10
-*- Angle 00
S-U- Angle -06
-- Angle 12
-- Angle 18
S 6 ---- Angle 24
4 4
0
( 0.2 0.4 0.6 0.8 1 1.2
-2
-4 Normalized Thickness
Figure 5-14: Variation of SIF K, along isotropic BD specimen thickness at differ-
ent Crack angle.
orthotropic specimen than for isotropic specimen (Figs. 5-18, 5-19 on page 49).
For load aligned with crack plane, KIII was found to be zero across the thickness.
Since K1II is a function of out of plane relative displacements (normal to the disk
plane) of nodes at the crack tip and because of perfect symmetry in loading and
geometry of the material, it ought to zero. But as the force angle was introduced,
because of poisson's effect, there were small out of plane relative displacements on
both sides of the mid plane of the disk (plane 3, Fig. 5-13 on page 45), which was
equal and opposite to each other. The absolute value of K1I reaches maximum
between 30-360 and it is ~ 15Kpsiin for isotropic and ~ 22Kpsivn for or-
thotropic specimen. Among all the SIFs K1I is more dominant at the crack edges
at higher force angles, whereas it is zero at the midplane for all the angles (Figs.
5-18, 5-19 on page 49). The average value of K1II is zero across the thickness for
both specimen.
From Figs. 5-21, 5-22 on page 52, it can be seen that K, decreases with
an increase in crack angle and crack closure angle (where K, is almost zero) was