Issue 36

I. Camagic et alii, Frattura ed Integrità Strutturale, 36 (2016) 1-7; DOI: 10.3221/IGF-ESIS.36.01 1 Focused on Fracture Mechanics in Central and East Europe Influence of temperature and exploitation period on fatigue crack growth parameters in different regions of welded joints Ivica Camagic, Nemanja Vasic, Bogdan Cirkovic Faculty of Technical Sciences, Kosovska Mitrovica, Kneza Milosa 7, Serbia Zijah Burzic Military Technical Institute, Rastka Resanovica 1, Belgrade, Serbia Aleksandar Sedmak Faculty of Mechanical Engineering, Kraljice Marije 16, Belgrade, Serbia asedmak@mas.bg.ac.rs Aleksandar Radovic Technical School Mihailo Petrovic Alas, Kosovska Mitrovica, Lole Ribara 29, Serbia A BSTRACT . The influence of exploitation period and temperature on the fatigue crack growth parameters in different regions of a welded joint is analysed for new and exploited low-alloyed Cr-Mo steel A-387 Gr . B . The parent metal is a part of a reactor mantle which was exploited for over 40 years, and recently replaced with new material. Fatigue crack growth parameters, threshold value  K th , coefficient C and exponent m, have been determined, both at room and exploitation temperature. Based on testing results, fatigue crack growth resistance in different regions of welded joint is analysed in order to justify the selected welding procedure specification. K EY WORDS : Welded joint; Crack; Yield stress; Tensile strength; Permanent dynamic strength. I NTRODUCTION he reactor analysed here has a form of a vertical pressure vessel with a cylindrical mantle and two welded lids, made of Cr-Mo steel A-387 Gr. B , [1]. It is used for some of the most important processes in the motor gasoline production, including platforming in order to change the structure of hydrocarbon compounds and to achieve a higher octane rating. Long-time, high temperature exploitation of the reactor, caused siginficant damage in reactor mantle, requiring a thorough inspection and repair of damaged parts, including replacement of a part of reactor mantle. For designed exploitation parameters ( p= 35 bar, t =537 °C), the material is prone to decarbonization, reducing its strength as a consequence, [2]. Testing of high-cycle fatigue behaviour of new and exploited parent metal (PM), weld metal (WM) and heat affected zone (HAZ), at room and service temperature (540 °C) is necessary to get detailed insight in all parameters influencing fatigue crack growth resistance of Cr-Mo steel A-387 Gr. B . welded joints. T