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<p>This study investigates the catastrophic failure of a connecting rod from a 2.4-L four-cylinder engine using an integrated experimental and numerical methodology. The three-dimensional geometry of the connecting rod was developed in CATIA and imported into ANSYS Workbench for static structural and fatigue finite-element analyses under realistic engine operating conditions. The applied loads were calculated based on combined gas pressure and inertia forces, resulting in a peak cyclic load of approximately 23.6&#xa0;kN. Numerical results revealed a pronounced stress concentration, minimum fatigue life, and maximum damage accumulation at the big-end fillet region. Mechanical testing confirmed that the connecting rod steel exhibits high strength and ductility (UTS ≈ 965 MPa, elongation ≈ 18 %), while fatigue data showed a significant reduction in allowable stress with increasing cycles. Fatigue-life prediction indicated a minimum life of about 3.75 × 10<sup>5</sup> cycles, consistent with the observed failure location. Fractographic analysis using scanning electron microscopy (SEM) demonstrated fatigue crack initiation followed by stable crack propagation and final ductile overload rupture, characterized by extensive dimpled morphology. Numerous non-metallic inclusions were observed at the centers of dimples. Energy-dispersive x-ray spectroscopy (EDS) identified these inclusions as MnS- and oxide-based particles enriched in Mn, S, Si, Ca, and O. These inclusions acted as local stress raisers, promoting micro-void nucleation and accelerating fatigue crack initiation. The combined numerical and experimental findings demonstrate that the failure mechanism is governed by inclusion-assisted fatigue crack initiation at the big-end fillet, progressive crack propagation under cyclic loading, and final ductile fracture, leading to catastrophic engine failure.</p>

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Integrated Failure Analysis of an Engine Connecting Rod using Finite-Element Modeling, Fatigue Life Prediction, and Microstructural Evaluation

  • 期刊论文

  • 发表日期：

    2026年5月17日

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  • M. A. Mohtadi-Bonab,
  • Mostafa Beheshtdoust,
  • Ashkan Ghoujehzadeh

摘要

This study investigates the catastrophic failure of a connecting rod from a 2.4-L four-cylinder engine using an integrated experimental and numerical methodology. The three-dimensional geometry of the connecting rod was developed in CATIA and imported into ANSYS Workbench for static structural and fatigue finite-element analyses under realistic engine operating conditions. The applied loads were calculated based on combined gas pressure and inertia forces, resulting in a peak cyclic load of approximately 23.6 kN. Numerical results revealed a pronounced stress concentration, minimum fatigue life, and maximum damage accumulation at the big-end fillet region. Mechanical testing confirmed that the connecting rod steel exhibits high strength and ductility (UTS ≈ 965 MPa, elongation ≈ 18 %), while fatigue data showed a significant reduction in allowable stress with increasing cycles. Fatigue-life prediction indicated a minimum life of about 3.75 × 105 cycles, consistent with the observed failure location. Fractographic analysis using scanning electron microscopy (SEM) demonstrated fatigue crack initiation followed by stable crack propagation and final ductile overload rupture, characterized by extensive dimpled morphology. Numerous non-metallic inclusions were observed at the centers of dimples. Energy-dispersive x-ray spectroscopy (EDS) identified these inclusions as MnS- and oxide-based particles enriched in Mn, S, Si, Ca, and O. These inclusions acted as local stress raisers, promoting micro-void nucleation and accelerating fatigue crack initiation. The combined numerical and experimental findings demonstrate that the failure mechanism is governed by inclusion-assisted fatigue crack initiation at the big-end fillet, progressive crack propagation under cyclic loading, and final ductile fracture, leading to catastrophic engine failure.