PSI - Issue 14

V. Srikanth et al. / Procedia Structural Integrity 14 (2019) 952–956 V. Srikanth/ Structural Integrity Procedia 00 (2018) 000–000

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The results of FEM calculations shown in Fig. 2, represents the distribution of the thermal stress components σ xx , σ yy and σ xy that are generated in a SS304L/Zr-2.5%Nb combination along the line marked in Fig. 1. It can be seen from Fig. 2(a) that σ xx reaches a maximum value of 260 MPa in SS part near the interface, while the minimum stress value of 314 MPa compressive was experienced by Zr-2.5%Nb near interface. From Fig. 2(b) it can be seen that the maximum value of σ yy acts on SS part near the interface, which was found to be 97 MPa tensile. Whereas the minimum value for σ yy on Zr-2.5%Nb side of the interface was 92 MPa compressive. Fig. 2(c) shows that maximum value of σ xy is 55 MPa at the SS304L/Zr-2.5%Nb interface. Similar simulations were also performed by introducing Ni and Ti interlayers of thickness 200 μm each between SS304L and Zr-2.5%Nb and the corresponding results are shown in Fig. 3. From Fig. 3, it can be seen that maximum value of σ xx and σ yy were found to be 243 MPa and 105 MPa, respectively in tension acting on SS part near the joint interface. Whereas the minimum value of σ xx and σ yy acting on Zr-2.5%Nb part near the joint interface were found to be 290 MPa and 55 MPa, respectively in compression. The maximum value of shear stress (σ xy ), 74 MPa, was found to act on the interface region of the joint. In both types of joints which were made with and without using interlayer materials, the SS part and Zr-2.5%Nb part experiences tensile and compressive stresses, respectively. The reason for such type of stress distribution can be explained as follows; the SS part which is having higher CTE than Zr-2.5%Nb tries to contract more on cooling by imposing compressive stresses on Zr-2.5%Nb part whereas to counteract this compressive stress, Zr-2.5%Nb imposes tensile stresses on SS part.

Figure 3: Variation of (a)σ x , (b)σ y and (c)σ xy across the interface of the joint bonded between SS 304L and Zr-2.5%Nb using Ni and Ti interlayers.

4. Conclusion The maximum and minimum values of normal stresses σ xx and σ yy were found to act on SS and Zr-2.5%Nb part, respectively near the joint interface. The maximum tensile stress σ xx acting in radial direction on SS part was found to decrease from 260 MPa to 243 MPa on introducing Ni and Ti interlayers during simulations. Whereas the minimum compressive stress acting on Zr-2.5%Nb side was found to reduce from 315 MPa to 290 MPa. Compression stress σ yy acting on Zr-2.5%Nb in axial direction also found to reduce from 92 MPa to 55 MPa. The