The browsable journal is available at this link

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 KIc, 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 Kth, 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 and either austenitic stainless steels or nickel-based alloys. The numerical simulations were performed using commercial finite element code MSC.Marc, and residual stress measurements were performed on welded joints to validate the simulation results. The validated residual stress distributions can be used for the life time assessment and failure mode predictions of the welded joints.
In the paper Scaling Of Compression Strength in Disordered Solids: Metallic Foams, authors J. Kováčik, J. Jerz, N. Mináriková, L. Marsavina, E. Linul, the scaling of compression strength with porosity for aluminium foams was investigated. Three different compositions Al 99.96, AlMg1Si0.6 and AlSi11Mg0.6 foams of various porosity, sample size with and without surface skin were tested in compression. It was observed that the compression strength of aluminium foams scales near the percolation threshold with Tf ≈ 1.9 - 2.0 almost independently on the matrix alloy, sample size and presence of surface skin.
V. Petrova, S. Schmauder, A. Shashkin in Modeling of edge cracks interaction investigated the effects of the interaction of edge cracks on further crack formation. The solution of singular integral equations is obtained by a numerical method which is based on Gauss-Chebyshev quadrature. The main fracture characteristics, such as, stress intensity factors, fracture angles and critical loads are provided in this study. A series of illustrative examples are presented for different geometries of arbitrarily inclined edge cracks.
Paper titled Failure analysis of dissimilar single-lap joints having authors F.A. Stuparu, D.A. Apostol. D.M. Constantinescu, M. Sandu, S. Sorohan investigates the single-lap joints made of aluminium and carbon fibre adherends of different thickness. The experimental tests and the use of 2D Digital Image Correlation were employed in order to understand better the behaviour of such dissimilar joints. The obtained results are suggesting that a complete monitoring of the failure processes in the overlap region can be fully understood only if local deformation measurements are possible.
The Special Issue is closed by two papers of T. Fekete Review of Pressurized Thermal Shock Studies of Large Scale Reactor Pressure Vessels in Hungary and Methodological Developments in the Field of Structural Integrity Analyses of Large Scale Reactor Pressure Vessels in Hungary. In the first one presents a comparative review of the methodologies used to investigate pressurized thermal shock which appear in the four nuclear power units from Hungary. The concept of structural integrity was the basis of research and development. The second paper presents in the first part of the paper, a short historic overview with the origins of the Structural Integrity concept are presented, and the beginnings of Structural Integrity in Hungary are summarized. In the second part, a new conceptual model of Structural Integrity is introduced. In the third part, a brief description of the VVER-440 V213 type RPV and its surrounding primary system is presented. In the fourth part, a conceptual model developed for PTS Structural Integrity Analyses is explained.

Aleksandar SEDMAK, University of Belgrade, Serbia
Liviu MARSAVINA, University Politehnica Timisoara, Roamnia

 

Articles

Influence of temperature and exploitation period on fatigue crack growth parameters in different regions of welded joints

Ivica Camagic, Nemanja Vasic, Bogdan Cirkovic, Zijah Burzic, Aleksandar Sedmak, Aleksandar Radovic
PDF

Pages 1-7

Modeling of edge cracks interaction

V. Petrova, S. Schmauder, A. Shashkin
PDF

Pages 8-26

Experimental examination of fatigue life of welded joint with stress concentration

Miodrag Arsic, Zoran Savic, Aleksandar Sedmak, Srdjan Bosnjak, Simon Sedmak
PDF

Pages 27-35

Fatigue life prediction of casing welded pipes by using the extended finite element method

Ljubica Lazi? Vuli?evi?, Aleksandar Raji?, Aleksandar Grbovi?, Aleksandar Sedmak, Živ?e Šarko?evi?
PDF

Pages 46-54

Scaling of compression strength in disordered solids: metallic foams

J. Ková?ik, J. Jerz, N. Mináriková, L. Marsavina, E. Linul
PDF

Pages 55-62

Integrity and life estimation of turbine runner cover in a hydro power plant

A. Sedmak, S. Bosnjak, M. Arsic, S.A. Sedmak, Z. Savic
PDF

Pages 63-68

Failure analysis of dissimilar single-lap joints

F.A. Stuparu, D.A. Apostol, D.M. Constantinescu, M. Sandu, S. Sorohan
PDF

Pages 69-77

Very high cycle fatigue strength and crack growth of thin steel sheets

Mohand Ouarabi, Ruben Perez Mora, Claude Bathias, Thierry Palin-Luc
PDF

Pages 112-118

Crack initiation and propagation paths in small diameter FSW 6082-T6 aluminium tubes under fatigue loading

Roberto Tovo, Luca Susmel, M. Neil James, Danie G. Hattingh, Enrico Maggiolini
PDF

Pages 119-129

Effect of flexural crack on plain concrete beam failure mechanism A numerical simulation

Abdoullah Namdar, Ershad Darvishi, Xiong Feng, Ideris Zakaria, Fadzil Mat Yahaya
PDF

Pages 168-181