of test pieces for the axle hardness testing was performed at the axle longitudinal cross-section. Hardness was measured at three cross-sections: on the axle surface, at mid-radius and in the center of the axle. At each location, hardness was measured at three measuring points. Test results obtained by the Brinell method are presented in Table 4. The highest values of hardness are on the axle surface and the lowest in the center. Measured values at each axle cross section were not significantly different.

Table 4. Measured material hardness through the cross section from surface to center of the axle Measured hardness (HBW) Mean value (HBW)

S: 146 – 148 – 149 M: 145 – 145 – 144 C: 143 – 145 - 143

145.3

Comment: S - Surface, M - Mid-radius, C - Centre In order to anticipate the ability of the tested steel to resist crack propagation, the fracture mechanics parameter - plane strain fracture toughness K Ic was estimated from the measured values of the yield strength and impact energy data. Estimation was based on the Barsom-Rolfe correlation model presented in literature Tauscher (1981): K Ic 2 =5 *CVN *  ys - 0.25 *  ys 2 (1) Where CVN represents Charpy V-notch impact energy in units [ft lbf],  ys represents yield strength in units [ksi], and K Ic was in units [ksi.in 0.5 ]. Equation (1) recalculated in SI units is as follows: K Ic 2 =0.619 * KV * R e - 0.00578 * R e 2 (2) Where KV is Charpy V-notch impact test data in units [J], Re is yield strength in units [MPa], and K Ic is in units [MPa.m 0.5 ]. Validity of Eq. (2) was checked for the similar steel C 45 in normalised and tempered condition, based on the data from the literature http://toscelikniksic.me (2016) and William (1973). For the input data for impact energy of KV=18 J and the yield strength of R e =275 MPa, calculated value for the plane strain fracture toughness was K Ic = 51.25 MPa.m 0.5 , while measured value for the same steel from literature William (1973), was K Ic =50 MPa.m 0.5 . These results confirmed the validity of Eq. (2). In performed investigation impact energy was measured on the samples with U grove (Table 3), and the relation between impact energies KV 2/300 in [J] and KU 2/300 in [J], was established as KV/KU = 0.44. Obtained relation is