Papers by Keyword: Pitting

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Authors: W. Brevis, Luca Susmel, J.B. Boxall
Abstract: The present paper summarises an attempt of using the so-called Modified Wöhler Curve Method (MWCM) to estimate fatigue damage in pitted cast iron water pipes subjected to in-service variable amplitude multiaxial fatigue loading. In this setting, pits are treated as hemispherical/hyperbolic notches whose depth increases over time due to conventional corrosion processes taking places in buried cast-iron pipes. The validity of such an approach is proven by showing, through a case study, that, under particular circumstances, the combined effect of corrosion and fatigue can remarkably shorten the in-service lifetime of cast-iron pipes as observed in the case study.
Authors: Yun Ha Yoo, Jung Gu Kim
Abstract: Aqueous corrosion behaviors of Fe3Al-based iron aluminides were investigated. From the result of cyclic anodic polarization tests conducted in 3.5 wt.% NaCl solution at 25, 48, 72 and 95°C, as the temperature increased, the resistance to pitting corrosion decreased significantly, especially over the range of 25~48°C. From the result of crevice corrosion tests, no crevice corrosion occurred on FAL-Mo in the lower chloride-containing solution (200 ppm Cl-), however, FAL-Mo did not perform as well as the 304L SS in the higher chloride-containing solution (3.5 wt.% NaCl). From the result of anodic polarization tests performed in sulfur-compound solutions, additions of Cr and Mo to the Fe3Al-based iron aluminides tend to improve the aqueous corrosion resistance. Aqueous corrosion behaviors with different Al content evaluated by cyclic anodic polarization test in the chloride-containing solution exhibited the more stable passive behavior and the higher pitting resistance as Al contents increased.
Authors: Radivoje Mitrovic, Dejan Momcilovic, Ivana Atanasovska
Abstract: Energy efficiency is a key issue worldwide, and not confined solely to the realm of engineers. Past failures of mechanical power system components must be examined carefully in order to minimise future occurrences and increase energy efficiencies. Improved design procedures have been highly sought by engineers and researchers over the past few decades. The latest verified method with strong application potential within the power industry is that of the Theory of Critical Distances (TCD). TCD is not one method, but a group of methods that have a common feature; the use of a characteristic material length parameter, the critical distance L, for calculating the influence of notch-like stress raisers under static and fatigue loading. A case study from a hydro power plant turbine shaft was chosen to illustrate the development of this methodology. The paper illustrates the application of TCD to the fatigue life assessment of a turbine shaft with stress concentrations due to pitting corrosion.
Authors: M. Janik-Czachor, A. Wolowik, Z. Werner
Authors: Cathy Smith, Drew Donnelly
Abstract: Components and systems of military aircraft are regularly subjected to severe operating conditions, which lead to the development of a wide range of failure modes. The Defence Science and Technology Organisations (DSTO) Forensic Engineering and Accident Investigation group investigates such failures for the Australian Defence Force (ADF). Correct diagnosis of these failures has provided the ADF with immediate advice that has contributed to increased aircraft safety, improved operational availability, and significant cost savings. This paper presents a number of case studies of recent fatigue failures which have occurred in Australian Defence aircraft. The case studies include examples of failures which occurred via differing fatigue initiating and driving mechanisms. Details of the forensic investigations relating to each case study are provided and the ensuing remedial actions discussed.
Authors: Hui Li, H.B. Xu, Jin Zhang
Abstract: In this paper, TiN coating was deposited onto the nitrided 32Cr2MoVA by multi arc ion plating and proceeded line contact fatigue experiment to investigate the influence of hard coatings on the contact failure properties of nitriding steel. The results of experiment show that pitting is primary type of contact fatigue failure for TiN coated 32Cr2MoV and the pits on the TiN coated surface are shallower and smaller than that of the nitrided 32Cr2MoV. After TiN coating produce crisping and desquamation under higher contact fatigue loads, the exposed matrix surface begin to bear the contact load. The superficial microstructure of TiN coated 32Cr2MoV was more fine, and content of nitrides were higher than that of the nitrided, which insured the distribution of hardness gradient of subsurface was more rational than that of nitrided 32Cr2MoV. The contact fatigue strength of TiN coated 32Cr2MoV is greater about 200MPa than that of the nitrided 32Cr2MoV.
Authors: Kalathur Kumar, S. Arul
Abstract: Literature reported extensive work on the failure of Industrial power transmission systems, during their routine torque transmission, rotary motion etc. During transmission through gear drive the noise, temperature, stresses, vibration etc are important factors to be considered. When one or more of above exceed certain design limits, the drive and its accessories must be examined for the cause and a preventive maintenance is to be followed. The latest research work carried out, in above area is reviewed. The cause of failure and failure analysis is examined. An attempt is made in this paper, to systematically analyze the modes of failures, the reasons for the same, issues and challenges involved, there in, and measures to be taken for addressing them. This analysis is likely to help the researchers to proceed further in analyzing the failure and to suggest means to prevent failure of gear power transmission systems. The major contribution of present work is, to present the common modes of failure of gear teeth in power transmission systems, and measures to be taken to address the same. In general various additives in the lubricating oil help in controlling initiation of pitting. The present work involves controlling one of the additives namely sulphur in the lubricating oil to control pitting. The present work forms an excellent basis for identifying various other parameters affecting the pitting failure of gear teeth in a gear box.
Authors: Yu Mei Han, X. Grant Chen
Abstract: The corrosion behavior of Al-B4C metal matrix composites in H3BO3 solutions with different Cl- contents was investigated using potentiodynamic polarization and zero resistance ammetry techniques. Results show that the corrosion of Al-B4C composites in H3BO3 solution increases with increasing B4C volume fraction in the composites. The main corrosion characteristic of Al-B4C composites in H3BO3 solution is the galvanic corrosion between Al matrix and B4C particles. In the galvanic couple, B4C particle acts as cathode and Al matrix acts as anode. The cathodic reaction is hydrogen revolution reaction, which controls the corrosion mechanism of Al-B4C composites. Pitting is not observed on the composite surface in the H3BO3 solution with zero Cl-. However, with addition of Cl- in H3BO3 solution, pitting occurs and the corrosion resistance remarkably decreases with increasing Cl- content. The corrosion resistance of Al-B4C composites in H3BO3 solutions is compared with that in the standard 3.5% NaCl solution.
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