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Failure analysis of welded joint with multiple defects was performed taking into account the effect of all defects, not just a dominant one. Four cases of multiple defects in welded joint under the uniaxial tensile loading were investigated using extended Finite Element Method. Two-dimensional Finite Element Models were made according to the tensile specimens with initial crack located in a critical area of welded joint. For each multiple defects case, numerical simulation was performed with three initial crack depth. Engineering Critical Analysis was made using Failure Assessment Diagrams for each defect that was determined as critical for its welded joint case. Numerical simulation showed that the geometry of the most prominent one from a point of view of structural integrity. It was concluded that the vertical misalignment in combination with a secondary defect, had the most adverse effect which can lead to failure of welded structure.

This paper presents an analysis of train screw coupling used mainly in Europe as mechanical connection of wagons in train. An analysis of train breaks apart incidents revealed that less than 30 % of the cases were caused by elements of the screw coupling, with coupling links accounting for only 5 % of the failures. Therefore, the investigation focused on testing the coupling links, which are safety elements of the screw coupling. The coupling links underwent various inspections, including visual inspection, dimensional control, non-destructive testing, examination of chemical composition, and mechanical tests. Dimensional control found longitudinal plastic deformations of the links. Chemical examination revealed that the links were made of different material than recommended, but their mechanical properties generally met the recommended values. However, variations were observed among different links, likely due to different rates of deformation during testing and operational conditions. Overall, the analysis and inspections provided insights into the condition and performance of coupling links in the screw coupling system, highlighting the importance of monitoring and maintaining these elements to ensure safe and efficient railway operations.

Successful application of Cr-Mo steel depends crucially on behaviour of all zones in welded joints, i.e. base metal (BM), heat-affected-zone (HAZ) and weld metal (WM), both at room and working temperature. Different amplitude loadings were applied for testing of specimens without a crack, made of welded joint as a whole and of BM, in order to obtain Woehler's curves and compare their dynamic strength. Amplitude loading was also applied for testing of specimens cracked in BM, HAZ and WM, in order to get fatigue crack growth curves and parameters C and m in Paris law. Results are analysed to get deeper insight into behaviour of welded joints, made of steel SA 387 Gr. 91, under amplitude loading both for room and working temperature.

The authors regret that a typographical error was made in Eqs. (15), (16), (20). In these three forms of the Jc cumulative distribution function (CDF), we omitted the minus sign in front of the argument of the exponential function.

This paper presents the results and methods used for determining of probability of cleavage fracture toughness of ferritic reactor steel in transition temperature area. The steel tested in this study is steel know as 20MnMoNi 55 by DIN standard, typically used for structures working at low temperatures. In addition, the effect of test specimen geometry, temperature and fatigue crack initiation rate on fracture toughness was investigated in order to predict the fracture behaviour and probability of cleavage fracture. Two main studies joined in on one are presented in this paper. Testing in both studies were performed according to ASTM 1820 standard and the Weibull distribution with regression analysis, which includes fitting the experimental results in a logarithmic coordinate system, was used to predict the Jc values. Cleavage fracture probabilities in the function of Jc for large test specimen, C(T)100 and C(T)200 were determined based on the results obtained by testing of small C(T)50 specimens, for the purpose of direct savings and decreased costs of specimen testing. Cleavage fracture probability, represented by using Weibull distribution of experimental data will provide a clear insight into material behaviour at different temperatures. The influence of Delta K values during fatigue pre-cracking procedure on the fracture toughness scatter was also presented and discussed.

Digital Image Correlation (DIC) is applied to evaluate stress-strain diagrams for welded joints in two different ways. The first one is based on the measures strains along the welded joint, including all 3 zones of interest, base metal (BM), weld metal (WM), and heat-affected-zone (HAZ) subdivided into fine grain (FG) and coarse grain (CG) subzones. Specially designed iterative procedure has been used to determine coefficient of Holomon law to get true stress-strain curves for welded joint made of HSLA steel Niomol 490. The second one presents new methodology for evaluating true stress-strain diagram, based on measured values of contraction, as obtained by 3D DIC, rather than more conventional analytical formulas. New methodology is applied to undermatched welded joint, made of martensitic steels X10 CrMoVNb 9-1.

The 1st Virtual European Conference on Fracture (VECF1) has gathered more than 300 researchers from all over the world. They have presented more 320 papers, including 9 plenary lectures in the scope of the main VECF1 topics. Starting with 1800 views on the first day, there were 9300 views in the "hottest period" (June 20-July 2), making this event a great success. Conference was organized through number of Symposia, managed by ESIS Technical Committees. In the scope of these topics number of papers dealt with damage, cracks and related failures, including large structures like bridges, aircrafts, pressure vessels, large rotational equipment, prestressed and reinforced concrete constructions. As guest editors, we hope the Damage, Cracks & Failure Special Issue provides a remarkable impact in the research related to residual life assessment, modelling of failure and crack growth analysis. We also would like to express our gratitude to all authors for their contributions and to all reviewers for their generous work to guarantee the excellence of the papers. Finally, the guest editors would like to express a special thanks to Professor Richard Clegg, Editor-in-Chief of Engineering Failure Analysis journal, and to Elsevier staff for their support during the preparation of this issue.

In the face of enormous costs of developing new aircraft, high fuel prices, increasingly demanding environmental standards, harsh economic race and the fight against competing manufacturers, today's aviation is adapting not by producing brand new, more advanced aircraft, but through modifying existing ones by incorporating new more energy efficient engines, in accordance with today's leading criterion that requires minimal fuel consumption, enabling at the same time the longest possible range. The structure of these "new" aircraft is metallic and almost identical as it has been for decades, but now with the new requirement that its service life has to be extended, as long as it is economically justified. In such environment, it is clear that one of the leading tasks is to have the best possible assessment of the negative impact of the mechanism of Multiple Site Damage (MSD), which represents an introduction to the phenomenon of Widespread Fatigue Damage (WFD), the most insidious degradation mechanism of a metallic structure, whose significance was supposed to be diminished in recent decades with accelerated growth in the application of the composite structures. In line with the aforementioned trends, this paper aims to evaluate to what extent today's numerical methods are capable to contribute to the assessment of behavior of such phenomena and which of the proposed approaches could be used for investigating of the fracture problems, both accurately and efficiently. This assignment was conducted through numerical computations of stress intensity factors (SIFs) for two penny shaped cracks in elastic solid estimated by the methods that the authors of this paper consider to be the most relevant in the last few years.

Failures of rotating equipment often cause severe consequences, so it is necessary to study their integrity and life as detailed as possible, especially when crack is detected. In the case studied here, hydro power plant turbine shaft is analysed by using fracture mechanics parameters both for static and dynamic loading in order to assess its structural integrity and life. In both cases classical engineering approach and Finite Element Method have been applied to evaluate stress state and number of cycles from a given initial crack length to its critical value. Results of analytical and numerical modelling are compared to verify both approaches.

The ESIS Executive Committee decided to nominate a new team for the leadership and management of the TC12/ESIS technical committee (TC), as well as update the TC name as "Risk Analysis and Safety of Large Structures and Components". In this paper, the new organization of the TC12/ESIS as well as the objectives and tasks, and forthcoming events are presented. In addition, this document has editorial purposes regarding the selected and published papers from the International Symposium on Risk Analysis and Safety of Large Structures and Components (ISRAS-TC12) organized within of the "2nd International Conference of Structural Integrity (ICSI)", which took place at Madeira Island, Portugal, on 4-7 September 2017. As guest editors and TC12/ESIS members, we hope the ISRAS-TC12 Special Issue provides a remarkable impact in the research related to fatigue, fracture, structural integrity, risk analysis and safety of complex structures and components. We also would like to express our gratitude to all authors for their contributions and to all reviewers for their generous work to guarantee the excellence of the papers. Finally, the guest editors would like to express a special thanks to Professor Richard Clegg, Editor-in-Chief of Engineering Failure Analysis journal, and to Elsevier staff for their support during the preparation of this issue.

The topic of this work is assessment of ductile fracture initiation and development in different zones of welded joint of a high strength low alloyed (HSLA) steel. A combined experimental-numerical procedure is applied for determination of properties of the weld metal and the heat affected zone - HAZ. One tensile specimen with rectangular cross-section is tested, and the surface strains are determined using stereometric 3D measurement (measurement system Gom Aramis with two cameras and software solution). This methodology enabled formation of the stress-strain curves for micromechanical analysis of fracture of specimens with initial fatigue pre-cracks. Two different geometries are considered: standard single-edge notched bend (SENB) specimens and surface-cracked tensile specimens. The cracks were positioned either in weld metal or in HAZ - within the fine-grained part. Micromechanical model (complete Gurson model, by Z.L. Zhang) is applied for assessment of crack growth onset and stable growth. Higher resistance to ductile fracture initiation and crack growth in HAZ is successfully predicted, as well as constraint effect caused by different crack shapes.

Working conditions of casing pipes in drilling rigs can significantly influence the initiation and development of damage in the material, and therefore also the safe service of the entire system. In this work, an integrity assessment of a pipe with initial defect (machined surface crack) is presented. The position of this defect is on the external surface; unlike transport pipes, where internal surface is often endangered due to the contact with the fluid, casing pipes are also often exposed to damages at the external surface. A pipe segment exposed to internal pressure is examined experimentally and numerically, using the finite element method. Experimental setup included tracking of crack mouth opening displacement (CMOD) values, as well as J integral. Criteria for pipe failure are determined on the finite element (FE) models of the pipe; fracture initiation and plastic collapse are considered as failure mechanisms. Several 3D models with different crack sizes are evaluated. 2D plane strain models are also examined, to determine the applicability limits of this simplified approach. Integrity assessment criteria for the analysed geometries are discussed. Assessment of fracture resistance of the pipeline material is also considered in this work. Besides the standard SENB specimens, Ring specimens cut from the pipe are tested, and the results are compared. Both specimen geometries are modelled using local approach to fracture, by application of the micromechanical Complete Gurson model (CGM), developed by Z.L. Zhang. It is shown that the Ring specimens have similar fracture conditions under bending load as SENB specimens. Since they are much simpler to fabricate from the pipe than standard specimens, it is concluded that they can be used for assessment of fracture of the pipes with axial cracks.

Many efforts have been made to understand the effects of hydrogen on steels, resulting in an abundance of theoretical models and papers. However, a fully developed and practically applicable predictive physical model still does not exist industrially for predicting and preventing hydrogen damage. In practice, it is observed that different types of damages to industrial boiler components have been associated with the presence and localization of hydrogen in metals. In this paper, a damaged boiler tube made of grade 20 - St. 20 (or 20G, equivalent to AISI 1020) was investigated. The experimental research was conducted in two distinctive phases: failure analysis of the boiler evaporator tube sample and subsequent postmortem analysis of the viable hydrogen embrittlement mechanisms (HE) in St. 20 steel. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack (HTHA) during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, tube wall thickness measurement, tensile testing, hardness measurement, impact strength testing (on instrumented Charpy machine), analysis of the chemical composition of corrosion products - deposit and the microstructural characterization by optical and scanning electron microscopy SEM/EDX. The HTHA damage mechanism is a primary cause of boiler tube fracture. Based on the multi-scale special model, applied in subsequent postmortem investigations, the results indicate a simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. The model is based on the correlation of mechanical properties to the SEM fractography analysis of fracture surfaces.