Analysis of Residual Stresses in Hot-Rolled H-shapes

Abstract

The generating mechanism of residual stresses in hot rolled H-shapes is studies to estimate the magnitude of residual stresses through numerical methods. A method for computation of the internal stresses from the temperature distribution throughout the cooling process is reported. The following results are obtained.
(1) The magnitude and the distribution of residual stresses are estimated through a simplified twodimensional model using the finite difference methods, The computed distributions of temperature during caoling and the residual stresses agree well with the experimental results.
(2) The principal cause for the formation of residual stresses is the large temperature difference between the flanges and the web during cooling. The maximum amount of difference (T₁-T₃) max. between the temperature at the flange-center and the web-center during cooling is the main factor to decide the magnitude of residual stresses.
(3) Shapes geometry has a large effects on magnitude of residual stresses. When the shape is geometrically similar, the larger shape has larger residual stresses. When the width and height is the same, the H-shapes with smaller t₁/t₂ has larger residual stresses. t₁/t₂ is the ratio of thickness of web (t₁) and that of flange (t₂).
(4) The effects of initial temperature difference (T₁-T₃) on the residual stresses is very large. When the initial temperature difference is large, the residual stresses becomes large.
However, the level of initial temperatures has little effects on residual stresses when teh temperature difference is fixed.