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3.6 To determine other factors’ influences on the Numerical Model
3.6.1 Introduction
In this section, it is important to show that the developed numerical model that has
been discussed in the previous section is the right and suitable model to be used in the
next stress and strain distribution studies. There are two methods of validating this
model. The first is to compare the numerical hoop and axial stress values of the chosen
model with several other models and validate them analytically. Details of this method
are going to be discussed further in this section. The second method is to compare this
chosen numerical model against the actual pipe specimen which has similar physical
and mechanical properties, dimension and geometry. This will be further explained and
discussed in a later chapter (i.e. experimental work). In this stress comparison study,
which involves several models, what must be clearly addressed is that the defect and
nominal pipe thicknesses of each model remain constant and follow the actual test rig
specifications.
3.6.2 Comparison of Results
As mentioned in the earlier section, in order to justify the preselected model (in
this case Model 3) as the right and most suitable model, the numerical results of hoop
stress (S11) and axial stress (S22) of each model from ABAQUS were obtained and
compared against the results of the manual calculation (analytical method). A simple
shell theory was applied in this manual calculation as shown below;
For Hoop stress, σh (S11), it was referred to as Hoop Strain, εh (Kaminski, 2005) and
multiplied by Young‘s Modulus as shown below;
and,
h
PD
4tE
h = E. h
(Equation 3.1)
(Equation 3.2)
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