PSI - Issue 71

Sudarshan Solanki et al. / Procedia Structural Integrity 71 (2025) 95–102

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5.1.1. Pure axial loading For pure axial loading (Fig. 4), the maximum strain gradient was observed along the axis of cylinder (r = 0). The strain amplitude changes from 1% to 0.25% in ~20 mm axial distance along loading direction for peak equivalent strain amplitude of 1%. However, the strain gradient along cylinder axis on outer surface (r = R) was marginally lower than that of centre-line, r = 0 (see Fig. 4(a)). The strain gradients along cylinder axis reduces with peak equivalent strain amplitudes (Fig. 4(b)). Fig. 4 (a) also shows that the peak equivalent strain amplitude occurs in the SS304LN regime (base). To compare the strain variations along radial direction at different axial locations, various axial positions have been taken. Total 8 axial positions are taken across the DMW joint as indicated in Fig. 4(c). This figure shows that strain gradient along radial direction is very small at all 8 axial locations. This is attributed due to membrane axial loading applied on uniform circular cross-section. 5.1.2. Pure torsion loading For pure torsional loading (Fig. 5), the peak equivalent strain amplitude occurs in SS304LN (base) on the outer surface (r = R) of cylinder, as depicted in Fig. 5 (a). Within this SS304LN region, the peak is taking place at fusion line axial location. For a given material region, away from dissimilar material juncture, the strain gradient is almost zero. However, at the material discontinuity junctures (SS-base to SS-weld and SS-weld to LAS-base), very steep strain gradient takes place (Fig. 5(a) and 5(b)). The strain discontinuity steps are smaller for smaller strain amplitude (Fig. 5(b)). Along radial directions, the strain varies linearly due to the pure torsional loading case. Seven different axial locations are taken for quantification of strain gradients along radial direction. The maximum values of strain gradient and absolute strain amplitude occur in the SS304LN base region (Fig. 5(c)). Maximum values of linearized strain amplitude gradient along axial and radial directions of the cylinder are given in Table 3.

(a)

(b) (c) Fig. 5. Variation of equivalent strain amplitude along (a) axial direction for different radial distances with 1% peak equivalent strain amplitude; (b) axial direction at r = R for different peak equivalent strain amplitudes and (c) radial direction with peak strain amplitude of 1%.