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Failure analysis of automatic coupler SA-3 in railway carriages
, Article Engineering Failure Analysis ; Volume 14, Issue 5 , 2007 , Pages 903-912 ; 13506307 (ISSN) ; Dehghani, K ; Pouranvari, M ; Sharif University of Technology
2007
Abstract
In the present work, failure analysis of an automatic coupler in railway carriages which failed in service and caused derailment, was carried out. An evaluation of the failed coupler was undertaken to assess its integrity, including visual examination, photo documentation, fractography, chemical analysis, hardness measurement, tensile and charpy impact testing and microstructural characterization. Results show that some casting defects (e.g. mis-run, cold lap, hot crack and inclusion) resulted in poor mechanical properties. Mis-runs were also responsible for fatigue crack nucleation from two different locations. Beach marks can be observed on the fracture surface. According to the results of...
Study the failure of casted copper anode: The formation of bumps defects on the surface of the anode during casting
, Article Engineering Failure Analysis ; Volume 138 , 2022 ; 13506307 (ISSN) ; Reza Khayati, G ; Javad Khorasani, S. M ; Assadat Yaghubi, N ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Copper anode (∼98%) is widely used to produce the cathode (99.995 wt%) in electrorefining process. These anodes sometimes become problematic from the production line due to the presence of bumps/holes on their surface. To find the reason of this defect, chemical composition of the three casted anodes was determined by the quantmeter analysis. Also, the microscopic and phase analysis were done by FESEM, EDS, XRD, and XRF for three types of anodes bump. The chemical analysis of anodes confirmed a high level of sulfur and oxygen, which have a key role in the formation of bumps. The results confirmed the presence of impurities including Cu2S, BaSO4, CaCO3 and MgCO3, which cause the formation of...
Understanding the occurrence of the surface turbulence in a nonpressurized bottom gating system: numerical simulation of the melt flow pattern
, Article Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications ; Volume 232, Issue 3 , March , 2018 , Pages 230-241 ; 14644207 (ISSN) ; Baghani, A ; Bahmani, A ; Tamizifar, M ; Davami, P ; Ostad Shabani, M ; Mazahery, A ; Sharif University of Technology
SAGE Publications Ltd
2018
Abstract
Surface turbulence during the filling of the mold triggers the entrainment of oxide films, which appears to be detrimental to the soundness of the final casting. Nonpressurized and bottom-gating systems have been employed in order to avoid such casting defects by reducing the surface velocity of the liquid metal. However, recent studies have shown that the melt front velocity in the mold entrance may exceed the critical value in the nonpressurized and bottom-gating systems. Therefore, a study was conducted on numerical simulation melt flow pattern in nonpressurized and bottom-gating systems. It was noted that the liquid metal enters the gate and then mold cavity with a higher velocity by...