On the Creep Behaviour at Periodic Holes in Thermal Equipment

Abstract

A large body of literature exists on investigations carried out earlier on the effects of holes in a continuum in the elastic regime of material behavior like for instance the case of the elastic analysis of tube sheets. Mathematical and finite element methods have been presented in detail for the solution of these design problems by a large number of authors in the sixties and seventies. However, it is observed that there is a paucity of reported research investigations on the creep behavior of equipment containing periodic holes such as boiler headers, heat exchangers etc. Material creep effects near holes in a continuum appear to have been investigated only during the past fifteen years and that too restricted to a limited number of configurations. Moreover, a large number of investigations seem to have been focused on the uni-axial behavior while the state of stress in most of the equipment utilized by industry is predominantly biaxial in nature. Creep behavior of substantial number of equipment subject to biaxial loading which is commonplace in industry remains to be relatively not understood fully. In view of the important applications of these mechanical equipment in thermal power stations and in chemical plants, it is essential to address the problem of creep behavior at single, multiple and periodic holes in the material continuum subjected to biaxial loading [1,2]. In order to obtain tractable solutions to the complex problems, it is felt appropriate to carry out detailed finite element analyses aimed at obtaining the strain and stress distribution near holes in the creep regime in certain generalized configurations so that the same can be applied in equipment where an array of holes is present.