„DESIGN, PRODUCTION AND SERVICE OF WELDED CONSTRUCTIONS AND PRODUCTS“ 1 ESTIMATION OF RESIDUAL STRESS IN THE HOT-ROLLED PIPES

The aim of this work is to estimate the residual stresses in the pipes manufactured by the hot rolling technique. Pipes manufactured by this method are mostly used in boilers and in most cases are delivered normalized, but not stress relieved too. Therefore, there are surely residual stresses present in pipes which are result of manufacturing technique, but also of uneven cooling after production process. Within this work, hoop stress as the most relevant for pipes is estimated by two methods: incremental hole drilling method and splitting method. Although residual stresses cause collapse of many constructions, still in most cases of analysis and design of individual parts, structures and plants residual stresses are not taken into consideration. Residual stresses are stresses which are present in material after all the external loads are removed and as such, they have significant effect on the fatigue behavior of materials as well as on the fracture toughness of material, therefore it is recommended to take them into account while calculating the lifetime of component or structure.