PSI - Issue 20

N.A. Makhutov et al. / Procedia Structural Integrity 20 (2019) 63–74 N.A. Makhutov and V.V. Zatsarinnyy / Structural Integrity Procedia 00 (2019) 000–000

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т � � т �� т � � � � � � � �� в � � в �� в � � � � � � � �� t , σ

(2)

(3)

where σ т , σ в and σ т

в t are yield stress and ultimate strength limits at room temperature Т

0 = 293 К and temperature

Т, where σ т t β т and β в are material characteristics. When the test temperature is reduced to the Т* critical temperature according to the A.F. Ioffe scheme the limits of yield σ т t , strength σ в t and true rupture strength S k t become equal; consequently, в � т ��� � � � в ��� � � � т (4) where S k is the rupture strength at room temperature. Temperature Т* is defined by the condition σ т t = σ T т* =S k at Т= Т*: ∗ � � � � � � ��� � � � т ����� т � �� (5) According to the integrated experimental data Makhutov (2008) the value ß т diminishes with the increase of yield stress limit (Fig. 3). t , σ в

Fig. 3. The dependence of the coefficient ßт on the yield limit.

Plasticity also depends on temperature changes – this property declines with the decrease in temperature. This dependence was approximated by Makhutov (2008) expression: where ψ k t , ψ k is the relative narrowing of cross sectional area at the temperatures Т and Т 0 ; σ T* – the yield stress limit at the temperature Т*; n ψ – the material characteristic.