PSI - Issue 60

Ganesh Nigudage et al. / Procedia Structural Integrity 60 (2024) 678–689 Ganesh Nigudage /Structural Integrity Procedia 00 (2023) 000 – 000

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testing and details of this is not a part of this paper), using slow speed cutting machine. The slightly oversized machined samples were polished to 0.5mm thickness using emery paper with grit size of 400 followed by fine grinding using 1000 grit emery paper. Table 1. Tensile properties of the Cr-Mo-V RPV steel in different condition and indicated test temperature.

Yield strength

Tensile strength

Total elongation

Reduction in area

Test temperature

( o C)

(MPa)

(MPa)

(%)

(%)

As-fabricated base

25

563 622 459 532 590 640 481 534

671 762 558 655 699 777 579 650

17 20 19 23 17 20 19 24

75 73 70 69 74 71 71 72

-60

As-fabricated weld

25

-60

Thermal base

25

-60

Thermal weld

25

-60

3. Analysis of SP test 3.1. Correlating uniaxial and SP properties

Characteristic values are identified from load-displacement plot and used to establish empirical correlations between the material properties to determine the yield stress, σ y and the ultimate tensile strength, σ UTS and total elongation. 3.1.1. Characteristic small punch forces used to correlate with yield strength The elastic plastic transition force (F e ) is used to correlate with yield strength. The elastic-plastic transition point is not as well defined since yielding occurs during the test successively in different areas of the specimen. The different approaches used to define F e are as follows- 1. Elastic-Plastic transition force (F e ) – It is the force at which there is transition from linearity to stage associated with spread of yield zone through specimen thickness or plastic bending stage. It is found by establishing a bilinear function from origin through points A and B (shown in Fig.4) on load displacement curve as follows ( ) = { × , 0 ≤ < ( − ) ( − ) × ( − )+ , ≤ ≤ (1) The variables f A , f B , and v A are obtained by minimizing the error: ⅇ = ∫ [ ( ) − ( )] 2 ⅆ 0 (2) In above equations, is taken as the original thickness of the specimen, i.e. , = h 0 = 0.5 mm and =0.25, f( )=force corresponding to displacement of 0.25mm. Here, F(v) is test force value. The corresponding yield displacement is v e = and the experimental transition force F e is obtained from the experimental test record as F e