附录：外文翻译
5.1Introduction
Cylindrical shells are used innuclear,fossil and petrochemical industries. They are also used in heat exchangers of the shell and tube type.Generally.These vessels are easy to fabricate and install and economical to maintain. The design procedures in pressure vessel codes for cylindrical shells are mostly based on linear elastic assumption,occasionally allowing for limited inelastic behavior over a localized region.The shell thickness is the major design parameter and is usually controlledby internal pressure and sometimes by external pressure which can produce buckling.Applied loads are also important in controlling thickness and so are the disconti-nuity and thermal stresses.The basic thicknesses of cylindrical shells are Based on simplified stress analysis and allowable stress for the material of construction.There are some variations of the basic equations in various design codes.Some of the equations are based on thick-wall Lame equations.In this chapter such equations will be discussed.Also we shall discuss the case of cylindrical shells under external pressure where there is a propensity of buckling or collapse.
5.2 Thin-shell equations
A shell is a curved plate-type structure.We shall limit our discussion to Shells of revolutions.Referring to Figure5.1 this is denoted by anangle ϕ,The meridional radius r1 and the conical radius r2,from the center line.The horizontal radius when the axis is vertical is r. If the shell thickness is t,with z being the coordinate across the thickness,following the convention of Flugge, We have the following stress resultants:
⎰-+
=
2
2
1 1) (
t
t
dz r
z
r
N
θ
θ
σ(5.1)
⎰-+
=
2
2
2 2) (
t
t
dz r
z
r
N
φ
φ
σ(5.2)
⎰-+
=
2
2
2 2) (
t
t
dz r
z
r
N
θφ
θφ
σ(5.3)
Figure 5.1 Thin shell of revolution .
⎰-+=2
21
1)(
t
t
dz r z r N θφφθσ (5.4) These stress resultants are assumed to be due only to an internal pressure, p,acting in the direction of r. For membrane shells where the Effects of bending can be ignored,all the moments are zero and further development leads to
θφφθN N =
The following equations result from considering force equilibrium along with the additional requirement of rotational symmetry:
0cos )
(1=-φφθφN r d rN d (5.6)
φφN r r pr N 122-
= (5.7) Noting that φsin 2r r = ,we have,by solving Eqs.(5.6)and(5.7),
2
2pr N =φ (5.8) )2(2122r r pr N -=
φ (5.9) The above two equations are the results for a general shell of revolution. Two specific cases result:
