Vibration Measurement on Diesel Engine Components under Adverse Conditions in Brazilian Application

The objective of this study is to investigate the root cause of cracks detected in the Turbocharger bracket belonging to the engine Mercedes-Benz OM471 (Power: 390kW, Torque: 2600Nm) from Vehicle Truck Mercedes-Benz Actros 2651LS 6x4 Euro V. The investigation started with the instrumentation of every related component (besides the bracket itself, the charge air pipe, the exhaust pipe and also the crankcase for reference) in order to perform a vibration measurement. The necessary equipment to execute this procedure, included accelerometers, temperature sensors, strain gages and an inductive engine speed sensor. All data had to be acquired directly from real application conditions in vehicle, maximum load of 74 ton in a previously defined mountain road track, due to the impossibility to generate similar results in comparison to the ones detected on road through bench tests (or any other in-door experiment). The bracket position is located on the right side of a diesel combustion engine, also known as “engine hot side”, and work under temperatures in a range from 300 to 400 Celsius degrees. The development of a solution to allow the measurements to occur under such inhospitable conditions became a mandatory step of the investigation. The addition of a cooling system for the accelerometers, its adaptation and also the installation in the vehicle had been a challenging operation in order to reach the necessary results. The analysis of the raw data (speed, acceleration, strain and temperature) through Fast Fourier Transformation calculation (FFT) led to the exact determination of the root cause. With a clear understanding of the part behavior, assertive proposals of solution could be developed thanks to the answers obtained in the results of these measurements.