H. Madej

Vibration Processing Techniques for Fault Detection in Gearboxes

Vibration analysis is a very important tool in condition monitoring of operating machines. Many signal processing methods have been developed to extract information about incipient faults from externally measured vibration signals. The article presents the laboratory examinations of some faults in spur and helical gears. In case of spur gears two types of progressing local faults of cracked and chipped gear tooth were simulated and the smoothed pseudo Wigner-Ville distribution was used to demonstrate fault advancement via residual vibration signal analysis. Observing changes in the features of the WV distribution in the contour plots and changes of Kurtosis value monitored the progression of a fault. In case of helical gears some signal changes of transverse vibration velocity of shafts during the process of pitting growth in the tooth working surface have been investigated. Some new indices of pitting wear have been suggested and compared with other non-dimensional discriminants.Copyright

Diagnostics of Internal Combustion Engine Mechanical Faults Masked by Adaptive Control Systems

We have to admit that the modern car engine is now a device of much higher level of reliability than it used to be some years ago, and the microprocessor—based control system, supported by the board diagnostic equipment, makes this reliability even higher. However, it doesn’t mean that mechanical failures caused by manufacturing errors, operation of the device, its exploitation or premature wearing cannot appear at all. Neither it means that the failures will be always recognized by diagnostic equipment. The OBD systems were actually created for environmental purposes and their development to the form that could guarantee proper diagnosing in the case of typical mechanical faults is currently a subject of many studies. However, the main topic of the paper does not consist of listing the cases of difficult or unidentifiable faults but of showing that there is a group of failures (mainly of a mechanical type) that stimulate the developed adaptive control system to regulate and weaken typical exterior symptoms, and subsequently to make the damage—in a certain propagation range—unidentifiable even for an experienced mechanic. Therefore, the main objective of the paper constitutes answering the question about the direction of the development of diagnostic systems, and suggesting some additional vibroacoustic symptoms that could be taken into account, as well as the way they should be analysed in order to minimize the possibility of such occurrences.