PSI - Issue 71

Shreebanta Kumar Jena et al. / Procedia Structural Integrity 71 (2025) 103–110

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Now, this mechanistic approach is extended for tube when subjected to remotely combined applied axial-torsion loading. For the case of remote in-phase axial-torsion condition, the remote axial and torsional strains reach their

maximum values at the same instant (refer time instant t=a in Fig. 6(a)). Thus, strain peaking due to remote axial (alone) would tend to get established at =0°, whereas, strain peaking due to remote torsion (alone) would occur at =45° location as shown by Jena et al. (2024, 2025). As these two individual peak strain locations occur simultaneously, it results in interaction of individual peak strain fields. The combined effect of this interaction would generate resultant strain peaking somewhere between = 0° and =45° (see Fig. 6(a))). The location of this peaking does not change with time as remote axial and torsional strain vary. Hence, the peak strain location remains fixed w.r.t. time for in-phase axial-torsion cycling. This interaction of individual strain fields results in higher equivalent strain amplitude as compared to individual remote axial/ individual remote torsional strains. For 90 ° out-of-phase condition, the time variations of remotely applied axial and torsional strains are such that if one of these attains its maximum/ minimum value at a time instant (t=a or t=c in Fig. 6(b)), the other would be zero at the same time instant. Due to this variation, the remote

Fig. 5. Schematic of infinite membrane structure with central circular hole subjected to remote uniform axial traction/ pure shear

axial maximum value (t=c, when torsional strain is zero) results in stress/ strain peaking at =0° location, whereas, the time instant corresponding to maximum torsional strain (t=a, when axial strain is zero), results in strain peaking at =45° location. As the localized strain peaking takes place at different locations for different time instants, therefore, the localized peak strain location keeps shifting during the remote cycling.

(a)