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Journal ArticleDOI

Elastoplastic stress and strain predictions for axisymmetric pressure vessel bodies under transient thermal loads

TL;DR: In this paper, a parametric study with geometry and material parameters as variables was carried out for three sizes of spheres with nozzles for the determination of peak strains and stresses under transient thermal loading using thermoelastoplastic finite element analyses and also by approximate methods.
Abstract: Evaluation of localized peak strains at stress concentration zones under transient thermal loading is essential for the determination of low cycle fatigue life of a number of pressure vessels like steam turbine components and reactor vessels. Finite element analysis is a powerful technique but there are some difficulties in using the method for inelastic analysis of large-sized components. Several investigators have proposed approximate methods to determine inelastic strains at notches and other stress concentration zones from elastically calculated stress distributions. The accuracy of three of these methods, namely the Neuber rule, the Molski-Glinka rule and GLOSS analysis under thermal loading for axisymmetric pressure vessel bodies was investigated. A parametric study with geometry and material parameters as variables was carried out for three sizes of spheres with nozzles for the determination of peak strains and stresses under transient thermal loading using thermoelastoplastic finite element analyses and also by approximate methods. The same analyses have also been carried out for a steam turbine valve body for the same thermal loading, which is normally encountered by the valve body under start-up conditions. It has been found that GLOSS analysis is more accurate and the use of approximate methods has been recommended, especially for preliminary analyses in the development of new components.
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TL;DR: In this article, the transient response of a clamped thin slab under pressure and thermal loads is investigated through analytical and finite difference approaches, and the superposition principle is implemented to treat each load individually and to obtain its corresponding response.
Abstract: The transient response of clamped thin slab under pressure and thermal loads is investigated through analytical and finite difference approaches. Due to the linear-elastic nature of the analysis, the superposition principle is implemented to treat each load individually and to obtain its corresponding response. The analysis introduced a new parameter, the pressure-temperature coupling term, in the mechanical stress solution. It is found that both mechanical and thermal stresses are of the same order of magnitude for coupling term values between 1000 and 10000 Pa/°C, the thermal stresses dominate for coupling term less than 1000 Pa/°C, and the mechanical stresses dominate otherwise.

2 citations


Cites background from "Elastoplastic stress and strain pre..."

  • ...Adinarayana and Alwar [4] investigated the elastoplastic stresses and strains in axisymmetric pressure vessel bodies under transient thermal loads....

    [...]

References
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Journal ArticleDOI
TL;DR: In this article, an energy-based method of local elastic-plastic stress and strain calculation is presented, where the theoretical stress concentration factor k t can be related to the unit elastic strain energy at a notch root.

418 citations

Journal ArticleDOI
R. Seshadri1
TL;DR: The GLOSS analysis is emerging as a useful technique for determining multiaxial stress relaxation, follow-up, creep damage, inelastic strain concentrations and low-cycle fatigue estimates, limit analysis and issues pertaining to stress classification as discussed by the authors.
Abstract: The underlying theory relates redistribution of inelastic stresses at a given location under consideration to the uniaxial stress relaxation process. GLOSS analysis is emerging as a useful technique for determining multiaxial stress relaxation, follow-up, creep damage, inelastic strain concentrations and low-cycle fatigue estimates, limit analysis and issues pertaining to stress-classification

119 citations

Journal ArticleDOI
TL;DR: In this paper, the facteurs de concentration de deformation plastique dans des analyses de fatigue elastiques are utilised for deformation deformation in the case ideal d'une paroi a materiau a durcissement cinematique lineaire.
Abstract: Utilisation des facteurs de concentration de deformation plastique dans des analyses de fatigue elastiques. Limite de cette methode pour des structures non entaillees sous charge thermique. Dans cet article, on tente de deriver des facteurs appropries au cas ideal d'une paroi a materiau a durcissement cinematique lineaire. Les resultats obtenus s'appliquent a de nombreux problemes pratiques

6 citations

Journal ArticleDOI
TL;DR: In this article, a 15 MW high-speed industrial turbine rotor is subjected to detailed thermal stress analysis using finite element technique and the results show that the rotor life is limited by low cycle fatigue strength.
Abstract: The turbine rotor is often the critical component that fixes the limits for transient operation of the turbine because of cyclic thermal strains. The common mode of failure of components subjected to cyclic stress-strains is fatigue. Particularly for high-temperature rotors, which are subjected to high inelastic strains at critical locations like notches, the rotor life is limited by low cycle fatigue strength. To predict the fatigue life for crack initiation, it is necessary to evaluate the local stress-strain history of a material element at the notch root for comparison with smooth bar fatigue data. The essential steps to evaluate thermal stresses in steam turbine rotors are reviewed by Hohn and Dawson and Neill. These methods are undergoing continuous development, including development of sophisticated finite element software and approximate methods. In the present paper a 15 MW high-speed industrial turbine rotor is subjected to detailed thermal stress analysis using finite element technique.

1 citations