PSI - Issue 14

Ritu. J. Singh et al. / Procedia Structural Integrity 14 (2019) 549–555 Ritu .J.Singh / Structural Integrity Procedia 00 (2018) 000–000

553

5

a

b

200 250 300 350 400 450 500 550 600 650 700 750 800 850

200 250 300 350 400 450 500 550 600 650 700

pw pw1-1 pw1-2 pw1-4 pw1-6 pw1-7

elastic pw1-1 pw1-2 pw1-4 pw1-6

Hoop stress (MPa)

Hoop Stress, MPa

Isotropic material model

Anisotropic material model

0

20

40

60

80

100

0

20

40

60

80

100

Distance from inner surface (%)

Distance from inner surface, %

0

0

-50

-50

-100

-100

-150

-150

-200

-200

pw pw1-1 pw1-2 pw1-4 pw1-6 pw-1-7

elastic pw1-1 pw1-2 pw1-4 pw1-6

-250 Radial Stress, MPa

-250 Radial Stress (MPa)

-300

-300

Isotropic material model

Anisotropic material model

-350

-350

0

20

40

60

80

100

0

20

40

60

80

100

Distance from inner surface (%)

Distance from inner surface, %

Fig. 4. Hoop and Radial Stress distribution for (a) isotropic (b) anisotropic material properties.

stress distribution that as the pressure increase, the elasto-plastic boundary moves towards the outer surface. The elasto-plastic boundary can be interpreted from equivalent plastic strain output or from the change in slope of hoop or von mises stresses. Radial stress at inner surface is same as the applied internal pressure. The radial stress at the outer surface is zero as no external pressure is applied. The trend of stress distribution in anisotropic case is similar to the isotropic case, however significant difference are

1.5

1.0

0.5

0.0

Initial Yield-Isotropic case

-0.5

Initial Yield-Anisotropic case

Radial Stress/Yield Stress

-1.0

Isotropic Yield Curve Anisotropic Yield Curve

-1.5

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Transverse Stress/Yield Stress

Fig. 5. Yield curve for orthotropic and isotropic material model

observed for the onset of plasticity. For the isotropic material properties, plasticity is initiated at internal pressure ~ 195 MPa whereas for anisotropic case, it initiates at ~230 MPa. For an applied internal pressure of 330 MPa, only 17 % of the thickness