Numerical analysis of the effect of torispherical head on the buckling of pressure vessel

The shape of end heads of a pressure vessel is usually torispherical. Buckling of this head is
one of the most important points for designing of pressure vessels. This subject has been studied
extensively since last years. In this field, the experimental methods are expensive and need a lot
of time. In addition, because of lack of accuracy in the producing procedure, sometimes two
models with identical geometry show different buckling behavior. Hence the use of finite element
method in analyzing of buckling behavior of heads has a lot of benefits. In this dissertation,
the finite element method has been used. Firstly with nonlinear buckling analysis, the effects
of geometrical parameters such as thickness, knuckle radius and diameter of cylindrical part,
on the buckling of heads have been studied, then the buckling behavior of different kinds of
heads with identical geometry have been analyzed. For the nonlinear analysis we used the Arc
Length method which can control the load level, the length of the displacement increment and
the maximum displacement. The most important characteristic of this method is its ability to
converge, even when the behavior is highly nonlinear. From the verification performed with
the European Convention for Constructional Steelwork (ECCS) code, it has been confirmed
that the nonlinear buckling analysis could assure accurate results for the buckling strength.
In the case of internal pressure, it has been shown that initial imperfection had no effect
on the pre-buckling behavior and buckling pressure of head; it just affects the post-buckling
behavior.