Influence of impact duration on fracture efficiency in rocks and on plastic deformation of metals

The proposed composite design piston ensures longer duration of unit blow as compared with the same mass and energy piston of one-piece construction. The blow efficiency estimation method for the contact fracture of rocks and for the local plastic deformation of metals consists in comparison of the blow energy with the work spent for making an indent of the same depth as in blowing but in the quasi-static conditions. The impact testing of plates made of sandstone ( sсж = 82–112 MPa), aluminum alloy (27 HB) and commercial copper (40 HB) shows that the piston of the composite design improves the indenter penetration depth in the test materials by 12.5–13%, 10% and 7–11%, respectively, at the reduction in the blow energy required to fracture sandstone by 9–10%, and enhances the blow efficiency by 36% in sandstone and by 25–30% in the metals. From the shapes of the oscillograms, it is concluded that the composite design piston inflicts two blows—one blow is delivered to rock (metal) by the piston body, the second blow is delivered by the inserter to the piston body bottom and, then, the impact momentum is transferred to rock (metal). The time of the joint impact effect of the two blows exceeds the duration of the blow inflicted by the one-piece construction piston of the same mass. To sum up, at the impact force sufficient for initiation of fractures, the increase in the blow duration leads to the improved efficiency of the contact and volumetric fracture of rocks and to the increased mass of deformed metal and higher energy spent to plastic deformation of metals.

Bolobov V. I., Plashchinsky V. A. Influence of impact duration on fracture efficiency in rocks and on plastic deformation of metals. MIAB. Mining Inf. Anal. Bull. 2022;(3):78-96. [In Russ]. DOI: 10.25018/0236_1493_2022_3_0_78.

The study was carried out under governmental sponsorship in the sphere of scientific work in 2021, Grant No. FSRW-2020-0014.

V.I. Bolobov¹, Dr. Sci. (Eng.), Professor, e-mail: boloboff@mail.ru,
V.A. Plaschinsky¹, Graduate Student,
¹ Saint-Petersburg Mining University, 199106, Saint-Petersburg, Russia.

V.I. Bolobov, e-mail: boloboff@mail.ru.

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