Browsing by Author "Elias Asega"

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    Analyzing the Phenomenal of Cracks and its Effect on Freight Wagon Coupler Head Through Numerical Methods for the Case of Ethio Djibouti Railway Share Company
    (Addis Ababa University, 2026-02) Elias Asega; Mulugeta H.Woldemariam
    The Ethiopian-Djibouti Railway Network is facing a serious problem of operational and economical nature due to failure of coupler heads. From the maintenance report, it was found out that coupler head cracks is one of the major cause more than 34 % of all coupler failures which cause big economical loss. An extensive statistical preliminary failure phenomenal of the field data presented coupler head pinhole as the main locus of failure. Chemical composition test using spectrometric was performed on the material and revealed almost similar with the standard except a slight carbon content deviate from the specified AAR- Grade E steel standard. The analysis of the 3D model at SOLIDWORKS using Finite Element Analysis (FEA) of ABAQUS showed that there is highest stress on the knuckle pinhole (70.8 MPa tensile, 281.2 compressive). Most importantly, it has been shown that the analysis of an already existing crack (7.5x19mm) behaves to intensify the distribution of stress along the crack. In response to this, the geometry modification analyzed at FEA proved a significant decrease of peak stress to (56.5 MPa) during tensile loading and, most importantly, a fundamental change of magnitude in fatigue lifetime over 1,000,000 cycles. This FEA confirms that the proposed design is effective in reducing the concentration of stress as well as improving the long-term performance of the coupler head.