Determination of Actual Tensile and Fracture Characteristics of Critical Components of Industrial Plants Under Long Term Operation by SPT

Abstract

The assessment of the residual lifetime of critical components of industrial plants requires the knowledge of mechanical properties prior to operation, respecting all technological operations realized throughout the manufacture of the component, and the knowledge of mechanical properties after actual time of operation (actual mechanical properties). Small Punch (SP) test technique enables measurement of the realistic material properties at the critical locations in the component both prior and after long-term operation. The paper shows the examples of the sampling of testing material from the critical components of the industrial plants and the procedures for determination of tensile and fracture characteristics by SP tests at ambient and low temperatures. The special attention is devoted to the test specimen orientation for determination of SP fracture energy ESP.

Development and validation of small punch testing at NIST

“…Many empirical correlations between SP characteristic values and tensile properties have been published in the literature [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33], mostly for steels.…”

“…Most authors have linearly correlated yield strength (Rp02) with the SP elastic-plastic transition force (Fe), normalized by the square of the initial specimen thickness (ℎ 0 2 ) [17][18][19][20][21][22][23].…”

“…• Fe(int) (corresponding to the value fA in Fig. 12) [19], • Fh0/10,off (intersection between the test record and a straight line parallel to the initial linear portion, with an offset of h0/10 ≈ 0.05 mm) [19], • F0.1mm,off (intersection between the test record and a straight line parallel to the initial linear portion, with an offset of 0.1 mm) [18,20], • Fept (force corresponding to the maximum curvature in the test record) [23], and • Fe1.5 (force corresponding to a ratio between area below and above the test record equal to 1.5) [23].…”

The Effect of Stiffness of the Loading System on Determination of Tensile Characteristics From the Results of Small Punch Tests

“…Empirical correlations were expressed as the dependences of yield stress on parameter F e /(h 0 ) 2 [15][16][17], where F e is the load characterizing the transition from linearity to the stage associated with the spread of the yield zone through the specimen thickness (see Fig. 1), because it was proved that the parameter F e /(h 0 ) 2 eliminated any difference in disc specimen thicknesses on load F e [1,18]. expressed as the dependences of tensile strength on parameter F m /(u m .…”

“…In this case the parameter F m /(u m . h 0 ) is used to eliminate any differences in disc specimen thicknesses on F m and u m [1,18].…”