Nonconservative Components of Follower Forces in the Classical Shell Theory

1989 ◽  
Vol 42 (11S) ◽  
pp. S13-S19
Author(s):  
Wolf Altman ◽  
Luiz Bevilacqua
Keyword(s):  
Dynamic Stability ◽  
Shell Theory ◽  
Shell Structures ◽  
Small Strains ◽  
Generalized Displacements ◽  
Order Of Magnitude ◽  
Classical Shell Theory ◽  
Follower Forces

An analysis of follower forces acting on shell structures is presented. Attention is focussed on the expressions of such forces as functions of the generalized displacements. Specific expressions for the follower forces are obtained, according to the order of magnitude of the strains and angles of rotation. For small strains the follower forces allow a decomposition into conservative and non-conservative components. This leads to the equations of dynamic stability of shell problems subjected to follower loads. The dynamic counterparts of Donnell-Mushtari-Vlasov stability equations are presented, by either retaining or omitting the prebuckling rotations.

scholarly journals Alternative derivation of the higher-order constitutive model for six-parameter elastic shells

2021 ◽  
Vol 72 (2) ◽  
Author(s):  
Mircea Bîrsan
Keyword(s):  
Energy Density ◽  
Constitutive Model ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Shell Theory ◽  
Constitutive Relations ◽  
Three Dimensional ◽  
Classical Shell Theory ◽  
Three Dimensional Elasticity ◽  
General Method

AbstractIn this paper, we present a general method to derive the explicit constitutive relations for isotropic elastic 6-parameter shells made from a Cosserat material. The dimensional reduction procedure extends the methods of the classical shell theory to the case of Cosserat shells. Starting from the three-dimensional Cosserat parent model, we perform the integration over the thickness and obtain a consistent shell model of order $$ O(h^5) $$ O ( h 5 ) with respect to the shell thickness h. We derive the explicit form of the strain energy density for 6-parameter (Cosserat) shells, in which the constitutive coefficients are expressed in terms of the three-dimensional elasticity constants and depend on the initial curvature of the shell. The obtained form of the shell strain energy density is compared with other previous variants from the literature, and the advantages of our constitutive model are discussed.

Some new results and current challenges in the finite element analysis of shells

Acta Numerica ◽  
2001 ◽  
Vol 10 ◽  
pp. 215-250 ◽  
Author(s):  
Dominique Chapelle
Keyword(s):  
Finite Element ◽  
Shell Theory ◽  
Shell Structures ◽  
Engineering Practice ◽  
Element Analysis ◽  
Shell Elements ◽  
Shell Models ◽  
The Finite Element Analysis ◽  
Shell Finite Element ◽  
Mathematical Analyses

This article, a companion to the article by Philippe G. Ciarlet on the mathematical modelling of shells also in this issue of Acta Numerica, focuses on numerical issues raised by the analysis of shells.Finite element procedures are widely used in engineering practice to analyse the behaviour of shell structures. However, the concept of ‘shell finite element’ is still somewhat fuzzy, as it may correspond to very different ideas and techniques in various actual implementations. In particular, a significant distinction can be made between shell elements that are obtained via the discretization of shell models, and shell elements – such as the general shell elements – derived from 3D formulations using some kinematic assumptions, without the use of any shell theory. Our first objective in this paper is to give a unified perspective of these two families of shell elements. This is expected to be very useful as it paves the way for further thorough mathematical analyses of shell elements. A particularly important motivation for this is the understanding and treatment of the deficiencies associated with the analysis of thin shells (among which is the locking phenomenon). We then survey these deficiencies, in the framework of the asymptotic behaviour of shell models. We conclude the article by giving some detailed guidelines to numerically assess the performance of shell finite elements when faced with these pathological phenomena, which is essential for the design of improved procedures.

Effect of Accuracy Loss in Classical Shell Theory

1992 ◽  
Vol 59 (2S) ◽  
pp. S217-S223 ◽  
Author(s):  
V. Berdichevsky ◽  
V. Misyura
Keyword(s):  
Shell Theory ◽  
Underlying Causes ◽  
Classical Shell Theory

It is shown that classical shell theory does not yield correct values of displacements in some shell problems. Underlying causes of this effect are discussed.

A Method to Estimate Deformation Strains in the Context of Coke Drum Life Assessments: Part 1

2019 ◽  
Author(s):  
John Huang ◽  
Kannan Subramanian ◽  
Patrick Boster ◽  
Julian J. Bedoya
Keyword(s):  
Theoretical Approach ◽  
Pressure Vessel ◽  
Analytical Method ◽  
Shell Theory ◽  
Theoretical Development ◽  
Strain Gages ◽  
Assessment Technique ◽  
Assessment Techniques ◽  
Classical Shell Theory ◽  
Comparison Of The Results

Abstract In this paper, an analytical method to estimate the deformation strains that can quantify the severity of bulges, as it applies to coke drums, is presented. The proposed method is based on classical shell theory and API 579-1/ASME FFS-1 (2016) procedures involving triaxiality limits. In this first part of the work, only the theoretical development is presented along with the comparison of the results from this theoretical approach with two case studies that emulate the bulging due to different loading scenarios. The developed approach is then applied to a deformed coke drum. In the next part of this paper, the application of this approach on selected in-service coke drums that are equipped with strain gages will be presented. The authors would like to emphasize the well-known fact that the coke drum is a complex pressure vessel for which any single simplified assessment technique may not be sufficient to quantify the life or fitness-for-service (FFS) of a coke drum due to the complexities associated with the various parameters that affect the mechanical integrity of the coke drum. This paper is an attempt to advance the assessment techniques that are currently utilized in the industry.

Sign in / Sign up

Export Citation Format

Share Document