PSI - Issue 46

Gaurav Singh et al. / Procedia Structural Integrity 46 (2023) 149–154

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Gaurav Singh et al. / Structural Integrity Procedia 00 (2021) 000–000

reduce the sample diameter from 21 mm to 16.2 mm. We have used Zr-4 alloy as the billet material with an Elastic Modulus of 99 GPa and Poisson’s ratio of 0.37. A rotation of 10 o was given after each bite, and a rotation of 180o after each pass was maintained across passes. Object type was elastic-plastic (Assumed strain brick mesh). Define primitive was chosen as the diameter of 21 mm and length was 500 mm. The brick mesh was used in this simulation and with a seed size of 0.5 mm. A contact condition was created where a shear friction coefficient value of 0.15 was assigned to the contact surface of billet and die. Lagrangian incremental criteria were taken in the simulation control module, and deformation mode 0.2 was assigned to the sub-stepping control for max polygon length.

Fig. 3. Cross-sectional diameter after each reduction (from 0% to 40%) of Zr-4 alloy.

Table 1: Example of 5 operations with initial Die Distance (Cross section value) of 18.4 mm

Operation

21x21

21x20

20x19

19x18.2

18.2x17.4

17.4x16.2

1.665

1.665

1.665

1.665

1.665

1.665

Axial feed per bite Radial feed per bite Cross section thickness

0

0

0

0

0

0

18.4

17.4

16.4

15.6

14.8

13.6

10

10

10

10

10

10

Rotation per bite Rotation per pass

180

180

180

180

180

180

2.4 Post-Processing Parameters The simulated samples with a diameter of 16.2 mm achieved upon processing are subjected to heat-treatment with a new operation in the dashboard. The dies are also removed in this step to measure the residual stress of the samples after no external force is applied. After completion of the simulation module with swaged samples, it was post processed using the Deform3D post-processing module. The samples are observed after different operations to ensure quality and desirable outcomes, as shown in Fig. 3. The samples are then sliced to the center for uniform results and 20 points are plotted using point tracking on a cross-sectional face to measure residual stress across these points. 3. Results Prediction and control of residual stresses and stress concentration in the materials are essential for understanding the components' fracture toughness and fatigue life. Residual stresses in the workpiece are periodically introduced during various thermo-mechanical forming processes. The relative effective stress, also termed residual stress, was plotted against the cross-sectional plane of the sample. A total of 20 reference points were taken to plot the residual stress graph. It was observed that residual stress at the surface was negative, meaning compressive, and it reached maxima around the center with a positive value. The slope turns negative, and drops to zero, and then attains negative values on the surface. The graphs are plotted for each die angle at two different feed rates of 1.25 m/min and 2 m/min, as shown in Fig. 4 (a and b).