PSI - Issue 16

Andrii Kotliarenko et al. / Procedia Structural Integrity 16 (2019) 223–229 Andrii Kotliarenko et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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3. Experimental and analytical results

3.1. Tension and creep tests

The following mechanical properties of the material were determined according to the uniaxial tension test results: Young modulus Е , σ 0,2 , σ в , δ and ψ. The values of δ and ψ were determined by measuring dimensions of the specimens after the test. Fig. 1a shows stress-strain diagrams and 1b shows creep ’s diagram. a b

Time, s

Fig. 1. (a) Stress-strain diagrams; (b) c reep diagram at 1000°C.

3.2. Relaxation test

Stress-strain diagram of the specimen of the tests of relaxation at a temperature of +650 °C is shown in Fig. 2a. At  = 0.64% tensile stress in specimen С012 is  max = 257.4 MPa. There are two main stages of relaxation. The first is a rapid drop in stress during 2000 s, the second is a relative stabilization of stress with periodic minor fluctuations of its magnitude. a b

Fig. 2. (a) Stress- strain diagram; (b) Strain diagram at relaxation test at Т = + 650°C .

From the diagram on Fig. 2a it is seen that the stress stabilized at a value of 104 MPa and do not tend to further decrease. It should be noted that strain of the specimen C012, after reaching the value of 0.64%, do not stop after the