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Calculation of the temperature field in nominal regime and corresponding stress field.
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Calculation of stress and deformation fields of the turbine for crack lengths (20–75 mm).
•
Analysis of the influence of crack length on corresponding stress field as well as on the
stress intensity factor.
For temperature field calculation, the 2-D grid consisted of 4400 8-node elements.
Generated grid comprised the space of the turbine housing and insulation.
In Fig. 6 the stress field induced by temperature and internal pressure is shown. The
effective stress for 2-D turbine model without insulation, for crack length 30 mm, is
shown in Fig. 7.
a)
b)
Figure 6. a) 2D model for calculation of the temperature field;
b) Temperature field of the turbine housing and insulation
Figure 8 shows the relationship between stress intensity factor
K
I
and crack length. It
can be seen from Fig. 8 that by increasing crack depth from 20 mm to 40 mm, the stress
intensity factor increases 30%. With crack length increase of over 50 mm, the stress
intensity factor increases more rapidly.
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