The research work reported in this thesis aims at developing a methodology and a procedure for the condition monitoring and diagnostics of heavy-duty wheels based on vibration measurements at the end of the production line. The early detection of manufacturing anomalies is necessary to sensibly reduce the time/money lost due to possible problems that can rise up during the operating phases. Heavy-duty wheels are used in applications as automatic vehicles and motor trucks and are mainly composed of a polyurethane tread glued to a cast iron hub. The adhesive application between tread and hub is the most critical assembly phase, since it is completely made by an operator and a contamination of the link area between polyurethane and cast iron may happen. Furthermore the presence of rust on the hub surface can contribute to worsen the adherence interface and to reduce the operating life.
As the author is aware, studies by other researchers concerning the fault detection in heavy-duty wheels are not present in literature.
In order to develop a detection procedure, several wheels with different types of faults have been manufactured “ad hoc” with anomalies similar to real ones. Such anomalies consist of incorrectly adherence zones between tread and hub as well as localized or distributed rust on the hub surface. Numerous experimental tests have been carried out in order to identify the vibration effects of these defects as a function of fault type and dimensions. The thesis concerns the detection and diagnostic capability of different vibration processing techniques using well-suited indicators and determining pass/fail decision thresholds through the Tukey’s non-statistical method.
Contemporary, an accurate dynamic analysis of this mechanical system has been conducted - both experimentally through modal analysis techniques and numerically through finite element method - in order to establish the influence of the dynamic properties of the system components (namely heavy-duty wheel, support, frame of the test set up) on the measured vibratory signal.
Based on this dynamic characterization, a multibody model of the system has been developed: the heavy-duty wheel is considered as rigid and the yielding part is focused in the contact patch between wheel and drum. A non-linear elastic contact algorithm is adopted, based on stiffness properties previously extracted from static tests conducted on both material specimens and complete components. The model makes it possible to reproduce the vibration effects of the defects and to simulate signal modifications due to different component materials and design. as Synchronous Average and Cyclostationarity Analysis
