PSI - Issue 13

T.D. Joy et al. / Procedia Structural Integrity 13 (2018) 328–333

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T. D. Joy et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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A practical example of Y-strainer is considered so as to illustrate the crack growth under the influence of temperature. Y-strainers are generally made of materials which can withstand very high pressures and temperatures which can raise up to 810K. One such material is low alloy chromium molybdenum steel which is used in cases of high temperatures, see Klueh (1982), Dobrzanski (2004). This type of strainers generally termed as Y-type is used to remove impurities in fluids, see Palcer (1953). Those can be solids that are in circulating fluids or liquids where cleaning process is not required frequently. For understanding the influence of temperature in the model, two different types of simulations were conducted in A DAPCRACK 3D. For the first simulation, a model was created only with the pressure on the inner surface and the temperature boundary conditions were not taken into account. The model for the second simulation was created with both pressure and temperature boundary conditions. Fig. 3 a shows the inner surface of the model where both the pressure and the inner temperature are introduced. In addition to that the outer surface of the model also has a temperature boundary condition. Simulations were performed by introducing cracks at two different places as shown in Fig. 4 a. Both the cracks were introduced from the inner surface. Due to casting defects there can be failures in a Y-strainer. The crack marked as 1 is such a crack and the one marked as 2 is the position where the principal stress is the highest.

Table 1. Material data used for the simulation. Conductivity Density

Young’s Modulus 210000 N/mm 2

Poisson’s Ratio

Expansion

Specific Heat 4.6 x 10 8 mm 2 /s 2 K

Inside Pressure

Inside Temperature

Outside Temperature

38.5 t mm/s 3 K

7.85E -9 t/mm 3

0.3

1.18E-005K -1

6.3 N/mm 2

393.15 K

323.15K

The pressure applied is 6.3N/mm 2 , inner temperature is 393.15K and the outer is 323.15K. Other material data and simulation parameters that are used for the simulations are presented in Table 1. The elements used for simulating the model with temperature boundary conditions are linear heat transfer tetrahedral elements – DC3D4. Crack growth simulation in A DAPCRACK 3D with temperature boundary conditions starts with a pre-simulation The results obtained from this pre-simulation are then taken over as a boundary condition for the following crack growth simulations. The global model is created with C3D10 elements, but as explained earlier ABAQUS TM calculates the nodal temperature through interpolation Fig. 3 b shows the temperature distribution in the Y-strainer obtained during this pre-simulation.

Fig. 3. (a) Inner surface of the model; (b) temperature distribution in the model.

Since the mechanical loading and the temperature boundary conditions are applied on the model at the same time it is considered as two loadings acting on the model of the Y-strainer proportional to each other. Thus the resulting stress will be a combination of the the maximum stress caused because of the mechanical loading and the maximum stress caused because of the temperature distribution inside the model. The crack growth obtained after simulating both the models are displayed in Fig. 4 b and Fig. 4 c. Crack fronts from only selected simulation steps are displayed.