PSI - Issue 60

Shreebanta Kumar Jena et al. / Procedia Structural Integrity 60 (2024) 115–122 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

119

5

equivalent strain amplitudes on test fatigue life under remote pure axial conditions Jena et al. (2023) For a given peak equivalent strain amplitude ( ̅ ) ,these figures clearly show that test fatigue life increases with decrease in hole size (or increase in strain gradient) for both remote axial and remote torsional conditions. Further, for a given hole size, the fatigue life reduces with increase in peak equivalent strain amplitude. Thus, the individual effect of strain gradient (in terms of hole sizes) and peak equivalent strain amplitude is evident in Fig. 3 and Fig. 4 for both pure axial and pure torsion remote strain controlled conditions. This test outcome needs to be further substantiated with large numbers of pure torsional test data. 3.2. Measurement of localized strains The localized and remote strain field information which play an important role in fatigue life assessment as well as quantifying the extent of strain gradient present ahead of the notch has been captured using strain gauge and DIC technique. The measurement process involves mounting the strain gauge on the notched tube specimen, painting the test specimen with white and black color to make speckle pattern which in turn used to capture the strain field using DIC system. strain amplitudes on test fatigue life under remote pure torsional conditions (present test outcomes)

(a) (c) Fig. 5. Typical steps for (a) strain gauge mounting (b)DIC speckle application on outer surface of tube for localized strain measurement (c) remote strain control using biaxial extensometer (b)

Fig. 6. Variation of shear strain amplitude from the hole tip along = 0° line in the circumference of the tube.