Determination of the metal toughness components in impact-bending test

A method for separating the work of impact into two parts - the work of the crack nucleation and that of crack growth - which consists in testing two samples with the same stress concentrators and different cross-sectional dimensions at the notch site is developed. It is assumed that the work of crack nucleation is proportional to the width of the sample face on which the crack originates and the specific energy of crack formation, whereas the work of the crack growth is proportional to the length of crack development and the specific crack growth energy. In case of the sample fracture upon testing, the crack growth length is assumed equal to the sample width. Data on the work of fracture of two samples and their geometrical dimensions at the site of the notch are used to form a system of two linear equations in two unknowns, i.e., the specific energy of crack formation and specific energy of crack growth. The determined specific energy values are then used to calculate the work of crack nucleation and work of crack growth. The use of the analytical method improves the accuracy compared to graphical - extrapolative procedures. The novelty of the method consists in using one and the same form of the notch in test samples, thus providing the same conditions of the stress-strain state for crack nucleation and growth. Moreover, specimens with different cross-section dimensions are used to eliminate the scale effects. Since the specific energy of the crack nu-cleation and specific energy of the crack growth are independent of the scale factor, they are determined only by the properties of the metal. Introduction the specific energy of crack formation and growth makes possible to assign a specific physical meaning to the fracture energy.

1. Otani M. Study of sensitivity of welded joints to cut at dynamic tests of double strike / J. Railway Engineering Research. 1957. Vol. 14. N 11. P. 503 – 529.

2. Pashkov Yu. I., Ivanov M. A. To the question of evaluation of crack resistance of pipes impact strength and the sample DWTT / Vestnik YuUrGU. Ser. Metallurg. 2014. Vol. 14. N 4. P. 52 – 58 [in Russian].

3. Livshits L. S., Rakhmanov A. S. On determination of impact strength at low temperatures and the tendency of the metal to the birth and development of cracks / Zavod. Lab. 1953. Vol. 19. N 2. P. 51 – 54 [in Russian].

4. USSR Inventor’s Certificate 1559267SSSR. The method of determining the toughness of the material / L. S. Livshits, A. S. Rakhmanov // Publ. 23.04.90. Byull. N 15.

5. Bakshi O. A., Monosikov A. N., Kukin A. G. Method of determining components of toughness / Zavod. Lab. 1969. Vol. 35. N 5. P. 615 – 619 [in Russian].

6. Drozdovskii B. A. On the application of static bending notched specimen for the quantitative evaluation of the crystallinity on fracture of steel / Zavod. Lab. 1946. Vol. 12. N 4. P. 489 – 499 [in Russian].

7. Gulyaev A. P. Pure steel. — Moscow: Metallurgiya, 1975. — 194 p. [in Russian].

8. RF Pat. 2621373. The method of determining the components of the toughness of the metal at test for impact strength / Maksimov A. B. // Publ. 02.06.2017. Byull. N 16.