PSI - Issue 36

V. Kharchenko et al. / Procedia Structural Integrity 36 (2022) 277–283 A.V. Sereda et al. / Structural Integrity Procedia 00 (2021) 000 – 000

281

5

n

n

n

     = = = = =       − − n i n i p p i i i p i p i i i i h n h h F n h F 1 2 1 2 1 1 1 max

max

i

a

=

(5)

,

where n is the number of loading cycles; hpi is the residual indentation depth after unloading Fma x і of ith cycle; Fmax i is the maximum test loading of іth cycle.

3. Results of Numerical Investigations and Their Analysis Table 1 lists the objects of investigation and their chemical composition.

Table 1 Chemical Composition of Steels Grade Mass, % С Mn

Cr

Ni

Mo

Cu

S

P

Si

V

Al

B

28GKhNMP

0.28 0.13 0.19 0.30

0.86 0.63 1.20

0.48 1.60 0.05 1.50

0.90 2.23 0.06 0.80

0.37 0.47

0.25

0.002 0.008 0.004 0.015

0.017 0.013 0.018

0.24 1.19 0.29 0.70

-

0.05

- - -

30Kh2СN2MFА

0.007

0.20

- - -

20GR

-

0.05

- -

28GRA

1.7

0.50

-

0.03

0.004

Table 2 presents the strength characteristics obtained from uniaxial tensile tests and Brinell HBW tests for high strength sheet steels in the longitudinal and transverse directions (relative to the rolling). The mechanical characteristics in Table were obtained by averaging the results: not less than three tensile tests and ten hardness measurements in two directions. The strength characteristics for high-strength steels were experimentally obtained via instrumented indentation along and across the sheet rolling as average values from the results of not less than 10 tests. The relations found in the Russian manuscripts (Chukin et al. (2016)) were used to assess the accuracy in the strength characteristics determination via instrumented indentation method: 0,2 p R = 8.62·HBW0.812 and m R = 3.61·HBW -154.9, which are used for express methods of strength determination for high-strength steels using the Brinell method. Table 2 lists the results of these measurements. Figure 4 illustrates the dependencies of m R obtained from the uniaxial tensile tests (ordinate axis) on the values of strength limit determined via calculation by and hardness tests by (abscise axis). Figure 5 shows the dependencies of 0,2 p R obtained from uniaxial tensile testing (ordinate axis) on the yield limit values determined via calculations using and hardness tests by (abscise axis). Figures 4 and 5 have dash-dotted lines showing 5% limits of deviations from values m R and R p0.2 in tension. Table 2 Strength Characteristics from Tensile Testing and Brinell HBW Hardness of High-Strength Sheet Steels in Longitudinal and Transverse Directions Steel Grades and Directions of the Mechanical Characteristics Determination Brinell Hardness НВ W , MPa Uniaxial Tension Yield Limit 0,2 p R , MPa Strength Limit m R , MPa 28GKhMR Direction ОX 497 1393 1706 Direction ОY 499 1381 1680 30Kh2SN2MFA Direction ОX 503 1324 1691