Finite element analysis of stresses and creep in turbine casings

Parkes, D.A.C. (1973) Finite element analysis of stresses and creep in turbine casings. PhD thesis, University of Nottingham.

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Abstract

The finite element method has been used to calculate the stresses and creep deformations of flanged turbine casing models subjected to internal pressure and bolting forces. The finite element results have been compared with results from photoelastic and lead model turbine casings.

An axisymmetric thin shell of revolution ring finite element has been developed to analyse casings subjected to pressure, thermal and creep loads. The thin shell of revolution ring finite element is shown to be extremely powerful and has been used to investigate the shell portions of the turbine casing away from the flange. The three-dimensional isoparametric finite elements have been used for more accurate idealisations of the turbine casing. A thick shell isoparametric finite element has also been developed which can be used with the more common hexahedral isoparametric finite elements.

A solution algorithm based on a frontal technique has been developed to solve the large number of linear equations given by the finite element equations. This algorithm, which is fully automatic and uses fast access backing store, has a resolution facility which is used to recalculate subsequent creep solutions assuming that the stiffness of the structure remains constant. The creep algorithms are based on time marching techniques where the creep solutions are found for small time increments, the final solution being the sum of all the incrementa1 solutions. During each time increment the stresses are assumed to remain constant and the change in stress between time increments is kept within a preset ratio. The creep algorithms have been used to predict the creep deformation of simple structures to compare with published results. The agreement between the finite element and lead model creep results is limited.

The finite clement programs have been written to be compatible with the PAFEC suite of finite element programs.

Item Type: Thesis (University of Nottingham only) (PhD)
Keywords: Steam-turbines, strains and stresses
Subjects: T Technology > TJ Mechanical engineering and machinery > TJ255 Heat engines. Turbines
Faculties/Schools: UK Campuses > Faculty of Engineering > Department of Mechanical, Materials and Manufacturing Engineering
Item ID: 29701
Depositing User: Airey, Ms Valerie
Date Deposited: 27 Aug 2015 07:18
Last Modified: 15 Sep 2016 01:20
URI: http://eprints.nottingham.ac.uk/id/eprint/29701

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