Elastic-Plastic Analysis of Some Pressure Vessel Heads

Popov, Egor P.; Khojasteh-Bakht, M.; Sharifi, P.

doi:10.1115/1.3427734

Cited by 2 publications

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“…The geometry of an axisymmetric curved shell element is illustrated in Figure 1. As has been its meridional curve in dimensionless co-ordinates f and 7 may be expressed as Note that the curve given by equation (1) satisfies the requirements of continuity of slopes and curvatures at the nodal circles.…”

Section: Geometry Of a Curved Elementmentioning

confidence: 99%

A refined curved element for thin shells of revolution

Popov

Sharifi

1971

Numerical Meth Engineering

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SUMMARYA refined axisymmetric curved finite element for the analysis of thin elastic-p.Jstic shells of revolution is described in the paper. The improved element is obtained by employing cubic polynomials in terms of local Cartesian co-ordinates for the assumed in-plane and out-of-plane displacements. This introduces into the solution two internal degrees of freedom in the cord direction of each element. These internal degrees of freedom are removed by static condensation before assembling the individual element stiffness matrices, and are subsequently recovered after the nodal displacements are obtained. On comparison with the previous formulation, this procedure greatly improves the accuracy of the solution especially with regards to in-plane stress-resultants at discontinuities in the meridional curvature and interelement equilibrium of forces. The latter fact makes it possible to analyse shells with a discontinuous meridional slope. In using this element, improvement in the convergence of the elastic-plastic solutions has also been observed.Several examples illustrate the quality of solutions. The reported study is limited to axisymmetric loadings and boundary conditions.

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Section: Geometry Of a Curved Elementmentioning

confidence: 99%

A refined curved element for thin shells of revolution

Popov

Sharifi

1971

Numerical Meth Engineering

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Torispherical Shells under Internal Pressure—Failure due to Asymmetric Plastic Buckling or Axisymmetric Yielding

Galletly

Błachut

1985

Proceedings of the Institution of Mechanical Engineers, Part C:

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In the diameter-to-thickness range 250 < D/t < 1000, internally pressurized torispherical shells can fail either by plastic buckling or by axisymmetric yielding. However, the present Code rules cater only for the axisymmetric yielding mode and they also restrict the D/t ratios to being less than 500. The rules are based on limit analysis results and these can be conservative for this problem. With regard to internal pressure buckling, there are as yet no design rules in either the American or the British pressure vessel Codes to prevent its occurrence. To provide guidance for a more accurate formulation of design rules for both of these failure modes over the range 300 < D/t < 1500, the authors have made a series of calculations to determine the values of Pcr (the internal buckling pressure) and pc (the axisymmetric yielding pressure) for perfect torispherical shells. The availability of these results, obtained with a finite-deflection shell theory, enables curves to be drawn showing when buckling is the controlling failure mode and when axisymmetric yield controls. A comparison is also made, for D/t < 600, between the controlling failure pressures mentioned above and the Drucker-Shield limit pressures. The ratio between the former and the latter varied between 1.2 and 1.8, depending on the geometry of the shell and the magnitude of the yield point, σyp. Considerable economies in the designs of many torispherical shells could, therefore, be achieved if the relevant sections of the Codes were to be modified to take advantage of the foregoing results. The controlling failure pressure curves also indicate how Code rules to prevent plastic buckling for D/t > 500 might be formulated. For the benefit of designers, the numerical values of pcr and pc were transformed, using curve-fitting techniques, into simple approximate equations. Although these equations are for perfect torispherical shells, they should be very beneficial when analysing the related problems of fabricated torispheres in practice.

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Elastic-Plastic Analysis of Some Pressure Vessel Heads

Cited by 2 publications

References 0 publications

A refined curved element for thin shells of revolution

A refined curved element for thin shells of revolution

Torispherical Shells under Internal Pressure—Failure due to Asymmetric Plastic Buckling or Axisymmetric Yielding

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