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1 – 6 of 6George Pantazopoulos, Athanasios Vazdirvanidis, Andreas Rikos and Dionysios Skarmoutsos
The purpose of this paper is to identify the corrosion failure mechanism of a Cu tube in a hydraulic installation and recommend corrective actions to improve the reliability of…
Abstract
Purpose
The purpose of this paper is to identify the corrosion failure mechanism of a Cu tube in a hydraulic installation and recommend corrective actions to improve the reliability of the entire unit.
Design/methodology/approach
Failure investigation process includes mainly stereo-, light optical microscopy and scanning electron microscopy as the main analytical tools for material characterization and root-cause analysis.
Findings
The investigation findings, obtained by corroded surface analysis and metallographic evaluation in transverse sections, suggest strongly that the failure was caused by the operation of Type I pitting corrosion mechanism initiated from the inner side and propagated towards the outer tube surface, assisted by the flowing medium composition.
Originality/value
This paper deals with an applied failure analysis/case history, summarizes the stages involved in the mechanism of pitting corrosion Type I, taken place in cold water systems together with the main parameters and corrosive species that enhance corrosion rates, shortening pipeline operation life.
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Keywords
Athanasios Vazdirvanidis, Sofia Papadopoulou, Spyros Papaefthymiou, George Pantazopoulos and Dionysios Skarmoutsos
The purpose of this paper is to address the main aspects of ant-nest corrosion failure mechanism of a Cu tube in heating ventilation and air-conditioning (HVAC) installations and…
Abstract
Purpose
The purpose of this paper is to address the main aspects of ant-nest corrosion failure mechanism of a Cu tube in heating ventilation and air-conditioning (HVAC) installations and analyze the possible root causes through various case studies presented.
Design/methodology/approach
Failure investigation process includes mainly stereo-, light optical and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy for elemental microanalysis, as the main analytical techniques for material characterization and root-cause analysis.
Findings
The investigation findings, obtained from corrosion products’ analysis in conjunction to metallographic evaluation in transverse sections, illustrate the principal characteristics (“fingerprints”) of ant-nest (formicary) corrosion mechanism.
Originality/value
This paper which deals with the presentation of applied failure analysis/case histories’ investigation, summarizing the main aspects of an important and insidious type of Cu corrosion, taken place in HVAC installation systems and, on the other hand, presenting a complementary analysis of the chemical processes involved in the progressive failure mechanism constitutes an integrated approach, aiming to become a concise contribution to this subject.
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Konstantinos Stamoulis, Dimitrios Panagiotopoulos, George Pantazopoulos and Spyros Papaefthymiou
The purpose of this paper is to deal with the failure analysis of a fractured spar stiffener, extruded from 7075-T6 aluminum alloy, which was found in the central wing, trailing…
Abstract
Purpose
The purpose of this paper is to deal with the failure analysis of a fractured spar stiffener, extruded from 7075-T6 aluminum alloy, which was found in the central wing, trailing edge structure of a military transport aircraft. The previous loading history and the dominant environmental factors (corrosive and humid atmosphere, water entrapment, etc.) suggest corrosion and fatigue as the principal failure modes, synergistically acting on the wing component.
Design/methodology/approach
This study presents the failure analysis concentrated on finding evidence of failure mechanisms and plausible root-cause(s) of the fractured spar stiffener. Chemical analysis, stereo and scanning electron microscopy, as well as finite element analysis employed as the main analytical tools for material characterization and failure investigation.
Findings
The overall evaluation of the findings suggest that the failure caused by a synergy of two mechanisms; a crack initiated in the longitudinal, extrusion direction by an environmentally assisted corrosion attack, then propagated by the superimposed transverse stress field, branched/deflected due to a low crack driving force and extended in a transverse path through a high cycle fatigue process. Finally, the complete fracture occurred as fast fracture, resulted by a ductile overload.
Originality/value
This paper deals with an industrial damage case study, providing analysis and modeling from structural engineering standpoint. The aforementioned findings concerning the fractured aircraft component allow gaining a deeper knowledge about the mechanisms of crack initiation and propagation which, in turn, can produce a valuable feedback to design, inspection and maintenance procedures. This includes a modified heat treatment from T6 to T73 temper for the redesigned component.
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George Pantazopoulos, Sylvia Zormalia and Athanasios Vazdirvanidis
The purpose of this paper is to identify a failure mechanism of an industrial tube and recommend corrective actions to improve the reliability of the entire unit.
Abstract
Purpose
The purpose of this paper is to identify a failure mechanism of an industrial tube and recommend corrective actions to improve the reliability of the entire unit.
Design/methodology/approach
Metallurgical failure investigation process included mainly stereo‐, light optical microscopy and scanning electron microscopy (SEM) as the main analytical tools for material characterization and root cause analysis.
Findings
The investigation findings, obtained by fractographic and metallographic evaluation, suggest strongly that the failure was caused by the operation of low cycle fatigue (LCF) mechanism initiated from the inner side and propagated towards the outer tube surface, assisted by the superposition of applied and residual stress fields.
Originality/value
This paper deals with an industrial case history, providing the findings of failure investigation of a compact refrigeration system, presented principally from structural material/component standpoint and highlighting recommendations for improvement and failure prevention.
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George Pantazopoulos, Anagnostis Toulfatzis, Athanasios Vazdirvanidis and Andreas Rikos
The purpose of this paper is to outline and document the failure root cause of a carbide cutting tool during machining of a hardened tool steel under automatic machining…
Abstract
Purpose
The purpose of this paper is to outline and document the failure root cause of a carbide cutting tool during machining of a hardened tool steel under automatic machining conditions.
Design/methodology/approach
Optical metallography and SEM/energy dispersive spectroscopy analysis, together with optical profilometry were employed for failure investigation. The use of an alternative cutting tool and modification of machining conditions are proposed as a failure preventive action.
Findings
Severe abrasive wear and adhesion of machining chips are observed in the flank zone, causing blunting of the cutting edge. The revision of cutting conditions, together with the use CBN-based tool insert leads to an overall improvement of the stability of the process and tool lifetime.
Originality/value
This paper places emphasis on a failure analysis case history following a structured approach in industrial machining problem solving, highlighting suggestions for process improvement.
The purpose of this report is to help companies and other organizations recognize the need for the adoption of antidiscrimination and inclusion practices.
Abstract
Purpose
The purpose of this report is to help companies and other organizations recognize the need for the adoption of antidiscrimination and inclusion practices.
Design/Methodology/Approach
The chapter describes the diversity practices employed and the results achieved by two companies in Greece, as reported through interviews with the Managers of Human Resources that are responsible for their implementation.
Findings
This chapter outlines the demographic and social profile of the population of the country, examining gender, race, religion, sexual orientation, age and disability. It also presents the practices of two companies operating in Greece, Vodafone and Coco-Mat, which tackle discrimination and inequality, proving that diversity management can be implemented successfully in the Greek workplace. The diverse policies implemented by the two companies also prove that every organization can incorporate relevant policies in a way that fits best their structure, processes and the mentality of the leadership team.
Social Implications
The development and activation of diversity and inclusion processes in the workplace should also dictate CSR practices, which address the needs of communities, both within and outside the organizations.
Originality
There is little research regarding discrimination and diversity in the Greek workplace, despite its growing relevance and importance for the community. This report aims to inspire further research, as well as the development and implementation of diversity management practices by managers and policy-makers.
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