PSI - Issue 28

V.V. Balandin et al. / Procedia Structural Integrity 28 (2020) 1802–1807 V.V. Balandin et al. / Structural Integrity Procedia 00 (2020) 000–000

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- high specific strength, corrosion resistance in many corrosive environments, non-magnetic, good heat resistance at operating temperatures up to 500–600 0 C. The paper presents the results of a study of the dynamic properties of titanium alloy 3M under tension, carried out using the Kolsky method, as well as the results of determining the spall strength obtained in a plane-wave shock experiment using a VISAR laser interferometer.

2. Tensile Strength Experiments

For dynamic tests at the Research Institute of Mechanics of the , an experimental setup (Bragov et al. (2014)) is used, which implements the Kolsky method (split Hopkinson tensile bar method). This setup includes a pneumatic loading device (20 mm caliber gas gun) with a control system, a complex of measuring and recording equipment and replaceable sets of split Hopkinson bars with a diameter of 20 mm for the production of tests under various types of stress-strain state. The loading of the sample with a tensile wave is carried out according to the scheme proposed by T. Nicholas (Nicholas (1981)). The test specimens (Fig. 1a) had a cylindrical working part 5 mm in diameter and 10 mm in length. The samples had threaded heads for fastening in measuring bars. A one-dimensional compression pulse is excited in the first measuring bar by the impact of the striker. This impulse passes freely through the split ring with a high yield strength and the sample into the second rod without causing plastic deformation in the sample. The compression pulse is reflected from the free end of the second bar by a tensile wave, which loads the sample (Fig. 1b).

Fig. 1. (a) sample after testing; (b) - wave pattern in measuring bars using the Nicholas scheme.

Experiments using a split Hopkinson bar were carried out in the range of strain rates 700 - 1500 s − 1 . In this experiments, dynamic deformation diagrams were obtained, from which the yield point σ 0 . 2 and the ultimate strength were determined. Fig. 2 shows diagrams of deformation of a titanium alloy at various rates of deformation. It is clearly seen that this alloy practically does not undergo hardening with increasing deformation. The yield stress of the material under study increases from 700 MPa to 800 MPa with an increase in the deformation rate from 700 to 1500 s − 1 (Fig. 3a). This value is 1.5 times higher than the value of the yield point (490 MPa) obtained during static tests. The tensile strength also slightly increases from 800 to 900 MPa with an increase in the deformation rate and is also higher than static values (540-785 MPa) (Fig. 3b).