Diagnosis of EMD645 diesel engine connection rod failure through modal testing and finite element modeling

Connection rods are best known through their use in internal combustion piston engines. GM-GT26 locomotive uses a 3300 horse power V type engine with 16 cylinders that works at maximum crank speed of 900 RPM. The present study is concerned with the failure of a 645E3B engine connection rod with a reported catastrophic deformation due to unknown reasons. This rod has suffered from simultaneous bends in two surfaces with obvious marks of failure. A theoretical procedure, an experimental modal analysis technique and simulation by using finite element engineering softwares are used for this study. It includes finding the natural frequencies and the corresponding mode shapes for a new connection rod. This is then used to validate the FEM simulated model. The critical loads and the buckling forces on the connection rod are then calculated. The maximum loads are calculated by using the classical approaches and are verified by simulation in ADAMS-Engine software. The dynamic modeling includes rigid and flexible beam models and the torsional modes of vibrations are also considered. It is concluded that the connection rod failure is due to buckling at the presence of hydrolock phenomenon. The outcome of this research provides vital information for the proper operation and maintenance of heavy duty Diesel engines.