Issue 36

Fracture and Structural Integrity, 36 (2016); ISSN 1971-9883 VI Fracture Mechanics in Central and East Europe This issue of Frattura ed Integrità Strutturale contains ten research papers focused on Fracture Mechanics in Central and East Europe. Four papers from Serbia deal with fatigue crack growth, presenting experimental and numerical results, obtained in the Military Institute, Institute for material testing and Faculty of Mechanical Engineering, all from Belgrade. Paper Integrity and life estimation of turbine runner cover in a hydro power plant by A.Sedmak, M. Arsić, S. Bošnjak, S. Sedmak and Z. Savić, presents integrity and life estimation of turbine runner cover in a vertical pipe turbine. Fatigue and corrosion-fatigue interaction have been taken into account using experimentally obtained material properties, as well as analytical and numerical calculations of stress state, to estimate appropriate safety factors. Fatigue crack growth rate was also calculated, indicating that internal defects of circular or elliptical shape, detected by ultrasonic testing, do not affect integrity of runner cover. Paper Experimental examination of fatigue life of welded joint with stress concentration by M. Arsic , A. Sedmak, S. Bosnjak, S. Sedmak and Z. Savic, presents results of experimental examinations of stress concentration influence on fatigue life of butt welded joints with K-groove, produced from the structural steel S355J2+N. Specimens with short cracks (with limited length of initial crack), defined on the basis of the experiences from fracture mechanics by the three points bending examinations, have been examined according to standard for the determination of S-N curve, and used to determine permanent fatigue strengths for different lengths of initial crack. In the paper Fatigue life prediction of casing welded pipes by applying the extended finite element method , Lj. Lazić Vulićević, A. Grbović, A. Sedmak, Ž. Šarkočević and A. Rajić use the extended finite element (XFEM) method to simulate fatigue crack growth in casing pipe, made of API J55 steel by high-frequency welding, in order estimate its structural integrity and life. Based on the critical value of stress intensity factor K Ic , measured in different regions of welded joint, the crack was located in the base metal as the region with the lowest resistance to crack initiation and propagation. The XFEM was first applied to the three point bending specimens to verify numerical results with the experimental ones, and afterwards to simulate fatigue crack growth and estimate its remaining life. In the paper Influence of exploitation duration and temperature on the fatigue growth parameters in different regions of a welded joints by I. Camagic, Z. Burzic, A. Sedmak, N. Vasic, B. Cirkovic and A. Radovic, the influence of exploitation duration 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 . 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 compared. The authors of the other six papers are from Germany, Hungary, Romania, Russia, Slovakia. Paper Numerical Simulation of Dissimilar Metal Welding and its Verification for Determination of Residual Stresses with authors Sz. Szávai, Z. Bezi and C. Ohms presents the through-thickness residual stress distributions on dissimilar metal weld (DMW) mock-up. DMWs, were considered as joints between ferritic steels