The paper with the title “Investigation of Cold Water Pitting Corrosion Failure of Deoxidized High Phosphorus (DHP) Copper Tube: A Case Study”, authored by Dr. G. Pantazopoulos from the Mechanical Testing and Manufacturing Technology Department, Mr. A. Vazdirvanidis and Mr. A. Rikos from the Metallography and Electron Optics Department of ELKEME S.A. and Dr. D. Skarmoutsos from Halcor S.A. Metal Works, was presented as oral announcement in the 4th International Conference of Engineering Against Failure (ICEAF IV), 24-26 June 2015, Skiathos, Greece. This paper was dealt with the failure investigation of Cu-DHP tube due to Type I – Cold Water Pitting Corrosion initiated from the inner tube surface. The light optical microscopic and SEM observations together with EDS analysis indicated the presence of chloride and hard scale deposits (mainly carbonates) supporting the stated corrosion failure mechanism. The detachment of loosely adherent corrosion scale deposits led to fresh metal exposure and the continuation of the corrosion process, while their presence was probably attributed to potential water system parameters.
The paper with the title “Failure Analysis of a Fractured Aluminium Extrusion Structural Component in an Aircraft Wing” authored by Dr. K. Stamoulis, from Aeronautics Department, Engineering Directorate, Hellenic Air Force Aircraft Depot, Elefsis AFB, Greece and Laboratory for Strength of Materials and Micromechanics, Department of Civil Engineering, University of Thessaly, Volos, Greece, Mr. D. I. Panagiotopoulos from Aeronautics Department, Engineering Directorate, Hellenic Air Force Aircraft Depot, Elefsis AFB, Greece and National Technical University of Athens, Department of Mechanics, School of Applied Mathematical and Physical Sciences, Zografos, Athens, Greece, Dr. G. Pantazopoulos from the Mechanical Testing and Manufacturing Technology Department of ELKEME S.A. and Dr. S. Papaefthymiou from National Technical University of Athens, School of Mining & Metallurgical Engineering, Laboratory of Physical Metallurgy and ELKEME S.A., was presented as oral announcement in the 4th International Conference of Engineering Against Failure (ICEAF IV), 24-26 June 2015, Skiathos, Greece. This paper aimed to investigate the failure of a fractured spar stiffener, from 7075-T6 aluminium extruded alloy, which was found in the central wing, trailing edge structure of a military transport aircraft. The investigation findings suggest that the failure caused by a synergy of a crack, induced by an environmentally assisted degradation, branched as a result of a low crack driving force and then grown in a lower resistance, transverse path through a high cycle fatigue process ending-up to fast ductile overload fracture. The findings allow acquiring a deeper knowledge concerning the failure mechanisms producing, therefore, valuable feedback to design, inspection and maintenance procedures.
The paper with the title “Root cause analysis of an early fatigue failure of a boron flat steel component designed for heavy duty structural applications” authored by Dr. S. Papaefthymiou from National Technical University of Athens, School of Mining & Metallurgical Engineering, Division of Metallurgy and Materials, Laboratory of Physical Metallurgy and ELKEME S.A., Mr. A. Vazdirvanidis from the Metallography and Electron Optics Department and Dr. G. Pantazopoulos from the Mechanical Testing and Manufacturing Technology Department of ELKEME S.A. and Mr. C. Goulas from Materials Innovation Institute (M2i), Delft University of Technology, Department of Materials Science & Engineering, Delft, The Netherlands was presented in the poster session in the 4th International Conference of Engineering Against Failure (ICEAF IV), 24-26 June 2015, Skiathos, Greece. This paper addressed the failure case history of a boron flat piece that fractured early under low cycle fatigue testing. The crack initiated at the corners of the steel plate where non-metallic inclusions were located. Typical non-metallic inclusions in representative cases were identified by means of light optical microscopic and SEM/EDS analysis.
The paper with the title “Typical defects in plate and long steel products” authored by Dr. S. Papaefthymiou from National Technical University of Athens, School of Mining & Metallurgical Engineering, Division of Metallurgy and Materials, Laboratory of Physical Metallurgy and ELKEME S.A., Dr. F. Tzevelekou, Mr. A. Antonopoulos from Foundry, Steel and Thermal Processing Department of ELKEME S.A. and Dr. A. Gypakis from the GSRT was presented in the 4th International Conference of Engineering Against Failure (ICEAF IV), 24-26 June 2015, Skiathos, Greece. The present work aims to provide a practical overview of typical defects (surface & internal) that occur and their route causes. The paper summarizes the principal surface and internal defects of steel rolled plate products found during steel making and further deformation processing or final fabrication. The major defect origins were identified, employing mainly optical metallography and SEM/EDS analysis, aiming to plan and implement the optimum set of corrective actions in order to minimize the risk of failure recurrence. The most commonly encountered defects from semi- finished (billets, blooms, slabs) and final (round bar, plate) steel products are: network cracks, porosity, gas holes, shrinkage, shells, slivers, casting powder entrapment, ladle slag entrapment, other non-metallic inclusions, low hot ductility, centerline segregation cracking, macro and micro segregation, mechanical defects (scratches, transverse cracks, seams. Characteristic microstructures from optical and scanning electron microscopy are included. A brief theoretical background for the defects is provided.
