On the Thermal Stresses Induced in a Thin Circular Disc When the Central Part is Welded. (2nd Report)

Formulae of Thermal Stresses

Abstract

In order to know the distribution of thermal stresses induced in a circular disc of mild steel with its central part welded, and to make clear the cause of appearance of Lüders, lines observed on the polished surface of the disc as reported in the first report, it becomes necessary to develope an analytical study of thermal stresses. As weld was made at the centre of the circular disc and the disc was thin enough, thermal stresses can be assumed to be a function of radius and time only. To know the distributioa of thermal stresses and especially, of residual stresses in the above-mentioned care, it is, at least, indispensable to erect formulae of thermal stresses which take into consideration the plastic deformation occuring by drastic heating in the neighbourhood of the central hot portion.
Here, making a rough assumption that in the above-mentioned welded dise the central region lying above a certain limiting temperature behaves as a pqrfectly plastic body, and the outer region of rather lower temperature as a perfectly elastic one, the author has erected formulae of thermal stresses taking into account the plastic deformation. It is, however, to be noticed that the plastic deformation which perhaps occurs by yielding is utterly out of consideration.