PSI - Issue 40

Vladlen Nazarov et al. / Procedia Structural Integrity 40 (2022) 325–333 Vladlen Nazarov / Structural Integrity Procedia 00 (2022) 000 – 000

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2

hydrogen with titanium is chemically reversible. Hydrogen is released from the titanium alloy when the dioxide film on its surface is destroyed at heated in a vacuum.

Nomenclature y 

material yield stress material tensile strength

s 

t

creep time tensile stress tangential stress elongation strain





 

shear strain 1 2 3 , ,    principal stresses 1 2 3 , ,       principal strain rates max  maximum normal stress max  maximum tangential stress

To date, the number of papers devoted to the experimental study of the creep properties for titanium alloys is limited. A significant part of such experimental data has obtained at different times by one of the authors of this review. The purpose of the work is to collect in one place experimental data obtained for various ti tanium alloys. The results of these experimental studies should be considered as separate series that are not related to each other. 2. Uniaxial tension at normal temperature The strength properties of titanium alloys increase and the plastic properties decrease with an increase in the content of impurities. Oxygen and nitrogen increase the tensile strength and the break creep stress. Titanium alloys with the low hydrogen content (less than 0.002%) retain high ductility up to the liquid helium temperature. Titanium alloys with low hydrogen content are characterized by large strains, which mean that the deformation from a certain time of the deformation process turns out to be more than 7% and logarithmic strain should be used to describe the deformation process. From the comparison of experimental diagrams obtained with uniaxial tension of two types of rectangular plates, the influence of the central circular hole on the yield strength and tensile strength of the titanium alloy VT1 – 0 (Fig. 1−3) , which exhibits developed plastic properties Nazarov et al. (2016), has been established. The central circular hole reduces the tensile strength by 10% and increases the yield strength by 25%.

a

b

a

b

Fig. 1. Plane specimens Nazarov et al. (2016) from the VT1−0 (English equivalent is Grade−2 ) titanium alloy: solid (a) and with a central circular hole (b). Dimensions: thickness is 0.5 mm, working length is 100 mm, width is 40 mm, circular hole diameter is 20 mm. The elongation was measured by the position of the gripping parts of the BISS P Ltd test machine. The rate of change in the position of the gripping parts was 2 mm/s.

Fig. 2. Shape change at the fracture Nazarov et al. (2016) of the solid specimen (a) and the specimen with a central circular hole (b). Features of the occurrence of main cracks: for the solid specimen (elongation is 33 mm) from the center (a) and for the specimen with a stress concentrator (elongation is 6.5 mm) from the hole boundary (b).